EFFECT OF HEPARIN LOADING DURING CONGENITAL HEART OPERATION ON THROMBIN GENERATION AND BLOOD-LOSS

Background. The heparin protocols used during cardiopulmonary bypass ( CPB) in children undergoing surgical repair for congenital heart disea se are extrapolated from adult data. Studies are needed that assess th e optimal heparin dosing in these children, whose heparin clearance is increased compared with that in adults. Methods. We assessed the effe cts of two commonly used doses of heparin in the prime solution at the start of CPB operation on plasma heparin levels, on thrombin producti on (thrombin-antithrombin III complexes, prothrombin fragment 1 + 2, D -dimer, and antithrombin III),, and on the risk of hemorrhage. Before CPB, 48 children with congenital heart disease received heparin intrav enously in a loading dose of 300 U/kg followed by either 1 U/mL, of he parin in the prime (low-dose group: 22 patients-acyanotic, 9; cyanotic , 13) or 3 U/mL of heparin in the prime (group: high-dose, 26 patients -acyanotic, 15; cyanotic, 11). Results. In all patients, CPB resulted in the generation of thrombin. The duration of CPB was a significant c ovariate factor for heparin levels (p = 0.002), thrombin production (p < 0.001), and postoperative blood loss (p < 0.001). In the patients i n the high-dose group, the total heparin dose and the plasma heparin l evels were higher (p = 0.0005 and 0.005, respectively) and the D-dimer levels tended to be lower (p = 0.06). The postoperative blood loss wa s higher in the cyanotic patients (p = 0.02; both high-dose and low-do se groups), with 2 cyanotic patients (1 in low-dose group, I in high-d ose group) requiring reoperation, one of whom subsequently died. The i ncreased heparin dose had no significant effect on the rate or volume of postoperative blood loss. Conclusions. Increasing the heparin dose in the prime solution from 1 to 3 U/mL increased the plasma heparin le vels and showed a trend toward reducing the postoperative laboratory v alues indicative of fibrinolysis. Thrombin generation during CPB and t he incidence of postoperative hemorrhage were not significantly altere d. Larger randomized trials are needed to determine the optimal hepari n-dosing regimen in patients with congenital heart disease. (C) 1997 b y The Society of Thoracic Surgeons.