Anxiety, lung function, post-op pain were concerns for Barbaro's medical team
How do you anesthetize a 1,100-pound skittish patient? With a special sling, rubber raft and all the drugs a racehorse needs.
After fracturing his right hind leg in three places on May 20 during the Preakness race, Kentucky Derby winner Barbaro underwent major orthopedic surgery at the George D. Widener Hospital for Large Animals at the University of Pennsylvania's New Bolton Center in Kennett Square. The team included two anesthesiologists, one resident and an anesthesia nurse.
One of the biggest challenges with horses involves the transition from a conscious to anesthetized state. While human and small animal patients can be restrained on a bed or surgery table, that option is nonexistent with horses. Plus, when the horse loses consciousness, it will drop to the floor, risking further injury. For the induction of anesthesia, Barbaro was suspended in a Liftex sling.
The Kentucky Derby winner was under general anesthesia for six hours, triple the average for horse surgery at a university-based clinical practice, said Eugene P. Steffey, VMD, PhD, Professor of Anesthesiology, University of California-Davis School of Veterinary Medicine.
"Much like human anesthesia, the longer the individual is down, the more chances there are for things to happen," Dr. Steffey told Anesthesiology News. "That goes across species and is not unique to the horse."
Barbaro was intubated nasotracheally to allow mechanical ventilation of his lungs with oxygen during surgery and in the early recovery period. "Even though the horse may be an athletic individual, we still do not have a lot of good tests to determine which of [them], during general anesthesia, are going to have problems oxygenating and [which] aren't," Dr. Steffey said.
The size and weight of the horse can damage dependent muscles and nerves when the animal is recumbent for long periods. Lung function can also be impaired, with blood–gas exchange deteriorating over time -- which is further exacerbated by the use of inhalant anesthetics, Dr. Driessen said. Maintaining adequate blood circulation with good blood pressure and tissue perfusion is essential, he noted.
"Unlike the vast majority of patients undergoing such a long anesthetic procedure, Barbaro never developed central or peripheral hypothermia, indicating his remarkable athletic performance level and hence very good cardiac function with excellent peripheral blood circulation. At the same time, the administration of epidural and intravenous analgesics helped reduce the amount of inhalant anesthetic needed, which likely further improved Barbaro's cardiovascular function," Dr. Driessen told Anesthesiology News.
The rubber raft helps skittish horses awaken from anesthesia without hurting themselves. Injuries to the musculoskeletal apparatus (e.g., fractures, myopathy) rank among the top three complications associated with perioperative death in the horse, according to Dr. Driessen. At the New Bolton Center, the raft is used in a unique pool-recovery system when the pharmacologic effects of the anesthetics -- such as central nervous system effects and muscle weakness -- wear off. Lying on the raft in warm water, the horse can move its limbs and body without hitting a solid surface, thus reducing the risk for reinjury. A harness is used to hoist the horse in and out of the pool. The raft also prevents the horse -- and its cast and bandages -- from getting wet. "It is completely dry. It's like you sitting in a boat on a lake," said Dr. Driessen.
Those involved with the anesthetic aspect played a "significant role" in Barbaro's surgery, Dr. Steffey noted. "That was not a trivial part of the support the horse had. That surgery, maintaining the animal under anesthesia and getting it back without destroying what they took six hours to develop, was a tremendous team effort," he said. "My hat's off to them."