Bb Obesity

Front 1

What is considered overweight, obese, and morbid obesity compared with ideal body weight?

Back 1

overweight: 20% greater,
obese: 20-99% Greater;
morbid obesity: 100% greater

Front 2

How do you calculate BMI?

Back 2

weight (kg) / height (meters) squared

Front 3

How do you classify overweight and obesity based on BMI?

Back 3

overweight=25-30;
obese=30-40;
severe obesity=any BMI >40,
morbid obesity=40-50;
super obesity=BMI>50

Front 4

What cardiac considerations should you consider preop in the obese patient?

Back 4

1. increase CO leading to HTN and LVH;
2. Cor Pulmonale secondary to hypoxia induced increase in PVR and pulm HTN;
3. CAD

Front 5

What can cause closing capacity to increase?

Back 5

1. age,
2. chronic bronchitis,
3. LV failure,
4. smoking,
5. surgery,

Front 6

What can cause FRC to decrease?

Back 6

"PANGOS)
P = pregnancy
A = ascites,
N = neonates,
G = GA,
O = obesity
S = supine position

Front 7

What gastric considerations should you consider preop in the obese patient?

Back 7

gastric volume is increased and pH of gastric fluid is decreased
-aspiration precautions are appropriate

Front 8

What happens to oxygenation in obese patients postop? How long does it take to normalize?

Back 8

maximal reduction in blood oxygenation in obese patients occurs 2-3 days postop,
-it takes 7-10 days for reductions in FRC, VC, and FEV1 to normalize

Front 9

What is closing capacity? What does it equal?

Back 9

closing volume + residual volume
-the volume at which small airways in the lungs begin to close

Front 10

What is the overall respiratory problem with obesity?

Back 10

Restrictive lung disease
-As a manifestation, the following occurs:
1. decreased FRC
2. Dec VC
3. Increased shunt (perfusion but no ventilation)

Front 11

What are other respiratory concerns in obese pts?

Back 11

1. Closing volume is increased and shunting is likely to occur - leads to chronic hypoxia
2. RV is normal but ERV is dec about 20%
3. Frequently hyperventilate to compensate for chronic hypoxia - CO2 low or normal
4. Dead space is not changed while shunting is increased - increased shunt primarily due to dec FRC

Front 12

Explain the trend of closing capacity based on age.

Back 12

-the lowest closing capacity is in ones teens
-It increases after than and becomes equal to FRC at 44 in the supine position and 66 in the upright position

Front 13

What factors increase closing capacity?

Back 13

1. PEEP
2. emphysema

Front 14

Why does FRC change in obese pts?

Back 14

ERV decreases with RV being unchanged

Front 15

What happens to closing capacity under general anesthesia? Why is this important?

Back 15

It decreases, paralleling the decrease in FRC.
-this is important bc if it were not so, FRC which is clearly reduced under GA could be reduced below closing capacity resulting in airway closure and shunting during GA.

Front 16

What happens if closing capacity is greater than FRC?

Back 16

shunting will occur during tidal breathing

Front 17

What happens to the pharmacokinetics of lipophilic drugs in obese pts?

Back 17

Lipophilic drugs have an increased Vd, more selective distribution to fat stores, and longer elimination t1/2, but clearance is unchanged.

Front 18

Explain the dosing of nondepolarizers in obese pts.

Back 18

-Nondepolarizers, bc of their quaternary ammonium groups, are highly ionizeed at physiolgic pH and have little lipid solubility therefore Vd is small
-in obesity, the absolute dose required is larger, but similar to nml weight pts if the dose is related to BSA
-ie to produce a given degree of NMB, a larger dose must be given but when this is related to BSA it is similar to the dose in nml wgt pts

Front 19

What endocrine disorders are associated with obesity?

Back 19

1. hypothyroidism
2. cushings
3. insulinoma

Front 20

What are potential postop problems in obese pts?

Back 20

1. hypoxemia1.
2. DVT
3. PE

Front 21

What preop labs should be obtained in an obese pt?

Back 21

1. CBC
2. electrolytes
3. EKG
4. ABG
5. PFTs if pt is obese smoker or w/ pulm symptoms
6. CXR looking for LVH and CHF

Front 22

What happens to the mechanics of breathing in obese pts?

Back 22

1. work of breathing increases
2. breathing becomes shallow
4. dec TVs
5. inc RRs
6. dec inspiratory capacity, dec ERV
7. inc closing volume
8. small airway closure
9. milary atelectasis
10. V/Q mismatch

Front 23

Describe the changes in lung volumes in obese pts.

Back 23

1. RV - little change while upright and supine in absence of anesthetic
2. ERV and FRC - dec dramatically especially in supine and anesthetized
3. TLC - decreases

Front 24

In what population is halothan hepatitis increased?

Back 24

1. obese females
2. middle age Mexican Americans
3. pts receiving multiple halothane exposures

Front 25

Why are obese pts more likely to get halothane hepatitis?

Back 25

-Fluorinated volatile anesthetics are metabolized to a greater extent in obese pts and plasma fluoride concentrations are increased
-Reductive metabolism of halothane is required for fluoride to apepar
-obese pt are more likely to have a fatty liver and pts w/ a fatty liver are predisposed to hepatocyte hypoxia which could favor reductive halothane biotransformation leading to production of hepatotoxic reactive metabolites

Front 26

What is obesity hypoventilation syndrome?

Back 26

1. loss of hypercarbic drive
2. sleep apnea
3. hypersomnolence

Front 27

What is pickwickian syndrome?

Back 27

1. hypercarbia
2. hypoxemia
3. polycythemia
4. hypersomnolence
5. pulm htn
6. biventricular failure