Comparison of the effects of dry and liquid heparin on neonatal arterial blood gases.

We compared the effects of liquid and vaporized dry heparin on neonatal arterial blood gases. A total of 35 paired simultaneously drawn neonatal arterial blood samples were collected. In one of every paired sample, 0.05 cc of liquid heparin was used and in the other sample vaporized heparin syringes were used. Blood was drawn into every syringe to a total volume of 0.2 ml, pH, arterial oxygen tension (PaO2), and arterial carbon dioxide tension (PaCO2) of the paired samples were analyzed using the paired Student t method. There was no statistical difference in pH and PaO2 but the PaCO2 was statistically lower (p less than 0.0005) with liquid heparin. We conclude that the effects of heparin on neonatal arterial blood gases is dilutional in nature and that they are due to mixing heparin with its very low PaCO2 with the blood sample. If by mistake more heparin than necessary is used, the effects can be dramatic. We therefore suggest using syringes with vaporized heparin in obtaining neonatal arterial blood gases to obtain reliable and consistent results.