The effect of heparin in arterial catheters on the coagulation in preterm infants.

The coagulation of 16 healthy preterm infants (control infants) was compared with 15 ventilated preterm infants (study infants) receiving 0.5 ml/hr of a solution containing 5 IU/ml heparin intra-arterially in order to keep a radial artery catheter patent. A venous sample was obtained in both groups, in the study group a sample from the arterial catheter was also taken. Both the heparin dependent (APTT, thrombin time) and the heparin independent coagulation factors (AT-III, Clotting Factors I, II, V and VII) were not different between the venous samples of both groups. The arterial samples showed a significantly elevated APTT and thrombin time compared with venous samples, especially when the heparin level in the sample was higher than 0.1 IU/ml. These elevations are due to heparin in the sample from the arterial line as the venous sample in the same patient did not show any heparin effect. The heparin non-dependent factors were not different between venous and arterial samples. We conclude that a solution containing 5 IU/ml heparin given at a rate of 0.5 ml/hr does not influence coagulation in preterm infants. Determination of heparin independent coagulation factors can be done in both venous samples and samples taken from the arterial catheter, in these arterial samples the heparin dependent factors can be influenced by the heparin present in the catheters.