COMPARISON OF ACTIVATED COAGULATION LIME AND WHOLE-BLOOD HEPARIN MEASUREMENTS WITH LABORATORY PLASMA ANTI-XA HEPARIN CONCENTRATION IN PATIENTS HAVING CARDIAC OPERATIONS

Previous reports suggest that activated clotting times do not correlat e with heparin concentration during cardiopulmonary bypass. This study was designed to compare whole blood heparin concentration acid activa ted clotting time measurements with laboratory-based plasma heparin co ncentration. Sixty-two patient having cardiac operations requiring car diopulmonary bypass were enrolled in this study. The study was conduct ed in two phases. In phase I of this trial, blood specimens were obtai ned from 30 patients before heparin administration and after each of t hree heparin doses (20, 80, and 150 U/kg). In phase II, blood specimen s were obtained from 32 patients before heparin administration and 10 minutes after each of the following: heparin administration (250 or 30 0 U/kg), initiation of cardiopulmonary bypass, achievement of hypother mia, initiation of rewarming, and immediately before discontinuation o f bypass. Blood specimens were used to measure activated clotting time (kaolin and celite), whole blood heparin concentration, and anti-fact or Xa plasma heparin concentration. In phase I, activated clotting tim e (celite: r = 0.91; kaolin: r = 0.93) and whole blood heparin concent ration (r = 0.98) measurements correlated web with plasma heparin conc entration. After initiation of cardiopulmonary bypass (phase II), weak correlations for activated clotting time measurements (celite: r = 0. 34; kaolin: r = 0.59) and a strong correlation for whole blood heparin concentration (r = 0.95) were evident when compared with plasma hepar in concentration. During bypass, activated clotting time measurements also inversely correlated with temperature (celite: r = -0.21; kaolin: -0.19) and hematocrit (celite: r = -0.26; kaolin: r = -0.21). A weak correlation between activated clotting time measurements and plasma he parin concentration is evident during the cardiopulmonary bypass perio d, probably because of the influence of both reduced hematocrit and te mperature on the activated clotting time assay. In contrast, whole blo od heparin measurements correlate wed with plasma heparin concentratio n before and during bypass. Further studies are needed to determine wh ether maintaining heparin levels during cardiopulmonary bypass by moni toring heparin concentration is more effective in preventing consumpti ve activation of the hemostatic system, reducing bleeding, and minimiz ing the use of blood products after cardiopulmonary bypass when compar ed with a protocol based on activated clotting time.