[Antithrombin III--an important factor in long-lasting microvascular operations].

Antithrombin III is an important factor in preventing thrombosis in the normal coagulation system. The antithrombotic effect of heparin is closely related to the presence of Antithrombin III (AT III) as cofactor. It is also known that the concentration of AT III decreases considerably during long-lasting gynaecological procedures and in visceral surgery. We have found that the serum concentration of AT III also decreases during long-lasting microvascular procedures as in free flap or toe transfers. The crucial points are the duration of the operation, the duration of ischaemia of the extremity and the preoperative concentration of AT III which heavily depends on the general condition of the patient. In ten cases the AT III concentration decreased by an average of 21.7%. In three patients the AT III factor decreased below the critical level of 80%. In these cases levels between 60 and 65% were measured at the end of long microvascular operations. This decrease of AT III can be avoided by application of the AT III factor in an active form during the procedure (AT III in solution with heparin). To avoid thrombosis of the anastomosed vessels the local application of AT III in its active form before anastomosis has proved very effective. In practice, measuring of the AT III level has proved to be very useful in long microvascular procedures before the operation and at intervals of two to four hours. Nevertheless, in spite of AT III application careful microsurgical anastomosis has to be made.