Platelet membrane receptors during short cardiopulmonary bypass - a flow cytometric study

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Abstract
To elucidate a mechanism of platelet dysfunction during extracorporeal circulation, we performed a study on the surface expression of platelet adhesive receptors (GPlb, GPIIb-IIIa) and activation markers (GMP140, GP53) during short cardiopulmonary bypass (CPB). Ten paediatric patients, age 6-13 years, with atrial or atrioventricular septal defects were studied. The mean CPB time was 52 min (21-110 min). During CPB, a significant drop in platelet count was observed, but not below 130 x 103/μl. The expression of platelet GPlb decreased slightly during CPB and the decrease was not significant. The decrease of GPIIb-IIIa was significant, but only in samples collected either at the end of CPB (89 ± 13%, p < 0.05) or before leaving the operating room (74 ± 14%, p < 0.05). The value of surface expression of platelet activation markers (GMP140, GP53) during CPB was in the range of values for resting platelets. Our results suggest that generalized CPB-induced defects of primary haemostasis are not directly connected to circulation of activated degranulated platelets or to loss of platelet adhesive receptors GPIb-IX and GPIIb-IIIa.