Twenty-eight patients undergoing cardiac surgery were prospectively studied
and were assigned to two groups. The patients received 0.8- (Group L) or 2
.0-fold (Group H) dose of protamine for the neutralization after cardiopulm
onary bypass (CPB) which was determined by Hepcon HMS(R) assay system in wh
ich the reagent chamber containing the concentration of protamine that comp
letely neutralized the heparin had the shortest clotting time. Mean dose of
protamine was 1.60 +/- 0.50 mg kg(-1) in Group L, and 3.56 +/- 1.48 mg kg(
-1), respectively. Activated clotting times (ACT) were comparable between t
he two groups through this study period. In Group H, platelet counts signif
icantly decreased to 69% of that before protamine administration, and plasm
a platelet factor 4 level significantly increased to approximate 2-fold of
that before protamine administration just after protamine administration, r
espectively. However, these phenomena were not observed in Group L. In addi
tion, these hemostatic changes occurred transiently just after protamine ad
ministration. We conclude that the low-dose protamine may prevent transient
platelet depletion following Cpa. Low-dose protamine can neutralize antico
agulation effect of heparin sufficiently and may mitigate protamine-induced
platelet dysfunction. Am. J. Hematol. 64:112-115, 2000. (C) 2000 Wiley-Lis
s, Inc.