The Hippo with Toothache

by Lucy H Spelman

  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 pathways 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.

  I hoped Aussie would feel a whole lot better soon. But the next morning, the polar bear refused to eat, drink, and take his medicine. We’d prescribed oral pain medication and antibiotics. He paced and panted. The keepers tempted him with all his favorite foods (bread, fish, and meat) to no avail. Even normally forbidden treats like soft-serve ice cream, jelly donuts, and honey failed. He wanted absolutely nothing to do with any of us.

  I hated to antagonize him after what he’d been through the day before, but I had no choice except to dart him with his medication. If infection was brewing, we needed to control it with antibiotics. And if we could control the pain he must be feeling after the two-and-a-half-hour surgery, he might feel like eating and drinking. This time Aussie reacted to being darted with a roar so loud I seemed to feel it as well as hear it. It was a sound that echoed through the cavernous access tunnels and could probably be heard throughout the park. Thank goodness I didn’t have to crawl through a small doorway into his den today.

  By the following morning, Aussie had improved. Although I was happy to see him feeling better, he was not at all happy to see me. He looked me up and down and from side to side, as if to see if I’d brought along another dart for him. Sadly, our patients often hold a grudge against us. We try so hard to help them, and then they remember us with fear, even hatred—strong emotions to assign to a bear, but certainly the impression Aussie gave at that moment. Nonetheless, he was soon eating and interacting with his keepers. They were still his friends.

  Though the surgery had been accomplished successfully, I still had a major concern: would the suture at Aussie’s hernia site hold up to the weight of his immense belly? After all, suture material is not designed with half-ton polar bears in mind. In the case of a large domestic animal, a belly bandage could be placed around the abdomen to support it and keep the wound clean. There was no way this would be possible with a polar bear. We’d just have to do our best to see that the surgery site stayed clean and that he didn’t overexert himself.

  Healthy polar bears are very active and spend much of their day walking or swimming. After recuperating in his den for over two weeks, Aussie began to go stir-crazy. He started banging on the door to let the keepers know he wanted access outside. Since his incision appeared healed, with no evidence of infection or hernia recurrence, we gave him a clean bill of health; it was time for him to go back on exhibit. The moment the door was opened, Aussie rushed out and headed straight for, you guessed it, the pool—just where you’d imagine a polar bear would go on a hot summer day. He hit the ice-cold water with a bounding belly flop, of course.

  ABOUT THE AUTH
OR

  Jennifer Langan has had a lifelong interest in both free-ranging and captive wildlife. After earning a bachelor’s degree in animal science at the Agricultural College of the University of Illinois, she completed her studies at its College of Veterinary Medicine. Dr. Langan did a small animal internship at Angell Memorial Animal Hospital in Boston and a residency in zoological medicine at the University of Tennessee, and then completed a fellowship with the Conservation Medicine Center of Chicago at Brookfield Zoo. Board certified by the American College of Zoological Medicine in 2001, she subsequently joined the faculty at the University of Illinois, where she is now an assistant clinical professor. Dr. Langan cofounded the Chicago Zoological and Aquatic Animal Residency Program, of which she is one of the directors. She spends the majority of her time as a clinical veterinarian working with students and residents at Brookfield Zoo.

  Water-Breathing Dragons

  by Ilze Berzins, PhD, DVM

  ALEX WALKED INTO my office with a frown on his face. “Dr. Berzins, we’re in trouble. The dragons are floating.”

  “What do you mean?!” I asked, trying not to panic. These are not words you want to hear about any new fish shipment, especially when the transport box contains a pair of rare weedy sea dragons, the first to arrive at your aquarium.

  “They’re at the surface and can’t seem to dive down.”

  A sea dragon is not, as the name suggests, the size of the Loch Ness Monster. It is a delicate, unusual-looking, and endangered fish from Australia, related to the sea horse, the tiny S-shaped fish you can buy almost anywhere. Dragons have elaborate leafy appendages, like fronds of seaweed, attached to their colorful bodies. At most, a full-grown weedy sea dragon reaches eighteen inches in length and weighs less than three ounces.

  Everyone on staff at the Florida Aquarium had been excited about the arrival of these special fish. In one way or another, we’d all helped in the planning, which had taken over a year, starting in the spring of 1998. As the aquarium’s head of veterinary services, I’d been involved in every step of the preparations. Our biologists had researched ideal water conditions, housing, and what to feed the fish. Using this information, our exhibit designers had custom-built a new tank, one that would also provide a great view of the dragons for aquarium guests. Our marketing and public relations people had taken it from there, naming the new exhibit Dragons Down Under. I’d talked to a number of other fish vets about dragon medicine, just in case something went wrong.

  The dragons had arrived at the aquarium that morning via special air cargo from Melbourne, Australia, with a stopover in Los Angeles. We’d planned that the fish would stay in a special holding tank for a minimum thirty-day quarantine. This would give them time to recover from the stress of transport. We’d also check them for parasites, deworm them if necessary, and keep a close eye on their feeding behavior. Next we’d move them to the new exhibit if they were healthy.

  Given their long plane flight and the two days they’d spent in a dark, sealed bag, I fully expected to find one or both of the dragons acting sluggish or looking thin. These are common signs of mild stress due to shipping, since fish are not fed during transport and are in a confined space.

  At worst, if the concentration of dissolved oxygen in the water had dropped more than it should have, or if a considerable level of nitrogen (the waste product of fish) had accumulated, I wouldn’t have been surprised if the dragons had a high gilling rate. This sign of stress is equivalent to breathing fast. By rapidly opening and closing their gills, which are supplied by a dense network of capillaries, fish can take in more oxygen and also get rid of waste products that build up in the bloodstream.

  Alex, one of our biologists, held the lid of the box open while I took my first look at the dragons. Just as he’d warned, they were floating at the surface and struggling to stay upright. I watched them for several minutes, thinking about what to do next. For whatever reason, they couldn’t keep their bodies beneath the water’s surface. This species of sea dragon has a long snout, and the gills sit right behind the angle of the jaw. Neither of the new dragons could keep its snout or gills under the water. They were piping, or gasping—not for air, but for water. This was a life-threatening situation. No vertebrate animal can survive without oxygen. Something must have gone wrong during the shipment, or perhaps the box hadn’t been properly prepared to begin with.

  I quickly directed Alex to take a sample of the shipment water to the water quality lab. He’d been instrumental in helping me get the animals to Florida, following up on every detail to make certain everything went smoothly. He looked just as worried about the dragons as I was. We tested for temperature, nitrogen waste product levels such as ammonia and nitrite, dissolved oxygen saturation, salinity, and pH. The results were normal.

  If the problem wasn’t in the water, it had to be inside the patients. Dragons, like many other types of fish, have air bladders (also called gas or swim bladders). This organ helps them with buoyancy control, so that they can maintain their position in the water. Maybe their air bladders had become overinflated during transport. Even worse, they might have ruptured, allowing free air into their body cavities. This excess air, whether inside the bladder or outside, would make it impossible for the fish to swim beneath the surface of the water.

  I ran through the possible reasons for an overinflated air bladder. Changes in air pressure during the flight could cause this; maybe the cargo hold hadn’t been properly pressurized. The lower pressure could result in gas leaving the bloodstream and forming gas bubbles in the tissues of the fish. Another possibility was that the box had been exposed to excessively low temperatures, which could have affected the concentration of oxygen and other gases in the water and bloodstream, increasing the amount of gas released into the air bladder, and then expanding when temperatures warmed up again. Or, and this last possibility was at the top of my rule-out list, the water in the sealed transport bag had been supersaturated with oxygen gas during some part of their trip.

  If you’ve ever purchased a pet fish for your home aquarium, you may have seen the salesperson tie the plastic bag so that it puffs out with air, like a half-filled water balloon. The oxygen in the air will help keep the oxygen levels in the water at a healthy level. When fish are transported long distances, pressurized oxygen gas is added to the container to ensure that oxygen levels remain high inside the bag for several days. But if the dragons’ sealed bag was inadvertently overpressurized, the gas pressure inside the air space, and thus the water, would have been initially too high, exposing the dragons to excessive, harmful gas pressures.

  It was going to be difficult, if not impossible, to find out for certain what had happened to the dragons during transport, and it wouldn’t necessarily change the treatment options. Time was of the essence. My priority was to confirm the diagnosis even if I couldn’t be certain of the root cause. The game plan was simple: radiograph the animals to look for overinflated air bladders.

  Since the dragons were small and relatively inactive, they didn’t need anesthesia for radiography. We could position them on the X-ray film cassettes the way we do other small fish, take the picture quickly, and replace them in the water. Gently I picked up the first patient, wearing powderless latex gloves to minimize damage to its skin and protective mucus, and placed it on its side directly onto the cassette. Susan, my veterinary technician, positioned the X-ray beam, lined everything up, and set the machine. She got ready to hit the exposure button while I darted behind the lead screen. Seconds later, I ran back into the room to return the dragon to the water. We repeated the procedure for our second patient.

  After developing the film, we could see that the body cavity of one dragon was completely filled with air. In the other, we saw the outline of an overinflated air bladder, which was most likely compressing the intestines directly below the bladder.

  There might appear to be a simple solution to this life-threatening problem: place a needle into the air bladder and withdraw the excess air. B
ut in a sea dragon, such a procedure can result in the introduction of infections or in laceration of other internal organs. To complicate matters further, the dragons’ thick scales, like a coat of bony armor, make it difficult to insert a needle through the skin without squashing the fish.

  I had another idea: treat the fish as you would a human. Put them in a high-pressure chamber that gradually moves the trapped gas out of the wrong places. Maybe we could take them to a dive chamber and treat them as if they had the bends, a common complication of scuba diving. Florida is a popular diving destination, and I knew there were several recompression chambers nearby.

  This thinking was based on what we know about fish anatomy. The air bladder is normally filled with various gases, oxygen being one of them, thanks to a system known as countercurrent exchange. The oxygen gets there via a complex bed of arterial and venous capillaries known as the rete mirabile (Latin for “wonderful net”). The capillaries are arranged in such a manner that blood rich in oxygen flows past blood low in oxygen; the gas then moves from areas of high to low concentration. The exchange takes place near the wall of the air bladder, so it can deflate or inflate depending on the concentration of the gases passing by in the blood vessels. By exposing the dragons to high pressure, simulating a dive, maybe we could drive the gas back out of the bladder and into the bloodstream.

  Fish also use countercurrent exchange to breathe. The arrangement of capillaries in the gills is not as elaborate as in the swim bladder rete, but the overall result is the same. The gas moves from high to low concentration, from the water into the bloodstream and then to the tissues. This is, of course, why our floating dragons were in big trouble. Their overinflated air bladders prevented them from keeping their gills underwater. If we could get the gas out of the air bladder and into the bloodstream, maybe it could leave via the gills.