DOES PLATELET SIZE CORRELATE WITH FUNCTION IN PATIENTS UNDERGOING CARDIAC-SURGERY

Objective: Platelet dysfunction secondary to cardiopulmonary bypass (CPB) is one of the major reasons for nonsurgical post-operative bleeding in cardiac surgery. Whether platelet size is an indicator for platelet function was investigated in patients undergoing coronary artery bypass grafting. Design: Prospective study. Setting: Intra-operative, cardiac surgery operations. Patients: 80 consecutive patients undergoing coronary artery bypass grafting. Excluding criteria were pre-operative coagulation disorders and medication with anticoagulants within the last 10 days before the operation day. Measurements and results: Platelet function was assessed by aggregometry using a turbidimetric method (inductors: ADP 2.0 mumol/l, collagen 4 mug/l, epinephrine 25 mumol/l). Mean platelet volume (MPV) was measured by an electrical conductivity method. Measurements were carried out before, during, and after CPB until the 1st post-operative day on intensive care unit (ICU). Platelet size decreased significantly during CPB (max. -25% after weaning from bypass) and returned to baseline values on the 1st post-operative day. Platelet count (ranging from 93-304 x 10(9)/l) did not correlate significantly with MPV or aggregation variables. Maximum aggregation and maximum gradient of aggregation induced by ADP and collagen were significantly decreased by CPB with the most pronounced reduction at the end of CPB (ranging from -25% to -45%). Analyses of co-variance revealed a significant correlation between changes in MPV and changes in aggregation variables (ADP, collagen). Conclusion: Platelet volume is easy to measure even in the operation room or in ICU and may indicate abnormalities in platelet function in the post-bypass period of cardiac surgery patients.