TECHNICAL AND SURGICAL ASPECTS OF CONTINUOUS VASCULAR ACCESS IN FREELY MOVING SMALL ANIMALS

Many systems and techniques for continuous vascular access in small an imals have been described. Problems with these systems have included ( 1) insufficient free movement, (2) sepsis, (3) high cost, (4) complica ted construction, (4) thrombosis, and (5) dislocations of the intraven ous catheter. the described operative techniques and a new experimenta l 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 cathe ter runs to the swivel. The swivel, a modified conventional glass syri nge, is positioned in ball bearings and a Johnson joint. The swivel, b all bearings, and Johnson joint are counterbalanced and can move up an d down. When this system was used, the catheters functioned well for a s 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 weigh t (3.53 +/- 0.37 gm/day (mean +/- SEM)). The rotary portion of the swi vel and the Johnson joint secure stressless movement of the animal, av oiding twisting and dislocation of the catheter, which overcomes typic al problems of existing methods. The low thrombogenicity of the polyur ethane catheter also reduces complications. A further advantage is low cost, because prefabricated, reusable materials are used.