Light microscopic and scanning electron microscopic findings on intravenous polyurethane catheters

Tips of two different types of unused and used intravenous polyurethane catheters as well as heads of the corresponding needles for venipuncture, artificially cut surfaces and longitudinally cut parts were either directly mounted on stubs or previously fixed in 1% phosphate buffered glutaraldehyde, postfixed in 1% phosphate buffered osmiumtetroxyde (pH 7.4), dehydrated with acidified 2,2-Dimethoxypropane, dried in a critical point drying apparatus using CO2, mounted with silver paint on stubs and sputter coated with 15 nm gold. In general, the surface of polyurethane catheters is smoother than that of catheters manufactured out of other materials. Distance marks, when placed on the surface and parts of the catheter wall, containing radio-opaque admixtures show a very irregular arranged structure. It could be demonstrated, that these parts of the catheter wall as well as roughnesses, caused by the manufacturing process, are much more favourable for adhesion of formed elements of the blood and bacteria or spores than other areas of the wall. In addition occasionally extensive fibrin layers and contamination of the surfaces by denaturated plasma proteins were observed. For better compatibility and for prevention of endothelial lesions some advice is given to the manufacturers and the medical staff.