Intravenous Infusion (via the External Jugular Vein) in Rats
Via a catheter, ALZET pumps can deliver directly into the venous or arterial circulation. ALZET pumps have been shown to pump successfully against arterial pressure with no alteration in flow. The following procedure details placement of a catheter in the external jugular vein. In many cases, this site is preferable because of its size and ease of access. Other sites may also be used.
Note: This procedure requires attachment of a catheter to the pump (more info)
When cannulating the jugular vein of rats, use the Rat Jugular Catheter (0007710), sold by DURECT Corporation. This catheter fits onto an ALZET Osmotic Pump with no modification and has been ETO sterilized.
Step 1. Prepare the pump and catheter (more info). Note: In applications involving a catheter, the pump must be primed before implantation (more info).
Step 2. Once the animal is anesthetized, shave and clean the ventral portion of the animal’s neck.
Step 3. For ease of manipulation during surgery, the animal can be placed in a sterile stockinette and the head and neck exposed for anesthesia administration and surgical access.
Step 4 . Position the animal in dorsal recumbency and secure its head and anesthetic delivery apparatus in place.
Step 5 . Place a small bolster beneath the animal’s neck to expose the ventral neck more fully.
Step 6. Use a small, sharp scalpel blade to make a single incision from the ramus of one side of the jaw to the tip of the sternum just lateral to the trachea/midline.
Step 7. Gently dissect down through the salivary and lymphoid glands, adipose tissue, and fascia to the external jugular vein, which is superficial to most of the neck musculature. Gently elevate and clean the jugular vein for a distance of 1.5 cm.
Step 8 . Tie off the cephalic end of the vein, leaving tails 4-5 inches long.
Step 9 . Place two loose ligatures around the cardiac end of the vein. Place hemostats on the cephalic suture and one cardiac suture to provide gentle counter-traction to the vessel.
Step 10 . To inhibit vasoconstriction, apply a few drops of lidocaine or other vasodilatory substance (at body temperature), and allow time for effect.
Step 11 . Use a fine gauge needle (22 – 20 gauge for rats)* bent at an approximate 90-degree angle to pierce the vessel. Alternately, a small ellipsoidal piece can be cut from the ventral aspect of the vessel with fine iris or micro scissors. Do not cut so much tissue as to weaken the vessel such that it breaks when traction is applied via the rostral ligature ends while passing the cannula.
Step 12 . Once the vessel has been pierced, control hemorrhage with gentle traction on the cephalic ligature ends.
Step 13 . The free end of the catheter can be inserted into the hole in the vein wall, and advanced gently to the level of the heart (about 2 cm in an adult rat). Tie the cardiac ligatures snugly around the catheter, being careful not to crimp the catheter. The cephalic ligature can then be tied around the catheter. Cut the ends of all three ligatures close to the knots.
Step 14 . Using a hemostat, tunnel over the neck, creating a pocket on the back of the animal in the midscapular region. Lead the pump into this pocket, allowing the catheter to reach over the neck to the external jugular vein with sufficient slack to permit free head and neck movement.
Step 15 . Pass the caudal end of the pump through this tunnel into the pocket.
Step 16 . Use a two-layer closure, with one layer of suture in the underlying fascial tissues, and one in the skin. The deep layer should be closed with 4-0 or 5-0 absorbable material in a simple continuous or interrupted stitch, but silk is acceptable for short-term survival studies of 2-4 weeks. The skin can be closed with the same material, nonabsorbable suture, or stainless steel wound clips.* Wound clips or ligatures in the skin should be removed in 1-2 weeks if the animals are to survive longer than 2-4 weeks.