CVP Physiological and Pathophysiological Concepts 2

Question 1

During cardiopulmonary bypass, which mechanism primarily accounts for the decrease in systemic vascular resistance seen with hemodilution?

Accepted Answer

Reduced blood viscosity lowering frictional resistance

Answer

Hemodilution reduces blood viscosity, which directly decreases frictional resistance in the vasculature and lowers SVR.

Question 2

A patient on CPB develops a mixed venous oxygen saturation (SvO2) of 55%. Which physiologic condition best explains this finding?

Accepted Answer

Inadequate perfusion flow relative to metabolic demand

Answer

An SvO2 of 55% indicates tissues are extracting more oxygen than normal, reflecting inadequate oxygen delivery relative to demand.

Question 3

Which ion channel is primarily responsible for the rapid depolarization phase (phase 0) of the cardiac action potential in ventricular myocytes?

Accepted Answer

Fast sodium channels

Answer

Fast voltage-gated sodium channels open rapidly during phase 0, producing the steep upstroke of the ventricular action potential.

Question 4

During deep hypothermic circulatory arrest, cerebral protection is enhanced by hypothermia primarily because it:

Accepted Answer

Reduces cerebral metabolic rate for oxygen (CMRO2)

Answer

Hypothermia markedly reduces CMRO2, extending the safe period of ischemia during circulatory arrest.

Question 5

Starling's law of the heart describes the relationship between:

Accepted Answer

End-diastolic volume and stroke volume

Answer

Frank-Starling law states that stroke volume increases with greater end-diastolic volume (preload) due to enhanced myofilament overlap.

(CVP) Cardiovascular Perfusionist Practice Test