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BARASH | Chapter Digest > CHAPTER 45 | Anesthesia and Obesity > Flashcards

CHAPTER 45 | Anesthesia and Obesity Flashcards

1
Q

When a patient is obese, succinylcholine dosage must be based on which of the following:

A. TBW

B. IBW

C. Actual body weight

A

A. TBW

Pseudocholinesterase activity increases linearly with
increasing weight and large extracellular fluid compartment.

Dose of succinylcholine should be INCREASED

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2
Q

____ is the total body weight (TBW) minus the adipose tissue. It is a combination of body cell mass, extracellular water, and nonfat connective tissue:

A. Lean body weight

B. Ideal body weight

C. Predicted body weight

A

A. Lean body weight

LBW is the total body weight (TBW) minus the
adipose tissue. It is a combination of body cell mass, extracellular water, and nonfat connective tissue.

It approximates 80% and 75% of TBW for
males and females, respectively,

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3
Q

TRUE or FALSE

Increasing the IBW by 20% gives an estimate of LBW.

A

TRUE

In morbidly obese patients, increasing the IBW by 20% to 30% gives an estimate of LBW.

In non-obese and non-muscular individuals, TBW approximates IBW

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4
Q

In an obese patient, induction with Propofol is ideally based on which parameter?

A. TBW

B. LBW

C. Actual body weight

D. Predicted body weight

A

B. Lean body weight

If used for maintenance of general anesthesia or TIVA, the dose should be based on TBW.

Increased VD at steady state and increased clearance
prevent increases in elimination half-life.

Total clearance and VD at steady state correlate with body weight during maintenance infusion.

Negative cardiovascular effects.

High affinity for fat and well-perfused organs.

High hepatic extraction and conjugation relate to TBW.

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5
Q

TRUE or FALSE

The pharmacokinetics and pharmacodynamics of ROCURONIUM is not altered in obese female patients

A

TRUE

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6
Q

In an obese patient, induction with Thiopental is ideally based on which of the following?

A. TBW

B. LBW

C. Actual body weight

D. Predicted body weight

A

Lean body weight

Increased initial dose due to increased blood volume,
CO, muscle mass.

  • Rapid distribution from plasma to periphery
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7
Q

Ideal IV analgesic adjuvant in the morbidly obese patient:

A. Dexmedetomidine

B. Remifentanil

C. Alfentanil

A

A. Dexmedetomidine

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8
Q

In Obese patient, Neostigmine should be based on ____ when used for the reversal of vecuronium.

A. TBW

B. IBW

C. LBW

A

Total body weight

Prompt early reversal but delayed full recovery during
neostigmine-induced reversal of vecuronium dosed
according to TBW.

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9
Q

TRUE or FALSE

A drug that is mainly distributed to lean tissues should have the loading dose calculated based on LBW

A

TRUE

In contrast, If the drug is equally distributed between adipose and lean tissues, dosing should be calculated based on TBW.

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10
Q

Which of the following physiologic changes in obesity is MOST ACCURATE?

A. increased total body water

B. decreased lean body mass

C. decreased cardiac output

D. increased α1-acid glycoprotein

A

D. increased α1-acid glycoprotein

Volume of distribution in Obese is affected by these changes:

reduced total body water
increased total body fat
increased lean body mass
altered protein binding
increased blood volume
increased cardiac output

increased blood concentrations of free fatty acids, triglycerides, cholesterol, and α1-acid glycoprotein, lipophilicity of the drug

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11
Q

Plasma albumin and total plasma protein concentrations and binding among obese patients is:

A. Increased
B. Decreased
C. Unchanged

A

C. Unchanged

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12
Q

TRUE or FALSE

In obese patients, phase II reactions (glucuronidation and sulfation) are ENHANCED.

A

TRUE

Phase I is unaffected while Phase II is enhanced.

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13
Q

Remifentanil when given in a continuous infusion should be based on:

A. LBW

B. TBW

C. Actual body weight

A

Lean body weight

High lipid solubility = LEAN BODY WEIGHT

Highly lipophilic substances such as barbiturates and benzodiazepines show significant increases in VD for obese
individuals.

These drugs have a more selective distribution to fat stores and therefore a longer elimination half-life but with comparable clearance values to normal individuals.

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14
Q

aminoglycoside dosing in obese patients should be:

A. Increased

B. Decreased

A

Increased

As a result of the increases in glomerular filtration rate and tubular secretion, drugs such as cimetidine and aminoglycoside antibiotics that depend on renal excretion
may require increased dosing.

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15
Q

The dosing of sugammadex should be based on:

A. actual body weight

B. IBW

C. TBW

A

A. actual body weight

Sugammadex dosing can therefore be based on actual
body weight in both obese and non-obese patients.

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16
Q

TRUE or FALSE

a neck circumference of ≥40 cm is the biggest predictor of difficult mask ventilation, difficult laryngoscopy, and difficult endotracheal intubation.

A

TRUE

17
Q

It is the weight associated with the lowest mortality rate for a given height and gender:

A. Ideal body weight

B. Total Body weight

C. Lean body weight

D. Predicted body weight

A

A. Ideal body weight

18
Q

Which of the following is NOT a risk factors for developing DVT among obese patients?

A. venous stasis disease

B. BMI ≥60

C. central obesity

D. OHS and/or OSA

E. Male

A

E. Male

Four important risk factors, namely venous stasis disease, BMI ≥60, central obesity, and OHS and/or OSA, are significant in the development of postoperative DVT, and if present, preoperative prophylactic placement of an inferior vena cava filter should be considered.

19
Q

Intra-abdominal pressure of more than ___ causes caval compression thereby decreasing cardiac output

A. 20 mmHg

B. 30 mmHg

C. 45 mmHg

A

A. 20 mmHg

Pneumoperitoneum should not be increased above 15 mmHg since intra-abdominal pressures of 20 mmHg
or greater can cause caval compression and decrease cardiac output

20
Q

Fluid management among obese patients should be ideally based on:

A. IBW

B. Total body weight

C. PBW

D. Actual body weight

A

A. IBW

Rapid infusion of intravenous fluids should be avoided because pre-existing congestive cardiac failure is common in the obese patient.

The use of IBW estimates and appropriate monitoring can help to avoid potential hyperhydration in morbidly obese patients.

21
Q

This is the only ventilator parameter that has consistently been shown to improve respiratory function in obese
subjects:

A. FiO2 1.0
B. CPAP
C. APRV
D. PEEP

A

D. PEEP

Positive PEEP is the only ventilatory parameter that has consistently
been shown to improve respiratory function in obese subjects, although the
ideal PEEP value is still unknown.

22
Q

Which is responsible for the decreased
effective dose of spinal local anesthetic
in obese patients?

A. Decreased CSF volume
B. Increased CSF volume
C. Exaggerated lordosis of lumbar spine
D. Exaggerated kyphosis of thoracic spine

A

A. Decreased CSF volume

The decreased spinal fluid volume results from displacement of the cerebral spinal fluid by soft tissue movement into the intervertebral foramen caused by an increase in abdominal pressure.

23
Q

The maximum safe dose of local anesthetic for any type of PNB or local infiltration should be based on:

A. IBW

B. Actual body weight

C. TBW

A

IBW

The maximum safe dose of local anesthetic for a peripheral nerve block or local infiltration should be based on IBW rather than actual weight due to the risk of local anesthetic systemic toxicity.

24
Q

TRUE or FALSE

A patient is using a PCA post-operatively should avoid using the continuous background infusions.

A

TRUE

If patient-controlled systemic opioids are used, continuous background infusions should be avoided or used with extreme caution.

24
Q

Reduction in FRC among obese patients is primarily a result of reduced _________

A. Tidal volume
B. Inspiratory capacity
C. Residual volume
D. Expiratory reserve volume (ERV)

A

D. Expiratory reserve volume (ERV)

25
Q

Morbid obesity is defined as
a BMI _____

A. >30 kg/m2
B. >35 kg/m2
C. >40 kg/m2
D. >45 kg/m2

A

C. >40 kg/m2

26
Q

This has been identified as the single
biggest predictor of problematic
intubation in morbidly obese patients.

A. Neck circumference
B. Mallampati score
C. Thyromental distance
D. Degree of mouth opening

A

A. Neck circumference

27
Q

A BMI of 34 kg/m2 is:

A. Overweight

B. Obese I

C. Obese II

A

Obese I

28
Q

An increased dose of succinylcholine is
necessary because of _______

A. Decrease in activity of pseudocholinesterase
B. Increase in activity of pseudocholinesterase
C. Increased volume of distribution
D. Decreased volume of distribution

A

B. Increase in activity of pseudocholinesterase

BARASH | Chapter Digest (24 decks)

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