Technical and surgical aspects of continuous vascular access in freely moving small animals

Many systems and techniques for continuous vascular access in small animals have been described. Problems with these systems have included (1) insufficient free movement, (2) sepsis, (3) high cost, (4) complicated construction, (4) thrombosis, and (5) dislocations of the intravenous catheter. The described operative techniques and a new experimental setup overcome these complications. The apparatus involves a swivel that is connected with an intravenously placed polyurethane catheter. A leather harness on the back of the animal is connected with the end of the swivel joint via a silicone tube in which the intravenous catheter runs to the swivel. The swivel, a modified conventional glass syringe, is positioned in ball bearings and a Johnson joint. The swivel, ball bearings, and Johnson joint are counterbalanced and can move up and down. When this system was used, the catheters functioned well for as long as 28 days, with a mean duration of 24.4 +/- 1.8 days (n = 420). Five catheter dislocations resulted from harness failure, and three dislocations were caused by animals twisting. All animals gained weight (3.53 +/- 0.37 gm/day (mean +/- SEM)). The rotary portion of the swivel and the Johnson joint secure stressless movement of the animal, avoiding twisting and dislocation of the catheter, which overcomes typical problems of existing methods. The low thrombogenicity of the polyurethane catheter also reduces complications. A further advantage is low cost, because prefabricated, reusable materials are used.