Spotlight on Zoo Science
April 28,
2003
From Africa to Natural Bridge, Virginia
Anesthesia is not risk free. In the United States today, about one human patient in 200,000 dies as a result of anesthesia; 25 years ago, that figure was one in 15,000. This is largely due to the fact that individuals vary in their responses to the various drugs used to induce anesthesia. Even with million of procedure’s worth of experience, physicians can’t predict with certainty how a patient of any particular age, sex, size, or medical condition will respond.
Imagine then, the dilemma zoo and wildlife veterinarians face when asked to use anesthesia a wild animal for the first time without the benefits that physicians have of conducting a pre-anesthetic physical examination and being able to control their patient during the induction and recovery of anesthesia. As veterinarians have learned, on top of individual variation, different species react remarkably differently, and some, such as giraffes, pose special problems.
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| Mitchell Bush and Scott Citino (former Zoo resident and Associate Veterinarian) collecting data on a field-anesthetized giraffe in Kruger National Park, South Africa. This ongoing study is documenting dosage rates and physiological parameters to ensure the safety of the patient. |
During the last three decades, the safety of anesthesia in wild animals has greatly improved from ten percent fatalities to less than 0.5%. This dramatic improvement has been due to improved anesthetic agents, better physiological monitoring equipment, increased training and experience of zoo veterinarians, and applied research in the area of anesthesia of zoological species.
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| Mitchell Bush and Carlos Sanchez, wearing a cap, examining and treating the anesthetized female giraffe at Natural Bridge Zoo in Virginia. Note that a tube has been placed in the animal’s trachea, which is attached to oxygen to support respiration during the procedure. An IV catheter is placed in the giraffe’s jugular vein for collecting blood samples and administering drugs. |
The National Zoo’s Mitchell Bush, Chief of Veterinary Services at the Conservation and Research Center (CRC) in Front Royal, Virginia, has devoted a large part of his professional career to studying how best to anesthetize captive and free living animals. A pioneer in this field, he has also taken on the toughest cases, giraffes being a prominent example. Bush has had a lifetime interest in giraffes and has developed safer anesthesia procedures for these sensitive, hard-to-manage animals.
So when veterinarian Mike Hepner was presented with a tall problem at the zoo in Natural Bridge, Virginia, he knew who to call for help. One of the zoo’s pregnant female giraffes suddenly was unable to eat, drink, or swallow, and was salivating profusely. Bush and Carlos Sanchez, the Zoo’s veterinary resident, traveled the 125 miles to Natural Bridge to see the giraffe and consult with Hepner and zoo owners Karl and Debbie Mogensen.
They found the female giraffe in severe distress. Her face was swollen, her tongue was protruding, and she was salivating copiously. They considered several possible diagnoses, including a foreign body in the mouth or throat, dental problems, and even rabies! Because the animal was a poor anesthetic risk, they proceeded cautiously and began supportive treatment with antibiotics and non-steroidal anti-inflammatory drugs.
The next day, Mogensen reported that the giraffe's condition had deteriorated. She was still unable to eat or drink, and was now showing increased respiratory effort and a nasal discharge. Bush and Sanchez decided that they would have to anesthetize the giraffe despite the risk. The team that traveled to Natural Bridge was expanded to includ Kitty Enqvist, the Zoo’s pathology resident with a special interest in giraffe oral diseases, and Lisa Ware, CRC’s veterinary technician.
The giraffe was anesthetized late in the evening using a technique Bush and his colleagues had developed during several field studies in South Africa’s Kruger National Park. The procedure went extremely well despite the giraffe’s poor condition. They were able to complete thorough physical and oral examinations, and collected blood samples and cultures. This provided an excellent training experience for both of the veterinary residents and the staff who participated.
The physical exam ruled out several possible diagnoses, including pharyngeal abscess, foreign bodies of the pharynx or trachea, dental problems, and abnormalities of the tongue. Because intensive supportive care was problematic, the animal was treated for the symptoms we observed in the hope that it would again start to eat and drink.
The next day, the giraffe looked bad despite the continuation of antibiotics and anti-inflammatory drugs. She spent most of the day on the ground and was still unable to eat or drink. The following day, the owners were thrilled to see that her condition had improved considerably. Not only had the swelling around her face decreased, but the animal stood, started to eat and drink, and almost resumed her normal behavior. Today she’s in great shape.
This is a good example of how the results of National Zoo field studies of animals in the wild can be applied to managing their counterparts in zoos. Giraffes have been safely anesthetized using Bush’s protocol in other zoos, including Fossil Rim in Texas, the Columbus Zoo in Ohio, and the White Oak Conservation Center in Florida.
- The art and science of anesthesia in giraffes remains
a challenge because the giraffe’s unique anatomy
and physiology presents inherent problems during anesthesia.
- Their large size limits physical control during
the critical times of induction and recovery, and limits
manipulation
once the animal is down.
- Their characteristic long
neck, which if not controlled, acts as a lever arm, creating
a danger to itself or
the support staff. In addition, a mal-positioned neck
leads
to airway obstruction or cramping of neck muscles,
which can produce fatalities.
- Improper substrate potentates
self-induced injury due to slipping during induction
and recovery.
- Their tendency to vomit or
regurgitate can lead to fatal inhalation pneumonia. Vomiting
may result
from the increased
intra-abdominal pressure that occurs when the animal
rests on the ground because the skin and muscles over
the abdomen
are very tense.
- Prolonged induction or recovery may lead to hyperthermia, myopathy (problems with muscle tissue), and secondary trauma. Other physiological adaptations in the giraffe may affect an anesthetic procedure as well.
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| Mitchell Bush and Scott Citino working with South African collaborators in Kruger National Park to develop safe elephant anesthesia techniques. The team is pulling a large, heavily sedated bull elephant down onto its left side, because if it lies down on its right side it would rest on another anesthetized male elephant. After this animal was down, both were monitored closely before their anesthesia was reversed. |
Bush has worked in Africa for the past two decades, developing safer anesthesia procedures for many species other than giraffes, including lion, cheetahs, gemsbok, wild dogs, impala, roan antelope, hartebeest, nyala, and black and white rhinoceros. These procedures have proven to be vital for a wide range of field investigations in which animals must be captured and handled for marking and for relocation and translocation programs.
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| This photo was taken during a collaborative study on anesthesia and reproductive physiology in free-ranging lions in the Ngorongoro Crater in Tanzania. The three veterinarians from left to right are Don Janssen, now at the San Diego Zoo and formerly Associate Veterinarian at the National Zoo; Steve Monfort, National Zoo endocrinologist; and Mitchell Bush. The three graduated from the School of Veterinary Medicine, University of California at Davis in the 1960s (Bush),1970s (Janssen), and 1980s (Monfort). |
Because many animals remain difficult to anesthetize safely, these investigations are ongoing, and Bush and his colleagues are seeking additional funds to support ongoing studies. To date, generous support has been provided by FONZ, British Airways, the Smithsonian Abbott Funds, and Shirley Sichel.
If you are interested in the history and scientific details of giraffe anesthesia, Bush has published an article on the topic in an Internet journal.
To find it, go to http://www.ivis.org/. Free registration and password are required. Enter the word “giraffe” in the site’s search engine to find “The Art and Science of Giraffe (Giraffa camelopardalis) Immobilization/Anesthesia.”
