An all-plastic double-lumen catheter for continuous blood sampling

The all-plastic double-lumen catheter described in this paper represents a significant improvement over previously reported catheters. It is used routinely for continuous blood withdrawal in two clinical investigation units and one experimental laboratory in Toronto. No experiments have been terminated due to catheter failure or clot formation and no maximum time limit of its use has been established. In clinical use with adult patients (4), the outer cannula has been kept open overnight with a slow saline drip after 18 hours of use. The same cannula has then been reused the next day for another 16 hours with a new adapter precut to size. Its design enzures that: (1) heparin is mixed with the blood at the site of blood sampling. (2) Blood is never brought into contact with glass or metal. (3) The blood channel is a uniform polyethylene tube with no discontinuities and no junctions, except where it is introduced into the peristaltic pump tube. The overall manufacturing process is simple, and percutaneous insertion is straightforward. Through its use, clotting in the blood withdrawal line and thrombus formations in the blood analyzer are no longer problems to limit the use of techniques requiring continuous blood withdrawal.