Abstract

In June of 2002, an immature, female smalltooth sawfish, Pristis pectinata, living in our 851,718- liter Open Ocean exhibit was reported to be lying on the bottom of the tank and bleeding from the cloaca. Multiple skin lacerations were visible just caudal to the cloaca, and trauma from a tank mate was suspected. When the animal was coaxed to swim, actively bleeding tissue was seen protruding from the cloaca.

The sawfish, estimated to weigh 55 kg, was sedated with a mixture of ketamine (2.3 mg/kg actual dose) and xylazine (6.6 mg/kg actual dose) administered intramuscularly by pole syringe. Additional ketamine (up to 300 mg) was given over the next 35 minutes. The animal was then captured, removed from the pool, weighed (65.2 kg) and placed into a large box (266 cm x 71.5 cm x 63 cm) of well-aerated artificial seawater containing tricaine methane sulfonate (80 mg/L). Ventilation was accomplished by directing water flow from a submersible pump through the mouth and over the gills of the animal. Examination revealed that the lower intestine had been completely severed and was protruding from the cloaca. Blood was collected; a low hematocrit (eight percent) confirmed that significant blood loss had occurred.

The animal was prepared for surgery by placing it in dorsal recumbency on a stretcher modified to accommodate the dorsal fins of a shark or similar elasmobranch, such as a sawfish. The stretcher was secured at an angle of approximately 30°in order to keep the animal's rostrum and gills submerged in the anesthetic. An intravenous line was established in the caudal vein through which elasmobranch Ringers, lactated Ringers buffered with sodium bicarbonate, ceftazidime (22mg/kg), and Oxyglobin® (Biopure Corporation, Cambridge, MA) (7.7 ml/kg) were administered during the surgery.

The caudal ventrum was cleansed with copious amounts of sterile saline, and a sterilized plastic medical waste bag was used as a drape. A 15-cm-long midline incision was made mid-coelom and the proximal portion of the intestine was rapidly located, having been severed just caudal to the spiral valve. Two large bleeding vessels located within the wall of the spiral valve were clamped and ligated. A third vessel running along the ventral aspect of the bowel was also ligated. Approximately 15 cm of lower intestine was missing and assumed to have been consumed by a tank mate. The distal portion of the intestine was retracted into the coelom for the repair. An intestinal anastomosis was performed by resecting approximately one cm of traumatized tissue from each end of the intestine before joining the ends with simple interrupted sutures (2-O Vicryl) placed every four to five mm. The junction was then oversewn using 2-O Vicryl in a continuous pattern, after which the coelom was flushed with one liter of saline mixed with 25 ml of gentamicin (50 mg/ml). O-Prolene was used to close the muscle, linea, and subcutaneous tissues using a simple interrupted pattern. The skin was closed with simple interrupted sutures using O-steel. The total surgery time was two hours.

The animal recovered well following surgery. Ceftazidime (20 mg/kg IM Q 72 hour) was administered intramuscularly for three weeks after which enrofloxacin was given orally (10 mg/kg PO Q 48 hr) for five weeks. The animal's appetite returned seven days post-operatively. The sawfish readily ate small meals of squid and shrimp by nine days. The animal was fed twice per day at 25 percent of the normal weekly ration (1.7 kg), increasing to 50 percent, 75 percent, and 100 percent of the normal ration 16, 29, and 42 days post-surgery, respectively. The percentage of whole fish in the diet was increased from 25 percent to 100 percent over the course of 40 days.

Intestinal eversion has been reported in carcharhinids,^1,2 and it appears that smalltooth sawfish are capable of this as well (Henningsen et al., in prep.). During the past five years, we have had a lemon shark, a sandbar shark, and one other smalltooth sawfish sustain serious injury to the lower bowel during intestinal eversion for the purpose of cleansing the tissues. In all of our cases, blood loss has been severe and the animals have not survived more than 48 hours beyond surgery. This is the first case in which we have used Oxyglobin®, a polymerized bovine hemoglobin in a modified Ringer's solution. Preliminary results in rainbow trout³ showed that this product improved blood oxygenation with no deleterious peripheral effects. We did not attempt to collect blood following recovery of the sawfish for fear of causing the wound repair to fail during capture. However, we believe that that our animal survived in part due to the administration of this hemoglobin-based oxygen carrier.

References

1.  Crow GL, JA Brock, JC Howe, BE Linnon. 1991. Shark bite wounds of the valvular intestine: the cause of an acute mortality syndrome of captive blacktip reef sharks, Carcharhinus melanopterus. Zoo Biology 10: 457-463.

2.  Crow GL, JC Howe, S Uchida, S Kamolnick, MG Wisner, JN Caira. 1990. Protrusion of the valvular intestine through the cloaca in sharks of the family Carcharhinidae. Copeia 1990(1): 226-229.

3.  Myliniczenko ND, LA Clayton, MG Greenwell, N Hettiger. 2002. Effects of oxyglobin administration in rainbow trout (Oncorhynchus mykiss). Proceedings of the American Association of Zoo Veterinarians. Pp. 332-336.