Evaluation of the pediatric surgical patient


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Evaluation of the pediatric surgical patient

  1. 1. Evaluation of the Pediatric Surgical Patient Parental considerations Complete care of the pediatric surgical patient includes establishing a good rapport with the child, as well as the child's parents or guardian. Parents and guardians are often anxious about the treatment of their child, and the responsibility to allay their fears lies with the pediatric surgeon. Fostering a good relationship with the family can be accomplished with skilled communication. The surgeon should always thoroughly explain the child's problem. Reviewing the results of imaging studies with the parents and patient is helpful. Freehand drawings and diagrams from books can also be used to aid the surgeon in illustrating anatomy and explaining the problem. Parents often gain a better understanding of their child's problem if the surgeon takes the time to explain how or why the problem arose. Be prepared to explain embryology in layperson's terms when talking to parents of patients with congenital lesions and/or defects. Also be familiar with basic genetics and modes of inheritance when counseling parents of a child with a genetic defect. Knowledge in oncology is useful when discussing tumors; be prepared to answer general questions regarding chemotherapy and radiation regimens for tumors commonly encountered in pediatric surgery. Notify parents that the oncology staff is part of the team involved in their child's care. The explanation of the proposed surgery in layperson's terms includes describing where the incision will be made, the steps of the surgery, how the incision will be closed, and the size of the scar. At this time, basic postoperative issues can also be addressed, including the anticipated length of hospital stay, the activity and dietary restrictions in the postoperative period, and the time the child will likely be away from school. Explicitly explaining why the surgery should be performed and what it should accomplish is important. This is also the time to discuss the risks of surgery. In addition, discussing options and alternative treatment plans is important. The consequences of not performing surgery should be addressed as well. Pause after providing important information so that parents have the opportunity to take in all the information. Leave time for questions at the end of the encounter, and give parents a means by which to contact you with questions. Refer parents to other resources, such as support groups, the hospital's family resource center, and reliable sources on the Internet. Caution parents with regard to the quality of information they might find on the Internet because the accuracy of information varies widely. HISTORY The surgeon must obtain a complete and detailed history from the patient and parents. The history, in concert with a well-performed physical examination, is the basis for a diagnosis and treatment plan. In an academic setting, the attending surgeon often sees the patient after a resident or medical student performs the initial evaluation. At this time, the surgeon must verify important points in the reported history and findings. This initial encounter with the surgeon also provides him or her with an opportunity to get to know the child and family. The chief complaint (CC) is the reason that the child presents to the pediatric surgery service. Statement of the CC should always include the duration of symptoms. The
  2. 2. history of present illness (HPI) should detail the course of the symptoms, including its acuity of onset, progression, and severity. Also include symptoms associated with the child's CC. Document pertinent negative findings. Aggravating or relieving factors are important and must be noted, as should any treatment the child has received. Any medical or surgical history relevant to the CC should be stated in the HPI. Birth history, medical conditions, and previous surgeries should be listed separately in the past medical history (PMH) and past surgical history (PSH). Of importance, a history of bleeding disorder or unusual bleeding should be noted, as well as any history of receiving anesthetics. Note the names, doses, and frequency of all medications that the child is currently taking. Include medications that are taken on a schedule and those taken as needed. Use of herbal supplements is increasingly popular, even in the pediatric population, and they should be included in the list of medications. Note drug allergies and reactions, along with symptoms that occur when the patient is given the drug. Food and environmental allergens may also be listed. Document the family history and the social history. For many pediatric surgical patients, the family history is noncontributory. However, it is clinically significant in children with congenital malformations, genetic diseases, or malignancies. A child's social history should address issues regarding the family and home environment and the child's academic and social development. Conduct a thorough review of systems (ROS); list pertinent positives and negatives already stated in the HPI. PHYSICAL EXAMINATION The goal of the physical examination is to identify the current surgical issues and to ensure that the organ systems other than the one being treated are healthy. Unlike the adult physical examination in which one can often follow the same routine every time, the pediatric examination must be modified for each patient. Interacting with children of different ages and temperaments in different settings can be challenging. Hand washing before and after performing the physical examination is essential. Hand washing serves purposes more than infection control. On a psychological level, it conveys a reassuring message to the parent that hygiene is important to the surgeon. On a practical level, it warms the surgeon's hands before he or she touches the child. In an older and cooperative child, physical examination can be performed by using a standard routine. However, this routine may need to be modified in young children or infants who do not cooperate. Infants should be positioned on the examination table for the entire examination. Toddlers and small children may sit in their parent's lap for the initial part of the examination, and they can be moved to the examination table, and for the abdominal, inguinal, genital, and rectal examinations, when required. Having the parent by the examination table reduces the child's anxiety and should be encouraged. Skin and integument
  3. 3. Always ask the patient to undress completely. The pediatric surgeon is often consulted to evaluate lesions, or lumps and bumps. The lesion in question should be inspected for its size, shape, consistency, circumscription, and mobility. Thoroughly search for other, similar lesions on the body. Also inspect the skin for rashes, which may indicate an infectious process or vasculitis. Scars indicating previous surgery should be noted. Cellulitis may arise after any trauma that interrupts the skin barrier (eg, scratch, laceration, foreign body, surgical wound). Erythema and warmth with induration and fluctuance indicates an abscess. Inspect the skin for birthmarks, noting any changes in their character. Bruises and burn scars, especially those resembling cigarette burns or burns that have a well-defined shape, should be suspected as signs of child abuse. Lymph nodes Lymphadenopathy can occur in many locations, and often involves the cervical, axillary, epitrochlear, or inguinal chains. In children, lymphadenopathy most commonly has an infectious etiology, and a source of infection should be sought throughout the examination. The infection may be bacterial, viral, fungal, or protozoal. Enlarged lymph nodes may represent metastatic disease, or they may be the presenting sign of malignancies, such as acute lymphoblastic leukemia (ALL), Hodgkin disease, and nonHodgkin lymphoma. Head, ears, eyes, nose, and throat On head, ears, eyes, nose, and throat (HEENT) examination, note the size and shape of the patient's head. Children with abnormal fusion of the coronal sutures are not normocephalic. Microcephaly or macrocephaly may indicate a neurologic or intracranial process. An icteric sclera suggests hepatic or biliary dysfunction. Otitis media can be excluded if tympanic membranes that are clear and if visible landmarks are found. Finding an erythematous oropharynx or inflamed nasal turbinates with associated rhinorrhea are common in upper respiratory tract infections. A quick dental examination to identify loose teeth is important in children scheduled to undergo surgery. Chest wall Breast tissue is commonly observed in infant boys and girls. This is normal and due to a slow decline in maternal hormones in the infant's bloodstream. On a similar note, the pediatric surgeon may be asked to evaluate a male adolescent for gynecomastia, which is often due to the changing hormonal environment associated with puberty. Evaluation of breast masses in girls requires particular attention. In preadolescent girls, one must distinguish a mass from a breast bud, keeping in mind that breast development does not occur at the same rate in both breasts. Normal breast tissue must be differentiated from a breast mass in female adolescents. The pediatric surgeon may also encounter deformities in the chest wall, such as pectus excavatum and pectus carinatum. Apart from discerning the degree of deformity, performing cardiac and pulmonary examinations is important in children with these deformities. Cardiovascular system Heart rate and rhythm should be noted on the cardiovascular examination. Many children have an audible murmur at some point between infancy and adolescence. Most murmurs fortunately occur in normal hearts and are benign. Murmurs that have a structural cause may indicate a need for preoperative antibiotic prophylaxis. Consult a
  4. 4. cardiologist a new-onset murmur is in question. Check proximal and distal pulses. Expect strong pulses throughout. Suspect coarctation of the aorta if pulses in the upper extremity are strong but pulses in the lower extremity are weak or absent. Lungs Good respiratory effort in a cooperative child is critical in the pulmonary examination. No layers of clothing should be present between the stethoscope and skin. Breath sounds should be clear on both sides. Abnormal breath sounds, such as rhonchi, wheezes, and crackles, indicate an underlying pulmonary process. Abdomen The abdominal examination should be performed systematically and gently. First, observe the patient's abdomen. If scars are present, their length and location can give the surgeon an idea of the previous surgeries performed. The shape of the abdomen may also be a clue to guide diagnosis. A scaphoid abdomen in a neonate or infant may suggest a diaphragmatic hernia but may be normal in a thin child. Intestinal obstruction, an abdominal mass, or ascitic fluid may cause abdominal distention. Second, listen for bowel sounds. Be patient because up to 2 minutes may pass before bowel sounds are heard. The absence of bowel sounds may suggest peritonitis. The character of the bowel sounds is also important; high-pitched sounds are consistent with bowel obstruction. While listening for bowel sounds in a young child, the clinician may use a stethoscope to palpate the abdomen, systematically covering the entire abdomen. Begin the palpation in an area away from the area of reported pain, leaving that area for last. Diffuse tenderness may suggest peritonitis or a generalized process. Focal points of tenderness often reflect the underlying pathology. Discern if the pain is superficial, musculoskeletal, or visceral. Gently evaluate the patient for peritoneal signs, such as rebound and guarding. Overly aggressive examination creates unnecessary pain and fear in the child. In young children, their facial expressions and behavior are often more reliable indicators of pain than their verbal report. Palpation can also give the surgeon an idea of the size, shape, and consistency of an abdominal mass. The size of the liver and spleen can be determined by percussion and palpation of their edges. Inguinal region The inguinal region is most commonly examined in the evaluation of a hernia or hydrocele. If an inguinal hernia is not visible on examination, the child should be coaxed to perform a Valsalva maneuver (eg, coughing or straining as during a bowel movement). Intra-abdominal pressure is increased in crying infants. Hernias should be easily reducible and not incarcerated or strangulated, which are surgical emergencies. Genitalia Children as young as 2 years understand the concept of modesty, and special attention must be given to modesty during the genital examination. In addition, always ensure
  5. 5. that a staff person of the same sex as the patient is present in the room during the examination. Genital examination in boys is necessary in the evaluation of a number of conditions, including hydroceles and undescended testes. Transillumination may be a useful technique to visualize the contents of an enlarged scrotum but cannot be relied on for a diagnosis, especially in infants. Note the size and shape of the testicle in the scrotal sac and the character of any fluid. Part of the male genital examination includes checking for the presence of both testes in the scrotal sac. The testis, epididymis, and spermatic cord should be appreciated as separate structures. Retractile testes can masquerade as undescended testes; always check to determine whether a testicle that is not in the scrotum can be brought down into the scrotum. The genital examination is one of the least comfortable parts of the physical examination; boys can assume the position most comfortable for them—lying down, sitting frog-legged, or standing. Performing a female genital examination to evaluate for fused labia, imperforate hymen, vaginal or perineal bleeding, and an assortment of other issues is not uncommon. Note that a pelvic examination performed by the surgeon is likely to be the first for a girl and has lasting psychologic consequences. Always suspect sexual abuse when vaginal tears are present. Vaginal discharge can be a sign of a sexually transmitted disease and should raise the surgeon's index of suspicion for abuse. Rectum The rectal examination may be traumatic to the child and their parents and should be performed quickly but thoroughly. Explaining the process to the child is useful to assure them that nothing will be done to them without first letting them know. First, inspect the anus. Fissures, fistulas, skin tags, and other lesions can be seen by gently separating the anal opening. Next, inform the child that they will feel a finger on the outside. Gentle external pressure often causes the anal sphincter to relax and facilitates passage into the anal canal. Condyloma acuminata, caused by the human papillomavirus, are consistent with sexual abuse. Always use water-soluble lubricant on a gloved finger and obtain a stool sample for a guaiac test whenever feasible. The little finger may be used in infants and toddlers, and the index finger may be used in larger children. Sphincter tone may be decreased in patients who have previously undergone anoplasty or have sustained traumatic injury to the sphincter muscle. Decreased sphincter tone is more alarming in the trauma setting because it indicates spinal cord injury. Palpate the entire circumferences of the anal canal and rectum. Note the location, size, and texture of a palpated mass. Presacral tumors may be the cause of a child presenting with constipation. The examiner must differentiate discomfort due to the examination itself from tenderness due to an underlying process. Many children can make this differentiation if asked. Pain on examination may be caused by anal fissures externally, appendicitis in a low-lying appendix, or pelvic inflammatory disease. The surgeon may also detect a fecal impaction during the rectal examination of a child with constipation. Back and spine
  6. 6. Scoliosis and other spinal deformities are obvious during examinations of the back. Vertebral tenderness to palpation may be a sign of trauma. Costovertebral angle tenderness may be indicative of pyelonephritis or appendicitis in a patient with a retrocecal appendix. Extremities Clubbing is observed in many patients with chronic illness, especially patients who have pulmonary disease. Cyanosis is an indicator of poor oxygenation or perfusion, and effort should be made to determine whether the cyanosis is chronic or acute. Edema may be a sign of impaired renal or cardiac function. Suspect abuse in patients with extremity deformities secondary to long-bone fractures. Nervous system Much can be gained from observing a child's behavior. An interactive and playful child is likely to have no focal neurologic findings on examination. However, a basic neurologic examination, which only takes a minute with practice, should be performed regardless. This comprises assessment of cranial nerve function, motor and sensory examination, reflex evaluation, and cognitive assessment. THE WELL CHILD A number of pediatric surgical problems are found on routine physical examination by a pediatrician or family physician. Children are then referred to the pediatric surgeon. Evaluation of an otherwise healthy child should still include a discussion of the child's health issues and a complete history and physical examination. Perform only the tests that are to be used for diagnostic purposes. Routine preoperative laboratory tests and chest radiography are not indicated for most children. Explain outpatient surgery and details of nothing-by-mouth (NPO) status to parents. Advising parents that surgery may be canceled in the event of upper respiratory tract symptoms or infection is wise. Postponing hernia surgery in an infant with a severe diaper rash is reasonable. A repeat history and thorough physical examination on the day of surgery is crucial; close attention should be paid to the respiratory system and the surgical area. Clearly mark the surgical site on the day of surgery. THE PATIENT WITH TRAUMA History The history of a patient with trauma is often brief and aimed at identifying the mechanism and circumstances surrounding the injury. Trauma can be divided by the mechanism of injury into blunt and penetrating. For blunt trauma, determining the mechanism and force of impact is important. Head and extremity injuries are extremely common in children. Acceleration-deceleration injuries commonly occur in motor vehicle accidents and falls from heights. Abdominal organs most susceptible to injury include the liver, spleen, and fluid-filled loops of the
  7. 7. small bowel. Blunt trauma at low velocities causes compression injuries to the area of trauma. These are often the liver or spleen in blunt abdominal trauma, fractures to the ribs, and crush injuries to the extremities. Pulmonary contusions are also common. Penetrating trauma may be accidental or nonaccidental. Knowledge of the impaling object or weapon used is a crucial piece of information. For stab wounds and impalement injuries, the size and length of the object should be documented. In gunshot wounds, the amount of damage caused is related to the amount of energy the bullet dissipated to the tissue in its trajectory. Therefore, the extent of injury can be gauged by the caliber of the firearm used. Other important information that may aid in assessment of the patient with trauma includes the time of injury, the treatment received before arrival, the patient's other symptoms, the character of pain, and the amount of blood loss. In addition, PMH and PSH, medications, allergies, and immunization status, if available, may influence management decisions. Also, note the time when the child last ate or drank. Always keep the possibility of child abuse in mind. Have a high index of suspicion for nonaccidental injury if the pattern of injuries is inconsistent with the described mechanism or if several injuries of various chronicities are found. Physical examination Initial evaluation of the pediatric trauma patient should follow the well-known ABCDE mnemonic for airway (with cervical-spine control), breathing, circulation, disability, and exposure the American College of Surgeons recommends. The secondary survey follows this initial assessment. Imaging studies may be indicated. Remember that pediatric patients with trauma are anatomically and physiologically different from adult patients with trauma. Airway Airway obstruction is the most rapidly lethal problem in the patient with trauma. Situations in which airway protection are needed include (1) maintaining an airway in an unresponsive patient, (2) protecting against aspiration, (3) preventing or reversing hypoxia, and (4) providing hyperventilation to decrease intracranial pressure. Provide supplemental oxygen to all patients with trauma. If the patient has any signs of respiratory distress or inadequate ventilation, immediately secure and maintain the airway. An intubated patient should also receive an orogastric or nasogastric tube for decompression and to minimize risk of aspiration. Protect the cervical spine at all times. Breathing When securing the airway, check to see that both lungs are ventilated. Ensure that chest expansion is symmetrical and that breath sounds can be auscultated over both lung fields. If an endotracheal tube was placed, listen over the stomach to ensure that the esophageal intubation has not occurred. Examine the chest for sucking wounds, flail chest, and subcutaneous emphysema. Circulation
  8. 8. Assess the presence and strength of pulses, skin color, capillary refill, and blood pressure. Apply direct pressure to any visible hemorrhage. Whenever possible, place 2 intravenous (IV) lines by using large-bore catheters. If peripheral access is not possible, consider placing a central line or intraosseous line (in children <6 y). Heart rate is a better indicator of impending circulatory collapse than blood pressure because hypotension does not occur until 25-30% of the child's blood volume is lost. Warmed isotonic crystalloids such as isotonic sodium chloride solution and lactated Ringer solution are the mainstays of fluid resuscitation. Administer an initial bolus of 20 mL/kg to treat shock. If the response is inadequate, this bolus may be repeated for a total of 3 boluses. If the child is still hemodynamically unstable, use 10 mL/kg of packed RBCs for resuscitation. If type-specific blood is not available, O-negative blood may be administered. The patient may have signs of hypovolemic shock if fluid resuscitation cannot keep up with hemorrhage. Age-appropriate parameters are as follows: • • • • • • • Aged 0-6 months - Weight 3-6 kg, heart rate 160-180 bpm, systolic blood pressure 60-80 mm Hg, respiratory rate 60 breaths per minute Infant - Weight 12 kg, heart rate 160 bpm, systolic blood pressure 80 mm Hg, respiratory rate 40 breaths per minute Preschool aged - Weight 16 kg, heart rate 120 bpm, systolic blood pressure 90 mm Hg, respiratory rate 30 breaths per minute Adolescent - Weight 35 kg, heart rate 100 bpm, systolic blood pressure 100 mm Hg, respiratory rate 20 breaths per minute Disability Rapid neurologic examination should be performed in any child with trauma. The Glasgow coma scale may be used in children; however, the verbal component must be modified for children younger than 4 years, as shown below: • • • • • • • • • Appropriate words, social smile, fixes and follows - Verbal score of 5 Cries but is consolable - Verbal score of 4 Persistently irritable - Verbal score of 3 Restless, agitated - Verbal score of 2 None - Verbal score of 1 Assess the patient for movement of extremities. If the patient is comatose, check for movement in response to noxious stimuli. Seek a sensory level if the patient is cooperative. Note if the Babinski reflex is present. Do not sedate or paralyze the patient until a good neurologic examination is performed (usually during the secondary survey).
  9. 9. Exposure The patient's clothing should be completely removed, and the entire body exposed. The body surface area–to-weight ratio is higher in children than in adults. Blankets and additional warming measures should be used to maintain the patient's body temperature. Examine the patient for occult injuries, making sure that a log roll is performed and the back is inspected for entry and exit wounds, vertebral deformities, and tenderness. At this time, perform a rectal examination to evaluate for sphincter tone and gross blood. Spinal precautions should be maintained, and movement of the patient should be minimized until the cervical spine, chest, and pelvis are cleared. Secondary survey The secondary survey, proceeding from head to toe, should follow initial assessment. The HEENT examination focuses on facial lacerations and fractures, hemotympanum, tympanic membrane rupture, CSF otorrhea, CSF rhinorrhea, epistaxis, septal hematoma, loose teeth, and maxillary-mandibular malocclusion. A quick cranial-nerve examination should include pupillary reactivity, extraocular movements, and facial symmetry (eg, raising eyebrows). The neck examination is performed to identify areas of tenderness, spinous process deformities, jugular venous distension, and tracheal deviation. The chest should be palpated, and rib fractures identified. Evaluate for signs of blunt or penetrating trauma. If not already identified in the primary survey, pneumothorax, hemothorax, sucking wounds, and flail chest should be recognized at this time. The abdominal examination includes auscultation of bowel sounds and palpation to detect tenderness. Always look for signs of blunt or penetrating trauma. Evaluate the pelvis for tenderness and instability. Neurovascular assessment of the extremities and identification of fractures, dislocations, and contusions should follow. Tertiary survey Despite careful primary and secondary surveys, 2-50% of injuries are still missed. Missed injuries are more common in patients with a blunt mechanism injury than those with a penetrating injury. A tertiary survey is therefore necessary and instrumental in identifying all injuries. The tertiary survey identifies and catalogs all injuries and is performed after the initial trauma resuscitation and operative intervention, typically within 24 hours of injury. A repeat survey should be performed when the patient is awake, responsive, and able to communicate at an age-appropriate level. The tertiary survey involves: • • • • • • • Comprehensive review of the medical record (mechanism, pertinent comorbidities) Repeat of primary and secondary surveys Review of all laboratory data Review of all radiographic studies with an attending radiologist Imaging examinations
  10. 10. Focused abdominal sonography for trauma Attempts to define the role of the focused abdominal sonography for trauma (FAST) in pediatric trauma are ongoing. Thus far, the FAST appears to have the greatest utility in a hemodynamically unstable patient with blunt abdominal trauma. In this group of patients, FAST can potentially demonstrate the presence or absence of free intraperitoneal fluid. However, as with any test, the quality of the study and interpretation of the images is technician dependent, and the results should be considered in this context. Radiography Radiologic imaging: Radiographically assess the cervical spine by obtaining anteroposterior (AP) and lateral views. Also obtain a chest AP view and pelvic images. Obtain these images as early in the evaluation as possible, but do not delay attempts at resuscitation. CT evaluation of the head is required if the patient has a history of loss of consciousness, evidence of head injury on physical examination. Spinal MRI may be needed to assess vertebral or spinal cord injury. Abdominal and pelvic CT is indicated if abdominal tenderness or distension is present on examination, if the chest radiograph depicts free air, or if intra-abdominal injury is a concern. Imaging of extremities and other studies can be delayed until all potentially life-threatening conditions are excluded or addressed. Laboratory tests In every patient with clinically significant trauma, order a complete blood cell count and urinalysis. Additional tests, such as an electrolyte panel, a coagulation panel, and typing and cross-matching may be indicated in selected patients. Serum transaminase, amylase, and lipase levels may be helpful in evaluating abdominal injury. Hematuria can be detected on urinalysis. THE CHILD WITH ACUTE ILLNESS Surgical evaluation and treatment of the child with acute illness is one of the most challenging aspects of pediatric surgery. Patients with intra-abdominal catastrophes, patients who have ingested foreign objects, and patients with trauma (addressed in the section above) are in this category. Physical examination of the child with acute illness is similar to that of the patient with trauma. The child's airway must be secured and maintained, breathing must provide adequate ventilation, and oxygenation, and circulation must adequately perfuse the end organs. Children with signs of hypovolemic shock are most commonly those with ongoing hemorrhage, peritonitis, intestinal obstruction, burns, vomiting, or diarrhea. A patient in hypovolemic shock should be resuscitated with a 20-mL/kg bolus of warm lactated Ringer solution administered by means of peripheral or central venous line. If the child's condition responds inadequately and if further resuscitation is necessary, the choice of fluid (eg, crystalloid, colloid, blood) depends on the type of fluid that the child has lost. In general, fluid lost because of burns, peritonitis, and bowel obstruction may be replaced by lactated Ringer solution, which has an electrolyte composition similar to that of the fluid lost from the intravascular space.
  11. 11. Acid-base imbalances and electrolyte disturbances must be corrected before surgery. Electrolytes and arterial blood gases must be monitored serially until corrected and stabilized. Adequate volume resuscitation is crucial because anesthetic agents cause vasodilation. Therefore, patients with hypovolemia can have sudden hypotension with possible endorgan damage if they undergo anesthesia before receiving sufficient resuscitation. The endpoint for volume resuscitation includes improvement in skin color and capillary refill and adequate urine output (1 mL/kg/h measured by using a urinary catheter). THE CHILD WITH CHRONIC ILLNESS Treating a child with chronic illness creates a unique set of challenges for the pediatric surgeon. These children tend to be deconditioned, and they often have several medical problems that require careful attention before surgery. Depression, malnutrition, anemia, and growth retardation are all characteristic findings in these children. In addition, some children are immunocompromised or have coagulopathies as a result of their illness or medical therapy. Whenever possible, children with chronic illnesses should be brought to their individual optimum level of health before undergoing a surgical procedure. Malnourished children can be fed a high-calorie diet, or their tube feedings can be increased. The target plasma protein concentration is 5 g/dL. Children with chronic disorders or renal disease often have associated anemia with usual hemoglobin concentrations of 6-9 g/dL. Target preoperative hemoglobin values should be individualized to the type of procedure planned and to the outcomes of a discussion with the anesthesiologist. Coagulopathies and electrolyte derangements must be corrected before surgery. Features of various chronic illnesses that require special attention are elaborated below. Diabetes mellitus Before surgery, blood glucose levels should be closely monitored in patients with diabetes mellitus, especially during the fasting. Hyperglycemia or hypoglycemia can be corrected with insulin or with the addition of dextrose to IV fluids, respectively. Patients taking regimens of short- and intermediate-acting insulin should continue this regimen until the morning of surgery. Patients who take long-acting insulin may receive intermediate-acting insulin the evening before surgery. If a patient is taking a complicated insulin regimen or if he or she has an insulin pump, consulting an endocrinologist regarding preoperative and postoperative care is prudent. Obesity With rates of obesity steadily on the rise and reaching epidemic proportions, the pediatric surgeon is encountering the obese patient with increasing frequency. Obese patients have an increased incidence of medical comorbidities, including glucose intolerance, diabetes mellitus, hypertension, hyperlipidemia, nonalcoholic steatohepatitis, obstructive sleep apnea, deep vein thrombosis, and pulmonary embolism. These conditions must be taken into account in the preoperative workup of a patient undergoing surgery.
  12. 12. Additional concerns are limitations regarding radiographic evaluation in obese patients. Weight limites for tables used to perform CT, MRI, and angiography are 250-450 lbs. and vary by the manufacturer. Sizes of gantries and patient compartments also vary. Alternative methods of evaluation must be sought if the patient's size exceeds the capacity of the machine. Cardiac disease To minimize the risk of bacterial endocarditis, children with congenital heart disease, prosthetic valves or patches, valvular prolapse, and valvular insufficiency should be given antibiotic prophylaxis before surgery of the GI, GU, or respiratory tract. In GI and GU surgery, ampicillin and gentamicin are the recommended regimen unless the patient has a penicillin allergy, in which case, vancomycin and gentamicin are recommended. Patients undergoing respiratory tract surgery require ampicillin prophylaxis. Cephalosporins, clindamycin, azithromycin, or clarithromycin may be used in patients with a penicillin allergy. For patients who have a complicated heart condition, the pediatric surgeon should communicate with the pediatric cardiologist before surgery. Close electrolyte monitoring is required for patients taking diuretics. Patients taking digitalis must be carefully observed for digitalis toxicity. The patient's intake and output must be strictly recorded, and the surgeon should watch for signs of heart failure. Pulmonary disease Common pulmonary diseases encountered by the pediatric surgeon include asthma and cystic fibrosis. Patients with asthma should be preoperatively asymptomatic; to resolve symptoms, pharmacologic, environmental, and/or dietary control may be needed. Patients should continue their medications during the preoperative period. Patients with cystic fibrosis are often deconditioned, and the pediatric surgeon should work in concert with the pulmonologist to optimize the patient's health before surgery to minimize the surgical risk. Hyaline membrane disease is a common problem in the neonatal population, and patients with this disease may develop bronchopulmonary dysplasia, which increases the risk of atelectasis and carbon dioxide retention. Chest radiography is routine for all patients with pulmonary disease. Hepatic disease Chronic liver disease can result from biliary atresia, cystic fibrosis, hepatitis of any etiology, or liver injury. If edema or ascites is present, the patient should be given diuretics and be on a sodium-restricted diet. In children with a history of any of these conditions, determine liver enzyme levels and perform coagulation tests before surgery. If a coagulopathy is present, administer vitamin K and fresh-frozen plasma (FFP) preoperatively and ensure that FFP is available in the operating room. Be careful when prescribing drugs that are metabolized and excreted by the liver; monitoring of serum drug levels is essential. Renal disease Renal function can be easily assessed by performing urinalysis and obtaining serum blood urea nitrogen (BUN) and creatinine levels. The fluid and electrolyte balance is often tenuous in patients with renal disease. Pay careful attention to the patient's intake
  13. 13. and output. Patients with difficulty concentrating urine often have increased fluid and salt intake to compensate for increased urine output. Closely monitor these patients during the fasting period before surgery because they can become dehydrated quickly. In such patients, securing peripheral IV access is always sensible, even before surgery. Electrolyte monitoring is important in the preoperative period, and any acid-base imbalances and electrolyte disturbances must be corrected before surgery. In its advanced stage, renal failure is manifested by hyperkalemia, hyperphosphatemia, and acidosis. Patients with renal failure require immediate attention. Be careful when prescribing drugs that are metabolized and excreted by the kidney; monitoring of serum drug levels is essential. HIV HIV infection in pediatric patients is often associated with medical manifestations such as failure to thrive, persistent lymphadenopathy, oral candidiasis, chronic parotitis, chronic cough, and generalized dermatitis. The surgical manifestations in pediatric patients with HIV or AIDS are less often discussed. Patients with HIV who come to the attention of surgeons often have infections and may be severely septic with opportunistic pathogens. Prompt recognition and treatment of the surgical problem is essential. Outcomes are improved when antiretroviral medications are used. Close consultation with pediatric immunodeficiency specialists is warranted in the management of pediatric patients with HIV who have a surgical problem. PREOPERATIVE MANAGEMENT Laboratory study Patients who have an isolated surgical problem and who are otherwise healthy do not require routine laboratory tests before surgery. In patients with other medical problems and those undergoing major operations, order a complete blood cell count, electrolyte tests, and coagulation studies. If clinically significant blood loss is anticipated, the patient's blood should be typed and screened or cross-matched so that blood can be immediately available if needed in the operating room. Establishing NPO status Anesthesia carries an inherent risk of the patient's vomiting and aspirating the stomach contents. NPO status should be discussed with the anesthesia team and assigned according to the guidelines and policies of the individual institution. General guidelines are as follows: • • • Solids or formula: Newborns and infants younger than 6 months should be assigned NPO status for 4 hours before surgery. Patients older than 6 months should be NPO for 6 hours before surgery. Clear liquids: All patients should be NPO for 3 hours before surgery. Anesthetic evaluation
  14. 14. Always consult the anesthesia team before complicated and unusual operations. These include procedures that involve repositioning the patient during the operation or manipulation of the great vessels or lungs. Notify the anesthesia team if the patient has a history of complications with previous anesthetics, malignant hyperthermia, or a coagulation disorder. Also, alert the anesthesia team if the patient has symptoms of an upper respiratory tract illness because this increases the risk of postintubation laryngotracheal edema. Preoperatively notify the anesthesia team about patients who might benefit from a caudal injection or an epidural catheter insertion for postoperative pain control. Preoperative pain consultation is appropriate if clinically significant postoperative pain is anticipated. The pain-management team can then proactively discuss postoperative pain treatment options with the family. In deciding whether to proceed with or cancel an operation, deferring to the anesthesiologists is always prudent. Medication Condition the patient's current medications. Patients who have been taking corticosteroids long-term may not be able to mount a natural stress response because of chronic suppression of the hypothalamic-pituitary-adrenal axis. During the perioperative period, these patients should receive stress dosing of corticosteroids proportional to the stress of surgery. Patients who are taking antihypertensives should continue them but must be closely monitored for intraoperative hypotension. Other drugs that should be continued in the perioperative period include antiepileptics, drugs for asthma, and immunosuppressants. Drugs that should be discontinued before surgery include anticoagulants, aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and diuretics. Regarding preoperative medications, bowel-preparation guidelines are as follows: • • • • • • • Administer polyethylene glycol-electrolyte solution (GoLYTELY) 50 mL/kg by mouth (PO) or by means of a nasogastric (NG) tube or gastrostomy tubes (GT). If the bowel is not clear after 4 hours, administer an additional 25 mL/kg. Administer 5% dextrose in 0.2% sodium chloride solution plus potassium chloride (KCl) 20 mEq per liter IV as a maintenance fluid. After the polyethylene glycol-electrolyte solution is given, administer neomycin and erythromycin (E.E.S.) base, each at a dose of 15 mg/kg PO every 90 minutes for 3 doses. If necessary, administer 2 doses of 1% neomycin enema per rectum (PR) or through a stoma or mucous fistula when the polyethylene glycol-electrolyte solution clears the bowel. For the neomycin enema, administer 10 mL/kg in infants, 100-150 mL in small children, 150-200 mL in large children, and 200-300 mL in adolescents.
  15. 15. Consider sedation. Patients who are unusually anxious in the immediate preoperative period may be given sedation with midazolam. Obtaining consent Obtaining consent from a parent or guardian for a procedure requires the clinician to discuss the indication for the procedure, describe the procedure, explain alternatives to the procedure, and declare the potential risks and complications. Bleeding and infection must always be mentioned, along with any other risks inherent to the surgery being performed. When appropriate, involve the child in the discussion of the surgery and the consent process. Be sure that the child has an age-appropriate understanding of why the surgery must be done and what participation it involves on his or her part. Children are often curious and may have questions and concerns, which should be addressed seriously. Ethical and legal pitfalls. The pediatric surgeon works at the juncture between surgery and pediatrics and, consequently, must deal with the surgical, medical, and ethical issues that concern both areas. Unique new challenges as well as ancient traditions in medicine can influence the pediatric surgeon's approach to ethical dilemmas. Historically, the Hippocratic oath defined the ethical principles guiding medicine, instructing physicians to use their knowledge and skills for the benefit of their patients and to protect their patients from harm. This tradition did not define a role for the patient, surrogate, or parents in the decision-making process. Consequently, a collaborative process has evolved, incorporating the ethical principles of patient autonomy, respect for persons, nonmaleficence, beneficence, and justice. In this model the physician contributes medical knowledge, skill, and judgment; the patient or the patient advocate contributes a personal evaluation of the potential benefits and risks inherent in the proposed treatment. Physicians enter a professional relationship with a pediatric patient by one of two routes, either electively or emergently. Usually, a parent or guardian of a child makes an appointment to see a physician about a medical problem, and the physician agrees to provide treatment in exchange for compensation. Alternatively, surgeons, as emergency call physicians, may encounter situations in which care must be rendered without a prior relationship. In such cases, a surgeon may need to operate on a pediatric trauma patient without informed consent from the parent. Responsibilities in emergent care If a children's hospital or a hospital with pediatric expertise represents itself as operating an emergency department or a trauma center for children, that hospital has several legal duties that reflect its ethical responsibilities, including the following: • A duty to accept and treat all patients coming to the emergency department
  16. 16. • • A duty to provide a properly equipped facility A duty to ensure that competent medical care is provided to each patient Once treatment is undertaken, the surgeon may not unilaterally terminate the legal relationship unless or until one of the following conditions is met: • • • Care is no longer needed. The parent or surrogate agrees to the termination of care. Appropriate transfer of care has been carried out. Responsibilities found in the routine care of pediatric surgery patients do not vary greatly from those of other pediatric patients, or indeed patients in general. The same ethical principles that guide all decision-making are pertinent, with attention to the special circumstances in the care of children. Thus, the obligation exists for nonmaleficence, ie, "in the first place, we should do no harm." The physician's professional obligation to place the patient's interest before his own may be sorely tested in the care of children, not only by the large number of underserved and uninsured patients in the field, but also by occasional difficulties in agreeing on what the child's best interest may be. Parents are allowed considerable latitude for medical decisions on behalf of their children, and the law protects the natural rights of parents to raise children free from unwanted interference. The presumption is that parents act in the best interests of their children and these rights are conditional on parental fulfillment of the duty to provide necessary care for minor children. In respecting patient autonomy and self-determination, physicians must obtain informed consent from a parent or surrogate before a child can undergo medical interventions, other than in the case of emergencies. As a component of informed consent, the surgeon must consider and discuss with the family the risks and benefits involved with each surgical procedure. Truly informed decisions require that parents or surrogates receive and understand accurate information about their child's condition and prognosis, the nature of the proposed intervention, the alternatives, and the risks and benefits. Parents or surrogates must be able to do the following: • • • • To deliberate and choose among alternatives To ask questions to their satisfaction To be able to relate the decision to a personal and stable framework of values To make decisions free of undue coercion Informed consent in children presents special problems, both philosophically and legally. In the United States, adult patients are presumed to have decision-making capacity unless a court of law has declared them incompetent to make such decisions. Children are persons in the social sense and they have rights, but they are not judged legally competent to make decisions about their medical treatments until they reach the age of majority, ie, 18 years. Therefore, children cannot give consent for themselves, but they can assent to procedures, either indirectly (by their acquiescence) or directly when they are involved in the discussion.
  17. 17. Because nothing miraculous happens on an 18th birthday to make a person a mature adult, it is a legal status only. Many young people can make morally mature decisions before they are legally entitled to do so. Therefore, older children and adolescents should be included in the decision-making process (patient assent), depending on their neurologic status, development, and level of maturity; however, legally, they require a surrogate decision-maker to act on their behalf (ie, parental permission). What parents actually do, therefore, is give permission for a treatment or surgery on their child; only a competent, fully autonomous individual is capable of giving consent, and then only for himself. Special circumstances Religious objections Conflicts of interest or religious preferences may lead parents to make decisions that may not be in the perceived best interests of the child. The children of Jehovah's Witnesses, particularly those who require an operative procedure that is associated with a risk of significant blood loss, are best considered in a distinct consent process that incorporates the religious views but upholds the rights of the child. Emergency care When a child is brought to an emergency department by prehospital care providers, no parent is in attendance, and the child needs emergency treatment or surgery, most hospitals and operating rooms allow treatment to be initiated under the theory of implied consent for emergency treatment. Aggressive attempts should be made by emergency department personnel to locate the child's parent(s) or guardian, but life-saving maneuvers, including surgical procedures, should not be withheld. Under the circumstance of need for urgent surgery, an institutional requirement may be in place for two or more physicians, generally those who are not involved in the technical procedure, to sign a consent form on behalf of the child, indicating their agreement that a true emergency exists and the proposed surgery is warranted. Children of divorced parents Many parents are divorced, and custodial arrangements for their child may be complex. If a child's parents are divorced, the custodial parent usually has the authority to make medical decisions on behalf of the child. For new pediatric patients coming to the clinic or office, registration forms should denote with whom the child lives and who has legal custody. At times, the custodial parent may indicate a desire to limit visitation or provision of information to a noncustodial parent. Antagonistic parental relationships may interfere with the physician's ability to render appropriate care to the child. Examining written divorce settlements may be necessary to determine what is legally appropriate. These tasks can be delegated to a member of the hospital legal department if necessary. Unfortunately, a parent may occasionally become offensive, abusive, or aggressive, and the security services of the hospital may have to be involved and/or visitation privileges may have to be restricted or rescinded. Neonates with major malformations
  18. 18. Baby Doe cases involve decisions by physicians and parents to withhold life-sustaining treatment from severely handicapped or critically ill newborns. The name was given to legal cases in which babies with Down syndrome or spinal bifida required surgeries, but their parents refused consent. These resulted in court challenges, executive rulings, and congressional action. At times these solutions were highly intrusive, even requiring the posting of hot-line numbers in the NICU for the use of anyone who was concerned that infants were being denied necessary care. Treatment may be withheld from neonates under the following conditions: • • The infant is chronically and irreversibly comatose. Treatment merely would prolong dying or would not be effective in ameliorating or correcting all the infant's life-threatening conditions. Treatment would be virtually futile in terms of survival and, therefore, inhumane. Neonatologists differ in their opinions regarding whether these guidelines lead to excessive treatment of infants who are hopelessly ill. The main ethical dilemma in these complex cases involves balancing the benefits of prolonging life through the use of multiple invasive medical and surgical procedures against the potential burden on the child and family. Do-not-resuscitate (DNR) is the traditional order given for an individual who should not receive cardiopulmonary resuscitation (CPR) in the event of a cardiopulmonary arrest. This term suggests that resuscitation would be successful if undertaken. The term donot-attempt-resuscitation (DNAR) may be a clearer indication that success at resuscitation is often not achieved. DNAR orders are written for children when an attempt to resuscitate would not benefit the child and if the parent or surrogate expresses his or her preference that CPR be withheld in the event that the child experiences a cardiopulmonary arrest, provided this is in the child's best interest. The American Heart Association has recently issued new guidelines for withholding CPR. A special circumstance for the pediatric surgeon involves the newly born child with certain chromosomal or anatomic defects with a uniformly poor prognosis or extreme prematurity. For the newly born, antenatal information about gestational age or congenital anomalies may be uncertain, and prediction of outcome may not be possible or accurate. In these cases, a trial of therapy and additional assessment of the infant may allow the surgeon to better assess diagnostic and prognostic data for family counseling and allow better-informed discussions about continuation or withdrawal of support. However, current data support the belief that resuscitation of infants with extremely low birth weight (<23 wk or <400 g) with certain chromosomal or anatomical defects is unlikely to result in survival or in survival without extreme disability. This constitutes quantitative or qualitative futility, and noninitiation of resuscitation in the delivery room is appropriate. Family presence during invasive procedures and CPR
  19. 19. A growing body of literature exists concerning the topic of family presence during invasive procedures and CPR. The Emergency Nurses Association (ENA) first developed family presence guidelines in 1995 and later revised them in 2001. Health care providers have expressed a variety of concerns regarding family presence, including the concern that it has the potential to interrupt or hinder patient care or to predispose members of the team to litigation if the family perceives that mistakes or wrong decisions have been made. Conversely, studies indicate that most family members want to be at the bedside. In cases when the patient dies, family presence removes the family's doubts and reassures that everything possible was done for their loved one; their presence facilitates grief and does not disrupt the actions of the medical team. Few formal studies have been performed in pediatric patients. Those that are available indicate that children prefer to have parents present both for the emotional support and to help them cope with pain during invasive procedures. Similar arguments support the presence of parents with their children until preoperative anesthesia is fully induced. Death by neurologic criteria (brain death) Cardiopulmonary support systems may be withdrawn from patients with brain death without fear of legal repercussions Organ and tissue recovery Patients who meet neurologic criteria for death may be appropriate candidates for organ or tissue recovery. In cases in which CPR is unsuccessful, tissue donation is possible. The shortage of recoverable organs has led to the enactment of required request laws, requiring documentation that families of potential donors are offered the option of organ and tissue donation and that the local organ procurement organization is notified of all potential donors. The declaration of brain death in cases of child abuse does not preclude the option of organ or tissue donation. Practicing resuscitation skills on the newly dead The use of newly dead patients for research and training raises ethical and legal issues. Obtaining consent of family members is ideal and respectful of the newly dead. Relevant procedures applicable to infants and children include placement of an endotracheal tube and vascular access procedures. This practice has the potential to be brief, beneficial to others, and an effective teaching technique. However, the cultural and emotional issues of family and staff may influence the suitability of this practice in a given institution. The Fetus as a Patient: Prenatal Diagnosis and Fetal Therapy Multidisciplinary approach Only in the past few decades has the fetus been considered a patient and become the subject of extensive scientific study and attempts at treatment. Fetal medicine is a complex multidisciplinary undertaking with a team consisting of the following:
  20. 20. • • • • • An obstetrician, who manages the pregnancy and performs many minimally invasive interventions such as percutaneous shunt and catheter placement A perinatologist or geneticist, who focuses on prenatal diagnosis, prognosis, genetic counseling, and the procedures involved in prenatal diagnosis A neonatologist or pediatric surgeon, who is responsible for the continued postnatal management of the fetus' disease process and formulates the fetal treatment plan An obstetric sonologist who has expertise in defining the fetal diagnosis and its severity and guiding diagnostic and therapeutic procedures Specialists, such as cardiologists, neurologists, and urologists, depending on the lesion Many problems are of particular significance to fetal medicine. • • • Unclear team leadership: The physician who takes responsibility for a particular procedure may be different from the one who made the diagnosis or the team taking care of the mother. Inadequate traditional roles and skills: The obstetrician may find that closing an empty uterus is entirely different from closing a gravid uterus. Surgeons who are accustomed to excising the posterior urethral valves in the neonate may find the same procedure difficult to perform in a half-exteriorized fetus. Incompletely resolved issues: These include the optimal agent and depth of anesthesia for both the fetus and mother and the best methods to control bleeding, maintain fetal exposure, monitor both patients, prevent preterm labor, and prevent the leak of amniotic fluid. PRENATAL DIAGNOSIS Prenatal diagnosis of fetal disorders and structural malformations is becoming increasingly important for several reasons. Approximately 3% of all pregnancies result in the delivery of an infant with a genetic disorder or birth defect. Such anomalies are also the biggest cause of infant mortality in the United States. Minor malformations are found in an additional 7-8% of neonates. Over the last 4 decades, the genetic basis of an increasing number of diseases is becoming understood. At the same time, safe and effective fetal diagnostic techniques are being developed. The advantage of prenatal diagnosis of fetal malformations is that genetic counseling can be provided. In addition, the parents, obstetrician, geneticist, and other specialists can discuss options ranging from abortion to intrauterine medical and surgical treatments. The optimal time, mode, and place of delivery can be determined, and a postnatal treatment plan can be formulated. Screening tests are safe, less-invasive tests performed on a large, relatively low-risk population in whom diagnostic tests are required to confirm the diagnosis. These test results can modify risk perception, and a positive screening test result is a stronger indication for invasive procedures such as amniocentesis. The tests screen for chromosomal anomalies and neural tube defects. They are also performed in mothers with a high-risk ethnic background for genetic diseases, such as Tay-Sachs disease in Ashkenazi Jews and α- and β-thalassemias in those of Mediterranean and Southeast Asian origin. Maternal serum alpha-fetoprotein test
  21. 21. Maternal serum alpha-fetoprotein (AFP) levels at 16-20 weeks' gestation are used to screen for open neural tube defects. The implications of an elevated AFP level vary with gestation, as well as with maternal weight and race. If an elevated AFP level is found, the test is followed by a targeted ultrasound and, perhaps, amniocentesis to distinguish among the possible etiologies. Causes of an elevated maternal serum AFP level include the following: • • • • • • • • • • • Neural tube defects Open abdominal wall defects Aneuploidy Renal diseases such as congenital nephrosis, infantile polycystic disease, and bilateral renal agenesis Skin diseases such as ectodermal dysplasia and aplasia cutis congenita Cystic adenomatoid malformation of the lung Maternal hepatic and ovarian tumors Uterine and placental anomalies Multiple gestation Fetomaternal hemorrhage Fetal demise Causes of low maternal serum AFP levels include the following: • • • Trisomy 18 Trisomy 13 Insulin-dependent diabetes mellitus in the mother The triple-panel test The panel includes maternal serum AFP, serum β-human chorionic gonadotropin (βHCG), and unconjugated estriol. The panel, along with maternal age, is a more sensitive (60-91%) screen for fetal aneuploidy. Maternal weight, race, and multiple pregnancies may affect the risk calculation. In a fetus with Down syndrome, β-HCG levels are elevated, and the other two levels are decreased. The triple panel can detect 57-67% of fetuses with Down syndrome in women younger than 35 years and 87% in older women. Maternal hexosaminidase test Maternal hexosaminidase levels increase in pregnancy and reflect a fetal origin. In a high-risk mother, persistent prepregnancy levels can indicate a fetus with the deficiency of the enzyme, as can occur in Tay-Sachs disease. Pregnancy-associated plasma protein A test Pregnancy-associated plasma protein A (PAPP-A) and free α-human chorionic gonadotropin (α-HCG), along with ultrasonographic markers in the first trimester, have a sensitivity of 80% and a high specificity in the detection of Down syndrome in the fetus. Diagnosis-directed tests are invasive and pose some risk to the mother and fetus, but they directly analyze the fetal material and confirm the diagnosis. Special circumstances indicate the use of these tests, which are not screening tests.
  22. 22. Indications for Diagnostic Tests Conditions that increase the risk of chromosomal anomaly include the following: • • • • • • • • • • Advanced maternal age (>35 y), the most common indication Previous offspring with chromosomal anomalies or other birth defects Parental balanced translocation, inversion (manifests as recurrent pregnancy loss), or both Suggestive fetal ultrasonographic findings Positive maternal screening test findings Mother having a disease or being exposed to drugs, medications, or infections known to be associated with congenital malformations in the fetus Mendelian genetic trait in the parents Molecular DNA diagnosis (cystic fibrosis, homozygous hemoglobin sickle disease [HbSS], fragile X) Enzymatic activities in villi, amniocytes, or both (Tay-Sachs disease, Refsum disease) Precursor levels in cell-free amniotic fluid (17-OH-progesterone in congenital adrenal hyperplasia) Genetic counseling As a prerequisite and as follow-up to prenatal diagnosis, families must be informed about the diagnosis, severity, prognosis, and available options for treatment and continuation of pregnancy. Chorionic villous sampling Chorionic villous sampling (CVS) is the technique of choice for prenatal diagnosis prior to 12 weeks' gestation for detection of a chromosomal anomaly, DNA molecular diagnosis of classic genetic disorders, and the detection of defects in lysosomal enzymes or mucopolysaccharidoses. A diagnosis of enzymatic defects, such as 21hydroxylase deficiency that causes congenital adrenal hyperplasia, can be made with an allele-specific amplification analysis technique of DNA obtained with CVS. A preliminary ultrasound is performed to establish fetal viability, gestation, and anatomy and to determine the placental location. A sample of placental tissue is obtained using a 16-gauge polyethylene catheter for analysis under ultrasonographic guidance. The test is usually performed at 8-12 weeks' gestation. The approach is based on the placental location. A transabdominal approach is preferred for anterior and fundal placentas after 13 weeks' gestation and in active vaginal and cervical infections. The sample is smaller than that obtained with the transcervical method. The transcervical approach is indicated in cases with interposed bowel loops or uterine retroversion and a posterior or low-lying placenta. The transvaginal approach has limited application and is used when the placenta is placed posteriorly, the uterus is retroverted and retroflexed, and the cervical canal points towards the abdomen. Chromosomal analysis of the sample is performed in 2 ways. The direct method evaluates the metaphysis from the outer layer of cytotrophoblasts in the chorionic villi. This method provides results in 2 days. A long-term culture of the inner mesenchymal
  23. 23. layer of trophoblasts provides results in 10-14 days. These results more closely correlate with the true karyotype. An abnormal direct result has to be confirmed with long-term cultures of trophoblasts, amniotic cells, or fetal lymphocytes. Rarely, a normal direct result is followed by abnormal culture findings, which are confirmed with fetal tissue results. Chromosomal mosaicism occurs in 1.2-2.5% of the samples and may cause diagnostic error. The mosaicism is purely extraembryonic in 70-80% of the cases, and it is more common in direct preparations. If found in both direct preparation and long-term cultures, a followup ultrasonographic level 2 screening for anomalies and amniocentesis or cordocentesis are indicated to verify mosaicism in the fetal blood. Maternal cell contamination may also distort the results. Complications associated with CVS include the following: • • Pregnancy loss is 0.6-0.8% more common than the natural pregnancy loss rate in the first trimester and more common that the rate in midtrimester amniocentesis. Limb reduction defects and oromandibular malformations are more likely in some studies, especially if the procedure is performed prior to 10 weeks' gestation. Fetomaternal transfusion can occur regardless of the approach used. Thus, Rh isoimmunization is considered a relative contraindication, and Rh immunoprophylaxis is administered to Rh-negative women after the procedure. Early amniocentesis This technique, performed at 12-14 weeks' gestation, assists in the diagnosis of chromosomal anomalies by providing fetal cells for karyotyping. It can also lead to the diagnosis of structural anomalies such as neural tube defects and omphalocele through the measurement of AFP and acetylcholinesterase levels. It is preferred to CVS in situations in which CVS is not reliable, such as twin pregnancy with fused placentae and in certain biochemical disorders. The procedure consists of the aspiration of amniotic fluid (approximately 1 mL/wk of gestation) from an amniotic fluid pocket with a 22-gauge needle and ultrasonographic guidance. Complications associated with amniocentesis include uterine bleeding (1.9%), uterine cramping, leakage of amniotic fluid (2.9%), pregnancy loss (1.4-4.2%), increased risk of club foot when performed prior to 12 weeks' gestation, failed procedure due to tenting of the membranes ahead of the needle, and culture failure rates of 1% overall and 5% if the procedure is performed prior to 12 weeks' gestation. Pseudomosaicism and maternal contamination are less likely than with CVS. Preimplantation biopsy This controversial procedure is performed for preimplantation diagnosis in a fetus of parents with substantial risk of a known genetic disorder and in women with repeated miscarriages due to chromosomal translocation. At the 8-cell stage of the embryo, a single cell is removed and analyzed (blastomere biopsy) for X-linked recessive diseases. Only XX embryos are transferred following in
  24. 24. vitro fertilization. More trophectodermal cells can be removed from the blastocyst for analysis. Because it has the same genetic constitution as the ovum, the second polar body can also be analyzed for diseases with known gene defects such as cystic fibrosis, hemophilia, and α1-antitrypsin deficiency. Coelocentesis Coelocentesis, defined as coelomic fluid aspiration, can be performed as early as 6-10 weeks' gestation but is still considered investigational because of the high rate of pregnancy loss reported. Fetal cells from maternal blood The isolation and analysis of nucleated fetal cells from maternal blood is a novel noninvasive technique of prenatal diagnosis of chromosomal aneuploidies. A direct micromanipulator isolation of histochemically identified fetal hemoglobin (HbF)–positive nucleated red cells is followed by fluorescent in situ hybridization (FISH) analysis for chromosomal aneuploidies. The results are obtained in 72 hours and correlate highly with amniocentesis results. Diagnostic Tests in the Second Trimester Midtrimester amniocentesis Amniocentesis performed at 16-18 weeks' gestation is the criterion standard of prenatal diagnostic techniques in both efficacy and safety. It is offered to all women older than 35 years or with an elevated serum AFP level. Genetic counseling to evaluate genetic risks and detailed ultrasonography to estimate gestation, placental location, and amount of amniotic fluid are important prior to the procedure. The procedure is the same as that of amniocentesis in early gestation, except that 2030 mL of amniotic fluid is aspirated for analysis. The amniotic fluid phase can be analyzed for several substances. • • • AFP and acetylcholinesterase levels are used to identify a fetus with a neural tube defect, with 98% sensitivity. Bilirubin levels in amniotic fluid are elevated in isoimmune hemolysis, and the risk to the fetus can be predicted based on the bilirubin level and gestational age. Pulmonary surfactant and surface-active phospholipids are measured in amniotic fluid to evaluate fetal pulmonary maturity. A lecithin-to-sphingomyelin ratio of greater than 2, as measured chromatographically in a noncontaminated sample, suggests lung maturity, except in fetuses of mothers with diabetes. Other fetal lung maturity assays measure the surfactant-to-albumin ratio with fluorescent polarization technology and provide early results. Both of these tests are affected by contamination with blood or meconium, and results are unreliable in fetuses of mothers with diabetes or preeclampsia or in cases of intrauterine asphyxia. The presence of phosphatidyl glycerol in amniotic fluid indicates lung maturity, particularly in fetuses of mothers with diabetes. Saturated phosphatidylcholine is unaffected by contamination with blood. A combination of these tests provides a more accurate indication of lung maturity.
  25. 25. • Enzyme analysis and measurement of metabolite levels, used for the diagnosis of urea cycle disorders and of other inborn errors of metabolism, may also be performed on the amniotic fluid at this stage. Fetal cells can be extracted from amniotic fluid samples and analyzed for the following chromosomal and genetic disorders: • • • Chromosome analysis through direct metaphase visualization is the traditional method; results are obtained in 1-2 weeks. FISH, when used in addition to standard cytogenetics, can analyze fetal cells for abnormalities in chromosomes 21, 18, 13, X, and Y and provide results in 48-72 hours. FISH can also detect microdeletions found in Prader-Willi, DiGeorge, Williams, and Angelman syndromes. Direct DNA analysis is done with polymerase chain reaction (PCR) gene amplification, followed by Southern blot analysis to detect gene deletions. Allelespecific oligonucleotide (ASO) analysis measures the specific binding of labeled probes to normal DNA or mutant sequences to detect gene mutations. This technique is important in identifying disorders in which multiple mutations have to be screened for, such as cystic fibrosis and thalassemia, or in which a restriction site is not created, such as Duchenne muscular dystrophy, Tay-Sachs disease, and phenylketonuria. Indirect DNA methods, such as linkage analysis with restriction fragment length polymorphisms (RFLPs), are performed in affected individuals and multiple other family members. This can help in making the diagnosis of diseases in which the exact gene defect and location are not known. Cross-over changes between the gene and the RFLP probe can distort the results. Survival motor neuron (SMN) analysis for gene deletion in the family of an affected patient is useful in the prenatal diagnosis of spinal muscular atrophy. Molecular analysis of the fibroblast growth factor receptor 3 gene with direct and restriction enzyme analysis can help to diagnose thanatophoric dysplasia. Fetal DNA obtained by amniocentesis can be analyzed for the same deletion as that of the index case. Complications of second trimester amniocentesis include the following: • • • • • The risk of pregnancy loss is 0.3-1%. The risk of amniotic fluid leakage is 1-2%. In rare cases, this may lead to oligohydramnios, arthrogryposis, and pulmonary hypoplasia. Amnionitis occurs in 0.1%. As the risk of Rh isoimmunization is increased 1% above the baseline risk, Rh immunoprophylaxis is recommended for Rh-negative nonsensitized women. Mosaicism on cytogenetic analysis is seen in 1% of samples. True fetal mosaicism is relatively rare, and fetal blood sampling is required for confirmation. Percutaneous umbilical blood sampling or cordocentesis The greatest advantage of this technique is that it provides a direct fetal sample and access to the fetus for in utero treatment. With ultrasound guidance, a sample of fetal blood is obtained from the umbilical vessel close to the cord insertion near the placenta. A 20- to 27-gauge needle is used, and the approach can be transplacental in an anterior placenta or transamniotic in a posterior placenta.
  26. 26. Diagnostic studies that can be performed include the following: • • • • • Direct karyotyping of fetal lymphocytes can provide results within 24-72 hours. DNA studies can be used to diagnose metabolic diseases. Hematologic problems are especially amenable to this technique. The diagnoses of thalassemias, sickle cell disease, hemophilia, von Willebrand disease, and alloimmune thrombocytopenia can be made. In Rh-isoimmunized fetuses, diagnosis and treatment of fetal anemia and thrombocytopenia is possible, as is intrauterine transfusion. Immunologic tests can be performed on blood samples for diagnosis of fetal infections (eg, specific immunoglobulin M [IgM] for toxoplasmosis, rubella, cytomegalovirus [CMV], varicella zoster, HIV). Viral DNA can be detected using PCR for certain infections, such as parvovirus B19. Determine fetal PaO2, PCO2, and pH levels, as these can provide critical indicators of fetal well-being in a small-for-date or compromised fetus. These data can guide management decisions. Complications associated with cordocentesis are more common in posterior placentae and when the procedure is performed prior to 19 weeks' gestation. These include fetal loss (1-2.3%), preterm labor (5-9%), hematoma of the umbilical cord and placental abruption, chorioamnionitis (0.6%), fetal exsanguination from the procedure site, and Rh isoimmunization. Rh immunoprophylaxis is mandatory in all Rh-negative nonsensitized women after the procedure. Late chorionic villus sampling The technique of placental biopsy is equally effective in the second and third trimesters, and karyotyping is possible with small amounts of placental tissue. It has the advantage of being as accurate as amniocentesis, and it provides rapid results. Fetal muscle and liver biopsy Muscle biopsy is used in rare cases of Duchenne muscular dystrophy in which findings from all previous investigations are nondiagnostic. Dystrophin levels are measured in myoblasts by in situ hybridization. Fetal liver biopsies have also been performed to measure enzyme levels of glucose-6-phosphatase and ornithine transcarbamylase in patients with suspected glycogenesis and urea cycle disorders when direct DNA techniques are not sensitive. Diagnostic Tests in the Third Trimester and During Labor The purpose of prenatal diagnosis in the third trimester is to confirm fetal growth, wellbeing, and lung maturity. For timely and appropriate intervention, fetal well-being needs to be assessed in the third trimester and particularly in labor. Fetal movement is monitored based on maternal perception. Lack of fetal movement for longer than 30 minutes suggests possible fetal compromise. Fetal lung maturity is determined as discussed previously in case of an impending preterm delivery and in making the decision to induce labor for any indication. Nonstress test
  27. 27. Nonstress testing is a simple low-risk procedure in which the fetal heart rate is monitored with Doppler ultrasonography or electrodes on the maternal abdomen or a fetal scalp electrode placed after rupture of membranes, along with the simultaneous recording of uterine activity with a tocodynamometer. After 32 weeks' gestation, the fetus responds to uterine contractions with tachycardia. The criteria for reactive test results are the following: • • • Heart rate of 120-160 beats per minute (bpm): Fetal tachycardia may be due to fever, drugs, or fetal arrhythmias or hypoxemia. Normal beat-to-beat variability of more than 5 bpm: Decreased beat-to-beat variability suggests fetal hypoxia, sleep, prematurity, maternal sedation, or narcotic use. Two accelerations of more than 15 bpm lasting more than 20 seconds each within a 15-minute test period: A reactive test is reassuring, with a high chance of intrauterine survival over the next 7 days. A nonreactive test, which does not meet these criteria, necessitates further testing for confirmation. The disadvantage of the test is variable reproducibility; nonreactivity may be a late sign of fetal hypoxia, a benign pattern, or the result of a prior asphyxial event. Contraction stress test The contraction stress test (CST) is used to monitor fetal heart rate in response to uterine contractions that are spontaneous or induced with oxytocin. The contraction should occur within 30 minutes and last 40-60 seconds with a frequency of 3 in 10 minutes. In a healthy fetus, uterine contractions cause transient hypoxia and hypoperfusion of the intervillous space, which is relatively well tolerated. Early decelerations start with the onset of uterine contractions, reach the nadir at the time of peak of the contraction, and end simultaneously. These are benign and are seen in late labor from fetal head compression. Variable decelerations vary in their timing and relation with uterine contractions and occur in response to cord compression. They are benign unless they are associated with severe or prolonged bradycardia, are less than 60 bpm, last more than 60 seconds, are associated with an overshoot acceleration lasting more than 1 minute after a variable deceleration, or have poor beat-to-beat variability. Under conditions of uteroplacental insufficiency, a late deceleration is induced. A late deceleration begins 10-30 seconds after the onset of uterine contraction, the nadir is later than the peak of the contraction, and it returns to baseline after the contraction ceases. A CST result is positive if late decelerations are present with 50% or more of contractions. A CST finding is equivocal if decelerations are inconsistent. A negative CST result, defined as the absence of late decelerations, is associated with a risk of fetal demise of 0.4 cases per 1000 within the week. Drawbacks of the test are its duration, which is approximately 90 minutes, and the need for oxytocin. Biophysical profile test The biophysical profile (BPP) combines the nonstress test with an assessment of amniotic fluid volume, fetal breathing movements, fetal activity, and fetal muscle tone. A score of 0-2 is given for each parameter. In a reactive nonstress test, each of the following criteria earns 2 points:
  28. 28. • • • • At least one pocket of amniotic fluid greater than or equal to 1 cm depth At least one episode of fetal breathing of 60 seconds duration within 30 minutes Three or more discrete episodes of fetal movement At least one episode of extension and flexion of extremities or spine Scores greater than 8 indicate a low risk and the need for weekly retesting. A score of 2 is strongly suggestive of hypoxia and indicates the need for immediate delivery (if persistent for 120 min). Intermediate scores need further evaluation. Maternal depressant medication and cerebral or neuromuscular anomalies may result in a low score. Doppler study A Doppler study of fetal umbilical arterial blood flow velocity or resistance to flow is another modality used to assess placental function, particularly to monitor high-risk fetuses. Decreased flow velocity during diastole indicates placental insufficiency, and, in severe cases, diastolic flow may stop completely or even reverse. Therefore, a systolicto-diastolic umbilical blood flow ratio of greater than 3 after 30 weeks' gestation is associated with fetal compromise. Researchers are still investigating the utility of measuring fetal arterial velocity in assessing redistribution in the hypoxic fetus and as indicators of placental circulation in pathologic placental processes, such as pregnancy-induced hypertension. Fetal scalp pH is used to accurately determine fetal hypoxia and acidosis. A pH level of less than 7.25 is considered abnormal, and a pH level of less than 7.1 mandates immediate delivery by the quickest route. Ultrasonographic Examination Ultrasonography is the single most valuable modality in the identification of fetal structural anomalies. It is also useful in the detection of abnormal growth patterns in the fetus, in estimating gestation, and in assessing fetal well-being in the third trimester and during labor and delivery. It is important in guiding the operator during procedures such as amniocentesis and cordocentesis. Ultrasonography is widely available and has no known adverse effects. Newer techniques, including high-resolution multiplanar imaging and Doppler imaging, have improved its yield. Disadvantages are beam attenuation with maternal adipose tissue and poor images with an engaged fetal head or oligohydramnios. Fetal gestation • • • Gestation is best estimated in the first trimester, with an error range of 3-5 days. The range increases to 1 week at 12 weeks' gestation and 3 weeks at 36 weeks' gestation. In the first trimester, the crown-rump length is the most accurate measure of gestation. This is measured from the top of the head to the bottom of the torso or the longest dimension of the fetus excluding the yolk sac and extremities. In the second and third trimesters, parameters used to estimate gestation are the biparietal diameter (BPD), head circumference, abdominal circumference, and femur lengths.
  29. 29. o o o o BPD is measured on the transaxial view of the head from the outer edge of the cranium nearest the transducer to the inner edge of the cranium farthest from the transducer. BPD, which is measured at the level of the thalami, including the cavum septum pellucidum, should not be used in cases of hydrocephalus, abnormal head shape, or late in the third trimester when the head may be engaged. Measures such as a corrected BPD have been devised to take into account differences in head shape. Abdominal circumference is the length of the outer perimeter of the fetal abdomen measured at the level of the stomach and intrahepatic umbilical vein on a transverse scan. This measure should not be used in cases of fetal growth abnormality in which the head size may be relatively preserved or in a fetus with diaphragmatic hernia. In comparison, femoral length is more affected by caliper placement and technically more difficult. Femoral length may be affected by skeletal dysplasias, Down syndrome, and fetal growth abnormalities. Only the length of the diaphysis is measured for femur length. A combination of these measurements yields the most accurate results. Abnormal fetal growth patterns • • Intrauterine growth retardation (IUGR): Serial ultrasonography can be used to monitor the rate of increase in fetal biparietal diameter, abdominal circumference, and femoral length, thus helping to identify a growth-restricted fetus. o In the third trimester, ratios of morphometric measures such as abdominal circumference and femoral length are used to diagnose growth retardation. o Oligohydramnios and a poor biophysical score support the diagnosis of growth retardation secondary to uteroplacental insufficiency. Oligohydramnios is defined as the absence of amniotic fluid pockets or the presence of an amniotic fluid index (AFI; sum of the vertical distance of the largest pocket in each of 4 equal uterine quadrants) of less than 5. o Estimated fetal weights, derived by combining several parameters (usually head, abdominal, and femur measurements), are useful. However, they are inaccurate at the extremes of birth weight. Symmetric growth retardation begins earlier in gestation, affects both head and abdominal measurements, and is caused by chromosomal or genetic anomalies or intrauterine infections. Macrosomia: Serial ultrasonography can be used to measure the ratio of abdominal circumference to head circumference to detect macrosomia. Detection of Fetal Anomalies Fetal CNS anomalies • • • Ultrasound is 95% sensitive in the diagnosis of hydrocephalus and myelomeningocele. Ventriculomegaly has been defined in some studies by a measurement at the atrium of the lateral ventricle of more than 10 mm at any time during pregnancy. In myelomeningocele, diagnosis is made by noting a divergence of the pedicles of the vertebrae or the presence of a fluid-filled sac. Some intracranial signs are associated, such as ventriculomegaly, small BPD, biconcave frontal bones at 18-
  30. 30. • 24 weeks, a distorted position of the cerebellum, and obliteration of the cisterna magna, especially if associated with Chiari II malformation. Diagnosis of anencephaly, encephalocele, craniosynostosis, and brain malformations, such as porencephaly, can be made based on ultrasound findings. Fetuses with hydrocephalus or meningomyelocele should be evaluated for chromosomal abnormalities or anatomic defects in the cardiac, renal, and skeletal systems. Associated defects are present in 90-95% of cases. Fetal chest abnormalities • • Pulmonary hypoplasia, pleural effusions, cystic adenomatoid malformations, sequestration, and bronchogenic cysts are all pulmonary lesions that can be diagnosed based on ultrasound findings. Congenital diaphragmatic hernia (CDH): Diagnosis of CDH is made based on the presence of bowel or liver in the thorax with the accompanying blood supply, mediastinal shift, and pulmonary hypoplasia. Polyhydramnios may be present. After the diagnosis, serial ultrasonography should be performed to monitor fetal growth and hydramnios and to evaluate for cardiac anomalies. Workup may include ultrafast MRI, echocardiography, and karyotyping with amniocentesis to exclude associated anomalies. Hydrops is a predictor of a poor outcome. Fetal cardiac abnormalities • • • • Detailed cardiac ultrasonography is indicated in fetuses with the following: o Chromosomal anomalies o Hydrops o Oligohydramnios or polyhydramnios o Exomphalos o Diaphragmatic hernia o Defects in other systems with known cardiac associations. Other indications for a cardiac echo antenatally include the following: o Family history of congenital heart defect o Maternal diabetes or systemic lupus erythematosus (SLE) o Maternal lithium, alcohol, or progesterone intake o Fetal arrhythmias M-mode echocardiography is used to measure chamber size, cardiac rhythm, pericardial effusions, and wall thickness and motion. Cross-sectional echocardiograms show the heart position and situs and the atrioventricular (AV) connections. Doppler echocardiograms show the direction and pattern of blood flow, and they can depict valvular regurgitation or stenotic lesions. Prenatally diagnosed heart disease has been associated with reduced early neurologic morbidity in certain lesions, such as a hypoplastic left heart. Conversely, whereas a poorer prognosis was reported earlier in prenatal cohorts because more severe lesions are more likely to be detected, especially when they are associated with a structural or chromosomal defect. Fetal gastrointestinal anomalies Gastroschisis and omphalocele are easily detected on ultrasound. Ultrasonography has low sensitivity in the diagnosis of obstruction, which is indirectly indicated by the presence of polyhydramnios, poorly visualized gut distal to the obstruction, and a fluidfilled portion proximal to it. An echogenic bowel, meconium peritonitis, and pseudocyst
  31. 31. formation are suggestive of cystic fibrosis. All of these findings indicate the need for further cytogenetic evaluation of the fetus. Fetal genitourinary tract anomalies Ultrasound can detect renal agenesis, cystic disease, obstructive lesions (uteropelvic junction obstruction and posterior urethral valves), and renal tumors. Renal dimensions, parenchymal thinning and cysts, ratios of renal circumference to abdominal circumference, pelvic diameters, and urinary ascites can be assessed, along with urethral and bladder anatomy. The amniotic fluid volume provides an indication of renal function. Oligohydramnios is associated with a poor prognosis. Fetal skeletal anomalies A detailed fetal ultrasound attempts to rule out skeletal dysplasias, achondroplasia, osteogenesis imperfecta, polydactyly, and absence of a bone. Long bones are evaluated for size, shape, symmetry, and proportions of the different segments, and the skull is evaluated for shape and deformity. Examination of the spine and ribs helps in the delineation of the disorder. Identification of a skeletal dysplasia and prognosis are relatively accurate; however, in one study, a specific antenatal diagnosis was made in 60% of cases, but these were incorrect in 19% postnatally. According to some reports, 3-dimensional ultrasonography seems to provide additional visualization of skeletal deformities and abnormal spatial relationships, such as short ribs and absent bones, and to enable specific diagnosis. Fetal chromosomal anomalies In a recent meta-analysis, nuchal thickening was found to be the most accurate marker in the second trimester. It was associated with a 17-fold increased risk of Down syndrome. Nuchal thickening in the first trimester has a sensitivity of 60-70% for the detection of Down syndrome, with a 5% false-positive rate, whereas ultrasonography and biochemical screening, in combination, improve the sensitivity to 80%. Other single subtle markers (eg, choroid plexus cysts, shortened long bones, echogenic bowel) are not sensitive. MRI Examination MRI is an important adjunct to ultrasonography. It is used mainly in the assessment of cases with equivocal ultrasonographic findings or when prenatal ultrasound is not reliable in the identification of fetal anomalies, such as in the setting of maternal obesity or oligohydramnios. The advantage of the newer fast and ultrafast sequence MRI is that they have minimized motion artifacts; thus, sedation is not needed. A variety of sequences have been used, including echoplanar, half-Fourier single-shot turbo spinecho (HASTE), and fast spin-echo sequences. Of these, HASTE has proven to be an excellent method of fetal imaging. A recent meta-analysis showed that ultrafast MRI in the third trimester provided additional information compared to ultrasound in fetal diagnosis in 23-100% of cases, particularly those involving the posterior fossa of the head. Advantages of MRI include the following:
  32. 32. • • • • • • • Absence of ionizing radiation Multiplanar capability Large field of view Superior soft tissue contrast enhancement Good image quality in oligohydramnios More precise volumetric measurement Better intracranial delineation Limitations of MRI include the following: • • • Spatial resolution inferior to that of ultrasonography Poor depiction prior to 20 weeks' gestation Safety question - not approved by the Food and Drug Administration (FDA), but no known significant risk beyond the first trimester MRI may be used if other nonionizing imaging modalities are inadequate or if ionizing radiation would otherwise be required for further evaluation. Indications for MRI evaluation include the following: • • • • • Fetal cerebral anomalies: MRI has been most successful in the identification of posterior fossa abnormalities, migrational anomalies (eg, lissencephaly, polymicrogyrias, schizencephaly) at 30-32 weeks' gestation, agenesis of the corpus callosum, white matter disease, hydrocephalus, and ischemic or hemorrhagic lesions. Volumetric analysis: The size of the fetus or individual organs, such as the liver, can be determined. In CDH, volumetric measurements of the right fetal lung and the position of the left hepatic lobe appear to be good prognostic indicators and help in planning therapeutic interventions. Congenital high airway obstruction syndrome: MRI can be used to confirm upper airway obstruction by demonstrating hyperinflation of both lungs and dilated fluidfilled airways below the level of obstruction. Fetal neck masses such as cystic hygromas and teratomas can be identified, allowing early intervention when indicated. Congenital hemochromatosis: T2-weighted MRI can be used to confirm the diagnosis. Amniotic band syndrome: MRI provides an accurate diagnosis. CT Scanning CT scanning has limited applications in prenatal diagnosis. It is used mainly when MRI is contraindicated in the mother (eg, if she has a pacemaker, an intraocular metallic foreign body, or intracranial ferromagnetic surgical clips). The advantage of CT scanning is that it better delineates fetal bony anatomy than other imaging modalities. The limitations of CT scanning include possible teratogenesis due to ionizing radiation if it is performed in the first trimester and a risk of cancer induction. In children, a risk of mortality from cancer of 1 per 220-440 cases has been reported.
  33. 33. Indications for CT scanning include pelvimetry and CT amniography to confirm monoamnionicity if ultrasonography provides inconclusive data. Fetal Magnetocardiography A prolonged QT interval or Wolff-Parkinson-White syndrome can be detected in the prenatal period on fetal magnetocardiograms through evaluating T waves and obtaining current arrow maps. A weak, prolonged T wave is likely a good indicator of the condition. FETAL THERAPY: SURGERY Anesthesia As new intrauterine surgical techniques have been developed, anesthesia for the procedures has also evolved. The major objectives are to ensure maternal and fetal safety. Specific goals are the prevention of maternal hypoxia and hypotension, together with the maintenance of optimal uterine blood flow. Lower doses of epidural and spinal anesthetic agents are needed in pregnant women because of increased epidural pressure and a lower volume of cerebrospinal fluid in the vertebral space. • • • • • To promote fetal safety, procedures are generally performed in the second trimester, if possible, to avoid potential teratogenicity from the anesthetic agents. Fetal asphyxia: Normal maternal PaO2 should be maintained, and blood pressure should be maintained (with intravenous fluids and, if necessary, ephedrine, a vasopressor with central adrenergic stimulant action). Tocolysis: Uterine contractions are stimulated with the uterine incision and need to be stopped before preterm labor sets in. The agents used for this purpose include indomethacin, magnesium sulphate, and terbutaline. Indomethacin is administered preoperatively and continued postoperatively for 35 days. Fetal adverse effects include premature closure of the ductus arteriosus. Anesthetic agents commonly used are isoflurane inhalation with 100% oxygen along with muscle relaxants. For surgeries involving direct fetal manipulation, direct intramuscular fentanyl and pancuronium (a muscle relaxant and vagolytic) administered to the fetus have been tried prior to hysterotomy under ultrasound guidance. Monitoring During Surgery The parameters monitored during and after surgery include the following: • • • • • Myometrial contractions and intrauterine pressures Maternal blood pressure, ECG, and pulse oximetric and blood gas levels Fetal pulse oximetric measurement (50-60% saturation), heart rate, blood gases, and ECG Ultrasonographic findings in cases of fetoscopic surgery Fetal temperature (Maintain temperature with continuous warm sodium chloride irrigation, minimized exposure, and increased ambient temperature.) Surgical Interventions
  34. 34. Three approaches are currently used for invasive fetal therapy. 1. Ultrasonography-guided vesicoamniotic and, less commonly, thoracoamniotic shunt placement, is used in a fetus from 16 weeks' gestation to when lung maturity makes postnatal treatment the best option. Complications are inadequate function, migration, and iatrogenic gastroschisis. 2. Fetoscopic techniques now have a clinical application in the ligation of umbilical cords in acardiac twins, in selective laser photocoagulation of communicating vessels in twin-to-twin transfusions, and in the ablation of posterior urethral valves. o The procedure is performed inside the uterus using endoscopes, with a much smaller hysterotomy than that needed for open procedures. This lessens the risks of preterm labor and fetal hypothermia and improves fetal hemostasis during the procedure. o The success of the procedure depends on the use of both a transabdominal ultrasound intraoperative view and a simultaneous endoscopic view to guide placement of the trocars and cannulae. o The drawbacks of fetoscopic surgery are the risk of bleeding (avoiding the transplacental route decreases this risk), rupture of membranes, and chorioamnionitis. Fetoscopy may also be difficult because of poor access to the fetus due to fetal position or polyhydramnios. 3. Open fetal surgery is currently performed at select centers in instances in which the risk of the procedure to the mother and fetus is overridden by a diagnosis with a known poor outcome. Complications such as chorioamnionitis, preterm labor, bleeding, and direct trauma to the fetus are risks in most of these procedures. These surgical techniques are considered appropriate for 9 lesions. 1. Obstructive uropathy Patients with severe obstructive uropathy with bilateral hydronephrosis and oligohydramnios revealed with ultrasonography should be evaluated for possible fetal therapy. o o o o o Prior to intervention, a cordocentesis is performed to document a normal karyotype and to exclude other major fetal anomalies. This is followed by serial fetal bladder aspirations of urine under ultrasonographic guidance, which can help in the diagnosis of progressive renal damage (tonicity and electrolyte levels in the urine) and can relieve pressure if performed prior to 20 weeks' gestation. A vesicoamniotic shunt is indicated in persistent megacystis with adequate ultrasonographic and biochemical renal function to reduce pressure in the urinary tract and to improve pulmonary development and decrease uterine compression. Fetoscopic techniques can be used for fulguration of posterior urethral valves, placement of vesicoamniotic shunts, and vesicostomy. If all of these procedures fail, open vesicostomy with marsupialization of the bladder wall to the abdomen may be attempted. Open surgery has a high fetal mortality rate (45%). In a study evaluating long-term postnatal outcomes after fetal surgery for posterior urethral valves in 14 patients, 8 patients lived to a follow-up period of 11.6 years.