A comparison between continuous infusion versus standard bolus administration of heparin based on monitoring in cardiac surgery

This study was designed to determine prospectively if stable heparin concentrations can be maintained during extracorporeal circulation by using a continuous infusion technique, compared with a bolus regimen based on whole blood heparin concentration monitoring. Forty patients were assigned randomly to either an infusion or a monitoring group. The reference heparin concentration was defined as the whole blood heparin concentration associated with a kaolin activated clotting time (ACT) of approximately 480 s prior to institution of cardiopulmonary bypass (CPB) for both cohorts. For infusion patients, doses of heparin were administered using a continuous infusion based on the initial patient-specific heparin dose per unit weight; heparin was also added to solutions administered after the initiation of CPB based on the reference heparin concentration. For monitoring patients, the dose of heparin administered during CPB was calculated by the Hepcon® instrument. Blood specimens collected prior to and during the CPB period were used to measure anti-Xa plasma heparin concentration and complete blood counts, kaolin ACT and whole blood heparin concentration. Doses of heparin and protamine administered and transfusion requirements were similar in patient cohorts. The apparent rate of clearance of heparin from plasma was variable among patients in the monitoring group prior to CPB. Stable heparin concentrations were maintained using whole blood heparin measurements, whereas mean heparin concentrations were slightly lower using the continuous infusion technique. Therefore, an optimal approach might involve the combined use of these regimens.