Jahnavi Srinivasan, MD Assistant Professor of General Surgery Emory University

Transcription

1 Jahnavi Srinivasan, MD Assistant Professor of General Surgery Emory University

2 Definition & Demographics

3 The branch of medicine dealing with the diagnosis and treatment of obesity.

4 BMI NIH Classification <18.5 Underweight BMI = weight (kg) height 2 (m) Normal weight Overweight Class I Obesity Class II Obesity >40 Extreme Obesity

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6 From 1984 to 2002 the prevalence of obesity increased by 60% 59% of Georgians are overweight or obese 6 th in the nation for obesity 15% deaths in 2002 were related to obesity $2.1 billion spent on obesity treatment

7 OBESITY LIST OF ASSOCIATED MEDICAL PROBLEMS Cardiovascular Hypertension Hyperlipidemia Atherosclerosis Coronary artery disease Deep venous thrombosis Pulmonary embolism Venous stasis ulcers Metabolic Diabetes Altered metabolic rate Fatty liver Cholelithiasis Amenorrhea Infertility Pulmonary Alveolar hypoventilation Sleep apnea Pulmonary hypertension Orthopedic / Mechanical Joint breakdown Chronic back pain Hernias Incontinence Other Cancer (colon, prostate, breast) Social / psychiatric issues

8 Some basic science

9 Insulin Resistance Type 2 Diabetes Mellitus Metabolic Syndrome Polycystic Ovary Sydrome (PCOS) *Aggressive early treatment can result in full reversal of metabolic disease and consequences thereof

10 Anabolic Hormone Glucose homeostasis Protein & fat metabolism Endothelial NO Suppresses hepatic gluconeogenesis and glycogen breakdown Promotes transport of glucose from bloodstream to peripheral tissues

11 Inability of insulin to produce typical effects Reduction of insulin receptors Decreased receptor phosphorylation

12 Impaired suppression of glucose output by liver Reduced postprandial uptake of glucose Increased TG breakdown by adipose tissue Free fatty acid release further impairing insulin function

13 Lipo-toxicity in hepatocytes, myocytes, and adipocytes leads to perturbed insulin signaling Specific steps in this sequence remain undefined Fat distribution affects risk of resistance Upper body fat (visceral/android)> lower body fat (gynoid) Lipolytic visceral cells (e.g. omentum) enhance FFA delivery to portal and systemic circulation Adipose tissue induces chronic low grade inflammation that impairs insulin function

14 Regulatory peptides secreted by adipocytes Adiponectin: Increases tissue sensitivity to insulin (only adipokine which does this) Levels inversely related to visceral obesity, type 2 DM, HTN, CAD Leptin: Regulates food intake and energy homeostasis Released in proportion to excess body weight Clear relationship to insulin resistance has not yet been established

15 2x increased risk of CV disease Increased coronary artery calcification Fasting hyperinsulinemia increases LDL and VLDL Non-ischemic functional alterations of myocadium 5x increased risk of type 2 DM Diagnosis if any of following 3 are present Central obesity (increased waist cirucmference), elevated TG, reduced HDL, HTN, elevated fasting glucose

16 $200 billion annual expense $93 billion direct medical costs $33 billion annually on diet foods/programs $3.9 billion lost annually in productivity 9.1% of national health expenditure

17 deaths annually 2 nd leading cause of preventable deaths (#1 tobacco, #3 alcohol) 3-4 times greater chance of premature death than nonobese

18 Behavioral & Medical

19 Avg weight loss of 19 lbs after 21 weeks..12 lbs after 53 weeks <1% patients maintain significant weight loss fo >1 year Pyschological and social support remains important part of weight management nevertheless

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21 Results in clinically irrelevant weight loss (avg lbs) <4% maintain wt loss Few recommendations for sustainable weight loss

22 MORBID OBESITY Costs of Medical Treatment Medication Weight loss in excess of placebo (lb.) Cost ($ mon / $ yr) Cost for 1 lb weight loss($) Lonamin (phenteramine) / 720 $ 42 Meridia (sibutramine) / 1392 $ 155 Xenical (Orlistat) / 1428 $ 179 *Arch Intern Med 2001; 161:

23 Indications, Procedures

24 Surgical indication based upon BMI BMI>40 or BMI>35 with recognized comorbidities American Society for Bariatric Surgery (ASBS) has suggested BMI>30 in presence of comorbidities Recognized diet and behavioral modification failures Insurance often requires 6 month medically supervised diet

25 Medical evaluation Nutritional evaluation Psychological evaluation Any additional testing as deemed appropriate by bariatric physician

26 Malabsorptive Diversion of nutrients from majority of small bowel into ileum Biliopancreatic diversion Combined with restriction Duodenal switch Roux-en-Y Gastric bypass Restrictive Small gastric pouch with narrow outlet Limits oral intake to induce satiety Weight loss without altering normal physiologic digestion elminating malabsorptive side effects Several iterations over the years Vertical banded gastroplasty (VBG) in 1990s Laparoscopic adjustable gastric band

27 Gastric Bypass

28 Developed from observed weight loss in gastrectomy BII patients Most common procedure in U.S. ( in 2005) ml pouch (restrictive) Limb length varies from 75 to 200 cm depending on BMI

29 Advantages Rapid initial weight loss 75% weight loss maintained at 14 years Dumping syndrome Diaphoresis, tachycardia, nausea, weakness Negative reinforcement for carbohydrate intake Disadvantages Cutting and stapling of stomach and bowel is required Technically complex More operative complications Portion of digestive track is bypassed, reducing absorption of essential nutrients Monthly B12 required, iron replacement Failure Rate 10-13% Death Risk = 1-2%

30 Silicone band around top of stomach Small pouch Restrictive only Adjustable FDA approved in 2001

31 Advantage Relatively simple procedure No intestinal bypass Fewer long-term nutritional concerns Low risk of operative complications Reversible Disadvantage New procedure - no long term data on effectiveness Less weight loss Artificial material in body (scarring and reoperation) Frequent followup for adjustments Failure Rate = 15% Death Risk < 1%

32 Removes 75-80% of stomach Leaves a narrow tube ( sleeve ) of stomach (3-4 ounce capacity) Restrictive only Increasingly performed in US Originally part of a double procedure

33 Advantages Rapid initial weight loss 50-66% weight loss at 36 months Removes most of hunger areas of stomach GI Tract maintains function No foreign body Disadvantages Cutting and stapling of stomach, not reversible 1% leaks 3% strictures Slower weight-loss than bypass Stomach can stretch Not covered by most insurances Failure Rate = 13%

34 Mean values from Meta-Analysis of Bariatric Surgery Cases Malabsorptive (BP, DS) Restrictive (Band) Combined (Roux Y) % EBW lost Abnormality Resolved T2DM 98% 48-68% 84% HTN 81% 38-73% 75% Dyslipidemia 100% 71-81% 94% Op Mortality 1.1% 0.1% 0.5% Data from Buchwald H, Avidor Y, Braunwald E, et al. Bariatric surgery: a systematic review and meta-analysis. JAMA 2004;292:

35 Regulates feeding behavior by acting on hypothalamus Stimulates growth hormone release Administration in animal models causes weight gain, and serum levels are increased in fasting and negative energy balance states (anorexia, starvation, weight loss) Suggested to be counter-regulatory hormone that blocks insulin secretion Levels are lower in obese subjects than non-obese subjects Most studies show decrease after gastric bypass (dietary weight loss increases it) likely because most cells are in fundus and vagal transection inhibits their stimulation

36 K cells of duodenum and proximal jejunum produce GIP in response to fat ingestion Defects in GIP are thought to underlie type 2 DM, with decreased receptor expression resulting in decreased GIP effects Gastric bypass patients with type 2 diabetes have decreased GIP (but not those without type 2 DM)

37 Released by endocrine L cells of ileum and colon Acts as ileal break of upper GI system GLP-1 exogenous administration increases satiety, and levels are decreased in obese sujects PYY is mediator of satiety, with lower postprandial levels in obese subjects than lean subjects

38 Mechanisms are unclear Caloric reduction is major factor Most metabolic effects are observed long before substantial weight loss occurs change in regulatory peptides Most popular mechanism implicates change in signaling pathway between gut and pancreas (overactive enteroinsular axis has been implicated in hyperinsulinism and type 2 DM) Bypass decreases ghrelin producing cells and ghrelin levels thus enhancing glucose metabolism Increased GLP-1and PYY may improve satiety and levels seem to be increased by more rapid transit to the hindgut

39 Hormone Cell Type & Location Effect on Insulin Secretion BPD RYGB LAGB Other Actions Ghrelin Stomach No Change GIP GLP-1 PYY K cells, foregut L cells, hindgut L cells, hindgut Unknown Orixigenic, stimulates GH Unknown Anorectic, ileal break Unknown Unknown Unknown Anorectic, ileal break

40 Some Basic Radiography

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42 Peterson s defect: Area between Roux limb mesentery and colon (retrocolic reconstruction) Jejunojejunostomy site Transverse colon mesentery

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48 Younger than 18 Avoidance of operations resulting in permanent anatomic changes Gastric band Gastric sleeve Older than 65 Gastric bypass is discouraged Restrictive procedures are considered better because of lower morbidity/mortality related to the procedures