Protamine sulphate and heparin rebound following open-heart surgery

The efficacy of heparin reversal was investigated in 35 patients undergoing open-heart surgery. A total protamine sulphate dose of 3.0 mgs/kg was administered in divided doses and given as a continuous infusion. On this regime complete heparin neutralisation was observed 10 min after decannulation, but heparin levels were again detectable in 29% of cases 2 hours later. This phenomenon was found to correlate with the total circulating load of heparin to be neutralised. All cases with detectable postoperative heparin levels had in-vivo protamine sulphate: heparin ratios of less than 1.6. These data suggest that in-vitro assays of protamine sulphate neutralisation of heparin may seriously underestimate the required dose of protamine sulphate following open-heart surgery.