Clot Impedence As An Indicator Of Platelet Dysfunction Following Cardiopulmonary Bypass
Thrombosis and Haemostasis
Post-operative bleeding following cardiopulmonary bypass remains a serious problem. Recent studies have indicated platelet dysfunction may be responsible for altered hemostasis in a significant number of patients. Although evaluation of coagulation factors can usually be done with speed and precision, evaluation of platelet function is time-consuming. We have evaluated a clot impedence device (Sonoclot®, Sieneo Inc., Colorado) to measure platelet function. The device measures and records the
... and records the clot impedence to a vibrating probe as the blood sample clots and retracts. In our evaluation of healthy subjects, we found the initial slope of the impedence curve and the entire retraction phase are influenced by the number of platelets. Extrapolating this information to the patients undergoing cardiovascular bypass, we found 7 out of 11 patients with postoperative bleeding had poor retraction phase in spite of an adequate platelet count. This suggested platelet dysfunction. All seven patients achieved satisfactory hemostasis after platelet transfusion. This was correlated with a normal clot impedence study. Four patients with normal clot impedence were found to have surgical bleeding. The test is easy to perform and the result is available within fifteen minutes of drawing the blood sample. In our hands, the measurement of clot impedence appears to be a reliable adjunct in the etiological diagnosis of post-operative bleeding.