A new
heparinized hydrophilic polymer,
H-RSD (graftcopolymer composed of
ethylene,
vinyl acetate,
vinyl chloride, polyethyleneglycolmethacrylate, quartenized dimethylaminoethylmethacrylate and ionically bound
heparin), continuously releases
heparin from its surface at the rate of approximately 0.004 units/cm2/min when placed in the plasma. It has excellent antithrombogenic and mechanical properties for a
biomaterial. In vivo evaluation for thrombogenically using IVC
indwelling catheter method in dogs revealed excellent antithrombogenicity over 2 wks. Use of
H-RSD as a coating material on other synthetic
polymers has also been studied,
Catheters made of
polyurethane were coated with
H-RSD 20 mu, 50 mu, 100 mu, and 150 mu in thickness, and were tested for thrombogenicity in the dog.
Catheters coated with 20 mu of
H-RSD caused moderate to severe
thrombus in the IVC after 2 wks, but
catheters coated with
H-RSD 50 mu or more were completely free of
thrombus formation after 2 wks. Scanning electron micrograph showed neither
fibrin clots nor platelet adhesion on the surface of
H-RSD catheters.
Heparin concentration in
H-RSD catheters was analyzed by electron probe X-ray microanalyzer before and after in vivo tests.
Heparin concentration became higher as the thickness of
H-RSD coating increased. After a 2 wk test,
heparin concentration in the
catheters decreased to about 85% of the initial value. Good retention of
heparin in the
H-RSD catheters after in vivo tests was found to correlate with continuous release of
heparin from its surface.
H-RSD catheters can be sterilized with
ethylene oxide gas.
Pyrogen and acute toxicity tests on extracts of
H-RSD were negative.
H-RSD catheters were used in 9 patients for up to 3 wks.
Thrombus formation observed by pullout venography or at autopsy in these patients was less than those seen in patients with
silicone rubber or
polyethylene catheters.