CVP Physiological and Pathophysiological Concepts 4

Question 1

Which hemodynamic parameter best reflects left ventricular preload in a patient on cardiopulmonary bypass?

Accepted Answer

Left ventricular end-diastolic volume (LVEDV)

Answer

Central venous pressure (CVP)

Answer

Pulmonary artery occlusion pressure (PAOP)

Answer

Mean arterial pressure (MAP)

Question 2

During hypothermic CPB at 28°C, the perfusionist notes a significant decrease in pump flow requirement to maintain adequate MAP. This is primarily due to:

Accepted Answer

Reduced oxygen consumption decreasing the required cardiac output

Answer

Hypothermia-induced vasoconstriction increasing SVR

Answer

Decreased blood viscosity reducing pump afterload

Answer

Hypothermia increasing endogenous catecholamine release

Question 3

In a patient with a pre-existing right-to-left intracardiac shunt, which CPB management consideration is most critical?

Accepted Answer

Vigilant air removal from the venous side of the circuit to prevent paradoxical embolism

Answer

Aggressive hyperventilation to reduce pulmonary vascular resistance

Answer

Avoidance of all vasodilators to maintain systemic pressure

Answer

Use of retrograde cerebral perfusion during all cooling phases

Question 4

The LaPlace relationship (wall stress = pressure × radius / 2 × wall thickness) predicts that in dilated cardiomyopathy, myocardial oxygen demand is increased because:

Accepted Answer

Increased radius raises wall stress despite normal or low pressure

Answer

Thin walls compensate completely for increased chamber size

Answer

Dilation always increases heart rate to compensate

Answer

Increased pressure from outflow obstruction raises wall stress

Question 5

Hyperosmolar cardioplegia solutions reduce myocardial edema during ischemia primarily by:

Accepted Answer

Creating an osmotic gradient that draws water out of myocytes

Answer

Blocking sodium channels to prevent intracellular sodium accumulation

Answer

Inhibiting aquaporin channels in the sarcolemma

Answer

Activating the sodium-potassium ATPase pump

Question 6

During normothermic CPB, the cerebral autoregulation curve defines the range of mean arterial pressure over which cerebral blood flow remains constant. This range is approximately:

Accepted Answer

50-150 mmHg MAP

Answer

20-50 mmHg MAP

Answer

80-180 mmHg MAP

Answer

100-200 mmHg MAP

Question 7

Which pathophysiologic consequence of prolonged low-flow CPB is most directly linked to postoperative acute kidney injury?

Accepted Answer

Renal ischemia from inadequate perfusion pressure and non-pulsatile flow

Answer

Hypothermia reducing renal tubular enzyme activity

Answer

Hemoglobinuria from excessive hemolysis blocking tubules

Answer

Microemboli from the arterial filter causing glomerular damage