IntroductionCardiac surgery of valvular replacement carries multiple complications, the commonest of which is bleeding. Effective anti-coagulation during valvular replacement is necessary to prevent excessive activation of the hemostatic system; protamine sulfate is used to neutralize the effect of circulating heparin. The Aim of the work was to determine the effectiveness of half dose Protamine in reversing the action of heparin in valvular replacement cardiac surgery without the appearance the side effect of protamine.Method40 patients undergoing valvular replacement divided into two groups. Group A: received 1mg of protamine per 100 unit heparin (common ratio 1:1, protamine: heparin). Group B: received 0.5 mg of protamine per100 unit of heparin (our ratio 1:2, protamine: heparin). Following data were detected in each patients (1) blood loss, 2 Activated clotting Time, (3) Hemoglobin, (4) unites of FFP requirements, (5) Clotting Time, and Maximum Clot Firmness (MCF) test.ResultsWe found that the administration of half (1/2) of Total Calculated Dose of protamine sulphate was always able to reverse the anticoagulant effect of heparin .with insignificant difference in hemodynamic parameters, and in the amount of blood loss and insignificant difference in unites of FFP requirement, on other hand there was mild significant results in MCF test between both groups.DiscussionOur present study suggests that the commonly applied ratio equal to 1:1 (ratio of protamine to heparin) could be higher than needed with potential and hazardous impacts and lowering it to be 1:2 ratio is similarly effective. Our results are in line with the findings obtained by Salvatore et al., who observed that reversal of heparin administered in patients undergoing cardiac surgery could be effectively achieved with 2/3 of the usual dose of Protamine and that the additional administration of protamine seems to induce an elongation of the clotting time with no impact on clot firmness. (1) While the impact of a high protamine to heparin ratio was even studied by Kahn et al., who studied blood samples of 46 patients undergoing cardiac surgery using CABG and found a significant worsening of the coagulation parameters using protamine to heparin ratio of more than 2:12.