What is the heparin concentration in ABG collection per milliliter of blood?

• A. 0.1 mL/mL
• B. 0.5 mL/mL
• C. 1.0 mL/mL
• D. 2.0 mL/mL

Answer: (B)

In ABG collection, a dilute amount of heparin is used to keep the sample from clotting while minimizing dilution of the blood. The balance is to provide enough anticoagulant without altering the gas measurements or electrolyte status. The standard practice is to mix about half a milliliter of heparin solution for every milliliter of blood drawn. This amount prevents clots during transport and analysis, yet avoids significant dilution that would skew pH and gas tensions. If too little heparin is used, clots can form; if too much is used, the sample becomes overly diluted and gas values may be distorted. Therefore the heparin concentration in ABG collection is about 0.5 mL per mL of blood.