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N931 Advanced Principles of Anesthesia I > Anesthesia for Obese Population > Flashcards

Anesthesia for Obese Population Flashcards

1
Q

overweight

A

increased body weight above a standard related to height

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2
Q

obesity

A
  • excessive body weight for the patient’s age, gender, and height
  • body weight of 20% or more above ideal weight
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3
Q

US population and obesity

A

-2 of 3 are overweight or obese
-33% obese
ages 2-19 1 of 6 are obese

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4
Q

factors that influence obesity

A
  • behavioral
  • genetic
  • cultural
  • SES what can people afford
  • food deserts
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5
Q

ideal body weight

A

weight associated with max life expectancy for given height and gender

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6
Q

broca’s index

A 
IBW = height cm - x
x = 100 males
x = 105 females
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7
Q

adjusted body weight

A
  • used by dieticians to predict basal energy expenditure
  • obese individuals have some metabolically active adipose tissue
  • AdBW = 0.4 (ABW - IBW) + IBW
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8
Q

lean body mass

A
  • drug calc for obese individuals
  • takes into account lean muscle mass developed from carrying extra adipose tissue
  • 120% of IBW
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9
Q

BMI

A

accepted measure of body habitus that normalizes adiposity for height
BMI = weight in kg/(height in meters)^2

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10
Q

overweight BMI

A

25-29.9

approximate body weight 20% more that IBW

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11
Q

class 1 obesity BMI

A

30-34.9

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12
Q

class 2 obesity BMI

A

35-39.9

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13
Q

class 3 obesity BMI

A

40-49.9

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14
Q

superobese BMI

A

> 50

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15
Q

obesity BMI

A

> 30

associated with increased morbidity r/t stroke, ischemic heart disease, HTN, and DM

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16
Q

android obesity

A
  • abdominal central obesity
  • fat more metabolically active
  • more common in men, higher incidence of metabolic disturbances, increased risk of ischemic heart disease, stroke, DM, death
  • “apple”
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17
Q

gynecoid obesity

A
  • fat around hips/buttocks

- more common in females

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18
Q

waist circumferene and risk of pathophysiology

A
  • 102 cm or 40 in men

- 89 cm or 35 in women

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19
Q

disturbances associated with obesity

A
  • OSA
  • hypoventilation syndrome
  • restrictive lung disease
  • HTN
  • CAD
  • hyperlipidemia
  • delayed gastric emptying/GERD
  • T II DM
  • gall bladder disease (cholelithiasis)
  • cirrhosis/fatty liver disease
  • venous stasis/thromboembolic disease
  • degenerative joint/disc disease
  • increased breast/prostate, cervical, uterine, and colorectal cancer
  • psychological and SES effects
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20
Q

RLD in obesity

A
  • chest wall and lung compliance reduced due to fat accumulation in thorax and abdomen –> breath at LOW lung vol
  • thoracic kyphosis/lumbar lordosis = further restrict
  • reduced lung volumes
  • cc is close to or within normal tidal breathing –> increased demand –> increased WOB –> closure of small airways –> V/Q mismatch –> hypoxemia
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21
Q

other resp alterations in obesity

A
  • increased pulmonary blood volume
  • increased O2 consumption and CO2 production
  • high Ve, increased WOB
  • with progression –> lung disease and pulm HTN
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22
Q

OSA risk factors

A
  • middle age
  • male
  • obesity
  • ETOH use
  • drug induced sleep
  • abdominal fat distribution
  • neck circumference > 40 cm
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23
Q

OSA

A
  • changes in airway dynamics during sleep but physiologic changes that endure beyond
  • repeated episodes of apnea/hypoventilation - oxygen desat, sympathetic arousal, awakening leading to fragmented sleep
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24
Q

OSA causes

A
  • mechanical obstruction of upper airway
  • loss of resp drive
  • BOTH
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25
Q

OSA pathophysiology

A
  • chronic hypoxia, hypercapnia, pulmonary and systemic vasoconstriction (HTN)
  • snoring
  • sleep fragmentation/daytime somnolence
  • impaired concentration/memory problems
  • morning HA
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26
Q

three types of OSA

A
  • OSA
  • central sleep apnea
  • obesity hypoventilation syndrome/pickwickian syndrome
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27
Q

reg OSA

A
  • cessation of airflow but maintain resp effort

- abnormal relaxation of genioglossus and pharyngeal muscles pull tongue forward causing obstruction

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28
Q

central sleep apnea

A
  • cessation of both airflow and resp effort
  • problem in ventilatory center of medulla
  • occurs as resp center exposed to chronic hypercarbia/hypoxia so it doesn’t respond as well
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29
Q

obesity hypoventilation syndrome/pickwickian syndrome

A
  • most severe chronic/long-term OSA leading to cor pulmonale
  • related to morbid obesity
  • extreme obesity with hypercapnia, hypoxia, cyanosis, induced polycythemia, somnolence and eventual RHF, + pulm HTN
  • PCO2 > 45 mmHg in an obese patient without significant COPD is diagnostic
  • clinically distinct from OSA –> has nocturnal central apneic events
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30
Q

polysomnography

A
  • used for OSA diagnosis
  • EEG, REM, EKG, SpO2, airflow, thoraco-abdominal excursion
  • apnea hypopnea index (# per hour measured)
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31
Q

apnea

A

> 10 seconds total cessation of airflow despite resp effort against closed glottis

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32
Q

hypopnea

A
  • 50% reduction in size or number of breaths that lasts at least 10 seconds compared to normal
  • reduction sufficient enough to cause a 4% or > decrease in arterial SaO2
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33
Q

severe OSA

A

apnea-hypopnea index >30

34
Q

moderate OSA

A

apnea-hypopnea index 16-30

35
Q

mild OSA

A

apnea-hypopnea index <15

36
Q

OSA treatment

A
  • Nasal CPAP
  • attenuates hemodynamic responses induced by apnea including BP surge and increased SNS activity
  • level of + pressure determined in sleep lap
  • improves neuropsychiatric functioning
  • less daytime somnolence
  • drugs not reliably effective in severe cases
  • noctural oxygen for those with severe arterial oxygen desaturation
37
Q

corrective procedures for OSA

A
  • uvulopalatopharyngoplasty (UPPP) - enlarges airway by removing tonsils, part of soft palate and uvula
  • diatherpy palatoplasty - heat tissue producing scar which tightens in 6-8 weeks
38
Q

pathophysiologic effects of OSA

A
  • hypoxemia
  • R heart failure
  • hypercapnia
  • pulmonary + systemic vasoconstriction
  • polycythemia
  • resp acidosis during sleep
  • arterial hypoxemia
  • systemic HTN
  • pulm HTN
  • cor pulmonale
39
Q

characteristics of OHS or pickwickian syndrome

A
  • obesity BMI > 30
  • hypercapnia PaCO2 > 45 mmHg in obese patient without significant COPD is diagnostic
  • chronic daytime hypoxemia
  • daytime hyper-somnolence
  • pulmonary HTN
  • resp acidosis
  • RHF
  • airway difficulty (actual structural changes)
40
Q

airway changes in obese individual

A
  • TMJ + alanto-axial joint and cervial spine movement limited by upper thoracic and low cervical fat pads
  • redundant tissue folds in mouth + pharynx = narrowed airway
  • short, thick neck
  • fat in suprasternal, presternal, posterior cervical and submental regions
  • shortened distance between mandible and sternal fat pads
  • OSA = increased risk excess pharyngeal tissue on lateral walls
  • difficulty maintaining mask airway
  • difficult laryngoscopy + intubation
41
Q

CV alterations in obesity

A
  • increased total blood volume
  • increased CO
  • increased RAAS + SNS activity –> HTN (RAAS activated by fat in flank area –> increased pressure on renal artery)
  • risk CAD doubled presents with angina, CHF, acute MI, and sudden death
  • increased L sided pressure and LV hypertrophy
  • ECG changes (d/t LV hypertrophy); can also have ischemia and conduction defects
  • increased LV wall stress = hypertrophy, decreased compliance, impaired filling (i.e., diastolic dysfunction), pulmonary edema
  • eventually systolic dysfunction (or obesity cardiomyopathy)
  • eventual biventricular failure
42
Q

heme alterations in obesity

A
  • polycythemia + hypercoagulation
  • increased risk of thrombotic events
  • DVT risk doubles
  • polycythemia leads to increased blood viscosity, so increased fibrinogen, factor VII, factor VIII, vWf, plasminogen
  • increased intra-abdominal pressure
  • immobility –> venous stasis
43
Q

GI alterations in obesity

A
  • increased incidence –> hiatal hernia, GERD, gallbladder disease
  • risk for asp pneumonitis –> obesity itself does not increase it but they have a higher chance of having more risk factors for aspiration
44
Q

hepatic alterations in obesity

A
  • fatty infiltration of liver - NAFLD, inflammation, cirrhosis
  • abnormal LFTs (weight loss of 5 lbs can reverse this)
45
Q

renal alterations in obesity

A
  • increased renal plasma flow and GFR
  • increased renal tubular resorption and impaired naturesis secondary to SNS + RAAS activation
  • eventually nephron fxn lost
46
Q

endocrine alterations in obesity

A
  • secrete more insulin, but resistant to effects of insulin –> develop T2DM
  • metabolic syndrome (at least 3 symptoms)
47
Q

what are the symptoms of metabolic syndrome?

A
  • large waist circumference (central obesity)
  • high triglycerides
  • low HDLs
  • glucose intolerance
  • HTN
48
Q

MSK alterations in obesity

A
  • osteoarthritis and degenerative joint disease
  • mechanical loading of weight-bearing joints
  • inflammatory response
  • back pain
  • stress fractures (bone dimineralization)
49
Q

CNS alterations in obesity

A
  • ANS dysfunction (resp centers impacted + SNS activation)
  • peripheral neuropathies
  • stroke
  • idiopathic intracranial hypertension
50
Q

hyperlipidemia

A
  • associated with obesity

- increased LDL and decreased HDL cholesterol linked to atherosclerosis

51
Q

what can hyperlipidemia lead to?

A
  • premature CAD
  • premature vascular disease
  • pancreatitis
52
Q

pharmacokinetic alterations in obese patient

A
  • increased blood volume and CO
  • decreased total body water
  • adipose and lean tissue increase
  • variable alterations in protein binding
  • organomegaly
53
Q

clearance alterations in obese patient

A
  • hepatic clearance unchanged despite histological and LFT alterations
  • renal clearance of drugs increased due to increased GFR, RBF, and tubular secretion
  • lipophilic drugs have an increased elimination half-life because of increased Vd but have normal clearance
54
Q

dosing drugs for obese

A

weak or moderate lipophilicity dose on IBW or LBM

55
Q

propofol for obese

A

induction on LBW; maintenance on TBW

56
Q

benzos for obese

A
  • highly lipophilic
  • initial doses on LBW, may titrate to TBW to reach adequate serum concentration
  • infusion on LBW
57
Q

NMBDs for obese

A
  • increased pseudocholinesterase activity (linear relationship with weight + ECF); succ dose on TBW
  • vec + roc on IBW
  • Cis on TBW
  • general trend = prolonged DOA and recovery
58
Q

fentanyl + sufentanil for obese

A
  • both highly lipid soluble
  • increased Vd and e1/2 life
  • dose on TBW but then decrease maintenance to IBW + response
59
Q

remifentanil for obese

A

IBW because PK similar in obese and non-obese individuals

60
Q

dexmedetomidine for obese

A
  • nice adjunct to avoid resp depression
  • 0.2-0.5 mcg/kg/min to reduce analgesic and anesthetic requirements
  • dose on TBW
61
Q

sugammadex for obese

A

-miller = IBW
-nagel = TBW
UNKNOWN LOL

62
Q

volatile anesthetics for obese

A

-N2O avoided to maximize PaO2

63
Q

appetite suppressant

A
  • used to treat obesity
  • adrenergic reuptake inhibitors
  • decrease appetite and increase metabolic rate
  • SE = HTN, tachycardia, abuse, N/V/D
  • 5-HT2C receptor agonist Lorcaserin is selective
  • reduces food intake through activation of pro-opiomelanocortin
64
Q

lipase inhibitor orlistat

A
  • acts by blocking absorption and digestion of dietary fat and binding lipases in GI tract
  • significant GI effects and interferes with fat soluble vitamins
65
Q

obesity pre-op eval

A
  • assess pt in non-judgmental fashion
  • emphasis on difficulties obesity presents to anesthesia
  • discuss likely post-op course
66
Q

S/S pulm HTN

A
  • dyspnea
  • fatigue
  • syncope
  • triscupid regurg
  • ECG = RVH, tall precordial R waves, R axis deviation
  • prominent pulm artery on CXR
67
Q

preop considerations for obese patient

A
  • morbid obesity = independent risk factor for sudden death from acute PE
  • thromboprophylaxis = IMPORTANT; heparin, pneumatic compression stockings, LMWH
68
Q

airway pre-op for obese

A
  • history of difficult airway
  • OSA
  • assess ROM
  • mouth opening
  • thyromental distance
  • interior of mouht
  • mallampati
  • neck size
69
Q

what is the single best predictor of problematic intubation?

A
  • neck circumference
  • 5% with neck circ of 40 cm
  • 35% with neck circ of 60 cm
70
Q

resp pre-op assessment obese

A
  • identify symptoms of severe resp disease
  • orthopnea
  • OSA
  • OHS
  • previous hx of upper airway obstruction (esp if had a past anesthetic)
71
Q

STOP BANG

A
  • S = snoring
  • T = tired (daytime sleepiness)
  • O = observed apneic
  • P = pressure (HTN)
  • B = BMI (greater than 30)
  • A = age older than 55
  • N = neck circumference greater than 40 cm
  • G = gender (male)
72
Q

potential resp pre-op tests for obese

A
  • CXR
  • room air SpO2
  • ABGs
  • optimize pulm status
  • PFTs
73
Q

CV assessment/tests pre-op for obese

A
  • identify signs of HTN, RV/LV hypertrophy, pulm HTN
  • assess venous access
  • EKG
  • CXR
  • ECHO
  • LV EF
  • Cardiac clearance
  • previous diet aids
74
Q

endo, metabolic, + GI pre-op for obese

A
  • fasting BG
  • diabetics non-insulin or insulin dependent
  • does patient have GERD?
75
Q

aspiration prophylaxis for obese

A
  • high risk

- treatment options = H2 antagonists, sodium citrate, metoclopramide, omeprazole

76
Q

induction

A
  • optimize the patient position
  • use neck roll
  • elevate HOB
  • ramp up!! (gravity baby!!)
77
Q

general anesthesia tips for obese

A
  • higher dose of succ
  • des, sevo, iso useful
  • avoid nitrous due to oxygen demands
  • short acting opioids to minimize resp depression
  • dex use bc no adverse resp effects
  • profound muscle relaxation needed for laparoscopic so use vec, roc, or cis
78
Q

mechanical vent of obese

A
  • PEEP to improve FRC and oxygenation
  • recruitment maneuvers
  • pressure controlled ventilation may help
  • changing I:E ratio
79
Q

fluid management of obese

A
  • calc of fluid requirement in obese based on LBW or IBW

- greater blood loss compared to non-obese r/t technical difficulties/extensive surgical dissection

80
Q

emergence of obese

A
  • resp failure = #1 problem
  • awake extubation (NMB fully reversed)
  • semi upright position (>30 degrees HOB)
  • wean on PS ventilation with PEEP
  • 100% O2 (controversial)
  • place NPA or OPA
81
Q

vent support post-op for obese

A
  • CPAP or BiPAP
  • mechanical ventilation
  • resp monitoring
82
Q

post-op analgesia for obese

A
  • multimodal approach because worried about opioid induced vent depression
  • nerve blocks with continuous infusion of LA
  • local infiltration of wound
  • opioids based on IBW if used

N931 Advanced Principles of Anesthesia I (19 decks)

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