Reversible shear-mediated platelet dysfunction during cardiac surgery as assessed by the PFA-100 (R) platelet function analyzer

We undertook this investigation to assess alterations in shear-mediated pla telet function during cardiac surgery and to determine the potential for th e PFA-100 (R) to predict post-operative bleeding. Platelet aggregation and PFA-100 (R) closure times were determined in 18 adult patients at five inte rvals during cardiac surgery. Associations between post-operative bleeding and closure times were examined in an additional 58 patients. Statistical a nalysis consisted of Student's t, Wilcoxon signed rank, and Spearman correl ation tests. All results are reported as mean +/- SEM. Collagen/epinephrine closure times were prolonged prior to and throughout surgery. Collagen/ade nosine-5 ' -diphosphate (ADP) closure times were significantly prolonged by heparin administration, 141 +/- 15 s versus 115 +/- 10 a (P = 0.01), and s ubsequent initiation of cardiopulmonary bypass (CPB), 203 +/- 12 s (P = 0.0 001); however, 15 min after protamine administration, closure times returne d to near pre-operative values, 138 +/- 12 s (P = not significant). In cont rast, platelet aggregation in response to ADP remained impaired in 17 of 19 patients after CPB. Neither ex vivo correction of sample hematocrits nor s upplementation with Humate P (R) affected closure times. Positive and negat ive predictive values for post-CPB collagen/ADP closure times to predict bl eeding were 18 and 96%, respectively. These results suggest that factors bo th intrinsic and extrinsic to the platelet contribute to reversible shear-m ediated platelet dysfunction during CPB, and that the PFA-100 (R) may prove useful after CPB to identify patients unlikely to benefit from platelet tr ansfusions. (C) 2001 Lippincott Williams & Wilkins.