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growing epidemic of obesity
§Estimated 65% of Americans are classified as overweight or obese.
- §Predisposes over 100 million Americans to multiple chronic diseases and serious medical
§Most rapidly growing segments of obese population are severely obese and superobese.
§Individuals with a BMI > 30, 40 and 50 kg/m2 doubled, quadrupled, and quintupled (respectively) 1986-2000.
§Whitewomen 20-30 years of age with a BMI > 45 will lose 8 years of life and males will lose 13 years.
§Bariatric operations in the U.S. rose from 12,775 in 1998 to over 150,000 in 2013.
§Weight in kilograms divided by square of height in meters (kg/m2)
classifications of obesity
§Normal weight 18.5-24.9 kg/m2
§Overweight 25-29.9 kg/m2
§Grade 1 30-34.9 kg/m2
§Grade 2 35-39.9 kg/m2
§Grade 3 40-49.9 kg/m2 (severe, extreme, morbid)
§Grade 4 > 50kg/m2 (superobese)
§Grade 5 > 60 kg/m2
§Ideal Body Weight (IBW)
§Height (cm) – x =IBW (kg)
§x =100 for males; 105 for females
Lean Body Weight (LBW
§Total Body Weight (TBW) – adipose tissue.
- Men = 50 + 2.3 x (height [in.] - 60)
Women = 45.5 + 2.3 x (height [in.] - 60)
§Obese: approximately 120% IBW.
Do Fat mass and LBW increase proportionately?
§Fat mass and LBW do NOT increase proportionately.
How do we need to adjust drug dosing for obese patients?
§As obesity increases, fat mass accounts for an increasing amount of TBW à LBW/TBW ratio decreases.
§Drug dosing based on TBW may result in overdose.
- §IBW is less than actual body weight à drug
- dosing based on IBW may result in under dosing.
§LBW is ideal weight scalar when dosing most medications in morbidly obese patients.
Adipose Tissue and Pharmicokinetics
§Most general anesthetic drugs are affected.
§Effects are prolonged and less predictable.
§Central compartment volume largely unchanged.
§Volume of distribution increased.
§Elimination half-life of lipophilic and polar drugs increased, despite increased clearance.
§Less fat-soluble drugs (some neuromuscular blockers) show little or no change in volume of distribution.
what Factors Affect Pharmacokinetics?
§Volume of distribution (seven things)
§Decreased fraction of total body water.
§Increased adipose tissue.
§Increased lean body mass.
§Altered tissue protein binding.
§Increased blood volume and cardiac output.
§Increased concentration free fatty acids, cholesterol, α1 acid glycoprotein.
How does Plasma protein binding change?
§Adsorption of lipophilic drugs to lipoproteins à increased free drug available.
§Plasma albumin unchanged.
§Increased α1-acid glycoprotein.
How is drug clearance affected?
§Increased renal blood flow.
§ Increased tubular secretion.
§ Decreased hepatic blood flow in congestive cardiac failure
What is the significance of body circumference?
§Waist circumference, waist-to-height ratio, and waist-to-hip ratio correlate with mortality and the risk for developing obesity-related diseases.
§Waist circumference correlates with abdominal fat.
§Independent risk predictor of disease.
§Android Obesity (central obesity)
§Truncal distribution of adipose tissue.
§Increased oxygen consumption
§Increased incidence of cardiovascular disease
§In particular, visceral fat associated with LV dysfunction.
§Gynecoid Obesity (peripheral obesity)
§Adipose distribution on hips, buttocks, thighs.
§Less metabolically active
What respiratory diseases are common in obese patients?
§Obstructive Sleep Apnea
§Obesity Hypoventilation Syndrome
what cardiac diseases are common in obese patients?
§Sudden Cardiac Death
Gastrointestinal diseases of obese patients?
- §Non-alcoholic Steatohepatitis/Non-alcoholic
- Fatty liver disease
what metabolic/endocrine diseases are common?
§Type 2 Diabetes
what hemotologic diseases are common?
what Genitourinary/Reproductive diseases are common?
§End-stage Renal Disease
§Preeclampsia and Eclampsia
what Neurologic issues are common?
§Pseudotumor Cerebri- symptoms are like brain tumor, pressure on occular nerve. Can have vision loss. Usually women of reproductive age
§Carpal Tunnel Syndrome
what Musculoskeletal problems are common?
How do obese patients end up with v/q mismatch?
§Increased demand for ventilation and breathing workload.
§Respiratory muscle inefficiency.
§Decreased FRC and ERV.
How does obesity result in a restrictive disease?
§Excess thoracic and abdominal fat decrease chest wall and lung compliance.
§Decreased total respiratory compliance in supine position due to:
§Increased elastic resistance.
§Decreased compliance of chest wall.
§Decreased pulmonary compliance leads to decreased FRC, VC and TLC.
What is a primary cause of decreased FRC?
§Reduced ERV is primary cause of decreased FRC.
What are the most common abnormalities in pulmonary function?
§Decreased ERV and FRC are most common abnormalities in pulmonary function.
What problems may reduced FRC lead to?
§Reduced FRC may lead to small airway closure, VQ mismatch, right-to-left shunting and ultimately, arterial hypoxemia.
§Anesthesia reduces FRC up to 50% in obese patients compared with 20% of non-obese.
What is the most sensitive indicator of the effect of obesity on pulmonary function?
§ERV is most sensitive indicator of the effect of obesity on pulmonary function.
§Increased workload on supportive tissues as well as metabolic activities increase oxygen consumption and CO2 production.
§Chronic hypoxemia may lead to pulmonary hypertension and cor pulmonale.
§complete cessation of airflow during breathing lasting 10 seconds or longer despite maintenance of ventilatory effort, occurring 5 or more times per hour of sleep, accompanied by a decrease of at least 4% in SaO2.
§– partial reduction of airflow of greater than 50% lasting at least 10 seconds, occurring 15 or more times per hour of sleep, accompanied by a decrease of at least 4% in SaO2.
How are OSA and OSH diagnosed?
Diagnosed by polysomnography with monitoring of: EEG, ECG, EOG, ETCO2, SaO2, blood pressure, nasal or oral airflow, esophageal pressure and electromyelogram
OSAHS- what is the greatest risk factor?
§Obesity is greatest risk factor
§Increased amount of oral and pharyngeal adipose tissue (uvula, tonsils, tonsillar pillars, tongue, aryepiglottic folds and lateral pharyngeal walls).
§70% of patients with OSAHS are obese.
§Up to 80% of males and 50% of females.
How does OSAHS play an important role in systemic inflammation?
§Plays an important role in systemic inflammation
- §Cyclic episodes of hypoxia and reoxygenation
- activate the SNS à elevated levels of pro inflammatory cytokines and oxidative stress of vascular endothelium à increases systemic inflammation.
What are the complications of OSA
- Alters control of breathing which causes
- CNS-mediated apneic episodes, leading to hypoxia driven ventilation (in most severe form).
§Pulmonary hypertension (less common)
§Secondary polycythemia (due to hypoxemia)
§Left ventricular hypertrophy
Increased risk for cerebral vascular disease
Obesity Hypoventilation Syndrome
(a.k.a. Pickwickian Syndrome)
§May result from long-term OSA.
§Recent studies suggest leptin resistance may play a role.
§Alveolar hypoventilation independent of intrinsic lung disease.
§Most common in older patients and the super obese.
what are the signs and symptoms of Obesity Hypoventilation Syndrome
§Hypoxemia and hypercarbia
§RV enlargement à failure
CO in the obese patient
§Cardiac output increases as weight increases (up to 20-30 ml/kg of excess body fat) à increased total blood volume.
HTN in obese patients
§Mild to moderate hypertension is seen in majority of obese patients.
§Causes eccentric ventricular hypertrophy.
§Left ventricular wall thickening and increased heart volume may lead to cardiac failure.
- Increased pre-load, after-load, PA pressures and elevated LV and RV stroke work are present in normotensive
Changes in stroke volume and ventricular dilation
- §Increased stroke volume and ventricular dilation lead to increased left ventricular wall
- §The result: hypertrophy, decreased compliance, and diastolic dysfunction with
- elevated left ventricular and diastolic pressures and pulmonary edema.
- §If rate of left ventricle dilation exceeds rate of thickening, cardiomyopathy, and
- potentially biventricular failure occur.
How does blood volume change?
§Increased total blood volume
§Due to perfusion of excess fat.
§Result of polycythemia of chronic hypoxemia.
§Altered LV structure and function lead to heart failure.
- §May be present in Grades 1 and 2 obesity, but most pronounced in the severely
Obesity Cardiomyopathy risk and S&S. What type of heart failure is it usually?
§Diastolic heart failure is most common, but some exhibit systolic and diastolic dysfunction.
§Risk of heart failure rises steeply after 10 years of severe obesity.
§Signs and symptoms most commonly occur in patients with a BMI > 40 or body size > 75% IBW.
- Many of the manifestations and cardiac structure and function are reversible with
- substantial weight loss
GI system changes in obesity
Increased gastric volume and acidity
§Many have volume >25 ml and pH <2.5.
§Delayed gastric emptying due to increased abdominal mass causing antral distention, gastrin release, and decreased pH.
§Altered hepatic function
§Increased incidence of hiatal hernia and GERD
§A greater than 3.5 kg/m2 increase in BMI is associated with a 2.7-fold increase in risk for developing reflux symptoms.
Changes in the liver
§Non-alcoholic Steatohepatitis/Non-alcoholic Fatty Liver Disease
§Obesity is a major risk factor.
§Very common among obese patients.
§Features: elevated liver enzymes, hepatomegaly, abnormal liver histology.
What % of obese patients have impaired glucose tolerance?
Describe the endocrine changes of obesity
§Impaired glucose tolerance leading to type 2 diabetes.
§Occurs in greater than 10% of obese patients.
§Predisposed to impaired wound healing and infection.
§Hyperinsulinemia activates SNS.
§Increased SNS activity leads to sodium retention, hypertension, insulin resistance and dyslipidemia.
§Subclinical hypothyroidism in approximately 25% of patients.
§Elevated levels of TSH.
§May be associated with hypoglycemia, hyponatremia, and impaired hepatic drug metabolism.
what does metabolic syndrome increase the risk for
§Type 2 diabetes leading to atherosclerotic disease
what are the Features of Metabolic Syndrome?
§Decreased high-density lipoprotein (HDL)
§Insulin resistance with or without glucose intolerance
§Polycystic ovary syndrome
§Nonalcoholic fatty liver disease
Clinical Criteria for Metabolic Syndrome
(require at least three)
Waist circumference >102 cm in men and >80 cm in women
§Elevated Fasting Glucose >110mg/dl
§Low HDL levels
<40 mg/dl in men and <50 mg/dl in women
Renal System changes
§Increased renal blood flow.
§May have increased clearance of drugs.
§Activation of sympathetic and renin-angiotensin systems and compression of kidneys lead to increased renal tubular resorption and impaired natriuresis.
Hematologic System changes
- §A large number of bioactive mediators are released by adipose tissue resulting in
- abnormal lipids, insulin resistance, inflammation, and coagulopathies.
§Increased levels of fibrinogen, factors VII and VIII, von Willebrand factor, and plasminogen activator inhibitor-1.
§Increased triglycerides leads to increased factor VII.
§Lipemia activates factor VII.
Hyperinsulinemia induces endothelial dysfunction leads to increases factor VIII levels and Von Willebrand factor leads to fibrin formation
Open intestinal bypass
- § Weight loss purely by malabsorption of
§ Bypassed all but 12-14 inches of small bowel (approximately 29 feet), the stomach left unchanged.
why was open intestinal bypass abandoned?
- Open intestinal bypass abandoned.
§Serious nutritional problems.
Vertical Banded Gastroplasty (VBG)
- §1970’s: Vertical Banded Gastroplasty
- (VBG) introduced by Dr Ed Mason in Iowa.
§Weight loss by restricting the intake of food in the stomach, with small bowel left unchanged.
- §Stomach was reduced from approximately two quarts to one ounce using a surgical
- stapler. The gastric outlet reduced to ½ inch (one cc) with a plastic band to
- keep it from stretching.
§The small pouch and rigid outlet resulted in vomiting and acid reflux.
§Average weight loss approximately half the patients’ excess weight.
§Long term, 50% of patients had revisions, conversions or reversals due to complications or weight loss failure.
Roux en Y Gastric Bypass (RNY)
§Early 90’s: Roux en Y Gastric Bypass (RNY) developed by Dr.’s Wittgrove and Clark
- §Combined gastric restriction to limit food intake with some limited malabsorption of
- food in the small bowel.
§Stomach reduced to a one-ounce pouch with a narrow opening, without utilizing band for permanent restriction of the outlet, and the distal stomach and proximal small bowel were bypassed for approximately 5 feet.
§Sustained and greater weight loss compared to the VBG.
§Ultimately became the most popular weight loss surgery in the U.S.
§Averaged 75% excess weight loss.
§90% success rate after 5 years in most studies.
§NIH set the standard to qualify for surgery:
what are they?
§ 100 pounds over IBW, or
§ BMI of 40 without health issues, or
§ BMI between 35- 39 with associated medical problems.
§ Endorsement by the NIH and establishment of clear standards convinced a number of physicians to begin recommending weight loss surgery to their patients.
§1990’s: Duodenal switch introduced by a small number of surgeons (< 5%) in the U.S.
- §Combined gastric and intestinal bypass procedures with both a reduction in stomach
- volume and a radical bypass of the small bowel, bypassing all but 3-5 feet of
- the 30 foot intestine.
- §Used more often in super obese patients with a BMI greater than 60, often weighing
- 600-800 pounds.
§Never widely accepted by patients or surgeons due to its significant risk of malnutrition and frequent watery diarrhea.
where did the Gastric sleeve procedure come from?
§Gastric sleeve procedure came out of the duodenal switch operation by accident.
§A group of surgeons began breaking the Duodenal Switch procedure into two separate operations performed 6 months apart in order to reduce operating time and associated risks.
- §The stomach size was first reduced by performing the gastric sleeve procedure
- resulting in about a 100-pound weight loss in 6 months.
- §The second operation would bypass the small bowel and reattach the gastric sleeve
- to the distal small bowel to form the completed duodenal switch.
What was an issue with the gastric sleeve? What BMI qualifies?
- §Some patients refused to undergo the second stage of the operation because
- they were satisfied with their initial weight loss from the gastric sleeve
§Surgeons began using the gastric sleeve in patients with a BMI of 40-50.
§Now recognized by several surgical societies as acceptable as a stand alone weight loss operation.
Roux-en-Y Gastric Bypass- how is it done?
§Routes food past most of the stomach and first part of the small intestine. This both restricts food intake and decreases absorption of nutrients.
§Using a surgical stapler, a small stomach pouch is created.
§Small bowel is divided approximately two feet from the stomach.
§Gastrojejunostomy is created, followed by a jejunojejunostomy.
How is a Sleeve Gastrectomy done?
§Restrictive procedure removing approximately 2/3 of the stomach, providing faster satiety and decreased appetite.
- §Small sleeve created with a surgical stapler along inside curve of the stomach, from
- the pylorus to the esophagus, and the remainder of the stomach removed.
§The pyloric valve remains, allowing for the feeling of fullness.
Adjustable Gastric Banding
- §A small pouch is created by placing an adjustable band at the top of the stomach
- to reduce it’s size.
- §A small epidermal port allows for adjustment of the band to make the pouch
- smaller or larger.
§Restrictive: Approximately 70% of the stomach is removed which produces both restriction of food intake and reduction of acid output.
- §Malabsorption: achieved by bypassing both the duodenum and jejunum of the small intestine and taking food from the stomach directly to the distal part of the digestive
§This bypass reduces the length of functioning small intestine (where most nutritional uptake occurs) so that a significant amount of fat and other macronutrients pass through, undigested.
§Greater weight loss and higher complication rate than other procedures.
Pros of Roux-en-Y Gastric Bypass
Sustained and greater weight loss with dietary compliance.
- Potential reversal of diabetes,
- hypertension, dyslipidemias,
- nonalcoholic steatohepatitis,
- sleep apnea and obesity-hypoventilation syndrome, cardiac dysfunction, reflux esophagitis, pseudotumor cerebri,
- arthritis, infertility, stress incontinence, and venous stasis ulcers.
Decreases secretion of ghrelin.
Cons of Roux-en-Y Gastric Bypass
Malabsorption leading to nutritional deficiencies and anemia (secondary to malabsorption of vitamin B12
Decreased absorption of calcium may lead to osteoporosis and metabolic bone disease.
Sleeve Gastrectomy pros
- Decreases size of stomach and decreases
- secretion of ghrelin.
No malabsorption so no vitamin or mineral deficiencies.
No anastomoses or rerouting of intestinal tract.
Cons Sleeve Gastrectomy
Potentially slower weight loss than RNY
Potential for gastric leaks at staple sites
Limited long-term clinical data.
Adjustable Gastric Band pros
No resection of stomach.
No vitamin or mineral deficiency.
No anastomoses or rerouting of intestinal tract.
No protein-calorie malabsortption.
Adjustable Gastric Band cons
Less weight loss
Routine follow-up adjustments required
- Mechanical failure due to port or tubing
Slippage or band erosion.
Biliopancreatic Diversion pros
- Greatest weight loss of all bariatric
Biliopancreatic Diversion cons
- More technically difficult to perform laparoscopically.
- Higher rate of complications.
Benefits of Gastric Bypass Surgery
§Study published in (JAMA) in 2004 showed improvements in the following conditions:
§Remission of type 2 diabetes in 76.8% and significantly improved in 86% of patients.
§Elimination of hypertension in 61.7% and significantly improved in 78.5% of patients.
§Sleep apnea was eliminated in 85.7% of patients.
§Joint disease, asthma and infertility dramatically improved or resolved.
§Patients lost between 62 and 75 percent of excess weight.
Early Complications of gastric bypass surgery
Late Complications of gastric bypass surgery
- and/or cholecystitis
Contraindications to Bariatric Surgery
§Persistent alcohol and drug dependence.
§Uncontrolled severe psychiatric illness.
Cardiopulmonary disease that would make surgical risk prohibitive
preop eval for gastric bypass
§Severe obesity is not associated with increased mortality but with increased length of hospital stay and greater risk of renal failure and prolonged assisted ventilation.
§BMI > 50kg/m2 and cigarette smoking associated with higher rate of surgical complications.
§Age greater than 65 associated with increased mortality.
Cardiac eval for gastrc bypass
§12-lead ECG in all patients with at least 1 risk factor for cardiac disease, poor exercise tolerance, or both.
- §Signs of right ventricular hypertrophy (including right-axis deviation and RBBB)
- suggest pulmonary hypertension.
§Physical exam and ECG often underestimate presence and degree of cardiac pathology and dysfunction in obese patients.
§Adipose tissue may obscure JVD.
§Heart sounds often distant.
What are we looking for in the cardiac eval?
§Evaluation for presence of:
§Pulmonary hypertension (fatigue, exertional dyspnea, syncope).
§Ischemic heart disease.
§Signs of LV failure.
Signs of RV failure
respiratory eval for gastric bypass
§Obstructive Sleep Apnea
§Hypertension or neck circumference > 40cm may indicate OSA.
§Literature suggests OSA is under-diagnosed in bariatric surgical patients.
§Mandatory polysomnography has been proposed but not currently part of practice guidelines.
§Unclear if PSG would improve outcomes.
what are the benefits of cpap for obese patients?
§CPAP reduces or reverses severe cardiovascular structural changes induced by severe OSA.§Fewer perioperative complications.Patients on home CPAP should bring machine to hospital
STOP BANG SCORE
- 1. SNORE
- 2. TIRED, fatigued, or sleepy during daytime
- 3. OBSERVED apnea
- 4. PRESSURE (HTN)
- 5. BMI more than 35
- 6. AGE over 50 years old
- 7. NECK circumference > 15.75 inches
- 8. GENDER (Male)
- ≥3 yes answers: High-risk for OSA
- <3 yes answers: Low-risk for OSA
Airway assessment of obese patients
- §Large neck circumference and high Mallampati score predictive of potential intubation
§Other factors contributing to difficult intubation:
§Excess tissue folds in mouth and pharynx.
§Limited neck mobility due to excess fat pads.
§Excess posterior cervical, suprasternal and presternal fat.
§Potential difficult mask ventilation.
Weight and BMI do not correlate with difficult intubation
Preoperative Medications for gastric bypass
§Heparin 5,000U SQ.
§Consider scopolamine patch, if not contraindicated.
§If administering anxiolytic, give supplemental oxygen and monitor pulse oximetry.
§Do NOT over-sedate; may compromise respiratory function.
meds Base on TBW
§Base on TBW:
§Propofol (maintenance dose)
Meds Base on LBW
§Base on LBW:
§Propofol (induction dose)
Meds Base on IBW
§Base on IBW
§Sedative analgesic, sympatholytic and anxiolytic effects.
- §Reduces requirement for volatile anesthetics, sedatives and analgesics without causing
- significant respiratory depression.
- §Side effects: hypotension, bradycardia,
- sinus arrest and transient hypertension.
§Dose approximately 120% of IBW.
§Loading dose – 1 mcg/kg over 10-20 minutes then, 0.2-0.7mcg/kg/hr.
§Preoperative oral clonidine reduces anesthetic and opioid requirements.
Advanced airway devices available (Glide scope, intubating LMA, fiberoptic equipment).
§Reverse Trendelenberg (30-45 degrees).
§May need “Troop Pillow” or ramp for optimal laryngoscopy.
§Pad and protect pressure areas.
§Carpal tunnel syndrome, brachial plexus and lower extremity nerve injuries common.
§Adequate pre oxygenation a must!
§Consider CPAP 10 cm H2O during preoxygenation.
- §If using dexmedatomidine, may
- begin bolus after monitors applied.
- §Study found no difference in measurement b/w upper arm and forearm for placement of
- BP cuff.
Maintenance for gastric bypass
§May use TIVA with proposal and remifentanil.
§If using Precedex; 0.5-0.7 mcg/kg/hr and decrease to 0.2 mcg/kg/hr prior to end of procedure.
- §Randomized trials show immediate and intermediate recoveries are more rapid and consistent
- and have higher oxygen saturation post-operatively.
§PEEP 15cm H2O has been shown to maintain FRC and improve oxygenation.
§Maintain euvolemia and normothermia.
§May require small doses of narcotic.
procedure specific requirements for gastric bypass Roux-en-Y
- §Place OGT after induction to decompress stomach, and remove prior to stapling for
- gastric pouch.
§Leak test to check integrity of anastomosis.
§Place OGT, clamp vent, insufflate with 2L oxygen.
Sleeve gastrectomy procedure specific requirements
- §Place OGT after induction to decompress stomach and remove prior to creation of
Place bougie (size determined by surgeon) and manipulate position at surgeon’s direction for the sizing and stapling of the stomach
Emergence from gastric bypass surgery
Reverse trendelenberg position.
§CPAP during spontaneous ventilation may increase vital capacity and oxygenation.
§Fully awake prior to extubation.
- §Consider titrating small doses of dilaudid or
- morphine (use sparingly) if respiratory effort and LOC adequate.
§Discontinue Precedex after extubation.
§Supplemental O2 and HOB elevated for transport.
Post-operative Care for gastric bypass
§Primary issue is underlying sleep apnea complicated by anesthetic agents and need for postoperative pain management.
§Early use of CPAP or BiPAP may reduce atelectasis and prevent hypoxemia.
§Incidence of anastomotic leak is not increased.
§PACU for 3 hours.
- §Continuous pulse oximetry until d/c from
post op pain control and issues with gastric bypass
§Pain control typically managed with PCA, without continuous infusion.
§If open procedure, opioid-free epidural for patients with OSA.
§No NSAIDS for 24 hours if intestinal anastamosis.
Removing excess skin
Lot of fluid shifts and blood loss
Sterile underbody bairhugger
obesity Closed Claims
§Obesity as a factor:
§28% had OSA.
§48% of adverse respiratory events secondary to opioid administration occurred in obese patients.
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