A novel technique for long-term vascular access in the unrestrained rat

A new system for long-term vascular access in the unrestrained rat (n = 380) is described that combines low cost with high reliability and free movement. It consists of a polyurethane catheter that is placed in the right atrium via the external jugular vein. A leather harness is applied to the animal and the catheter passed subcutaneously to the neck into the harness. The harness is connected to the outside of a swivel joint via a silicone tube in which the catheter runs. The catheter is connected to the inside of the swivel. The swivel is a modified conventional 5-mL glass syringe and is positioned in ball bearings and a Johnson joint. Swivel, ball bearings, and the Johnson joint are counterbalanced and can move up and down. With this system all catheters functioned well until they were electively removed after 28 days. Four catheter dislocations resulted from harness failure and three from a twisted catheter. Seven cases of septicemia and eight of thrombosis occurred. All animals gained weight (3.53 +- 0.37 [SEM] g/d) during the time the system was in place. The entire apparatus is simple and inexpensive to construct. The rotary portion of the swivel and the Johnson joint avoid twisting of the catheter, and the counterbalance enables the animal to move up and down. The low thrombogenicity of polyurethane further reduced complications. This system reduces stress for the animal during long-term investigations.