Cardiopulmonary bypass is extremely damaging to platelets. In fact, it causes a quantitative and qualitative alteration in their function.When platelets adhere and aggregate or are broken up on foreign surfaces they release their. granular contents. We evaluated the release of two platelet specific proteins B-thromboglobulin (BTG) and Platelet factor 4 (PF4) in 20 patients who underwent extracorporeal circulation for open heart surgery. All the patients were perfused with Pemco modular pump and a Bently disposable oxygenator. BTG and PF4 were estimated using commercial radioimmunoassay kits. A parallel release (basal value, under anesthesia and sternotomy, BTG:119.6 ng/ml, PF4:30 ng/ml) was present for both proteins in time dependent fashion until the end of extracorporeal circulation. High average levels were observed in patients in whom the bypass was stopped after about one hour (BTG 1606 ng/ml, PF4 745 ng/ml) and similarly in those in whom bypass was stopped after about two hours (BTG 1540 ng/ml, 745 ng/ml). No correlation was found either between the level of PF4 and the additional heparin administered after the initial standard dose (r = 0.29. p>0.10) and between the level of PF4 and the amount of heparin consumed during the bypass (r = 0.05, p>0.47).
