INCREASED PREOPERATIVE AND POSTOPERATIVE PLATELET ACTIVITY IN VASCULAR SURGICAL PATIENTS

To determine the effect of vascular surgery on platelet function, a pe rioperative investigation of 37 patients with peripheral arterial dise ase (PAD) was performed using the Stagnation Point Adhesio-Aggregomete r (SPAA). The SPAA provides well defined flow conditions. By means of dark field microscopy platelet microthrombus formation can be directly observed and measured continuously. Mathematical evaluation of result ing growth curves renders the constants for adhesion and aggregation. Kpw and Kpp, respectively The PAD patients were divided into 2 groups: diabetics (n = 9) and nondiabetics (n = 28), and were examined periop eratively at regular intervals (average: n = 8). Preoperatively all pa tients received aspirin and low molecular weight heparin (LMWH). As of surgery and up to the third postoperative day all patients received u nfractionated heparin (UH), at which time LMWH was resumed. Plasma fib rinogen concentration was also determined. Data obtained preoperativel y were compared to those of 40 healthy volunteers (without medications ). In the present study a significant increase (p < 0.001) in platelet reactivity was verified in PAD patients in spite of aspirin and LMWH administration. As of the first and up to the 8th day after surgery, a marked increase in platelet adhesivity and aggregability as well as p lasma fibrinogen concentration and a concomitant decrease in platelet count was observed. Maximum values were obtained during intravenous ad ministration of UH. Thrombocytopenia (< 150000/ml) was observed in 12 patients. The hypercoagulability response to vascular surgery observed in the present study occurred in spite of therapy with aspirin and he parin. Our findings indicate the need for further improvement in conve ntional therapy and the SPAA as a useful tool in monitoring the effect iveness of current as well as of future inhibitors of platelet functio n.