In terms of surgical anatomy, we had few bipedal mammals to use for comparison. Dr. Harris frequently asked us what was normal and what was not. He pointed to a place where one of the neck muscles split in two. Was that normal anatomy, or had it occurred when the kangaroo hit the fence? We really didn’t know. No textbooks existed for the kangaroo spine.
Fortunately, many aspects of anatomy and surgery are universal among mammals. For example, both kangaroos and humans have cartilage lining the articular surfaces (facets) between the vertebral wings and cartilaginous discs between the vertebral bodies. Both have ligaments holding the vertebrae in alignment, tendons that attach bone to muscle, and muscles crossing the surfaces of multiple vertebrae to give the spinal column strength. And in any species, the rate of post-operative healing depends on the degree of tissue damage and the quality of the blood supply to the affected area.
With these principles in mind, Dr. Harris was diligent, careful, and delicate, extrapolating from his experience in humans to preserve the normal anatomy and blood supply while making his way down to the misaligned bones. After half an hour, the affected vertebrae had been exposed with minimal bleeding. That in itself was an amazing feat.
Then came the most difficult, risky part of the procedure: realigning the spinal canal. In pushing the vertebrae back into their original positions, we faced one of two outcomes. We could successfully align the spinal canal and remove the pressure on the cord, allowing the damaged nerves a chance to heal. Or we could align the bones but in the process damage the cord further by increasing the trauma and bleeding in the area.
Carefully, and still ever so slowly, Dr. Harris pushed the vertebrae back into their original positions with his skillful hands. We heard a slight pop. Everyone held his or her breath except for the anesthetized Sally, who continued to breathe normally. A good sign, given that any manipulation of the spinal cord can disrupt descending signals from the brain. Nothing seemed to have worsened, so we continued the procedure.
After placing the spinal canal in what we hoped would be its normal position, Dr. Harris drilled small steel pins through the spinal processes of the second and third vertebrae. He wired the pins to each other and across the top, forming an H-shaped pattern. “It’s known as a modified Dewar’s technique,” he explained. The repair held both vertebrae firmly in place.
Next, we used bone cement to reinforce the pins and wire, knowing we couldn’t ask the kangaroo to sit still and stay in bed for a couple of months. We considered a bone graft to add support, but rejected the idea for the same reason. She needed complete, or near-complete, stability the moment she woke up. Her first hop, no matter how soft, would send vibrations right up to the unstable area. A bone graft would take weeks to solidify. We questioned whether the bone cement, the kind used to secure a new hip joint in a human, would be strong enough in the long run, but it was our only option.
During the entire procedure, Dr. Harris had remained calm, methodical, and relaxed. Even during tense moments, his voice and manner remained steady. When he removed his mask after the surgery, he looked pleased as he surveyed his handiwork. I guessed that he saw the entire effort as fairly routine. He simply applied what he already knew to a different species. To me, it was nothing short of a small miracle.
Dr. Harris knelt down next to the kangaroo while she woke up from the anesthesia. Watching the two of them, I noticed a linear scar crossing the back of the neurosurgeon’s neck. My mind came to an instant conclusion, confirmed months later when I finally got up the nerve to ask: the doctor had undergone a similar surgical procedure years earlier. Maybe that’s why he’d become an expert in this field.
Sally lay on her side, shivering as the anesthetic wore off. It would be some time before we knew if the kangaroo could use her limbs. We’d taken radiographs at the end of the procedure and everything looked good—in perfect alignment. Nevertheless, we could not be certain she still had nerve function.
I saw the surgeon’s clinical expression soften into a look of gentle, benevolent concern. It lasted only briefly—a few seconds—and then he smiled. From then on, I knew that Sally would be a patient our kind surgeon would never forget. He had felt what she felt.
Animals often represent more to us than their simple selves. Every patient deserves our empathy and compassion. Many also earn our respect, affection, or sympathy for a variety of reasons. We often try to control these emotions when they surface, as Dr. Harris did while working on Sally. Too much feeling can get in the way of good medicine. Too much worry about what the animal is feeling can draw your attention away from the task at hand. Alternatively, too little makes it impossible to do your best.
Sally made a relatively rapid and complete recovery. It was not easy, but we kept her in a heavily bedded and padded recovery stall, much like the ones used for horses recovering from anesthesia. Four heavy pads covered the walls, preventing the animal from hurting herself if she stumbled trying to sit up or stand. The abundant straw bedding helped make the kangaroo comfortable. By the third day she had recovered movement in her legs and tone in her cloaca. Her appetite picked up and she accepted all of her food treats.
Over the following weeks, Sally became stronger and her movements gained coordination. We often looked in on her, only to find her looking curiously back at us while munching on a piece of hay. For her physical therapy, we helped her to her feet and held her tail while she hopped in place. After thirty days in our hospital, she could stand for several minutes at a time. After ninety days, she had completely recovered. We walked the kangaroo into a large plastic kennel and took her back to the exhibit.
For years afterward, I offered Dr. Harris an update every time I saw him. I’d describe how well the kangaroo was doing on exhibit. She appeared healthy and active, indistinguishable from the others. Dr. Harris would smile broadly and say, “Of course she’s fantastic. She’s Sally!”
Our neurosurgeon, a physician and scientist, took a great leap in this case. He allowed himself to identify with a kangaroo. I’d like to see that kind of emotional crossover into the animal kingdom happen more often.
ABOUT THE AUTHOR
Born and raised in Mexico City, Mexico, Roberto F. Aguilar graduated from the National Autonomous University of Mexico in 1987. He did an internship in veterinary medicine at Oklahoma State University and a clinical residency in orthopedic avian surgery at the University of Minnesota. He served as staff veterinarian and then senior veterinarian at the Audubon Zoo in New Orleans from 1992 to 2005 and is currently director of conservation and science at the Phoenix Zoo. The author of numerous publications, including a book on exotic animal medicine, Dr. Aguilar has lectured extensively in most of Latin America and is the manager for Latinvets, a Listserv with more than 600 members in Latin America, Europe, and the United States.
Polar Bears STAT
by Jennifer Langan, DVM
I was preparing for the day’s cases when I heard over the radio, “Any 500 veterinary unit, 10-76 polar bear dens stat!” At Chicago’s Brookfield Zoo, our vet hospital call number is 500. The urgent message directed that any and all zoo vets go straight (called 10-76) to the polar bear grottoes. Since I was the only one working that day, that meant me.
Running out the door, I called to our two vet students to follow. This would be a learning experience for them, no matter what the problem was. We sped across the park to assess the situation. The polar bear keepers met me at the entrance to the dens and took me to see Aussie, down a long, cavelike, cement-floored corridor to the inside holding dens. Despite the rising summer heat outside, the cool, moist air carried the unmistakable smell of bear—a strong musty odor. Aussie, our twenty-year-old male breeding polar bear, stood at the cage front. He had a very large swelling, about half the size of a basketball, protruding from his belly button.
I bent down to look at him through thick iron bars, so that the big polar bear and I were face-to-face. He was obviously in extreme discomfort, legs splayed, swaying back and forth with the b
iggest hernia I had ever seen. Aussie needed emergency surgery.
I’d repaired hernias before, but never in such a large patient. The students searched the literature about hernia repair in bears, finding very little. I spoke to a vet at another zoo who’d done a similar—and successful—surgery on their polar bear. It helped to know that we wouldn’t be the first to attempt this procedure and that we could use a standard domestic-animal surgical approach. Moving Aussie to and from the operating room presented the biggest challenge.
I decided to call the vet school for help. Unlike zoo vets, veterinary surgeons operate daily and repair hernias often. They don’t work on bears, of course, but this was not a bear-specific problem. Any species can develop a hernia. I’d anesthetize Aussie by dart, we’d move him to the hospital clinic for the surgery, and the experts would take it from there. They’d extrapolate using techniques established for domestic animals. The operation would go faster, and I’d be able to focus my attention on the logistics of working on a polar bear.
Four hours later, we were ready to start. A veterinary surgeon and an anesthesiologist from the University of Illinois at Urbana-Champaign College of Veterinary Medicine were on their way. Our vet techs had prepped the large-animal surgery room for a thousand-pound patient. The chief of police had organized an escort; the zoo’s forklift driver was on his way. A crowd of keepers, assistant curators, and curators had gathered to help.
Earlier, I’d contemplated the best choice of anesthetic agents for this older, compromised polar bear. Patient safety, the safety of all the staff who would be helping to carry the bear, and the safety of the visitors in the park were all of equal concern. Polar bears are extremely dangerous animals, smart and quick, one of nature’s most powerful carnivores. If I miscalculated the amount of drug needed and Aussie woke up from his anesthesia during transport across the zoo grounds on a busy summer day, we would have a serious problem. There isn’t an anesthetic dart that would work fast enough. In that case, our zoo police force had the authority to shoot to kill our patient.
This is a part of our emergency response plan I hope never to see implemented during my career. But like all zoos, we have policies in place to ensure human as well as animal safety. I briefed the group on the potential dangers involved. We needed to take every precaution and work together as a team.
Pushing the possibility of disaster out of my mind, I picked up my darting kit and walked down the hall to the den. As I approached the cage, Aussie finally sat down and let me have a good look at his belly. About five years earlier, the polar bear had developed a golf-ball–sized fatty swelling at his navel, a small umbilical hernia that was hard to see even in strong light. It hadn’t changed in years, nor had it caused Aussie any discomfort—until today. Now the hernia was impossible to miss. The area was hugely swollen.
When we first noticed the hernia, we’d anesthetized Aussie for ultrasound examination and physical palpation to confirm our diagnosis. The cause of this problem is usually a small amount of fatty tissue caught in the area around the umbilical cord (belly button) at birth, creating a small opening in the muscles in the middle of the abdominal wall. If this hole enlarges over time, organs like the intestines can follow.
Many small umbilical hernias never change during the life of the patient, so they are monitored rather than removed surgically unless the animal shows signs of pain or the swelling changes in size. If this happens, the chances are that more than fat is wedged in the area. It can be a life-threatening condition, particularly when it happens acutely.
Usually, by this time in the morning, Aussie would be banging on the door to be given access to his outside exhibit and pool. Today he had no such interest. He was vocalizing and panting at the front of his cage. I darted Aussie with a combination of anesthetic agents (medetomidine and tiletamine-zolazepam) in his right front shoulder. He hardly reacted, probably distracted by the discomfort from his hernia. Within about fifteen minutes, the polar bear lay on his side, eyes partially closed, breathing deeply.
It was my responsibility to make sure that Aussie was really asleep and that he would stay that way until we could hook him up to gas anesthesia for surgery. One of the assets of bear dens is their solid, bunkerlike construction, which helps them maintain comfortable constant temperatures for the animals. But that construction also means the doorways are small, requiring humans to bend down and negotiate a large cement step to get in and out. I crawled into the den slowly, hoping to find a deeply anesthetized polar bear while also contemplating my what-if plan.
Fortunately, the anesthetic drugs had done their job. With the help of about twenty keepers, I was able to roll Aussie onto a cargo net, lift him through the narrow doorway (no easy feat),and heave him onto a wooden pallet. Aussie was so large that his head and legs still hung over all sides of the polar-bear–sized stretcher we had constructed earlier that day. The forklift slowly picked him up and backed down the long, dimly lit access hall to where a flatbed truck awaited us. Though security staff had roped off our immediate work area, a large crowd of spectators had gathered, recognizing that something out of the ordinary was transpiring.
For the ride through the zoo grounds, I climbed up onto the flatbed to monitor the bear’s anesthesia. The flatbed was a narrow space with low wooden sidewalls, barely wide enough for both of us. Wedged between the wet, smelly bear and the wall, I felt a rush of adrenaline when Aussie voluntarily moved one of his huge paws. It had only been a short time since I’d darted him. Maybe he wasn’t as deeply asleep as I’d thought? I gave him an additional amount of anesthetic intravenously using a vein in his rear leg. Thankfully, it worked quickly. A few minutes later, we were ready to begin our trip from the bear dens to the vet hospital.
Our zoo is a beautifully planted park with winding path-ways leading from one animal exhibit to another—but no back access road. We had no choice but to drive right through the park, slowly. Zoo police cleared the way as we drove. A crowd of several hundred people watched as we wound our way from the bear exhibit to Roosevelt Fountain, past the back side of Tropic World, and finally off the grounds and out of sight. Our supersized patient slept through it all.
At the hospital, we inserted a breathing tube normally used for fifteen-hundred-pound horses into Aussie’s airway so that we could administer gas anesthesia during the surgery. We placed intravenous catheters attached to fluid lines in order to administer preoperative antibiotics, fluids, and pain medication. The polar bear’s entire belly was shaved and scrubbed with antiseptic solution, revealing the black skin under his white fur—normal for polar bears. We rolled him into surgery and positioned him on his back with all four legs and neck extended. Earlier, I’d asked carpenters to reinforce the surgery table so it could handle Aussie’s unusual weight and size, and to my relief the emergency modifications held.
Soon a great many blue surgical drapes covered all of Aussie’s body except the area of the distended hernia. The specialists from the veterinary school went right to work. Dr. Rachael Carpenter helped monitor anesthesia while Dr. Chris Byron got started on the surgery. He began with an incision in front of the hernia in order to feel inside Aussie’s abdomen to see if there were intestines or a piece of the spleen or other organ trapped within the swelling. If this was the case, a longer and more difficult surgery would be required, and Aussie’s health would be at greater risk.
The danger is that when these tissues squeeze through the small hernia opening, their blood supply can be compromised; this can result in death of the tissue and severe infection in a patient, particularly when loops of intestine are involved. Sometimes the damaged intestine must also be removed, a surgery known as a bowel resection. Fortunately, this was not the case. The herniated tissue consisted only of fat. The object of the surgery was relatively simple: expose the hole in the muscle, remove the herniated fat, and suture the rent in the abdominal wall so it never splits open again.
To access the area, Dr. Byron incised the skin in an elliptical fashion on
both sides of the hernia using electrocautery to control any bleeding. Over the next hour, he removed several pounds of traumatized skin and subcutaneous tissue from the hernia site, as well as a large amount of necrotic (dead) fat. The actual defect through which the abdominal fat had squeezed to form the swelling was surprisingly small, only about four inches long. Once the edges of the hernia had been sutured to close the hole, the site was lavaged with saline. Then the surgeon closed the subcutaneous fat and tissue in three separate layers, a technique designed to hold the weight of Aussie’s heavy belly when he stood up. Finally, the skin was closed with absorbable stitches to spare us from having to remove them at a later date.
We moved our patient back to his den at around seven pm in the same way he’d been brought to the hospital. Though the logistics were easier this time and the commute much quicker, the drive back was still a bit scary: by now it was dark, requiring us to monitor the bear’s anesthesia with flashlights. Back in the den, I stayed with Aussie until he woke up, acutely aware that I was once again jammed in a small space—about the size of my bathroom—with one of North America’s largest and most dangerous carnivores. Fortunately, Aussie woke up slowly and quietly, a smooth recovery that gave me plenty of time to exit safely. Tired and filthy, I got to my feet, heaved a sigh of relief, and thanked everyone for their extraordinary efforts. All the planning and preparation had paid off.
The Rhino with Glue-On Shoes Page 21