Lecture 7 - The Obese Patient

Lean Body Weight (LBW)

TBW - adispose tissue

80%, 75%

LBW is about ___ of TBW in males and ___ of TBW in females

true

t/f - TBW = IBW in nonobese and muscular patients

LBW

in morbidly obese, decreasing TBW by about 20-30% is an estimate of ___

22 * height squared (m)

IBW in kg

height (cm) - 100

IBW in males

height (cm) - 105

IBW in females

TLC, FRC, VC, ERV

Obesity can cause what lung capacities to decrease

increased

How does obesity affect:

- work of breathing, oxygen consumption and CO2 production

reduced

how does obesity affect:

- chest wall and lung compliance

decreased

how does obesity affect:

FRC, MVV, ERV

ERV

what is the most sensitive indicator of effect of obesity on pulmonary function

decrease

FEV1 and FRC both ___ but ratio is unchanged

26

ERV decreases ___ ml for each kg of weight gained

false (remains normal)

t/f - obesity decreases RV

FRC

there is a 50% reduction in ___ in obese with anesthesia compared to 20% reduction in nonobese

PEEP

Only ventilatory parameter that is shown to improve respiratory function, but may decrease venous return and CO

hypoxemia

chronic ___ can cause polycythemia, pulmonary hypertension and cor pulmonale

Snoring, Tired, Observed apnea, Pressure (HTN), BMI > 35, Age > 50, Neck circumference, Gender

STOP BANG

three

a high risk of OSA is answering yes to __ or more of the STOP BANG questions

Apnea-hypopnea index (AHI)

total number of apneas and hypopneas per hour of sleep

- used to quantify severity of OSA

>30

AHI associated with severe OSA

5-15

AHI associated with mild OSA

16-30

AHI associated with moderate OSA

Hypoxemia, hypercapnia, increased risk of CVA, heart block, dysrhythmias

Physiologic abnormalities associated with OSA

Obesity-hypoventilation Syndrome (OHS)

combination of obesity and hypoventilation that results in pulmonary HTN and cor pulmonale

true

t/f - SVR is normal in obese

They all increase

What happens to total blood volume, cardiac output, left ventricular wall stress?

hypertension, ischemic heart disease, cardiac failure, cardiomyopathy, arrhythmias, dyslipidemia, sudden death

what are some examples of cardiovascular system issues associated with obesity?

adipose

Obese patients have increased total blood volume, but most goes to ___ requiring increased cardiac output

atherosclerosis

obesity accelerates ___, but they may not have symptoms since they are so immobile

2

blood volume and cardiac output in obese patients are __x that of normal patients

arrhythmias

due to fatty infiltration of conduction system, hypoxia, hypercarbia, electrolyte imbalance, CAD, increased circulating catecholamines, OSA, and myocardial hypertrophy

insulin

___ resistance increases pressor response of NE and angiotensin

sodium

____ retention worsens hypertesnion

left ventricular

___ wall thickening increases risk of heart failure

obese are in a hypofibrinolytic and hypercoagulable state

Why are obese patients at an increased risk of DVT and PE?

increased

obese patients have ___ gastric volume and acidity

hiatal hernia, GE reflux

larger gastric volume is associated with increased incidence of ___ and ___

hepatic

obese patients can have altered ___ function, which can affect drug metabolism

false (no clear correlation)

t/f - there is a clear correlation between routine liver function tests and the capacity of the liver to metabolize drugs

nonalcoholic steatohepatitis (NASH)

Aggressive form of NAFLD that can progress to cirrhosis or hepatocellular carcinoma

hypothyroidism

25% of all morbidly obese have subclinical ____

increased risk of wound infection and increased risk of MI

What are two risks of diabetes in obese patients?

Metabolic syndrome

Central obesity plus 2 of the following 4 factors - increased triglycerides, low HDL, HTN, or abnormal fasting glucose/type 2 DM

IBW

drugs mainly distributed to lean tissues should have loading dose based in ____

TBW

drugs equally distributed between lean and adipose tissues should be dose according to ___

LBW

Drug with similar clearance values in obese and non obese use ___

TBW

For a drug whose clearance increases with obesity maintenance dose is calculated on ___

decreased, increased

obese patients have ___ absolute body water and ____ lean body adipose tissue

volume of distribution

___ in obese is affected by:

- Reduced total body water

- Increased total body fat

- Increased cardiac output

- Increased serum fatty acids, triglycerides, cholesterol, and alph1 acid glycoprotein

- Lipophilicity of drug

- Organomegaly

kidneys

drugs that depend on ___ for elimination are more consistently cleared in obese

true

t/f - fat has poor blood flow

LBW

for induction, what should you base propofol dose on

cardiac depression

why should you not use TBW for propofol induction dosing

TBW

what should propofol maintenance dose be based on

TBW

a single IV dose of midazolam is based on ____

LBW

a continuous infusion of midazolam is based on___

LBW

opioids are generally dosed according to ___

TBW

succinylcholine is dosed based on ___

false (polar, hydrophilic, distributed poorly)

t/f - muscle relaxants are nonpolar and lipophilic, so they distribute easily into excess adipose

LBW or IBW

roc and vec doses are based on ____

true

t/f - thiopental is highly lipophilic and has a half life much longer in obese, meaning it needs a larger induction dose

LBW

Opioid dosing is generally dosed according to ___

decreased FRC, increased oxygen consumption

why do obese patients desaturate very rapidly

bariatric

peripheral neuropathy is more common after ___ surgery

lateral decubitus

which position has the benefit of displacing the panniculus off the diaphragm

supine, trendelenburg

which positions cause aortic and IVC compression, decreasing FRC and oxygenation

sitting

which position has an increase in cardiac output, oxygen consumption and pulmonary artery pressure

prone

which position has increased intraabdominal pressure, compression of IVC, aortic compression and decreased FRC

ulnar

which neuropathy is associated with increased BMI

semirecumbent

which position should an obese patient ideally be extubated in

insulin, hypoglycemic meds

all drugs can be continued except

true

t/f - obesity is a major independent risk factor for DVT and PE

false

t/f - BMI is a major factor influencing difficulty of laryngoscopy

neck circumference

what is the biggest predictor of problematic intubation in morbidly obese

true

t/f - patients with OSA are more difficult to intubate than those without OSA

false

t/f - a patient with severe OSA is more difficult to intubate than a patient with moderate OSA

regional

what is helpful in obese to avoid airway manipulation and decrease opioid use

18.5-24.9

normal BMI

25-29.9

overweight BMI

30-40

obese BMI

>40

morbidly obese BMI

obstructive sleep apnea

cessation of airflow for more than 10 seconds, 5 or more times per hour of sleep despite continuous respiratory effort against a closed glottis in combination with decrease in arterial oxygen saturation of greater than 4%

resistance of peripheral fatty tissues to insulin

why is there high prevalence of Type II DM in obese?

increased risk of wound infection and MI

what are risks of diabetes in obese?

false

t/f - there is an increased risk of periop cardiovascular events in the obese patients undergoing ambulatory surgery

4

___ VC breaths with 100% oxygen is better than preoxygenation with 100% oxygen

increased pseudocholinesterase activity

why might you need an increased dose of sux for an obese patient

blood volume, muscle mass, cardiac output

you may need a larger induction dose due to increase ___, ___, and ___

tip of chin

the proper head elevated laryngoscopy position is to have the ___ higher than the chest