Abstract

Introduction

Historic methods of surgical contraception in felids have included ovariohysterectomy, hysterectomy, tubal ligation, and ovariectomy through a large ventral midline laparotomy incision. Complications associated with these procedures include prolonged anesthetic time, infection, dehiscence, self-mutilation of the incision, and prolonged recovery.^1,2

Evaluation of the reproductive tract as well as assisted reproduction and ovariohysterectomy have been documented through the use of laparoscopic instrumentation in felids.^1,4,6 Advances in human laparoscopic surgical techniques have resulted in decreased anesthetic time, self-mutilation, and recovery time.³

Materials and Methods

Two female African lions (Panthera leo) were selected for management-related contraception, though permanent sterilization was not desired. One adult, a 5-year-old, overweight (160 kg) female (lion 1) and her 18-month-old female offspring (lion 2), weighing 111 kg, were immobilized with a combination of 5 mg/kg ketamine hydrochloride (Ketaset, Fort Dodge Laboratories, Inc., Fort Dodge, IA, USA), lyophilized by Congaree Veterinary Pharmacy, Cayce, SC, USA, 0.5 mg/kg xylazine hydrochloride (Rompun, Bayer Corp., Shawnee Mission, KS, USA) and 0.1 mg/kg midazolam hydrochloride (Faulding Pharmaceutical Co., Elizabeth, NJ, USA) IM via blowdart (Telinject, Saugus, CA, USA) in lion 1 and hand-syringe in lion 2. The lions were placed in dorsal recumbency, intubated, and maintained on isoflurane (IsoFlo, Solvay Animal Health, Inc., Mendota Heights, MN, USA). Respirations were controlled with a time-cycled ventilator (Mallard Medical, Inc., Irvine, CA, USA) attached to a circle anesthetic system. Mechanical ventilation was initiated upon abdominal insufflation with carbon dioxide (CO₂).

A cephalic intravenous catheter was placed, and 10 ml/kg/h of lactated Ringer’s solution (Abbott Laboratories, North Chicago, IL, USA) was administered throughout the procedure. A urinary catheter (Rusch Inc., Duluth, GA, USA) was placed to maintain an empty bladder, facilitating visualization of the reproductive tract. Continuous electrocardiography, direct arterial blood pressure (BP), capnography (Critikon, Inc., Southington, CT, USA), respiratory excursions, and oxygen saturation (Pulse Oximetry, Nonin Medical, Inc., Plymouth, MN, USA) were monitored and recorded every 5 minutes. A dorsal pedal arterial catheter was placed to facilitate serial blood gas and direct BP analysis throughout surgery (Critikon, Inc.). Indirect BP (Cardell™, CAS Medical Systems, Inc., Branford, CT, USA) values were monitored during the surgical procedures by placing the cuff over the base of the tail. Indirect BP values closely paralleled direct BP measurements. Mean arterial pressure (MAP) in lion 1 dropped below 80 mm Hg, and 0.1 mg/kg of ephedrine sulfate (Bedford Laboratories, Bedford, OH, USA) was administered IV. MAP rose to acceptable levels within 10 minutes.

After sterile preparation, a 1.5-cm ventral midline incision was made 6 cm caudal to the umbilicus into the abdominal cavity. A purse-string suture (0 Polydioxanone PDS, Ethicon, Inc., Somerville, NJ, USA) was placed in order to tack the abdominal fascia to the peritoneum. An optical obturator (Optiview Disposable Surgical Trocar, Ethicon Endo-Surgery, Inc., Cincinnati, OH, USA) with a 10-mm surgical telescope (Olympus Corp., Melville, NY, USA) was used to visualize the subcutaneous tissues, fascia, peritoneum and abdominal cavity. Insufflation with CO₂ to 15 mm Hg of pressure was achieved with an endoscopic CO₂ insufflator (Olympus Corp., Melville, NY, USA) attached to the optical obturator. In lion 1, extensive deposits of adipose tissue were observed, at times obscuring the field of view. Once the uterine horn was identified, it was followed cranially to the ovary, whereupon the ovarian tube was identified between the ovary and the mesosalpinx.⁵ The ovarian tube was gently elevated away from adjacent tissues with laparoscopic Kleppinger® forceps and subsequently cauterized with bipolar current (Richard Wolf GmbH, Knittlingen, Germany). The procedure was repeated for the opposite ovarian pedicle. Extreme caution was used when cauterizing the ovarian tube to minimize contact with adjacent tissues. Once both ovarian tubes were cauterized, the surgical sites were observed for hemorrhage, and upon finding none, the abdominal CO₂ pressure was decreased to <5 mm Hg. The trocar was removed, and the incision closed via the original purse-string suture. A subcuticular simple continuous suture (0-PDS, Ethicon, Inc.) was placed, and topical formulated cyanoacrylate (Nexaband, Veterinary Products Laboratories, Phoenix, AZ, USA) was applied to the incisions. The incisions were infiltrated with 20 ml of 0.5% bupivacaine hydrochloride with 1:200,000 epinephrine (Marcaine, Abbott Laboratories, North Chicago, IL, USA) for site-specific analgesia.

Both lions recovered without complication and began eating the same day. Lion 1 was observed to occasionally lick the incision, causing dehiscence of the subcuticular layer; it was allowed to heal by second intention. Lion 2 was not observed to debride the incision, but dehiscence of the subcuticular layer was observed along with significant seromatous formation. The incision was allowed to heal by second intention. Both lions were returned to the pride the same day as surgery, returned to the exhibit within 10 days of the procedure, and recovered without further complications.

Discussion

Megestrol acetate implants have been used historically for contraception in felids. Current recommendations advise removal of the implant and a return to normal reproductive cyclicity for a period of 1 year after removal. In this case, space was not available to keep the females separated from the intact male of the pride. Tubal cauterization was elected in these lions for potential reversal in the future. In humans, >75% of re-anastomoses surgeries are successful, with more than 30–40% of women becoming pregnant. Total surgical time was approximately 35 minutes, and a rapid return to normal function was apparent in both animals. In this case, lion 1 was imported from Africa, and her genetic lineage could become important when future breeding recommendations are considered.

Tubal cauterization via laparoscopy is associated with shorter surgical times than laparotomy, facilitating decreased total anesthesia time. Disruption of tubal function may also be accomplished by ligation. This procedure may be more easily reversed but requires more initial operative time and expertise to perform. The shorter incision length (1.5 cm vs. >10 cm) reduces the risk of dehiscence and may reduce self-mutilation behavior. Although both subcuticular suture lines dehisced in these lions, both subsequently healed via second intention. Additional therapy was not necessary for healing.

In humans, abdominal insufflation activates peritoneal stretch receptors, resulting in pain that persists even after the intra-abdominal pressure has been decreased. Residual CO₂ within the abdomen is also associated with discomfort. Neither of these lions demonstrated observable discomfort after the procedure and returned to normal behavior the same day as surgery.

Laparoscopic surgery requires specialized equipment and technical expertise. In addition, a ventilator is required to prevent severe hypoventilation and hypercapnia that results from abdominal insufflation with CO₂.

Use of laparoscopic tubal ligation in lions appears to be a valuable tool for long-term contraception with the added benefit of potential reversibility while maintaining reproductive cyclicity.

Acknowledgments

The authors would like to thank DiAnn Roberts, Shirley Williams, Kim Wanders, Sarah Dunkard, Eric Vaught, Kristine Kasparson, Jennifer Pollard, Dr. Dawn Parker, and the rest of the animal staff for the care of both lions.

Literature Cited

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