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Anesthesia for Bariatric Surgery Miller, ch:64 Ashish C. Sinha, David M. Eckmann 1.

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Presentation on theme: "Anesthesia for Bariatric Surgery Miller, ch:64 Ashish C. Sinha, David M. Eckmann 1."— Presentation transcript:

1 Anesthesia for Bariatric Surgery Miller, ch:64 Ashish C. Sinha, David M. Eckmann 1

2 Obesity Common enemy of surgeon and anestethist. A rarity until the middle of the 20th century. 200 million Americans, or 65% of the U.S. adult population, are overweight or obese. It is second only to smoking as a preventable cause of death. 2

3 Obesity Obesity can be defined as a “disease” because it is a physiologic dysfunction of the human organism. Food calorie intake exceeds energy expenditure over a long period. 3

4 Obesity Obesity influenced by genetic, behavioral, cultural, and socioeconomic factors. Syndromes associated with obesity:  Leptin deficiency  Prader-Willi syndrome  Lawrence-Moon-Biedl syndrome 4 Genetics Behavior Environment

5 BMI: kg/m2 BMI: kg/m2 5

6 6

7 Obesity Waist Circumference and Risk Obese Class 1Overweight Normal Weight Waist Circumference High riskIncreased riskLeast risk <102 cm(M) <88 cm(F) Very high riskHigh riskIncreased risk ≥102 cm(M) ≥88 cm(F) 7 BMI has been shown to be a relatively insensitive indicator of the risk for obesity-associated metabolic and cardiovascular disease.

8 Table 64-3 -- Health Risks Associated with Increasing Body Mass Index 8

9 Metabolic Syndrome 9 A group of defined metabolic and physical abnormalities.

10 Metabolic Syndrome 10 Defining ValueCriteria Waist circumference >102 cm in men and >88 cm in women Abdominal obesity ≥150 mg/dLTriglycerides <40 mg/dL in men and <50 mg/dL in women High-density lipoprotein cholesterol ≥130/85 mm HgBlood pressure ≥110 mg/dLFasting glucose Clinical Criteria for Diagnosing Metabolic Syndrome * * Three of five criteria must be met.

11 Metabolic Syndrome In the United States, nearly 50 million people have metabolic syndrome. More than 83% meet the criterion of abdominal obesity. The incidence of metabolic syndrome increases with age. 11

12 Metabolic Syndrome Men are affected more commonly than women. Hispanics and south Asians appear to be susceptible. Its frequency is lower in African American than in white men. 12

13 Metabolic Syndrome May result from the use of some drugs. Have a higher risk for cardiovascular disease and type 2 diabetes. Metabolic syndrome is also associated with a variety of other conditions, such as:  polycystic ovary syndrome  nonalcoholic fatty liver disease  gallstones  sleep disturbances  sexual impotence  some forms of cancer 13

14 Inflammatory processes appear to play an important role in the metabolic syndrome. Visceral adipose tissue has been identified as an important source of proinflammatory cytokines:  Cytokines (primarily IL-6 and TNF-a)  Adipokines (leptin, adiponectin, adipose-derived resistin) 14 Metabolic Syndrome

15 Obstructive Sleep Apnea/Hypopnea Syndrome ((OSA/OSAHS Recurrent episodes of upper airway obstruction occurring during sleep.  Complete cessation of airflow  Lasting 10 seconds or longer despite maintenance of neuromuscular ventilatory effort  Occurring five or more times per hour of sleep  Accompanied by a decrease of at least 4% in SaO2. The results of polysomnography are reported as the apnea/hypopnea index (AHI). 15

16 Obstructive Sleep Apnea/Hypopnea Syndrome ((OSA/OSAHS Mild disease: ◦ AHI of 5 to 15 events per hour Moderate disease: ◦ AHI of 15 to 30 events per hour Severe disease: ◦ AHI of greater than 30 events per hour 16

17 Obstructive Sleep Apnea/Hypopnea Syndrome Numerous studies have confirmed that obesity is the greatest risk factor for OSAHS. It is important that obese patients scheduled for bariatric surgery undergo preoperative polysomnographic testing for OSAHS. Preoperative diagnosis and appropriate interventional management can have the following benefits:  less postoperative sleep deprivation, improved response to analgesic and anesthetic drugs, and normalization of cardiovascular disturbances 17

18 Obstructive Sleep Apnea/Hypopnea Syndrome Increased amounts of adipose tissue in their oral and pharyngeal tissues. This can contribute to the development:  Airway obstruction  Difficult mask ventilation  Difficult laryngoscopy and endotracheal intubation Additionally, airway obstruction after extubation is likely to be complicated by the use of opiate and sedative drugs needed for postoperative pain management. 18

19 Obstructive Sleep Apnea/Hypopnea Syndrome OSA also plays an important role in inflammation and the metabolic syndrome. The sympathetic nervous system is activated as patients with untreated OSA undergo cyclic episodes of hypoxia and reoxygenation; such activation leads to elevated levels of proinflammatory cytokines and potentially oxidative stress of vascular endothelium, which induces an even more heightened state of systemic inflammation in obese patients with OSA Inflammatory mediators:  IL-6  C-reactive protein  Leptin  TNF-a  IL-1  Reactive oxygen species  Adhesion molecules such as intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) Obesity, metabolic syndrome, and OSAHS are interrelated diseases that significantly alter a patient's inflammatory disease profile. 19

20 Nonsurgical Management of Obesity The primary goals of nonsurgical management of obesity:  Weight loss  Treatment of the abnormalities associated with metabolic syndrome The goal of weight loss in therapeutic lifestyle change is not to achieve normal or ideal body weight (IBW). 20

21 Nonsurgical Management of Obesity Statin therapy Ezetimibe Fibrates Omega-3 fatty acids Nicotinic acid 21

22 Nonsurgical Management of Obesity Antihypertensive drug therapy Oral hypoglycemic agents Antiplatelet therapy 22

23 23 framingham risk score

24 Pharmacotherapy for Weight Loss BMI of 30 or greater (=27 for patients with obesity-related risk factors ). Two categories of weight loss drugs: ◦ Appetite suppressants  Phentermine  Sibutramine ◦ Lipase inhibitors  Orlistat 24

25 Dietary and Herbal Medications Chitosan Chromium picolinate Conjugated linoleic acid Ephedra alkaloids (ma huang) Garcinia cambogia 25

26 Implanted Electrical Stimulators Subcutaneously placed Stimulate regions along the lesser curvature One study documented:  25% excess weight loss  Improved response to the oral glucose tolerance test  Decreases in blood pressure  Improvement in symptoms of gastroesophageal reflux disease, along with increased parasympathetic drive. Modification of Ghrelin levels may play a role in the success of these devices. 26

27 27 Implanted Electrical Stimulators

28 Surgical Management of Obesity Gastric-restrictive procedures Combine gastric restriction with induction of nutrient malabsorption 28

29 Restrictive Procedures Creating a small pouch from the proximal part of the stomach just distal to the gastroesophageal junction.  This increases mechanical resistance to gastric emptying of ingested solids, whereas emptying of liquids proceeds normally. Vertical band gastroplasty (VBG) Laparoscopic gastric band (LGB) 29

30 VERTICAL BANDED GASTROPLASTY (VBG) VBG is a purely restrictive procedure in which the upper stomach is stapled and divided, forming a small pouch that reduces the size of the stomach and the amount of food the stomach can hold.

31 Laparoscopic gastric band (LGB) 31

32 Sleeve Gastrectomy  Removes 2/3 of the stomach  Can be used as a single stage procedure 32

33 Malabsorptive Procedures Two commonly performed malabsorptive operations: ◦ Gastric bypass (GBP) ◦ Biliary pancreatic diversion (BPD) GBP surgery involves the creation of a small gastric pouch by stapling or banding the stomach, which results in an element of gastric restriction. GBP also involves the creation of a Roux-en-Y anastomosis in which the small gastric pouch is directly connected to the middle portion of the jejunum 33

34 Gastric bypass (GBP) 34

35 Biliopancreatic Diversion (BPD)  Mixed restrictive and malabsorptive  Connect pouch to small intestine The more proximal biliopancreatic limb is anastomosed to the alimentary limb about 50 cm from the ileocecal valve.

36 Health Benefits of Bariatric Surgery The two most significant outcome: ◦ Weight loss ◦ Resolution of comorbid conditions Absolute weight loss averaged: (meta-analyses) ◦ 46.4 kg for BPD ◦ 43.5 kg for GBP ◦ 39.8 kg for VBG ◦ 28.6 kg for gastric banding Far greater than that nonsurgical methods Closer to patients’ desired and expected weight loss Long-term maintenance of weight loss 36

37 Health Benefits of Bariatric Surgery Diabetes resolved in more than 75% overall: ◦ 98.9% for BPD ◦ 87.3% for GBP ◦ 71.6% for VBG ◦ 47.9% for gastric banding  nonsurgical weight loss is accompanied by relapsing disease in nearly 100% of patients within 5 years. Postsurgical effects on hypertension were: ◦ Greatest after BPD (83%) ◦ Intermediate after GBP (67.5%) and VBG (69%) ◦ Least after gastric banding (43%) Resolution of OSAHS occurring in 85.7% of patients overall. Improvement in:  fatty infiltration of the liver  respiratory function and asthmatic symptoms  reversal of the cardiomyopathy of obesity  joint pain and mobility 37

38 Anesthetic Management of Bariatric Surgical Patients Preoperative Evaluation Comorbidity AHI score greater than 30, implying severe sleep apnea. CPAP levels greater than 10 imply a patient with the potential for difficult mask ventilation. 38

39 Preoperative Evaluation History of previous surgeries Preoperative laboratory evaluations ◦ Fasting blood glucose ◦ Lipid profile ◦ Serum chemistries (to evaluate renal and hepatic Function) ◦ Complete blood count ◦ Ferritin ◦ Vitamin B12 ◦ Thyrotropin ◦ 25-hydroxyvitamin D ◦ LFT 39

40 Preoperative Evaluation Contraindications to bariatric surgery: ◦ Unstable CAD ◦ Uncontrolled severe OSA ◦ Uncontrolled psychiatric disorder ◦ Mental retardation (IQ < 60) ◦ Inability to understand the surgery ◦ Perceived inability to adhere to postoperative restrictions ◦ Continued drug abuse ◦ Cirrhotic liver disease with portal hypertension ◦ Malignancy with a poor 5-year survival prognosis 40

41 Intraoperative Care Airway management Positioning Monitoring Choice of anesthetic technique Anesthetic agents Pain control Fluid management Specific interventions, techniques, and approaches used by the anesthesia care team providing anesthesia for obese patients are important determinants of outcome. 41

42 Airway Management Difficulty with laryngoscopy and intubation.  Short, thick neck, large tongue, and significant redundant pharyngeal soft tissue The correlation between morbid obesity and difficult laryngoscopy and intubation is not universally observed in clinical practice. One study found an association between oropharyngeal Mallampati classification and BMI as a predictor of difficult laryngoscopy. Mallampati score had low specificity and low positive predictive value (62% and 29%, respectively) for difficult intubation. 42

43 Airway Management Only an abundance of pretracheal soft tissue measured ultrasonically and neck circumferences were found to be positive predictors of difficult intubation.  The authors also assessed the airway by measurement of the thyromental distance, mouth opening, degree of neck mobility, Mallampati score, neck circumference, and the presence of OSA. The incidence of difficult intubation in obese patients was three times the incidence in the nonobese population. (A meta-analysis of 35 studies: suboptimal patient positioning ) Ramped positioning 43

44 44 “stacking,” is to position the patient so that the tip of the chin is at a higher level than the chest to facilitate laryngoscopy and intubation. The head- elevated laryngoscopy position (HELP) is a step beyond stacking. It significantly elevates the obese patient's head, upper body, and shoulders above the chest to the extent that an imaginary horizontal line connects the sternal notch with the external auditory meatus to better improve laryngoscopy and intubation Airway Management

45 45 Airway Management

46 Awake intubation Sedated fiberoptic intubation Laryngeal masks 46

47 Pulmonary physiology Decreased VC, IC, ERV, and FRC. Closing capacity in obese individuals is close to or may fall within tidal breathing, particularly in the supine position. 47

48 Pulmonary physiology Obese patients reached the end point in less than 3 minutes, whereas it took 6 minutes in patients with a normal BMI. Use of 10 cm H2O CPAP during preoxygenation PEEP Waist-to-hip ratio Patients in the supine position reached the end point in 2 minutes, but it took 30 seconds longer if the supine position with the back elevated 30 degrees was used and 1 minute longer if the 30-degree reverse Trendelenburg position was used.  Reduce the alveolar-to-arterial oxygen difference, as well as to increase total ventilatory compliance and reduce peak and plateau airway pressure when compared with the supine position 48

49 Pulmonary physiology Alveolar recruitment by repeated sustained lung inflation to 50 cm H2O 15 cm H2O PEEP In summary, the most favorable patient position or optimal amount of PEEP during preoxygenation, induction of anesthesia, or intraoperatively has not been clearly established for obese patients. 49

50 Pulmonary physiology There are no published guidelines to address the issues of maintenance of oxygenation and ventilatory mechanics in obese patients undergoing general anesthesia. Anesthesia care providers should position patients to achieve the combined goals of providing a superior laryngoscopic view for ease of endotracheal intubation while establishing optimal conditions for oxygenation and preservation of pulmonary mechanical function. 50

51 In our institution Ramped position (25- to 30-degree) Reverse Trendelenburg position, if needed Preoxygenated for 3 to 5 minutes with 100% oxygen CPAP or pressure-support (identical to the patient's home CPAP setting) Vntilation by facemask After induction, it is reasonable to maintain 10 to 12 cm H2O PEEP intraoperatively Return the patient to the head-up position before emergence and extubation (sustained tetanus with the nerve stimulator and performance of a 5-second head lift) Pressure support or CPAP can be delivered immediately by mask applied to the face 51

52 Patient Positioning Morbidly obese patients do require extra care in positioning.  lack of evidence-based studies demonstrating that obese patients have more frequent complications from positioning Supine position Prone position Pressure points Protect the dependent hip Excess axillary tissue Lithotomy position  compartment syndrome, the duration during which the legs are held in stirrups. 52

53 53

54 Anesthetic Drugs and Dosing Opioids, propofol, and benzodiazepines have exaggerated responses in patients with OSA  Decrease pharyngeal musculature tone. Volatile agents diminish the ventilatory response to carbon dioxide in the setting of OSA. It therefore becomes attractive to use short-acting drugs and nondepressors of ventilation such as the α 2 -agonist dexmedetomidine. 54

55 Anesthetic Drugs and Dosing Lean body mass is a good weight approximation to use when dosing hydrophilic medications. Dosing of commonly used anesthetic drugs such as propofol, vecuronium, rocuronium, and remifentanil is based on IBW. In contrast, thiopental, midazolam, succinylcholine, atracurium, cisatracurium, fentanyl, and sufentanil should be dosed on the basis of TBW. Maintenance doses of propofol should be based on TBW and, conversely, on IBW for sufentanil. Some evidence suggests that desflurane may be the anesthetic of choice. (stability and recovery) N 2 O: (analgesic effect and is eliminated rapidly, we prefer to avoid it) 55

56 IBW 56 J. D. Robinson Formula (1983) 52 kg + 1.9 kg per inch over 5 feet (man) 49 kg + 1.7 kg per inch over 5 feet (woman) D. R. Miller Formula (1983) 56.2 kg + 1.41 kg per inch over 5 feet (man) 53.1 kg + 1.36 kg per inch over 5 feet (woman) G. J. Hamwi Formula (1964) 48.0 kg + 2.7 kg per inch over 5 feet (man) 45.5 kg + 2.2 kg per inch over 5 feet (woman) B. J. Devine Formula (1974) 50.0 + 2.3 kg per inch over 5 feet (man) 45.5 + 2.3 kg per inch over 5 feet (woman)

57 57

58 58

59 Aspiration Obesity itself does not increase the risk for aspiration. However, acid aspiration prophylaxis, including H2 receptor antagonists or proton pump inhibitors, must be considered in patients with identifiable risk for spiration. Awake fiberoptic intubation may also be considered in such patients. 59

60 Induction of Anesthesia Regional anesthesia: ◦ Safe&difficult (Position, landmarkers, catheters, needles, special ultrasound probes) ◦ Increased cephalad spread (larger magnitude respiratory compromise) Obesity per se does not require invasive monitoring, so GPB surgery can be performed safely with routine monitoring. The rationale for central venous access may stem from difficulties in peripheral access rather than any other indication. 60

61 Induction of Anesthesia Postoperative pain management: ◦ Intravenous analgesia via PCA ◦ Thoracic epidural analgesia ◦ Opioid-based PCA with local anesthetic infiltration of the wound ◦ Non-narcotic medication 61

62 Induction of Anesthesia Using the appropriate table for the patient's weight. It may be useful to keep the patient strapped throughout the period of sedation. Apply a bean bag under the patient to keep the patient from sliding off the operating room table. 62

63 Induction of Anesthesia Armboards may need extra padding to keep the patient from having the arm and shoulder out of an anatomic position. Fluid requirements may be greater than predicted, and in even a relatively short, 2- to 3-hour case, 4 to 5 L of crystalloid fluid may be needed to prevent acute tubular necrosis in the kidneys. Predisposing factors: ◦ Hypovolemia ◦ BMI greater than 50 kg/m2 ◦ Prolonged surgical time ◦ Previous history of renal disease ◦ Intraoperative hypotension 63

64 Management of Complications Very safe, but not without potential complications In-hospital mortality rates:  LGB: 0.27%  Open GBP: 0.81%  Statistically significant difference In-hospital immediate postoperative morbidity:  Wound  Gastrointestinal  Intestinal leakage  Pulmonary  Cardiovascular complications 64

65 Management of Complications Range from 1.35% (wound complications) to 4.52% (gastrointestinal complications) after LGB From 1.98% (wound complications) to 5.33% (gastrointestinal complications) after open GBP. The most common complications requiring reoperation include:  Postoperative intra-abdominal bleeding  Anastomotic leakage  Suture line dehiscence  Small bowel obstruction  Deep wound infection 65

66 Management of Complications Reoperation: ◦ Hypovolemia&dehydration:  Bleeding, vasodilatation, and insensitive fluid losses associated with fever and Infection. ◦ Aspiration:  Postoperative ileus  Small bowel obstruction,  Surgical creation of a Roux-en-Y gastric bypass limb that excludes the pylorus as an element of protection from reflux.  NGT, ICU 66

67 Management of Complications Delayed complications: ◦ Surgical intervention:  Anastomotic strictures or ulcers  Ventral hernias  Gastrogastric fistulas  Severe reflux  Small bowel obstruction  Cosmetic operations to remove excess skin  Adjustment of a gastric band ◦ Neurologic: (VitB12, Copper)  Polyneuropathy  Polyradiculoneuropathy  Myelopathy  Encephalopathy  Optic neuropathy ◦ Nutritional and metabolic: (Enteral, Parenteral, Revision)  Malnutrition.  Excessive weight loss  Steatorrhea or severe diarrhea  Hypoalbuminemia,  Marasmus  Edema  Hyperphagia 67

68 Management of Complications 68

69 Considerations for Management of Obese Patients Undergoing Nonbariatric Surgery Dindo and coworkers evaluated 6336 patients: ◦ Did not find any difference in the incidence or severity of complications after elective general surgery, except for surgical site infections. Multiple studies had demonstrated that obese patients are at higher risk after gynecologic, orthopedic, cardiovascular, urologic, and transplantation surgery, whereas other studies have not. 69

70 Dindo: Independent risk factors for postoperative complications: ◦ Operative severity ◦ Open laparoscopic surgery Surgeries may last longer, about 25% more time for laparoscopic than for open cholecystectomy in the morbidly obese. Significantly, the wound infection rate was much better after laparoscopic than after open surgery, which supports the practice of performing laparoscopic surgery in obese patients rather than the alternative. Anesthesia: same as bariatrics. 70 Considerations for Management of Obese Patients Undergoing Nonbariatric Surgery

71 Fed up with how her diet is going Charlene takes a more serious aim at her target weight

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