A 44-year-old Asian elephant, the matriarch of a herd of breeding elephants at a zoo, developed a foot infection that progressed to osteomyelitis of the phalanges. Surgical removal of P-3 and part of P-2 was recommended. A complicating factor was that degenerative joint disease had developed over the years, and the right elbow was nearly ankylosed. According to the keepers, the elephant had not laid down for 8 years. The animal slept leaning against a wall or a fence. Although docile, well trained and managed under free contact, it would not or could not lie down on command.
A decision was made to modify existing facilities to allow immobilization in the standing position and then gently lower the elephant to the floor. The patient weighed 2817 kg. The suspension system consisted of two steel “I” beams braced on the top with right angle and diagonal steel strips bolted to the “I” beams. The beams spanned a distance of 9.8 m (32.2 ft) and were set on brackets anchored to solid concrete walls.
The hoist system was powered by a hydraulic pump used to operate the door system in the elephant house. The hoist was designed to move horizontally on a “hammerhead” trolley, rolling on the suspension system’s I beams. A continuous loop of wire cable extended from one wall to the other, under the control of an electro/hydraulic diverter valve. Vertical movement was achieved by a swivel hook/load block (with two sheave) having a lifting capacity at the hook of 9072 kg (20,000 lb).
The sling bed (heavy nylon fabric) was supported by 22 5.08-cm (2 inches) nylon straps, each having a breaking strength of over 5443.2 kg (12,000 lb). The frame superstructure of the sling was constructed of square, metal-welded tubing with a wall thickness of 0.64 cm (1/4 inch) and outside dimension of 5 cm (2 inches). The frame was 1.12 m (44 inches) long and 0.74 m (29 inches) wide, with 22 eye rings to attach straps. Four choker cables were used to attach the metal frame to the hook on the hoist.
A special waterbed was constructed that was 4.27 m (14 ft) long by 3.66 m (12 ft) wide, and 38 cm (15 inches) deep when fully inflated. The bed was constructed of 30-mm polyvinyl geotextile fabric, with four hose ports installed on one end.
Food was withheld from the elephant for 36 hours. Water was withheld for 12 hours. The elephant was moved from its normal night quarters into the room where the support beam and the hoist were in place. The animal had walked through this room previously and was generally acquainted with the apparatus. The only people in the room with the elephant were its regular keepers. The animal was moved to the center of the support beam and maintained at 90° to its long axis.
The keepers moved the sling into position and began to attach the straps to the metal framework at the top of the sling. The elephant became agitated and did not respond to the calming efforts of the keepers. Etorphine hydrochloride (M99) was administered (1.75 mg) intramuscularly in the hind limb via a pole syringe. By 15 minutes after the initial etorphine injection, it had quieted, and the remaining straps were anchored to the metal frame. The breast band was positioned ventral to the point of the shoulders to limit tracheal compression. In an attempt to reduce abdominal compression, which in turn inhibits excursion of the rib diaphragm, the butt strap was adjusted to support the tuber ischii and caudal thigh muscles. The belly band was positioned cranially to support the sternum. An indwelling IV catheter was inserted into an ear vein and anchored in place.
After the sling was in place, long ropes were attached to each leg. The ropes on the two left legs were attached by a bowline knot just above the widest area of the foot. Those ropes were then thrown over the back of the elephant and extended to block and tackles anchored to rings in the wall. The other ropes were attached to the right limbs in a similar fashion.
The right front limb was given special attention. Two ropes were applied to that limb: one to pull the leg under the body, and the other (attached to a block and tackle) to pull the leg forward at the same time. The intent was to keep that leg in a position that did not make a direct fulcrum from the foot upward, but which by pulling forward would gently roll the elephant into lateral recumbency. The rolled-up, deflated waterbed was pulled into the room and positioned for unrolling after the elephant was immobilized and lifted off its feet.
When all positions were manned, an additional 0.75 mg of etorphine was slowly administered through the IV catheter, 40 minutes after the first dose of etorphine. The sling was raised by the hoist as the animal began to visibly become immobilized. Within 3 minutes, the elephant was hanging in the sling. The hoist operator was directed to lift the elephant off the floor so the waterbed could be unrolled and pulled beneath the elephant’s feet. Tension on the leg ropes was applied and slackened as required during the lowering process. When the feet solidly contacted the waterbed, the hoist operator began to move the hoist on the support beam toward the right side of the room while continuing to lower the elephant. The elephant was completely immobilized and offered no resistance. The sling was left in place throughout the surgery. Two water hoses were attached to the waterbed ports, and filling began.
Following positioning of the elephant in right lateral recumbency, the trachea was manually intubated with a 30-mm equine style, cuffed endotracheal tube and the tube cuff inflated. The orotracheal tube was connected to a standard large animal anesthesia circle system. A latex weather balloon replaced the traditional 20–30-L rebreathing bag used for equine anesthesia. The isoflurane vaporizer dial setting was maintained at settings of 1.5–2.0% for most of the anesthetic period to supplement periodic IV bolus doses of etorphine (total additional etorphine was 1.4 mg).
Thirty minutes before the completion of the surgery, the isoflurane vaporizer was turned off, but oxygen continued to flow. As the inhalation anesthesia began to wane, additional etorphine was intermittently administered intravenously (total dose over the remaining 45 minutes of recumbency was 0.4 mg).
The waterbed was deflated by opening the four ports before the completion of the surgery, so that when the foot had been wrapped and the elephant was under the effects of etorphine, the lifting process could begin.
The direction of pull on the leg ropes was reversed. As the lift progressed, the body was rolled into an upright position with the feet 10–15 cm (4–6 inches) above the waterbed, which was pulled from beneath the animal. The animal was then lowered so the feet contacted the floor, and the immobilization was reversed with naltrexone (250 mg), administered intravenously. In 3 minutes, it was standing on its feet with little or no support from the sling. The animal was allowed to stand and move about for another 2–3 minutes while we observed, watching for signs of complete reversal.
When the keepers began to release the sling straps from the metal frame, the elephant became agitated, and it was not safe for anyone to be near its head. The animal began vocalizing and trying to lunge away from the slinging site. It was impossible to administer additional drugs intravenously, so 1.25 mg of etorphine was administered intramuscularly. In approximately 5 minutes it quieted down, and the keepers could release the rest of the straps and remove the sling from its body. No additional etorphine reversal agent was given. Within 1 hour of the last etorphine injection, it was possible for the keepers to approach and treat it as they had before the immobilization episode.
The keys to this successful standing immobilization were (1) a trained elephant that responded to direct control by its keepers, (2) a well-designed and installed suspension system, (3) an excellently designed and constructed hoist system that was able to track along the suspension system, and (4) an adjustable, sturdy sling. It was also necessary to use both an injectable narcotic and isoflurane inhalation anesthesia.