A simple technique for continuous intravenous infusion in rats.

Abstract

I deally, a technique for continuous intravenous infusion over long periods must inhibit as little as possible the freedom of the rat within its cage. To this end, techniques have been described by Little and associate9 and Eve and Robinson’ in which the rat’s movements are facilitated by a “swivel” interposed between the vascular catheter and the infusing pump. However, the cost of the necessarily finely engineered swivels can become considerable in experiments in which large numbers of rats are used. Furthermore, we have found such swivels are not cntircly reliable when used over long periods. We have developed a comparatively simple technique based on the use of “curtain wire.” “Curtain wire” is a metal helical extension spring, external diameter about 3 mm., used to suspend lightweight curtains or drapes and is available at most home furnishing or hardware stores. A comparable product is the spirally coiled wire sheath of cables in some automobile throttle connections and cycle brakes. The “wire” is very flexible, but the spiral winding limits the extent to which the rat can rotate the wire, and hence the catheter, about its fixed end. The metal “wire” is also so strong that the rat cannot chew through it. When attached through a harness to the rat, the “wire” permits freedom of movement within the cage including a rotation of 3 or 4 turns in either direction about the axis. This torque is insufficient to cause serious twisting and, hence, occlusion of the fine polythene catheter which passes directly from that rat’s jugular vein through the harness and then up through the center of the “wire” to the infusion pump. The apparatus is illustrated in Fig. 1. The harness is made of 2 pieces of