Anesthetic agents

Greyhounds have lower hepatic clearance of thiobarbiturates than nongreyhounds, which results in prolonged recoveries after repeated doses of the drug. Complete recovery in these cases may take up to eight hours, compared with one or two hours in nongreyhounds. Many anesthesiologists think that a single injection of a thiobarbiturate will not be harmful to a greyhound,²⁹ but I think that too many other safer anesthetics are available to justify its use.

A ketamine-diazepam combination and propofol are the two most commonly used injectable anesthetic protocols (tiletamine/zolazepam is an alternative to ketamine and diazepam but anecdotally seems to result in rougher recoveries).²⁶ As with any breed, premedication to decrease stress and pain will result in less stressful recoveries. Lower doses of acepromazine should be used in greyhounds (< 0.1 mg/kg), as greyhounds appear to be more sensitive to acepromazine's effects, which can prolong sedation and worsen hypothermia.²⁹ Acepromazine is usually administered intramuscularly with an opioid. Maintaining anesthesia with isoflurane or sevoflurane is preferred because they are metabolized to a lesser degree than halothane or methoxyflurane, though halothane is considered acceptable. Halothane is more well-known for triggering malignant hyperthermia than isoflurane or sevoflurane.

Greyhounds have many idiosyncrasies that can affect their medical care. Being aware of these idiosyncrasies will prevent misdiagnoses and allow for more appropriate treatment and diagnostic testing. Many studies are pending publication that will describe additional idiosyncrasies. For those veterinarians interested in learning more about greyhounds and interacting with other veterinarians who also work with greyhounds, please visit the Greyhound Health Research and Information Network Web site at http://www.ghrin.org/.

ACKNOWLEDGMENTS

Special thanks to Dr. Richard Bednarski, Dr. Walter Threlfall, Dr. Lori Hitchcock, Dr. Guillermo Couto, and Dr. Suzanne Stack for their help in writing this article.

William E. Feeman III, DVM
Animal Medical Centre of Medina
1060 S. Court St.
Medina, OH 44256

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