The anticoagulant effect of protamine sulfate is attenuated in the presence of platelets or elevated factor VIII concentrations.
BACKGROUND
Protamine sulfate is the antidote for heparin, but in excess it exerts weak anticoagulation.


METHODS
We evaluated the effects of increasing protamine concentrations (0 to 24 microg/mL) on prothrombin time and diluted Russell's viper venom time measurements on thrombin generation in platelet-poor and platelet-rich plasma after activation by tissue factor or actin, and on thromboelastometry in platelet-poor plasma and whole blood from 6 healthy volunteers. The reversibility of excess protamine (24 microg/mL) by recombinant factor VIIa or factor VIII/von Willebrand factor concentrate was also tested.


RESULTS
Protamine prolonged prothrombin time and Russell's viper venom time, concentration dependently. Protamine also increased lag time and decreased peak of thrombin generation in platelet-poor plasma after tissue factor and actin activation. In platelet-rich plasma with platelets at 50 to 200 x 10(3)/microL, protamine (24 microg/mL) prolonged the lag time, but had no effect on peak thrombin generation. The addition of factor VIII/von Willebrand factor (1.5-3.0 U/mL) to platelet-poor plasma with protamine (24 microg/mL) decreased lag time and increased peak thrombin generation with actin activation. A therapeutic concentration of recombinant factor VIIa (60 nM) only affected the lag time of thrombin generation triggered with actin. In agreement, protamine increased coagulation time evaluated by thromboelastometry significantly more in platelet-poor plasma than in whole blood.


CONCLUSIONS
We demonstrated that protamine affects the propagation of thrombin generation, which is partially reversed by platelets or increased factor VIII/von Willebrand factor concentrations. The present data suggest that excess protamine might potentially increase bleeding in the case of severe thrombocytopenia or low factor VIII.
Bolliger
Daniel
D
Department of Anesthesiology, Emory University School of Medicine, 1364 Clifton Road NE, Atlanta, GA 30322, USA.
Szlam
Fania
F
Azran
Marc
M
Koyama
Kaoru
K
Levy
Jerrold H
JH
Molinaro
Ross J
RJ
Tanaka
Kenichi A
KA
D000328:Adult; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D003627:Data Interpretation, Statistical; D004305:Dose-Response Relationship, Drug; D005169:Factor VIII / Q000502:physiology*; D005260:Female; D006494:Heparin Antagonists / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011479:Protamines / Q000494:pharmacology*; D011517:Prothrombin Time; D013916:Thrombelastography; D013917:Thrombin / Q000096:biosynthesis
D006494:Heparin Antagonists; D011479:Protamines; D005169:Factor VIII; D013917:Thrombin