In an effort to better mimic the thromboresistive nature of vascular endothelium, extracorporeal circuits bonded with
heparin or
phospholipids were developed. Using no systemic heparinization, these circuits were compared with standard poly(
vinyl)chloride (
PVC) (Tygon) in a rabbit model of
extracorporeal circulation (ECC). Control circuits were run with and without systemic heparinization and used as comparison groups against the test circuits. Two New Zealand White rabbits were used per study: One was used as the platelet donor for 111Indium platelet labeling; the other animal was placed on bicaval ECC for 4 hours. Circuits (
heparin coated n = 6,
phospholipid coated n = 8, nonheparinized controls n = 14, heparinized controls n = 18) consisted of 1 m of tubing, two downsizing connectors, and two venous
cannulae. ECC blood flow was at least 75 ml/min. Platelet and
fibrinogen measurements were made hourly, and circuit dosimetry was performed at the end of the study or on circuit
thrombosis.
Thrombosis of the circuit occurred in one
heparin coated, two
phospholipid coated, and eight nonheparinized control circuits. None of the heparinized control circuits thrombosed. There was no significant difference between the groups with regard to platelet count or platelet adhesion. Test circuits exhibited preservation of
fibrinogen levels. In this rabbit model of ECC, circuits coated with
heparin or
phospholipids appeared to preserve
fibrinogen levels but did not reduce platelet adhesion or consumption.