Anesthesia for bariatric surgery Dr. POONAM KALRA ASSOCIATE PROFESSOR Department of Anaesthesiology S.M.S Medical College, Jaipur
Introduction Approximately 7% of the world population is obese. Obesity is a global health problem & prevalence varies with socio economic status. In affluent countries like U.S the poor have the highest prevalence In developing countries it is the affluent that are at the highest risk Recently there is increase in incidence of childhood & adolescent obesity & importantly these children remain obese as adults.
Body mass index(BMI) is normally used to define obesity BMI=Weight in kilograms/Height in meter square Classification: BMI in Kg/m2 Category Less than 25 Normal 25-30 Overweight 30-35 Obese More than 35with coexisting Morbidly Obese disease or More than 40 More than 50 Super Obese
Other indices: BMI = TBW in kg/height in m2 IBW ( Ideal body weight)IBW = height (cm) – 100 for men or 105 for womenorIBW = 0.8 × TBW for men or 0.75 × TBW for women LBW ( Lean body weight)LBW = IBW × 1.3 Broca’s Index:Height in Cm-100 for MenHeight in Cm-105 for Women.
Psychological complications ofObesity Emotional distress Discrimination Social stigma Anxiety,fear,insecurity
Surgical treatment of obesity Surgeries performed for the treatment of morbid obesity is known as bariatric surgery Surgery is a option for weight loss in patients with1. BMI of > 40 kg/m2, or > 35 kg/m2 with comorbidities2. Failure to lose weight with dietary restrictions and pharmacologic therapy for > 1 y3. Obesity for > 5 y4. Understanding of the surgical and anesthetic risks and benefits5. Willingness to adhere to lifelong dietary restrictions6. Acceptable operative risk
Surgical approaches can be1) Malabsorptive a) Jejuno-ileal bypass b) Biliopancreatic bypass2) Restrictive a) Vertical banded gastroplasty b) Adjustable gastric banding c) Sleeve Gastrectomy
RestrictiveLaproscopicVertical banded Type Sleeve Gastrectomy Decrease the size of thegastroplasty adjustable gastricSurgical creation of a gastric stomach to approximately banding 20% of its original sizepouch that can In this a band is placedaccommodate 25 to 30 mL and Gastric fundus and body is around the stomach just resected to form a tube likerestricts the amount of food that below the esophagealcan be consumed opening from the gastro gastric junction & esophageal junction to the tightened with a balloon pyloric valve. filled with 15ml saline. The reconstructed stomach Advantages: the tension will have a total volume of on the band is adjustable between 100 and 200 mL. & the system is removable
Roux-en-Y gastric bypass Biliopancreatic Diversion With Duodenal SwitchInvolves anastomosing the proximal gastric Includes a hemigastrectomy or sleevepouch to a segment of the proximal jejunum, gastrectomy to create a 75- to 100-mL pouch.bypassing most of the stomach and the entire The ileum is connected directly to the gastricduodenum. pouch, completely bypassing the duodenumAdvantages : Reversible and jejunum (alimentary limb). The distalDisadvantages: Leak from anastomosis portion of the biliopancreatic limb is then Bowel obstruction reconnected 100 cm from the ileocecal valve. Vitamin Deficiency Disadvantages: Gallstones & various Intestinal Stenosis deficiencies.
A new procedure under investigation is an implantable gastric stimulator. A pulse generator the size of a cardiac pacemaker is implanted on the surface of the stomach. The afferent impulses that are sensed by the brain allow the person to feel satiated.
Contraindications for Surgery Unreasonable surgical risk Untreated hypothyroidism Gastrointestinal inflammatory disease (e.g., ulcers, Crohn disease, ulcerative colitis) Severe cardiopulmonary disease Pain intolerance to implantable devices Alcohol and/or drug addiction Severe cognitive disabilities Allergy to silicone
Complications Associated With Bariatric SurgeryAdjustable gastric band Malabsorptive Potential complications procedures of both types of proceduresGastric mucosal erosion Bowel obstruction Hemorrhagearound the band Wound dehiscence Dumping syndrome (moreGastritis Leakage and/or ulcers at common in gastric bypass)Erosion of gastric mucosa the sites of anastomosis Postoperative respiratoryunder the band, causing Nutritional deficiency insufficiencyperforation Incisional hernia Deep veinFilling port malfunction Gastrojejunostomy thromboembolismGastric prolapse stenosis Pulmonary embolismMalposition of the band SepsisBarrett esophagusDysphagiaGastroesophageal reflux
Medical Therapy for Obesity Indicated if BMI of ≥30 kg/m2 or a BMI from 27 and 29.9 kg/m2 with obesity-related co morbid disease. Phentermine - sympathomimetic agent similar to amphetamine Causes anorexia Side effects: pulmonary hypertension with valvular heart disease. Precaution: a) poor risk benefit ratio b) use only for short term
SibutramineInhibits the reuptake of norepinephrine, serotonin, and dopamineAnorexia & increase satietySide effects – a) dry mouth b) insomnia c) constipation d) Increase in BP & HR
Orlistat Lipase inhibitor in the GI tract. Inhibits fat absorption in intestine. Side effects: a) fecal urgency, b) diarrhea, c) abdominal pain, d)liver injury. Precaution: Interfere with absorption of fat soluble vitamins, so requires supplementation of the same.
Anaesthesia ManagementPre operative evaluationGoal of the preoperative assessment is treatment and optimization of co morbid conditions such as hypertension, CAD, diabetes, venous thromboembolism, and/or obstructive sleep apnea. Thorough history and physical examination, vital signs, baseline laboratory studies, and informed consent should be obtained during the initial assessment.
Obesity Surgery–Mortality Risk Score The Obesity Surgery–Mortality Risk Score to predict the risk of mortality in patients undergoing bariatric surgery. One point is assigned to each of 5 preoperative variables:1. BMI 50 kg/m2 or more2. Male gender3. Hypertension4. Risk for pulmonary embolism (history of venous thromboembolism, pulmonary hypertension, and/or obesity hypoventilation)5. Older than 45 yearsScore Category Mortality0 or 1 A or Low Risk 0.2%2 or 3 B or Intermediate risk 1.3%4 or 5 C or High risk 2.4%
Interaction between Obesity, Systemichypertension and Ischemic heart disease
Cardiovascular system evaluation H/O dyspnea,orthopnea or PND, limitation in exercise in tolerance, palpitations. Look for prior MI,HTN,Angina, PVD Signs of cardiac failure1. Raised JVP2. S3, S43. Pulmonary crackles4. Hepatomegaly5. Peripheral edema
Cont.. Functional capacity can be better assessed according to the patient’s ability to undertake activities of daily living. Those able to perform activities requiring at least 4 metabolic equivalents (METs), e.g. climbing a flight of stairs, walking up-hill or walking on level ground at 4 miles per hour, are classified as having moderate functional capacity.
Cont.. Measure non invasive BP with proper sized cuff Cuff size should be greater than 20% of upper diameter If cuff is small measured BP will be spuriously high In morbidly obese invasive BP monitoring is advised
In CXR look for LVH/RVH/lung disease/prominent pulmonary artery ECG – Look for rate, rhythm & ischemic changes. Low voltage ECG may be recorded because of fat. To rule out CAD an exercise or dobutamine stress echo should be done
Cont..More prone to arrhythmia’s because of Hypoxemia Fatty infiltration of cardiac conduction system. Sleep apnea Dyslipidemia Glucose intolerance
Pulmonary hypertensionImplications to Anaesthesia Hypoxemia should be avoided because it causes pulmonary vasoconstriction further aggravating the condition N2O should be avoided Inhalational agents are beneficial as they cause bronco dilation & decrease hypoxic pulmonary vasoconstriction In severe pulm HTN – Pulmonary Artery catherization is useful for monitoring.
Thromboprophylaxis Deep vein thrombosis is the most common postoperative complication of bariatric surgery So, adequate thromboprophylactic measures are therefore imperative Patients at risk of post operative venous thromboembolism should be considered for an IVC filter before bariatric surgery Pneumatic compressive device can be used Heparin 5000 IU S C before surgery followed every 12 hrly till patient is mobilized LMWH 40 mg every 12 hrly till patient is mobilized Early ambulation
Respiratory system changes Increased basal oxygen consumption and carbon dioxide production. Results ini. lung & chest wall compliance atelectasis,ii. airways resistance V/P mismatch and impairediii. FRC oxygenation Supine position, induction of anaesthesia and pneumoperitoneum aggravate these effects.
Cont.. There is restrictive lung disease because1. Decreased chest wall compliance2. Diaphragm pushed cephalad3. Decreased lung volume4. Supine and trendelenberg positionLung volume changes TV - Normal or decreased IRV - decreased ERV - decreased greatly FRC - decreased greatly FEV1 - normal or decreased
Obstructive sleep apnea 5% obese patients have OSA Take a history of snoring and subsequent apnea(ask relative or sleeping partner) Ask for day time somnolence History of dry mouth and short arousal during sleep Diagnosis confirmed with a polysomnographic study
Respiratory system changes & OSAImplications for anaesthesia As oxygen reserve is reduced, they desaturate rapidly when apneic therefore should be well pre oxygenated before intubation. Higher inflation pressure needed because of decreased chest wall compliance Application of PEEP to improve oxygenation Patient should be trained with CPAP or BIPAP machine preoperatively PFT should be done to anticipate need for post operative ventilation Avoid sedative premedication Since these patients are hypoxemic and hypercapnic ABG should be done preoperatively
GI changes & its implications Increased abdominal pressure Increased gastro esophageal reflux Hiatal hernia may be associated. After 8 hours of fast 85%-90% morbidly obese patients have gastric volume greater than 25 ml and gastric ph less than 2.5 Hence Metaclopromide,Rantidine should be given. Increased risk of aspiration Diabetics are at risk for gastroparesis. Need a rapid sequence intubation technique after adequate pre-oxygenation. There may be non alcoholic fatty liver disease, So many bariatric surgeon prefer to take liver biopsy during surgery to stage liver disease
Airway Management Airway examination should be done to predict difficult intubation Predictors of difficult intubation1. Mallampatti score of 3 or more2. Neck circumference > 40 cm at thyroid cartilage.3. Thyromental distance <6 cm4. High BMI5. Decreased incisor gap6. Sternal pad of fat7. Limited mobility of TM joint or AO joint8. Short thick neck9. Large breasts
Cont.. Use oropharyngeal airway during mask ventilation as airway collapses as soon as consciousness is lost. If airway management and intubation prove difficult, emergency airway adjuncts, including a gum elastic bougie, laryngeal mask airway, video laryngoscope, or fiber optic endoscope, may be used Tracheasotomy kit should be available & surgeon should stand by Breath sounds are distant therefore EtCo2 should be used to confirm tracheal placement of ET tube
Cont.. Intravenous & intraarterial access should be checked. Central venous catheter should be used The conical shape of the upper arm may present difficulties in obtaining an accurate noninvasive blood pressure reading, and invasive monitoring may be deemed necessary.
Concurrent and PreoperativeMedications Usual medications, except insulin and oral hypoglycemics, be continued until the time of surgery. Medications for IHD & HTN should be continued. Antibiotic prophylaxis is important because of increased risk of postoperative wound infection. Anxiolysis, analgesia, and prophylaxis against both aspiration pneumonitis and DVT should be addressed during premedication
Intraoperative AnestheticManagement. Major areas of concern include1. Airway management,2. Maintenance of oxygenation,3. Patient positioning4. Monitoring.5. Pneumoperitonium6. Maintenance of Anaesthesia
Prevent hypoxemia duringinduction HOB elevated(back-up Fowler Mayor reverse Trendelenburg) 30° increase Use of CPAP during induction the safe apnea period Preoxygenate with 100% O2 during induction
Position for intubation • Supine sniffing position with 30° back-up position provides optimal conditions for successful intubation. • Aligning the external auditory meatus with the sternum horizontally has been shown to improve the laryngoscopic view
Positioning 2 OT tables can be kept side by side if body weight is more than 150kgs All pressure points should be padded properly. Patients are prone to slipping off the operating table during table position changes; therefore, they should be well strapped to the operating table Bean bags are soft pads available in various sizes and shapes that are filled with thousands of tiny plastic beads
Cont.. When compared with the supine position, the use of a 30° reverse Trendelenburg position during bariatric surgery Advantages from RTP1)Reduces the alveolar to-arterial oxygen difference,2)Increases total ventilatory compliance,3)Reduces peak airway pressures,4)Increases oxygenation. RTP is a better solution than large tidal volume and high PEEP.
Intra Operative VentilatoryManagement Prevent/reverse atelectasis Restrict the use of Fio2 to < 0.8 during Maintain lung recruitment Use PEEP (10-12 cm/H2O) Avoid lung overdistension Use tidal volume of 6-10 mL/kg of ideal body weight Keep peak-inspiratory pressure < 30 cm/H2O Consider mild permissive hypercapnia if necessary
Fluid Management Patients ,may have hypovolemia due to bowel preparation and preoperative fasting. In addition, obese patients are frequently receiving antihypertensive medications that increase the potential for hypotension during induction. This potential, coupled with the propensity for postoperative acute renal failure, highlights the importance of fluid replacement. Intra-operative ventricular dysfunction may be precipitated by rapid fluid administration in patients with IHD. Early detection of ischemia and aggressive management of hypotension with intravenous fluids and vasopressors is important as these patients frequently have minimal reserve. Central venous pressure monitoring is more reliable and should be used to guide fluid management in patients with ischemic heart disease or cardiac failure
Monitoring ECG, Pulse oximetry,Temperature, Capnography, Urine Output, BIS, Neuro Muscular monitoring Transesophageal echo &Invasive arterial monitoring should be used for the super morbidly obese Blood pressure measurements can be falsely increased if a cuff too small for the arm PA catheters are reserved for serious cardiopulmonary disease. Central venous pressure monitoring is more reliable and should be used to guide fluid management in patients with ischemic heart disease or cardiac failure.
Extubation Extubation in morbid obesity carries serious risk of loss of airway control, rapid onset of hypoxaemia, haemodynamic instability and pulmonary aspiration Should be done in semi-upright or sitting position, When fully awake, After complete resolution of neuromuscular blockade. (evidenced by neuro-muscular stimulation, return of airway reflexes, sustained head lift for >5 s and generation of adequate peak inspiratory pressure and vital capacity). Emergency airway equipment should be immediately available in case re-intubation is required
Pharmacology Highly lipophilic drugs, show significant increases in volume of distribution (VD) for obese individuals relative to normal- weight individuals Less-lipophilic compounds have little or no change in VD with obesity Weak or moderate lipophilicity drugs can be dosed on the basis of ideal body weight (IBW) or, more accurately, lean body mass (LBM)
Drug Dose recommendationPropofol Induction dose based on LBW; maintenance Increased fat mass does not affect initial dose based on TBWThiopental Induction dose based on TBWSuccinylcholine Intubating dose based on TBWND muscle relaxants All doses based on IBWFentanyl Loading dose based on TBW; maintenance Increased distribution volume and elimination dose based on LBW and responseDexmedetomidine Infusion rates of 0.2 μg/kg/min
Desflurane has been suggested as the inhaled anesthetic of choice in this patient population because of its more rapid and consistent recovery profile Rapid elimination and analgesic properties make nitrous oxide a good inhaled choice during bariatric surgery, but high oxygen demand in the obese limits its use. But TIVA is preferred over inhalational agents because can diffuse into the fatty tissue & delayed recovery can happen. Studies show TIVA has advatages like1. Better intraoperative hemodynamic stability2. Early recovery from GA3. Better postoperative analgesia. Short acting agents like Remifentanyl,Propofol & dexmed can be used.
In Our Institution? Two Bariatric Surgeries are conducted. They are1. Sleeve gasrectomy2. RYGB In Sleeve gasrectomy we insert gastric calibration tube, so that surgeon cuts the stomach along that tube& gastric pouch can be sized properly. We must remove all NG tubes before gastric division to avoid unplanned stapling & transection of these devices. Later leak test is performed with 50ml methelene blue with saline to ensure anastomotic integrity. At this time the cuff should be tight seal otherwise aspiration of dye can occur leading to chemical pneumonitits. After anastomosis, if NG tube is inserted it should be done by watching on monitor otherwise disruption of anastomosis can occur.
RYGB In bypass procedure metallic anastomotic device Orovil is introduced. It has metallic part which is attached to a plastic tubing. During insertion metallic portion should be guided into esophagus with the help of index finger & followed in the pharynx as deep as possible. Problems that may be encountered is that metallic part may get detached from the plastic tubing. In that case direct laryngoscopy is done, if its visible in pharynx it should be removed. If its deep then it should be removed endoscopically.
Regional Anaesthesia Mainly for post operative pain management Combined Epidural & general anaesthesia can be given to decrease the doses of GA drugs. Epidural anaesthesia may decrease the post operative pulmonary complications Technically more difficult Fatty infiltration of the epidural space, as wellas increased blood volume caused by the increasedintra-abdominal pressure, may reduce the volumeof the epidural space, resulting in an unpredictablespread of the anesthetic solution and block height.
Post operative management Initial post-operative considerations include airway and respiratory support, pain control and prevention of thromboembolism. Risk of post operative respiratory failure is increased by1. Preoperative hypoxemia2. Vertical incision Postoperatively, supplemental humidified oxygen should be administered at an appropriate inspiratoryfraction.
Cont.. Postoperative incentive spirometry and/or continuous positive airway pressure (CPAP) may facilitate am earlier return to preoperative pulmonary function and decrease respiratory complications. Patients receiving continuous positive airway pressure or bilevel positive airway pressure preoperatively should receive it immediately postoperatively
Management of postoperative pain Is very challenging. Morbidly obese patients have exaggerated respiratory depression from opioids. In patients with obstructive sleep apnea – opioid sparing techniques help avoid respiratory complications. A multimodal approach is best. It include 1)Intravenous opioid administration , 2)Local anesthetics injected into the wound or port site,3)Neuraxial anesthesia,4)NSAIDs Infusion of dexmedetomidine decreases postoperative opioid requirements. Recent technique is the continuous intraperitoneal infusion of bupivacaine.
Laproscopy & anaesthesia Carbon dioxide is used to create pneumoperitonium. Systemic vascular resistance is increased with increased intraabdominal pressure (IAP) The degree of IAP determines its effects on venous return and myocardial performance There is a biphasic cardiovascular response to increases in IAP. At an IAP <10 mm Hg, there is an increase in venous return, with a subsequent increase in cardiac output and arterial pressure. At an IAP >20 mm Hg, Compression of the inferior vena cava occurs with decreased venous return from the lower body and consequent decreased cardiac output . Decrease renal blood flow and GFR also occurs Cephalad displacement of the diaphragm and carina from pneumoperitoneum may displace endotracheal tube into a bronchial mainstem causing Endobronchial intubation reflected by hypercarbia and hypoxemia Catastrophic complications that should be kept in mind include massive gas embolism, pneumothorax, and mediastinal emphysema
Postoperative Complications Anastomotic Leak Respiratory (i.e. atelectasis,pneumonia) Vascular (thrombophlebitis, deep venous thrombosis) Wound(infection, dehiscence) Rhabdomyolysis may occur in morbidly obese patients after prolonged surgeries. Suspected if unexplained increases of serum creatinine and creatine phosphokinase and patients complain of buttock, hip or shoulder pain.
Patients scheduled for repeat bariatric surgery or any surgery with previous history of bariatricsurgery. These patients have long-term nutritional abnormalities like vitamin B12, iron, calcium, and folate deficiencies and hypoproteinemia. Electrolyte and coagulation indices should be checked before surgery, particularly if patient compliance has been poor or if the patient is acutely ill. prothrombin time with partial thromboplastin time will be abnormal because of deficiency of clotting factors II, VII, IX, and X. So administration of a vitamin K analog, such as phytonadione, can be used to correct the coagulopathy within 6–24 h. Fresh frozen plasma will be required for emergency surgery or active bleeding
Conclusion The number of patients resorting to bariatric surgery for sustained weight loss is increasing exponentially. These patients are at increased risk of peri- operative complications by the presence of obesity related co-morbidities. Preoperative identification and optimization of associated disease in conjunction with perioperative management by a multidisciplinary team is essential to optimize patient outcome.