[Antithrombin III substitution for optimization of the heparin effect during extracorporeal circulation in heart surgery].

In a prospective randomised study 20 patients undergoing coronary bypass surgery were assigned to two groups. Patients in group I (n = 10) received initially 250 IU heparin X kg-1 before the start of extracorporeal circulation. Patients in group II (n = 10) were given the same amount of heparin and in addition 1 000 units of purified human antithrombin III (AT III) concentrate. A highly significant lower heparin coefficient [2.69 +/- 0.57 IU X kg-1 X min-1, which is a parameter of heparin consumption (units of heparin X kg-1 given per minute during the time of heparinisation)], was found in group II compared to group I (3.73 +/- 0.56 IU X kg-1 min-1). Heparin sensitivity, measured as an increase in the ratio of activated coagulation time (ACT) X IU heparin-1 X kg-1 as a response to initial heparin dose, was found to be significantly higher (1.22 +/- 0.30 sec X IU heparin-1 X kg-1) in patients receiving AT III as measured in the control group (0.95 +/- 0.23 s X IU heparin-1 X kg-1). Mean values of ACT during the period of heparinisation were comparable (group I: 533 +/- 81 s, group II: 512 +/- 62 s) in the two groups. The substitution of AT III led to an increase of plasma AT III activity of 1.4% per substituted unit AT III X kg-1. AT III plasma activity, corrected to initial haematocrit levels to avoid dilution dependency, decreased as a consequence of extracorporeal circulation.(ABSTRACT TRUNCATED AT 250 WORDS)