Effect of heparin or saline dilution of blood on PCO2 and pH.

The effect of different dilutions with heparin solutions or saline on blood PCO2, pH and standard bicarbonate was investigated. Blood was first equilibrated to give about 40 or 60 mmHg PCO2. The solutions were in equilibrium with room air. The effect on blood PCO2 etc. could be fully explained by the dilution with a medium having a much lower PCO2. Thus, correction of the heparin solution to pH 7.40 and PCO2 40 mmHg eliminated the effect on PCO2, pH and standard bicarbonate. With ordinary procedure for blood heparinization (about 2% dilution) the effect is practically negligible.