CCP Blood Gas & Acid-Base Interpretation 3

Question 1

Which of the following causes a LEFT shift of the oxyhemoglobin dissociation curve, increasing hemoglobin's affinity for oxygen?

Accepted Answer

Alkalosis and hypothermia

Answer

Alkalosis and hypothermia both increase hemoglobin's affinity for oxygen, shifting the dissociation curve to the left and impairing oxygen release to tissues.

Question 2

A perfusionist notes SvO2 dropping from 75% to 55% during stable CPB. Without changing pump flow, which blood gas change would MOST likely explain this?

Accepted Answer

Falling hemoglobin from 9 to 6 g/dL

Answer

A fall in hemoglobin reduces oxygen delivery (DO2 = CO × CaO2), forcing tissues to extract more oxygen and lowering SvO2.

Question 3

What is the anion gap in a patient with Na+ 140, Cl- 102, HCO3- 18 mEq/L?

Accepted Answer

20 mEq/L

Answer

Anion gap = Na+ − (Cl- + HCO3-) = 140 − (102 + 18) = 20 mEq/L, which is elevated above the normal range of 8–12 mEq/L.

Question 4

During CPB, a blood gas taken from the arterial line shows PaO2 450 mmHg. The perfusionist should:

Accepted Answer

Reduce FiO2 on the oxygenator to avoid hyperoxia-related free radical damage

Answer

Excessive hyperoxia during CPB generates reactive oxygen species that contribute to reperfusion injury; FiO2 should be reduced to maintain PaO2 in an appropriate range (150-200 mmHg).

Question 5

A patient presents with pH 7.48, PaCO2 48 mmHg, HCO3- 35 mEq/L after prolonged NG suction. This is BEST described as:

Accepted Answer

Metabolic alkalosis with partial respiratory compensation

Answer

Loss of gastric HCl causes metabolic alkalosis; the elevated PaCO2 represents partial respiratory compensation (hypoventilation) to retain CO2.

(CCP) Certified Clinical Perfusionist Practice Test

(CCP) Certified Clinical Perfusionist Practice Test

CCP Blood Gas & Acid-Base Interpretation 3