Postoperative bleeding in cardiovascular surgery. Does heparin rebound really exist?

Postoperative bleeding following cardiovascular procedures is troublesome and often life-threatening. The effect of heparin (H) is usually reversed with protamine sulfate (P) at the end of vascular procedures; subsequent bleeding or abnormal coagulation times are ascribed to so-called heparin rebound and are treated with extra empiric doses of P. H rebound has heretofore been described only by using biologic clotting tests, which are often abnormal postoperatively. Thus, many instances of postoperative bleeding are treated with inappropriate and dangerous doses of P in the mistaken impression that more H needs to be reversed. Using the new test for plasma H, the azure A Assay, which measures H chemically rather than biologically, 27 patients were tested after cardiac bypass surgery to determine whether H rebound truly exists. Azure A levels of H were measured before the bypass procedure and every half hour from 0-8 hours after bypass in routine coronary artery bypass patients. Tests for prothrombin time (PT) and partial thromboplastin time (PTT) were performed simultaneously. The azure A test was performed on 252 samples of blood in the 27 patients; only one sample drawn anytime except immediately after bypass contained measurable H (0.4%). This sample became negative for H in the ensuing 30 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)