Characteristics of heparin-induced platelet aggregates in chronic hemodialysis with long-term heparin use

This study investigated the usefulness of a new platelet aggregometer with a laser-scattering method for detection of heparin-induced small platelet a ggregates in chronic hemodialysis patients. Using this device, small platel et aggregates (particle size 9-25 mum) were detectable, but these aggregate s could not be detected using a conventional light transmittance aggregomet er. The laser-scattering intensity of the small aggregates was increased wi th an increasing dosage of heparin as agonist. These aggregates were disagg regated by heparin neutralization with protamine sulfate. Induction of smal l platelet aggregates by heparin was inhibited by preincubation with nafamo stat mesilate, a synthetic protease inhibitor, and cilostazol, a platelet p hosphodiesterase inhibitor, but not by the therapeutic doses of aspirin or argatroban, a selective thrombin inhibitor. The dialysis patients with long term heparin use could be divided into two groups: responders to heparin, w ho formed small aggregates with a scattering intensity over 0.51 x 10(5) V after addition of 0.5 IU/ml of heparin obtained from normal platelet-rich p lasma without inductor, and nonresponders, who showed an intensity under 0. 51 x 10(5) V. The rate of heparin responders among dialysis patients was si gnificantly higher than the rate among normal subjects. Heparin-induced sma ll aggregates were detected in 13 (36.1%) of 36 normal subjects with no his tory of heparin infusion and in 37 (62.7%) of 59 dialysis patients who rece ived heparin anticoagulation during each dialysis session. Dialysis patient s with coronary heart disease did not have a significantly higher rate of h eparin responders than patients without complications. There was no signifi cant difference in the positivity rate between cases complicated by diabete s and those without diabetes. In patients who had more than 2 episodes of t hrombotic occlusions of an arteriovenous fistula, the rate of responders an d the enhancement of scattering intensity of smalt aggregates by heparin we re significantly increased compared with these in patients without occlusio ns during the preceding 2 years. Moreover, dialysis patients with a positiv e heparin response showed a marked increase in scattering intensity of smal l aggregates after heparin infusion in each dialysis session. Determination of the response to heparin prior to heparin use in dialysis patients with repeated thromboembolic com plication may be useful in choosing anticoagula nt regimens. Copyright (C) 2001 S. Karger AG, Basel.