Analgesia and anaesthyesia


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Analgesia and anaesthyesia

  1. 1. Chapter 15 ANALGESICA AND ANESTHESIA 2004-11-29 R3 길민경
  2. 2. <ul><li>  Pain relief in labor : unique problems </li></ul><ul><li>Host of disorders unique to pregnancy (preeclampsia, pl abruption, chorioamnionitis, unique physiological adaptations of pregnancy) : directly affected by the choice of analgesia and anesthesia selected </li></ul><ul><li>3.8% of total 4097 preg-related deaths </li></ul><ul><li>Most important single factor associated with anesthesia-related maternal mortality : experience of the anesthetist </li></ul>
  4. 4. OBSTETRICAL ANESTHESIA SERVICES <ul><li>Certain risk factors should be communicated to the anesthesia-care provider in advance of delivery </li></ul><ul><ul><li>1. Marked obesity </li></ul></ul><ul><ul><li>2.   severe edema or anatomical anomalies of the face and neck </li></ul></ul><ul><ul><li>3. protuberant teeth, small mandible, or difficulty in opening the mouth </li></ul></ul><ul><ul><li>4. short stature, short neck, or arthritis of the neck </li></ul></ul><ul><ul><li>5.   large thyroid </li></ul></ul><ul><ul><li>6.   asthma, chronic pul dis, or cardiac dis </li></ul></ul><ul><ul><li>7.   bleeding disorders </li></ul></ul><ul><ul><li>8.   severe preeclampsia-ecalmpsia </li></ul></ul><ul><ul><li>9.   prev history of anesthetic Cx </li></ul></ul><ul><ul><li>10.other significant medical or obstetrical Cx </li></ul></ul>
  5. 5. PRINCIPLES OF PAIN RELIEF <ul><li>Simplicity </li></ul><ul><li>Safety </li></ul><ul><li>Preservation of fetal homeostasis </li></ul>
  7. 7. MEPERIDINE AND PROMETHAZINE <ul><li>Meperidine(50~100mg) + promethazine(25mg) : IM/2-4hrs </li></ul><ul><li>More rapid effect – meperidine(25~50mg) IV/1-2hrs </li></ul><ul><li>Depressant effect in the fetus : closely behind the peak analgesic effect in the mother </li></ul><ul><li>Meperidine : readily crosses the pl, half-life- 2 1/2hrs in mother, 13hrs in newborn </li></ul>
  8. 8. OTHER DRUGS <ul><li>Butorphanol (synthetic narcotics) : 1~2mg – compares favorably with 40~60mg meperidine </li></ul><ul><ul><li>Neonatal respiratory depression ↓ </li></ul></ul><ul><ul><li>Not given with meperidine (antagonizes the narcotic effects of meperidine) </li></ul></ul><ul><li>Nalbuphine </li></ul><ul><li>Fentanyl </li></ul><ul><ul><li>short acting, very potent synthetic opoid </li></ul></ul><ul><ul><li>50~100ug IV/hr, if needed </li></ul></ul>
  9. 9. NARCOTIC ANTAGONISTS <ul><li>May cause newborn respiratory depression, 2~3hrs after meperidine administration </li></ul><ul><li>Naloxone(narcotic antagonist) : 0.1mg/kg injected into the umbilical vein </li></ul><ul><ul><li>Acts within 2min with an effective duration of at least 30min </li></ul></ul><ul><ul><li>Repeated in 3~5min </li></ul></ul><ul><ul><li>exhibits no adverse effects in the newborn </li></ul></ul>
  11. 11. <ul><li>Without exception, all anesthetic agents that depress the maternal CNS cross the pl and depress the fetal CNS </li></ul><ul><li>Aspiration of gastric contents and particulate matter </li></ul>
  12. 12. INHALATION ANESTHESIA <ul><li>GAS ANESTHETICS </li></ul><ul><ul><li>Nitrous oxide(N2O) : provide pain relief during labor as well as at delivery </li></ul></ul><ul><ul><ul><li>Produces analgesia and altered consciousness </li></ul></ul></ul><ul><ul><ul><li>Does not provide true anesthesia </li></ul></ul></ul><ul><ul><ul><li>Does not prolong labor or interfere with Ut contractions </li></ul></ul></ul><ul><ul><ul><li>N20 50% mixture with 50% oxygen (Nitronox) : excellent pain relief during the 2 nd stage of labor </li></ul></ul></ul><ul><ul><ul><li>Used as part of a balanced GA for c/sec and some forceps deliveries </li></ul></ul></ul>
  13. 13. INHALATION ANESTHESIA <ul><li>VOLATILE ANESTHETICS </li></ul><ul><ul><li>Cause unconsciousness, potential for aspiration with an unprotected airway </li></ul></ul><ul><ul><li>Cross pl : producing narcosis in the fetus </li></ul></ul><ul><ul><li>Isoflurane, Halothane </li></ul></ul><ul><ul><ul><li>Potent, nonexplosive agents that produce remarkable Ut relaxation when given in high inhaled concentrations </li></ul></ul></ul><ul><ul><ul><li>Used for Int podalic version of 2 nd twin, breech decomposition, replacement of acutely inverted Ut </li></ul></ul></ul><ul><ul><ul><li>Maneuver has been completed, anesthetic administration should be stopped and immediate efforts made to promote myometrial contraction to minimize hemorrhage </li></ul></ul></ul>
  14. 14. INHALATION ANESTHESIA <ul><li>BALANCED GENERAL ANESTESIA </li></ul><ul><ul><li>Nitronox given for balanced general nesthesia : some degree of maternal awareness </li></ul></ul><ul><ul><li>Able to increase the inspired concentration of oxygen </li></ul></ul><ul><ul><li>50% N20 + 100% oxygen + halogenated agents(1%↓) </li></ul></ul>
  15. 15. INHALATION ANESTHESIA <ul><li>ANESTHETIC GAS EXPOSURE AND PREGNANCY OUTCOME </li></ul><ul><ul><li>Although exact fetal risk of chronic maternal exposure to waste anesthetic gas is unknown, available data suggest that there is not a substantial risk for either preg loss or congenital anomalies </li></ul></ul>
  16. 16. INTRAVENOUS DRUGS DURING ANESTHESIA <ul><li>THIOPENTAL </li></ul><ul><ul><li>Thiobarbituate, IV : widely used in conjunction with other agents for GA </li></ul></ul><ul><ul><li>Advantages : ease and extreme rapidity of induction, ready controllability, prompt recovery with minimal risk of vomiting </li></ul></ul><ul><ul><li>Poor analgesic agents : not used as the sole anesthetic agent </li></ul></ul>
  17. 17. INTRAVENOUS DRUGS DURING ANESTHESIA <ul><li>KETAMINE </li></ul><ul><ul><li>IV in low doses of 0.2~0.3mg/kg : analgesia and sedation just prior to delivery </li></ul></ul><ul><ul><li>1mg/kg : induce GA </li></ul></ul><ul><ul><li>useful in women with acute hemorrhage ← not associated with hypotension </li></ul></ul><ul><ul><li>avoided in women already hypertensive </li></ul></ul><ul><ul><li>unpleasant delirium and hallucinations </li></ul></ul>
  18. 18. ASPIRATION DURING GENERAL ANESTHESIA <ul><li>pneumonitis from inhalation of gastric contents : m/c cause of anesthetic deaths in obstetrics </li></ul>
  19. 19. ASPIRATION DURING GENERAL ANESTHESIA <ul><li>PROPHYLAXIS </li></ul><ul><li>Fasting from solids for at least 8 hrs and preferably longer before anesthesia </li></ul><ul><li>Use of agents to reduce gastric acidity during the induction and maintenace of GA </li></ul><ul><li>Skillful tracheal intubation </li></ul><ul><li>After intubation, and during the surgery, passage of a N-G tube to empty the stomach of all contents </li></ul><ul><li>Awake extubation with protective airway reflexes </li></ul><ul><li>Use of regional analgesia techniques when appropriate </li></ul>
  20. 20. ASPIRATION DURING GENERAL ANESTHESIA <ul><li>PATHOPHYSIOLOGY </li></ul><ul><ul><li>Rt mainstem bronchus usually offers simplest pathway for aspirated material to reach the lung paraenchyma </li></ul></ul><ul><ul><li>Highly acidic liquid is inspired : O2 sat↓ c tachypnea, bornchospasm, rhonchi, rales, atelectasis, cyanosis, tachycardia, hypotension </li></ul></ul>
  21. 21. ASPIRATION DURING GENERAL ANESTHESIA <ul><li>TREAMENT </li></ul><ul><ul><li>Close monitoring : attention to RR, O2 sat – most sensitive and earliest indicators of injury </li></ul></ul><ul><ul><li>As much as possible of the inhalated fluid should be immediately wiped out of the mouth and removed from the pharynx and trachea by suction </li></ul></ul><ul><ul><li>Saline lavage : not recommended (disseminated the acid throughout the lung) </li></ul></ul><ul><ul><li>No convincing clinical or experimental evidence that corticosteroid therapy or prophylatic antimicrobial administration is beneficial </li></ul></ul>
  22. 22. FAILED INTUBATION <ul><li>Uncommon, often associated with aspiration – major cause of anesthetic-related maternal mortality </li></ul>
  24. 24. SENSORY INNERVATION OF THE GENITAL TRACT <ul><li>UTERINE INNERVATION </li></ul><ul><ul><li>Pain in the 1 st stage of labor is generated largely from the Ut </li></ul></ul><ul><ul><li>Visceral sensory fibers from the Ut, Cx, upper vagina -> frankenhauser ganglion(lies just lat to Cx) -> pelvic plexus -> mid & sup int iliac plexuses -> 10 th , 11 th , 12 th thoracic & 1 st lumbar nerves </li></ul></ul><ul><li>LOWER GENITAL TRACT INNERVATION </li></ul><ul><ul><li>Pain with vag del : arises from stimuli from the lower genital tract </li></ul></ul><ul><ul><li>Pudendal nerve(peripheral braches of which provide sensory innervation to the perineum, anus, more medial and inf parts of the vulva & clitoris) -> 2 nd , 3 rd & 4 th sacral nerves </li></ul></ul>
  25. 25. ANESTHETIC AGENTS <ul><li>Most often, serious toxicity follows injection of an anesthetic into a blood vessel, but it may also be induced by administration of excessive amounts </li></ul><ul><li>Two manifestations of systemic toxicity : CNS & cardiovascular system(CVS) </li></ul>
  26. 26. ANESTHETIC AGENTS <ul><li>CENTRAL NERVOUS SYSTEM TOXICITY </li></ul><ul><ul><li>Sx : light-headedness, dizziness, tinnitus, bizarre behavior, slurred speech, metallic taste, numbness of the tongue and mouth, muscle fasciculation and excitation, generalized convulsions, loss of consciousness </li></ul></ul><ul><ul><li>Convulsions should be controlled, an airway established, oxygen delivered </li></ul></ul><ul><ul><li>Abnormal FHR pattern (late decelerations, persistent bradycardia) : may develop from maternal hypoxia and lactic acidosis induced by convulsions </li></ul></ul><ul><ul><li>Fetus likely will recover more quickly in utero than following immediate c/sec </li></ul></ul>
  27. 27. ANESTHETIC AGENTS <ul><li>CARDIOVASCULAR TOXICITY </li></ul><ul><ul><li>Do not always follow CNS involvement </li></ul></ul><ul><ul><li>Develop later than those from cerebral toxicity ← induced by higher blood levels of drug </li></ul></ul><ul><ul><li>Characterized first by stimulation and then depression </li></ul></ul><ul><ul><ul><li>Hypertension & tachycardia -> hypotension & cardiac arrhythmias </li></ul></ul></ul><ul><ul><li>Impaired U-P perfusion & fetal distress </li></ul></ul><ul><ul><li>Turning the woman onto either side to avoid aortocaval compression </li></ul></ul><ul><ul><li>Crystalloid solution : infused rapidly, IV ephedrine </li></ul></ul><ul><ul><li>Emergency c/sec : maternal vital signs have not been restored within 5 min of cardiac arrest </li></ul></ul>
  28. 28. LOCAL INFLITRATION <ul><li>Before episiotomy and delivery </li></ul><ul><li>After delivery into the site of lacerations to be repaired </li></ul>
  30. 30. PUDENDAL BLOCK <ul><li>Lower vagina & post vulva </li></ul><ul><li>Works well and is an extremely safe and relatively simple method of providing analgesia for spontaneous delivery </li></ul>
  31. 31. PUDENDAL BLOCK <ul><li>COMPLICATIONS </li></ul><ul><ul><li>IV injection of a local anesthetic agent : serious systemic toxicity (stimulation of cerebral cortex leading to convulsions) </li></ul></ul><ul><ul><li>Hematoma </li></ul></ul><ul><ul><li>Severe infection at the injection site (rare) </li></ul></ul>
  32. 32. PARACERVICAL BLOCK <ul><li>Excellent pain relief during the 1 st stage of labor </li></ul><ul><li>Additional analgesia is required for delivery </li></ul>
  33. 33. PARACERVICAL BLOCK <ul><li>COMPLICAITONS </li></ul><ul><ul><li>Fetal bradycarida : 10~70% </li></ul></ul><ul><ul><ul><li>Within 10 min, last up to 30min </li></ul></ul></ul><ul><ul><ul><li>Not a sign of fetal asphyxia ← usually transient and newborns are in most instances vigorous at birth </li></ul></ul></ul><ul><ul><ul><li>Result form decreased pl perfusion (drug-induced Ut a. vasoconstriction & myometrial hypertonus) </li></ul></ul></ul><ul><ul><li>Should not be used in situations of potential fetal compromise </li></ul></ul>
  34. 34. SPINAL (SUBARACHNOID) BLOCK <ul><li>VAGINAL DELIVERY </li></ul><ul><ul><li>Low spinal block : popular form a analgesia for forceps or vacuum delivery </li></ul></ul><ul><ul><li>Level of analgesia : 10 th thoracic – corresponds to level of umbilicus </li></ul></ul><ul><ul><li>Excellent relief from the pain of Ut contraction </li></ul></ul>
  35. 35. SPINAL (SUBARACHNOID) BLOCK <ul><li>CESAREAN DELIVERY </li></ul><ul><ul><li>Level of analgesia : extend at least 8 th thoracic – just below xiphoid process </li></ul></ul><ul><li>COMPLICATIONS </li></ul><ul><ul><li>HYPOTENSION </li></ul></ul><ul><ul><ul><li>Develop very soon after injection of local anesthetic agent </li></ul></ul></ul><ul><ul><ul><li>Definition : 20% decrease from baseline </li></ul></ul></ul>
  36. 36. SPINAL (SUBARACHNOID) BLOCK <ul><ul><ul><li>Vasodilatation from sympathetic blockade + obstructed venous return from Ut compression of the vena cava & adjacent large veins </li></ul></ul></ul><ul><ul><ul><li>Supine position : absence of maternal hypotension measured in brachial a. -> pl blood flow may still be significantly reduced </li></ul></ul></ul><ul><ul><ul><li>Prevention : 1000ml Ringer lactate infused over 20min before spinal injection and 5mg bolus of ephedrine as needed to maintain blood pressure </li></ul></ul></ul>
  37. 37. SPINAL (SUBARACHNOID) BLOCK <ul><ul><li>TOTAL SPINAL BOLCKADE </li></ul></ul><ul><ul><ul><li>Excessive dose of analgesic agent </li></ul></ul></ul><ul><ul><ul><li>Hypotension & apnea -> immediately treated to prevent cardiac arrest </li></ul></ul></ul><ul><ul><li>SPINAL (POSTPUNCUTRE) HEADACHE </li></ul></ul><ul><ul><ul><li>22 or 24 gauage needles : 1.5% develop postdural puncture headaches </li></ul></ul></ul><ul><ul><ul><li>reduced by using a small-gauge spinal needle and avoiding multiple punctures </li></ul></ul></ul>
  38. 38. SPINAL (SUBARACHNOID) BLOCK <ul><ul><ul><li>no good evidence that placing the woman absolutely flat on her back for several hours is very effective in preventing headache </li></ul></ul></ul><ul><ul><ul><li>vigorous hydration may be of value, also without compelling evidence to support its use </li></ul></ul></ul><ul><ul><ul><li>remarkably improved by the 3 rd day and absent by the 5 th </li></ul></ul></ul><ul><ul><ul><li>severe cases, a blood patch is effective </li></ul></ul></ul>
  39. 39. SPINAL (SUBARACHNOID) BLOCK <ul><ul><li>CONVULSIONS </li></ul></ul><ul><ul><li>BLADDER DYSFUNCTION </li></ul></ul><ul><ul><li>OXYTOCICS AND HYPERTENSION </li></ul></ul><ul><ul><li>ARACHNOIDITIS AND MENINGITIS </li></ul></ul>
  40. 40. SPINAL (SUBARACHNOID) BLOCK <ul><li>CONTRAINDICATIONS TO SPINAL ANALGESIA </li></ul><ul><ul><li>m/c serious Cx from spinal block : hypotension </li></ul></ul><ul><ul><li>Obstetrical Cx that are associated with maternal hypovolemia and hypotension </li></ul></ul><ul><ul><li>Severe preeclampsia ? </li></ul></ul><ul><ul><li>Disorders of coagulation and defective hemostasis </li></ul></ul><ul><ul><li>Skin or underlying tissue at the site of needle entry is infected </li></ul></ul><ul><ul><li>Neurological disorders </li></ul></ul>
  41. 41. EPIDURAL ANALGESIA <ul><li>CONTINUOUS LUMBAR EPIDURAL BLOCK </li></ul><ul><ul><li>Complete analgesia for the pain of labor and vaginal delivery ← block from 10 th thoracic to 5 th sacral dermatomes </li></ul></ul><ul><ul><li>Abdominal delivery : block 8 th thoracic level ~ 1 st sacral dermatome </li></ul></ul>
  42. 42. EPIDURAL ANALGESIA <ul><li>COMPLICATIONS </li></ul><ul><ul><li>TOTAL SPINAL BLOCKADE </li></ul></ul><ul><ul><ul><li>Dural puncture with inadvertent subarachnoid injection </li></ul></ul></ul><ul><ul><li>HYPOTENSION </li></ul></ul><ul><ul><ul><li>Normal preg women hypotension can be prevented by rapid infusion of 500-1000ml of crystalloid solution </li></ul></ul></ul>
  43. 43. EPIDURAL ANALGESIA <ul><ul><li>CENTRAL NERVOUS STIMULATION </li></ul></ul><ul><ul><li>MATERNAL PYREXIA </li></ul></ul><ul><ul><ul><li>Mean temperature ↑ </li></ul></ul></ul><ul><ul><ul><li>Significantly associated with neonatal sepsis evaluation and antibiotic therapy </li></ul></ul></ul><ul><ul><ul><li>Presence of pl inflammation </li></ul></ul></ul><ul><ul><ul><li>⇒ due to infection rather than the analgesia itself </li></ul></ul></ul><ul><ul><ul><li>Pyrexia : associated with a higher incidence of IU infection from longer 1 st stage labor </li></ul></ul></ul><ul><ul><li>BACK PAIN </li></ul></ul>
  44. 44. EPIDURAL ANALGESIA <ul><li>EFFECT ON LABOR </li></ul><ul><ul><li>Epidural analgesia usually prolongs the 1 st stage of labor, increases the need for labor stimulation with oxytocin </li></ul></ul>
  45. 45. EPIDURAL ANALGESIA <ul><li>Did not significantly increase cesarean deliveries in either nulliparous or parous women in any individual trial or in their aggregate </li></ul>
  46. 46. EPIDURAL ANALGESIA <ul><li>TIMING OF EPIDURAL PALCEMENT </li></ul><ul><ul><li>No increase in either operative vaginal delivery or cesarean delivery with early (≤3cm dilatation) administration of epidural analgesia compared with later administration </li></ul></ul><ul><ul><li>Parkland Hospital : not begun prior to 3-5cm Cx dilatation </li></ul></ul>
  47. 47. EPIDURAL ANALGESIA <ul><li>SAFETY </li></ul><ul><ul><li>1968-1985, 26000 women : no maternal deaths </li></ul></ul><ul><li>CONTRAINDICATIONS </li></ul><ul><ul><li>actual or anticipated serious maternal hemorrhage, infection at or near the sites for puncture, suspicion of neurological disease </li></ul></ul>
  48. 48. EPIDURAL ANALGESIA <ul><ul><li>SEVERE PREECLAMPSIA-ECLAMPSIA </li></ul></ul><ul><ul><ul><li>Ideal labor analgesia for women with severe preeclampsia : controversial </li></ul></ul></ul><ul><ul><ul><li>Past two to three decades, most obstetrical anesthesiologists : favor epidural blockade for labor and delivery in women with severe preecalmpsia </li></ul></ul></ul><ul><ul><ul><li>1995, Wallace and colleagues : GA and RA are equally acceptable for cesarean delivery in women with severe preecalmpsia </li></ul></ul></ul>
  49. 49. EPIDURAL ANALGESIA <ul><li>INTRAVENOUS FLUID PRELOADING </li></ul><ul><ul><li>Most authorities recommend prehydration, usually with 500~1000ml of crystalloid solution </li></ul></ul><ul><ul><li>Aggressive volume replacement in severe preeclampsia women increases their risk for pul edema, especially in the first 72 hrs postpartum </li></ul></ul><ul><ul><li>No instances of pul edema in 738 women in whom crystalloid preload was limited to 500ml </li></ul></ul>
  50. 50. EPIDURAL ANALGESIA <ul><li>EPIDURAL OPIATE ANALGESIA </li></ul><ul><ul><li>Injection of opiates into the epidural space to relieve pain from labor become popular -> rapid onset of pain relief, decrease in shevering, less dense motor blockade </li></ul></ul><ul><ul><li>Side effect : pruritus(80%), urinary retention(55%), N/V(45%), headaches(10%) </li></ul></ul>
  51. 51. EPIDURAL ANALGESIA <ul><li>COMBINED SPINAL-EPIDURAL TECHNIQUES </li></ul><ul><ul><li>No consensus regarding maternal Cx when comparing spinal or epidural analgesia with combined techniques </li></ul></ul>
  52. 52. EPIDURAL ANALGESIA <ul><ul><li>Parkland Hospital : 1223 women with uncomplicated term preg(combine Vs IV meperidine) </li></ul></ul><ul><ul><ul><li>Emergency c/sec for profound fetal tachycardia </li></ul></ul></ul><ul><ul><ul><li>Fetal bardycardia occurred within 30min </li></ul></ul></ul><ul><ul><ul><li>None of the cases responded to conservative measures </li></ul></ul></ul><ul><ul><ul><li>⇒ avoid the combined spinal-epidural technique </li></ul></ul></ul>