Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Which anticoagulant is primarily used for the collection of blood gases?

1. EDTA

2. Heparin

3. Oxalate

4. Citrate

The correct answer is: Heparin

Heparin is the anticoagulant primarily used for the collection of blood gases due to its ability to prevent clotting without significantly altering the concentration of gases such as oxygen and carbon dioxide in the sample. It functions as a direct thrombin inhibitor and is specifically effective in maintaining the integrity of the gas measurements in whole blood samples, which is crucial for accurate analysis in critical care settings. In contrast, EDTA is mainly used for hematology and certain other applications because it chelates calcium, which can interfere with the gas measurements. Oxalate is another type of anticoagulant that also chelates calcium but tends to form precipitates that can alter the concentration of certain ions, thereby affecting gas analysis. Citrate is typically used for coagulation studies and can also interfere with blood gas measurements since it can bind calcium and other substances. Thus, although all these anticoagulants serve important roles in laboratory settings, heparin is uniquely suited for blood gas collection.