CVP Physiological and Pathophysiological Concepts 5

Question 1

Alpha-stat pH management during hypothermic CPB maintains pH at 7.40 (temperature-uncorrected). Compared to pH-stat management, alpha-stat:

Accepted Answer

Preserves cerebrovascular autoregulation and reduces cerebral microembolism risk

Answer

Causes cerebral vasodilation and increased cerebral blood flow

Answer

Results in greater intracellular acidosis during cooling

Answer

Requires higher CO2 sweep gas flows during hypothermia

Question 2

In a patient with severe mitral regurgitation undergoing CPB, inadequate left heart venting can lead to:

Accepted Answer

Left ventricular distension and subendocardial ischemia

Answer

Decreased left atrial pressure from regurgitant flow being captured

Answer

Right ventricular volume overload from reduced pulmonary venous return

Answer

Systemic hypertension from increased LV stroke volume

Question 3

The phenomenon of 'stunned myocardium' following ischemia-reperfusion is characterized by:

Accepted Answer

Prolonged but reversible contractile dysfunction despite restored blood flow

Answer

Permanent myocyte necrosis with fibrotic replacement

Answer

Apoptosis triggered by calcium overload during reperfusion

Answer

Microvascular occlusion preventing effective reperfusion

Question 4

During CPB, a sudden rise in line pressure on the arterial side of the circuit most likely indicates:

Accepted Answer

Arterial cannula malposition or partial obstruction

Answer

Venous air lock reducing venous return

Answer

Oxygenator membrane rupture

Answer

Pump head failure causing retrograde flow

Question 5

Which metabolic derangement is most likely to cause ventricular fibrillation during rewarming from hypothermic CPB?

Accepted Answer

Hyperkalemia from cardioplegia washout and cell lysis

Answer

Hyponatremia from hemodilution with hypotonic priming solutions

Answer

Respiratory alkalosis from aggressive ventilation

Answer

Hypoglycemia from insulin administration during bypass

Question 6

Pulsatile perfusion during CPB is theorized to provide physiologic benefit primarily by:

Accepted Answer

Providing mechanical stimulation of baroreceptors and improving microcirculatory flow

Answer

Increasing mean arterial pressure above non-pulsatile equivalents

Answer

Reducing the need for vasopressors by eliminating vasoplegia

Answer

Decreasing hemolysis by reducing shear stress in the pump

Question 7

In a patient with hypertrophic obstructive cardiomyopathy (HOCM) on CPB, which management strategy during separation from bypass is most important to avoid dynamic outflow tract obstruction?

Accepted Answer

Maintain adequate preload and afterload while avoiding tachycardia

Answer

Administer high-dose inotropes to improve ejection fraction

Answer

Use intra-aortic balloon pump to increase diastolic coronary perfusion

Answer

Pace the heart at high rates to reduce end-diastolic volume