CCP Blood Gas & Acid-Base Interpretation 4

Question 1

During rewarming from hypothermic CPB, the perfusionist observes increasing metabolic acidosis. The MOST likely cause is:

Accepted Answer

Washout of lactate from previously ischemic peripheral tissues

Answer

Rewarming mobilizes lactate accumulated during hypothermic ischemia in peripheral tissues, causing a transient metabolic acidosis as lactate washes into the central circulation.

Question 2

The Henderson-Hasselbalch equation applied to the bicarbonate system is: pH = 6.1 + log([HCO3-] / 0.03 × PaCO2). If HCO3- is 24 mEq/L and PaCO2 is 40 mmHg, pH equals:

Accepted Answer

7.40

Answer

pH = 6.1 + log(24 / 1.2) = 6.1 + log(20) = 6.1 + 1.30 = 7.40, confirming these are normal reference values.

Question 3

Which acid-base disturbance is MOST commonly associated with post-cardiac surgery patients receiving large volumes of 0.9% normal saline?

Accepted Answer

Hyperchloremic metabolic acidosis

Answer

Large volumes of 0.9% normal saline (154 mEq/L Cl-) cause hyperchloremic metabolic acidosis by diluting bicarbonate and increasing chloride, narrowing the anion gap.

Question 4

A perfusionist is managing a neonate on DHCA. Regarding acid-base strategy, the benefit of pH-stat management in neonates and infants is:

Accepted Answer

Improved cerebral oxygen delivery through CO2-induced vasodilation and better homogeneous brain cooling

Answer

pH-stat causes cerebral vasodilation via hypercapnia, increasing cerebral blood flow and improving homogeneous brain cooling before circulatory arrest in neonates.

Question 5

A patient's blood gas shows pH 7.25, PaCO2 55 mmHg, HCO3- 23 mEq/L. This is BEST classified as:

Accepted Answer

Acute respiratory acidosis without metabolic compensation

Answer

Elevated PaCO2 with low pH and normal HCO3- indicates acute respiratory acidosis; the kidney has not yet had time to retain bicarbonate to compensate.

(CCP) Certified Clinical Perfusionist Practice Test

(CCP) Certified Clinical Perfusionist Practice Test

CCP Blood Gas & Acid-Base Interpretation 4