The value of heparin concentration monitoring in off-pump coronary bypass surgery

In recent years, a remarcable increase in off-pump coronary bypass surgery (OPCAB) was observed. The identical anticoagulation treatment in cardiac surgery with cardiopulmonary bypass (CPB) and OPCAB makes the hemodynamic management in OPCAB procedures essential, since a perioperative compensation of blood loss is difficult and the hemodynamic stability has to be maintained by infusions. The aim of this study was to evaluate the circulating heparin concentration measurement in OPCAB patients by using the heparin/protamine titration method with Hepcon/HMSplus (HMS).

In 8 patients (3F/5M) undergoing elective OPCAB, the calculated heparin dose was administered and heparin concentration was registered together with activated clotting time (ACT) 5 min after administration. Measurements were carried out in 45 min periods and additional heparin was administered if the measured heparin concentration was lower than the calculated. The protamin dose was also automatically calculated by HMS.

The mean operation time was 155 +/- 36 min (80-210) with 2.3 bypass grafts per patient. There was a significant difference between the demand for heparin as determined by HMS and the conventionally calculated value (p<0.05). Similarly, the calculated and measured concentration of heparin diverged significantly from each other (p<0.05), independent of ACT. In spite of an initially higher administration of heparin as calculated by HMS, the concentration of circulating heparin was below the estimated value in 7 patients which made a further administration of heparin necessary. The 24 h postoperative blood loss was 550 +/- 176 mL (300-850). No rethoracotomy for bleeding was necessary.

HMS could be a useful method for appropriate anticoagulative treatment in OPCAB procedures, if there is a sufficient hemodynamic management with restrictive administration of infusions guaranted during surgery.