Heparin solution locked in acute hemodialysis catheters: impact on activated partial thromboplastin time

Fifteen patients on hemodialysis, wearing acute dual lumen hemodialysis catheters (DLHCs) locked with a 4 ml heparin solution (HS) containing 7,500 IU of conventional heparin (3,750 IU/lumen), were studied. After the preexisting HS was aspirated and discarded, 10 ml of blood was withdrawn from each lumen in a syringe. Then, two 3 ml blood samples (A and B) were withdrawn in a row from the venous lumen; a third blood sample (C) was withdrawn from a peripheral vein, and the 20 ml of blood in the syringe was returned to the patient. Patient to control ratios of activated partial thromboplastin time (aPTT) in samples A, B, and C were 2.87 +/- 1.04, 2.02 +/- 0.85, and 1.06 +/- 0.14, respectively (p < 0.002 comparing A to B and B to C). In these patients, we also studied the effect of the same HS on the aPTT, 10 minutes after the filling of the DLHCs postdialysis. A blood sample (H1) was withdrawn at the end of the session; 10 minutes after injecting each lumen of the DLHC with a 2 ml HS containing 3,750 IU of heparin, a second blood sample (H2) was drawn from a peripheral vein. The aPTT ratios in samples H1 and H2 were 1.15 +/- 0.13 and 3.58 +/- 0.61 respectively (p < 0.0001). We concluded that even after the aspiration of 15 ml from the venous lumen of a DLHC filled with a 2 ml HS containing 3,750 IU of heparin, the next blood sample remains contaminated by heparin. Filling each lumen of a DLHC with the same HS results in a significant increment of the aPTT 10 minutes later.