Pump-induced platelet aggregation in albumin-coated extracorporeal systems.
OBJECTIVE
Coating of extracorporeal systems with heparin does not prevent platelet activation and subsequent bleeding disorders. We investigated whether this could be due to elevated shear stress caused by a roller pump.


METHODS
Human or rat blood was made to flow through an uncoated or an albumin-coated medical polyvinyl chloride tube with or without a roller pump. Aggregation of platelets in the tubing was recorded continuously with a photometric device.


RESULTS
Although in vitro gravitational flow in uncoated tubes caused immediate platelet aggregation and platelet loss, this remained absent in coated tubes. When the pump was started in experiments with a coated tube strong platelet aggregation was observed and platelet count fell within 5 minutes to 78% +/- 2% and 71% +/- 3% of control values in human and rat blood, respectively. In vivo, no aggregation was observed during spontaneous flow in rats with an albumin-coated tube running from the carotid artery to the femoral artery, but aggregation started as soon as the blood was pumped. Pump-induced platelet aggregation, both in vitro and in vivo, could be prevented with aurintricarboxylic acid, which specifically inhibits shear-induced platelet aggregation as has recently been shown. Pump perfusion of blood in an uncoated tube did not elicit platelet aggregation.


CONCLUSIONS
Pump perfusion of blood in coated systems elicits shear-induced platelet aggregation, which may be prevented by administration of substances that block the binding of von Willebrand factor to glycoprotein Ib receptors on the platelets. The effects of pumping on platelets are masked in uncoated circuits because of the dominant influence of blood-material contact.
Borgdorff
P
P
Laboratory for Physiology, Institute for Cardiovascular Research Vrije Universiteit (ICaR-VU), Amsterdam, The Netherlands. p.borgdorff.physiol@med.vu.nl
van den Berg
R H
RH
Vis
M A
MA
van den Bos
G C
GC
Tangelder
G J
GJ
D000418:Albumins / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001312:Aurintricarboxylic Acid / Q000494:pharmacology; D020099:Coated Materials, Biocompatible; D005112:Extracorporeal Circulation / Q000295:instrumentation*; D018056:Hemorheology; D006801:Humans; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
D000418:Albumins; D020099:Coated Materials, Biocompatible; D001312:Aurintricarboxylic Acid