Obesity Flashcards
What is the equation for BMI?
BMI = wt (kg) / ht^2 (m)
What BMI is considered: underweight, normal, overweight, obese 1, obese 2, morbid obesity
underweight <
How do lung capacities compare in obese vs non-obese?
obese - smaller ERV due to decreased lung, chest wall compliance (weight on chest limiting causing normal inspiration to occur in ERV zone)
What is Pickwickian syndrome (obesity hypoventilation syndrome)? what can it lead to and how?
low PaO2, high PaCO2, +/- OSA caused by failure to breath rapidly or deeply enough; can lead to cor pulmonale (R heart failure) because hi CO2 in lungs causes vasoconstriction
What is a rough estimate of EBV/kg in the obese?
50cc/kg
What are some common ECG changes seen in obesity?
low voltage, LAE/LVH, T wave flattening, L axis deviation of P-wave/QRS/T-wave
How does obesity effect: gastric volume, pH; gastric emptying
volume up to 75% larger (may be 25cc+ fasting); pH decreased (<2.5); gastric emptying normal to faster
How does the heart compensate for the increased CO demanded by obesity?
increasing SV (no increase in HR)
What effect does obesity have on wake-up time?
minimal, even following long procedures
Which types of drugs would you want to dose based on ideal body weight?
water-solube (see M&M p.742)
How does obesity effect epidural dosing?
20-25% smaller dose due to increased epidural fat and distended veins
What is the general plan for extubation of obese patients?
do not extubate until there is no doubt that an adequate airway and tidal volume will be maintained
How does obesity effect hepatic and renal clearance?
hepatic clearance uneffected; renal clearance increased (due to increased CO)
What anatomical abnormality is a major cause of OSA and a consideration for intubation?
excessive fat in the lateral pharyngeal walls
What is the best predictor of problematic intubation in the morbidly obese?
neck circumference: 40cm+ 5% chance, 60cm+ 35% chance
What might you want to consider during pre-oxygenation to decrease incidence of desaturation?
use PEEP to decrease atelectasis
What is the max tidal volume you should deliver to an obese patient (cc/kg)?
13cc/kg - beyond this increases PIP without increasing PaO2
What is the only ventilatory parameter that has been shown to improve respiratory function in the obese?
PEEP
CO increases as much as ____cc per kg of extra body fat?
20-30cc/kg
What are signs of heart failure that you can see from looking at a patient?
distended neck veins, pulmonary crackles, peripheral edema
What symptoms might accompany pulmonary HTN?
OSA, fatigue, exertional dyspnea, syncope
What is the equation for wall stress?
wall stress = pressure x radius / (2 x wall thickness)
