Preservation of platelet function and number by prostacyclin during cardiopulmonary bypass

Thirty-four dogs underwent total cardiopulmonary bypass for 1 or 2 hours with a bubble oxygenator and cardiotomy suction. The dogs were divided into three groups: control dogs which received heparin alone, dogs which received prostacyclin (PGI2) and heparin, and dogs which received prostacyclin alone. PGI2 was given as a bolus (6 to 60 microgram) and then as a constant infusion (0.2 to 0.8 microgram/kg/min) in the venous outflow line. The pump flows were equal in the three groups. PGI2 as a bolus led to transient hypotension, and 60 microgram reduced cardiac output temporarily. During cardiopulmonary bypass, dogs treated with prostacyclin and heparin had low mean arterial perfusion pressures which responded to fluid infusion or phenylephrine. After 1 hour of cardiopulmonary bypass and reversal with protamine, dogs treated with prostacyclin and heparin had shorter bleeding times (p < 0.02) and better platelet function than control animals. After 2 hours, they had normal platelet number, but only half showed preservation of platelet function. When heparin was omitted, PGI2 preserved platelet number, but consumption coagulopathy developed, with prolonged prothrombin, partial thromboplastin, and bleeding times and decreased fibrinogen levels. PGI 2 preserves platelet number and function but may cause hypotension, and it cannot replace heparin in cardiopulmonary bypass.