In Vitro Inhibition of Platelet Aggregatton by the Gelatin Plasma Expander Haemaccel.(R)

In a study concerning open-heart surgery we found that, platelet aggregates present in heparinised human blood disappeared immediately after addition of the gelatin plasma expander haemaccel. A study was therefore initiated of the effect of haemaccei on platelet appregation (Payton apprepometer, 4W RPM as controlled by stroboscope, 37°C, final platelet count 200-300 χ 109/1) and compared with the effect of bovine serum albumin (USA) and platelet poor plasma (PPP). Haemaccel powder was kindly supplied by Rehringwerke and contained 0.98% sodium, 0.015% calcium and no measurable potassium. 0.3 ml human platelet rich plasma (PRP) was nixed with 0.2 ml haemaccel (final concentrations 0-20 mg/ml) in Tyrode’s solution (2 mM Ca++. pH 7,4), Haemaccel inhibited apgrepation in both citrated and heparinised PRP induced by collagen, ADP or adrenalin, both in the presence or absence of indomethacin (90/μM), PPP (0.2 ml) and BSA (in Tyrode’s solution, final concentrations 0-16 mp/ml) were also inhihitinp, hut on a weipht hasis less than haemaccel. Different Ca++ concentrations in the Tyrode’s solution did not alter the inhibition by haemaccel. Final pH in aggregation mixtures varied by less than 0.10 for a given experiment. It is concluded that, under the conditions used, haemaccel and USA inhibit platelet appregation, probably by a non-specific mechanism.