ABCP Perfusion Basic Science (PBSE) Practice Exam

During CPB, you want to know not just how much oxygen is being delivered, but how well the tissues are using it. Base deficit measures metabolic acidosis, which grows when nonvolatile acids accumulate from tissue hypoperfusion or increased acid production. Lactate is a direct product of anaerobic glycolysis, so rising lactate signals that tissues are switching to anaerobic metabolism due to inadequate oxygen delivery or uneven perfusion. Together, these two measurements give a dynamic readout of perfusion adequacy and metabolic status during CPB, guiding adjustments to flow, perfusion strategy, and temperature. While cardiac index, overall oxygen delivery, and hematocrit are important, they don’t directly reflect the metabolic consequences of perfusion adequacy as clearly as base deficit and lactate do.