A technique for long-term venous cannulation in rats.

We require repeated blood samples from rats over long periods in our studies on obese hyperlipemic animals and normal controls. Under our conditions of lipid adnormality and exercise previously reported techniques did not give long-term cannula patency. We have thus developed a technique using thromboresistant heparin-treated Silastic tubing and a mesh-stabilized metal cannula at the base of the skull. The tubing is inserted into the vena cava without occlusion and the tip lying in the region of the termination of the hepatic veins. The tubing exists from the abdomen through the incision and runs subcutaneously to a metal tube protruding from the skin. It is closed with a short length of polyethylene tubing folded over and secured with a tight Teflon sleeve. Heparinized saline is used to fill the cannula and flush it at biweekly intervals. The cannulas remain patent for long periods with 59% permitting withdrawal of blood at 120 days. Loss of function is random after 30 days when 100% were patent. A significant number remain functional at 200 days.