Certified Pulmonary Function Technologist (CPFT) Practice Exam

What is the effect of excessive heparin on an ABG sample?

1. PO2 decrease, PCO2 increase, pH decrease

2. PO2 increase, PCO2 decrease, pH decrease

3. PO2 increase, PCO2 increase, pH increase

4. PO2 decrease, PCO2 decrease, pH increase

The correct answer is: PO2 increase, PCO2 decrease, pH decrease

Excessive heparin, an anticoagulant used to prevent blood clots, can impact the analysis of arterial blood gas (ABG) samples. When there is an excessive amount of heparin in the sample, it can lead to dilution effects. This dilution tends to introduce changes in blood gas measurements. One critical effect of excessive heparin is that it can cause a decrease in both arterial carbon dioxide (PCO2) levels and an increase in oxygen partial pressure (PO2). The decrease in PCO2 is related to the dilution of the sample, which can influence the balance between CO2 production and elimination in the body. Less CO2 results in a shift towards a more alkaline environment, typically contributing to a decrease in the acidity of the blood. The lowering of carbon dioxide and the accompanying decrease in acidity (pH) aligns with physiological responses that can occur in mixed respiratory and metabolic conditions, where excessive heparin might alter the expected gas tensions during standard testing. Given these effects, the correct conclusion is that in the presence of excessive heparin, the PO2 increases, the PCO2 decreases, and the pH also decreases in the context of a mixed or metabolic change.