Anesthesia for Bariatric Surgery

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Anesthesia for Bariatric Surgery
2014-04-13 10:23:29
BC Nurse Anesthesia

Show Answers:

  1. What BMI is considered superobese
    > = 50 kg / m2
  2. Obese lean body weight equals
    120% of lean body weight for their ht
  3. Lean body wt calculation for men
    50+ 2.3 x (ht (in) - 60)
  4. Lean body wt calculation for women
    45.5 + 2.3 x (ht (in) - 60)
  5. As obesity how does fat mass compare to TBW?
    Adipose tissue accounts for an increasing amount of TBW
  6. Dosing based on TBW in an obese pt will result in over or underdosing?
  7. Dosing based on IBW in an obese pt will result in over or underdosing?
  8. How does the central volume compartment change in an obese pt?
  9. How are the pharmacokinetics of most anesthetic drugs altered in an obese pt
    Prolonged effects and less predictable
  10. How does the Vd and elimination half life of lipophilic drugs change in an obese pt?
    • Vd increased
    • Elim half life increased despite increased clearance
  11. How does the Vd of less lipophilic drugs (roc and vec) change in an obese pt?
    Min or no change
  12. What factors affecting Vd and Pd occur in the obese pt?
    • decreased fx TBW
    • increased adipose tissue
    • increased lean body mass
    • altered tissue protein binding
    • increased blood volume and CO
    • increased concentration free fatty acids, cholesterol, and alpha 1 acid glycoprotein
    • organomegaly
  13. How is drug clearance affected in the obese pt? What factors contribute to this?
    • Increased drug clearance due to:
    • increased renal blood flow, GFR, tubular secretion
  14. T or F, waist circ correlates with abd fat and is an ind predictor of disease?
  15. Is android (central) or gynecoid (peripheral) obesity associated with increased incidence of CV disease?
    • Android
    • increased O2 consumption vs. gynecoid fat is less metabolically active
  16. Describe android vs. gynecoid body fat dist
    • Android- fat is central, truncal fat
    • Gynecoid- fat is on hips, but, and thighs
  17. What resp issues are obese pts prone to?
    • OSA
    • PH
    • asthma
    • obesity hypoventilation syndrome
  18. What GI issues are obese pts prone to?
    • GERD
    • Hernias
    • Gallbladder disease
    • Colon cancer
    • Non-alc fatty liver disease
  19. What heme issues are obese pts prone to?
    • Polycythemia
    • Hypercoag
  20. What GU / Reproductive issues are obese pts prone to?
    • ESRD
    • Macrosomia- large BW infant
    • Menorrhagia
    • Pre-eclampsia / eclampsia
    • prostate ca
    • urinary inc
  21. Respiratory effects of obesity
    -resp muscles
    -FRC and ERV
    • increased WOB
    • inefficient resp muscles
    • decreased FRC and ERV
  22. Results of resp issues associated with obesity
    V/Q mismatch esp. in supine position
  23. Why is pulmonary compliance decreased in the obese pt?  How does it affect VC, FRC, and TLC
    • Excess thoracic and abd fat leads to decreased chest wall and lung compliance
    • All are decreased
  24. What is the primary cause of reduced FRC in the obese pt?
    Reduced ERV
  25. What is ERV?
    • Expiratory reserve volume
    • FRC minus RV
  26. Effects of reduced FRC
    • small airway closure
    • V/Q mismatch
    • R to L shunting
    • arterial hypoxemia
  27. How does anesthesia affect FRC in an obese pt vs. a non obese pt?
    FRC reduced up to 50% in an obese pt vs. only 20% in non obese pt
  28. What BMI is considered obese?
    > = to 30 kg / m2
  29. What BMI is considered normal weight
    18.5 - 24.9 kg / m2
  30. What is the most sensitive indicator of the effect of obesity on pulmonary function?
  31. T or F, OSA/ OSH has no effect on chronic inflammation?
    F, cycles of hypoxia and reoxygenation activate the SNS causes elevated levels of pro inflammatory cytokines and oxidative stress of endothelium which increases systemic inflammation
  32. SE r/t OSA
    • HTN
    • Secondary polycythemia (due to hypoxemia)
    • LVH
    • Arrythmias
    • Increased risk cerebral vascular disease
    • PH
  33. What is Pickwickian syndrome?
    • AKA obesity hypoventilation syndrome
    • May result from LT OSA
    • leptin rx may play a role
    • most common in older pts and the super obese
  34. Leptin
    regulates food intake and body weight
  35. SE r/t Obesity hypoventilation syndrome
    • Hypersomnulence
    • Polycythemia
    • Hypoxia and hypercarbia
    • PH
    • RV enlargement and failure
    • Hypervolemia
  36. How are OSA and OHS differentiated?
    OSA complete obstruction, lasts 10 secs or longer, occurs 5x or more / hr

    OHS partial obstruction, lasts 10 secs or longer, occurs 15x or more / hr

    both have a decrease in O2 sat of at least 4%
  37. How are CO and total blood volume affected by obesity?
    • Both increased
    • up to 20-30 ml / kg of excess body fat
  38. What type of ventricular hypertrophy is typically seen in obese pts?
    Eccentric (increased volume)
  39. T or F, an obese pt with a normal BP also has normal CO?
    F, CO is still increased
  40. How are pre-load, after load, PA pressures, and stroke work affected in obesity?
  41. Why do obese pts have hypertrophy, decreased compliance, diastolic dysfunction, and pulmonary edema?
    Increased SV and ventricular dilation causes increased LV wall stress
  42. Why do obese pts have increased total blood volume?
    • Perfusion of excess fat
    • Polycythemia of chronic hypoxia
  43. Is diastolic or systolic HF more common in obese pts?
  44. Are the cardiac changes and associated affect on function that occur with obesity reversible with weight loss?
    Yes many are
  45. How are gastric volume and acidity affected in obesity?  Why?
    • Increased gastric volume, >25 ml
    • increased acidity, <2.5
    • Due to delayed gastric emptying 2/2 increased abd mass which causes astral distention, gastrin release, and decreased pH
  46. How are the clearance of hepatically cleared drugs affected by obesity?
    No change even though liver function is altered
  47. S/sx of non-alcoholic steatohepatitis (fatty liver disease)
    • Elevated LFTs
    • Hepatomegaly
    • Abn liver histology
  48. Glucose tolerance in the obese pt
    • Impaired, leads to DM2
    • Hyperinsulinemia activates SNS leading to Na retention, ins rx, and dyslipidemia
  49. T or F, subclinical hypothyroidism seen in up to 25% of obese pts?
  50. Does metabolic syndrome affect more men or women?
  51. Metabolic syndrome puts pts at risk for?
    • CAD
    • DM2 and atherosclerotic disease
    • all around mortality
  52. Features of metabolic syndrome
    • Abd obesity
    • Hyperinsulinemia
    • Insulin rx
    • HTN
    • Decreased HDL
    • Proinflammatory state
    • Procoag state
    • Endothelial dysfunction
    • Polycystic ovary syndrome
    • Hypoandrogenism
    • Non -alc fatty liver disease
    • Hyperuricemia
  53. What are the clinical criteria for diagnosis of metabolic syndrome?
    • At least 3 of the following:
    • abd obesity (> 102 cm for men and > 80 cm in women)
    • elevated fasting glucose (> 110)
    • HTN (>= 130-85)
    • Low HDL (< 40 for men and <50 in women)
    • High triglycerides (>= 150)
  54. What change in the renal system may lead to increased drug clearance?
    Increased GFR and renal blood flow
  55. What effect does activation of SNS and RAAS and compression of the kidneys have?
    • Increased tubular reabsorption
    • Impaired natriuresis
  56. RNY procedure
    • developed in early 90's
    • combined gastric restriction to limit food intake and some malabsorption of the small intestines
    • minimal complications compared to prior methods
  57. Gastric sleeve
    • reduces stomach size only, by about 2/3's
    • restrictive procedure
  58. Biliopancreatic diversion
    • restriction and malabsorption
    • intestine is bypassed to a greater extent than in RNY
    • greater weight loss but also higher complications
  59. Cons of RNY
    • Malabsorption leading to vit deficiencies (B12)
    • Decreased Calcium abs may lead to osteoporosis
    • Risk anastomotic leaks
    • Dumping syndrome
  60. What is ghrelin?
    • Appetite stimulant
    • Reduced with both RNY and sleeve gastrectomy
  61. Pros of RNY
    • sustained wt loss
    • decreased ghrelin secretion
    • potential reversal of DM, HTN, non-alc fatty liver, OSA, cardiac dysfunction, GERD, arthritis, infertility, stress inc
  62. Early complications of bariatric surgeries
    • Bleeding
    • infection
    • dehydration
    • peritonitis
    • bowel obstruction
    • perforation
    • PNA
    • DVT / PE
    • death!
  63. Late complications of bariatric surgeries
    • cholecystitis or cholelithiasis
    • pouch dilation
    • GERD / dysphagia
    • incisional hernia
    • malnutrition
    • vitamin deficiencies
  64. Contraind to bariatric surgery
    • Chronic alcohol or drug dependence
    • Uncontrolled severe psych illness
    • cardiopulm disease that would prohibit the surgery
  65. T or F, BMI >= 50 and cig smoking are associated with greater rate of complications?
  66. Super obese pts have an associated increased LOS and mortality from bariatric surgery, T or F?
    • F, no increase in mortality
    • There IS an increased LOS and increased risk RF and assisted ventilation
  67. Is OSA assessment by polysomnography required for pts undergoing bariatric surgery?
  68. What criteria are evaluated with the stop bang score?
    • Snoring
    • Tired
    • Observed apnea
    • Pressure (HTN)
    • BMI > 35
    • Age > 50
    • Neck circ > 15.75 "
    • Gender- male
  69. What stop bang score = high risk for OSA?
    >= 3 yes answers
  70. T or F, wt and BMI correlate with difficult intubation?
  71. What pre-op meds are given for pts undergoing bariatric surgery?
    • 5000 U SQ heparin
    • scop patch (if not contraind), want to avoid PONV
    • if anxiolytic is given ensure supplemental O2 and pulse ox are used!!
  72. Prop and succ are dosed on ____?
  73. Induction dose prop, etomidate, fent, and remi are dosed on _____?
  74. Vec, roc, benzos, and barbs are dosed on _____?
    IBW- but not really done in practice...
  75. dexmedetominine MOA
    • alpha 2 agonist
    • sedative, analgesic, sympatholytic, and anxiolytic effects
  76. benefits of using dexmedetominine
    reduces requirement for volatiles, sedatives, and analgesics
  77. SE of dexmedetominine
    bradycardia, hypotension, sinus arrest, transient hypotension
  78. dexmedetominine dosing 
    • 120% of IBW
    • loading dose 1 mcg/ kg over 10-20 mins then 0.2-0.7 mcg/ kg / hr
  79. T or F, pts can wake up low dose dexmedetominine? 
    T, can wake up on 0.2 mcg/ kg/ hr
  80. clonidine MOA
    • alpha 2 agonist
    • reduces anesthetic and analgesia requirements
  81. Optimal position for induction
    • pre-oxygenate with ramp and reverse T-burg
    • Sniff position with a ramp
  82. T or F, the forearm BP is less accurate than the upper arm BP in an obese pt
    F, both accurate
  83. Best volatile to use for bariatric surgery?
    des- faster recovery and higher O2 sat
  84. PEEP of ___ cmH20 has been shown to maintain FRC and improve oxygenation
  85. Position for RNY
    Reverse T-burg
  86. OGT and RNY
    • Insert to decompress stomach
    • Remove BEFORE stomach stapling!!
  87. Is incidence of anastomotic leak increased with the use of Bipap / Cpap post-op?
  88. What monitoring is required post-op on floor?
    pulse ox, ETCO2 sometimes as well
  89. Major issues of post-op care for bariatric surgery pts?
    Underlying OSA complicated by anesthetic agents and need for post-op pain management
  90. NSAIDs and bariatric surgery
    Avoided if intestinal anastomosis
  91. Is it ok to blindly place an OGT in a pt s/p RNY or gastric sleeve?