[Changes in antithrombin III values during and after extracorporeal circulation in heart surgery, measured on the day of operation using a chromogenic substrate and a laser nephelometer].

The changes in antithrombin III in 31 patients who underwent open-heart surgery were measured during the period of extracorporeal circulation and afterwards over a total period of 24 hours by means of a chromogenic substrate, as well as by laser nephelometry. Both the actual changes in antithrombin III, as well as the theoretical changes calculated by eliminating the effect of haemodilution are discussed. The functional test indicates that the loss of antithrombin-III activity, in general, is due to the effect of haemodilution. However, marked individual differences were noted in the reaction pattern. The results of nephelometric measurements were inconsistent and seemed to indicate that routine procedures in laser nephelometry are hardly suitable for the purpose of comparison of samples with marked haematocrit differences.