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

Increased cardiac output from volume loading

Answer

Vasodilation from hypothermia

Answer

Release of atrial natriuretic peptide

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

Hyperdynamic circulation with excessive oxygen delivery

Answer

Left-to-right intracardiac shunt

Answer

Hypothermia reducing oxygen consumption

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

L-type calcium channels

Answer

Potassium rectifier channels

Answer

Funny (HCN) channels

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

Increases cerebral blood flow to wash out metabolites

Answer

Prevents cerebral vasoconstriction

Answer

Alkalizes cerebrospinal fluid

Question 5

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

Accepted Answer

End-diastolic volume and stroke volume

Answer

Heart rate and stroke volume

Answer

Afterload and ejection fraction

Answer

Contractility and cardiac output

Question 6

In a patient with severe aortic stenosis undergoing cardiac surgery, the perfusionist must consider that elevated left ventricular end-diastolic pressure (LVEDP) predisposes the heart to:

Accepted Answer

Subendocardial ischemia due to impaired coronary perfusion pressure

Answer

Pulmonary venous hypertension only

Answer

Right ventricular dilation from increased preload

Answer

Decreased oxygen demand from hypertrophy

Question 7

Which buffer system provides the most immediate response to acute changes in blood pH during cardiopulmonary bypass?

Accepted Answer

Bicarbonate-carbonic acid system

Answer

Phosphate buffer system

Answer

Protein (hemoglobin) buffer system

Answer

Renal ammonium excretion