Obesity

Question 1

What is the equation for BMI?

Answer 1

BMI = wt (kg) / ht^2 (m)

Question 2

What BMI is considered: underweight, normal, overweight, obese 1, obese 2, morbid obesity

Answer 2

underweight <

Question 3

How do lung capacities compare in obese vs non-obese?

Answer 3

obese - smaller ERV due to decreased lung, chest wall compliance (weight on chest limiting causing normal inspiration to occur in ERV zone)

Question 4

What is Pickwickian syndrome (obesity hypoventilation syndrome)? what can it lead to and how?

Answer 4

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

Question 5

What is a rough estimate of EBV/kg in the obese?

Answer 5

50cc/kg

Question 6

What are some common ECG changes seen in obesity?

Answer 6

low voltage, LAE/LVH, T wave flattening, L axis deviation of P-wave/QRS/T-wave

Question 7

How does obesity effect: gastric volume, pH; gastric emptying

Answer 7

volume up to 75% larger (may be 25cc+ fasting); pH decreased (<2.5); gastric emptying normal to faster

Question 8

How does the heart compensate for the increased CO demanded by obesity?

Answer 8

increasing SV (no increase in HR)

Question 9

What effect does obesity have on wake-up time?

Answer 9

minimal, even following long procedures

Question 10

Which types of drugs would you want to dose based on ideal body weight?

Answer 10

water-solube (see M&M p.742)

Question 11

How does obesity effect epidural dosing?

Answer 11

20-25% smaller dose due to increased epidural fat and distended veins

Question 12

What is the general plan for extubation of obese patients?

Answer 12

do not extubate until there is no doubt that an adequate airway and tidal volume will be maintained

Question 13

How does obesity effect hepatic and renal clearance?

Answer 13

hepatic clearance uneffected; renal clearance increased (due to increased CO)

Question 14

What anatomical abnormality is a major cause of OSA and a consideration for intubation?

Answer 14

excessive fat in the lateral pharyngeal walls

Question 15

What is the best predictor of problematic intubation in the morbidly obese?

Answer 15

neck circumference: 40cm+ 5% chance, 60cm+ 35% chance

Question 16

What might you want to consider during pre-oxygenation to decrease incidence of desaturation?

Answer 16

use PEEP to decrease atelectasis

Question 17

What is the max tidal volume you should deliver to an obese patient (cc/kg)?

Answer 17

13cc/kg - beyond this increases PIP without increasing PaO2

Question 18

What is the only ventilatory parameter that has been shown to improve respiratory function in the obese?

Answer 18

PEEP

Question 19

CO increases as much as ____cc per kg of extra body fat?

Answer 19

20-30cc/kg

Question 20

What are signs of heart failure that you can see from looking at a patient?

Answer 20

distended neck veins, pulmonary crackles, peripheral edema

Question 21

What symptoms might accompany pulmonary HTN?

Answer 21

OSA, fatigue, exertional dyspnea, syncope

Question 22

What is the equation for wall stress?

Answer 22

wall stress = pressure x radius / (2 x wall thickness)