Chronic, nonocclusive, and maintenance-free central venous cannula in the rat

To provide a means of taking repeated blood samples from conscious, stress-free rats, we devised a method to chronically cannulate the inferior vena cava. The rat was anesthetized with pentobarbital sodium plus methoxyflurane. The inferior vena cava was exposed through a midline abdominal incision. Silastic tubing (0.020 in. ID, 0.037 in. OD) was pushed through a tiny hole punctured in the wall of the vein; it remained in place without leaking due to the elasticity of the vessel wall. The cannula was advanced towards the heart until its tip lay at the level of the xiphisternum at which point blood could be aspirated. A series of silk (4-0) sutures to the psoas muscle and body wall held the cannula secure without compromising blood flow. The cannula ran subcutaneously to the back of the neck where it was ligated to the underside of the skin (prolene 4-0 suture), plugged with a short metal obturator, and exteriorized through a small stab wound. The cannula was filled with heparinized saline, but it was not necessary to regularly flush it through to maintain patency. Sepsis did not occur and animals autopsied several months after cannulation showed no tissue reaction around the cannula.