A comparative study of prostacyclin infusion given before and during cardiopulmonary bypass to assess the first pass effect of the circuit on platelet number and function

Abstract

Platelet damage during cardiopulmonary bypass (CPB), althoughproportional to the duration of bypass, may result in significantdysfunction after the initial contact with an extracorporeal circuit, theso-called 'first pass' phenomenon. The platelet sparing effect ofprostacyclin (PGI2) infusion was studied in a double-blind randomized trialon male patients undergoing coronary artery bypass grafts to assess theeffect of the 'first pass' through the CPB circuit. Prostacyclin infusionwas begun before the onset of CPB or during CPB in two groups which werecompared to a placebo control group. A standardized anaesthetic, surgicaland perfusion technique were used. Preoperatively and during surgery atpre-set intervals, whole blood platelet aggregation was studied using ADPand collagen agonists. Platelet numbers and function measured by ADPaggregation were conserved in the two PGI2 groups. There was no significantdifference between the treated groups. We conclude, therefore, that theinitial contact of platelets with the CPB circuit, in the absence of PGI2did not irreversibly affect platelet function. In addition, the hypotensiveaction of PGI2 was easier to control once on bypass. It may therefore bepreferable to delay PGI2 infusion until CPB has been established.