Research Updates: Examining the risk factors for anesthetic-related deaths


Research Updates: Examining the risk factors for anesthetic-related deaths

Jan 01, 2009

Joseph Harari
In small animals, anesthetic-related death rates have been reported to range between 0.1% and 0.24%. Previous (1998 or earlier) studies identified poor patient health, use of xylazine, and increased age as factors associated with increased perioperative deaths, while premedication with acepromazine and atropine reduced the risk of mortality.

Risk factors associated with anesthetic-related deaths were examined in this case study involving 117 private and referral practices in England. Information from 98,036 anesthesia and sedation events over a two-year period was obtained. Two groups of animals were statistically evaluated: 148 dogs that died or were euthanized within 48 hours after anesthesia or sedation, and 487 randomly selected control dogs that did not die within 48 hours after anesthesia or sedation. An independent review panel of veterinary anesthesiologists and a surgeon classified the deaths as anesthetic related or not.

Sedation was used in eight of the 148 dogs that died and 36 of the 487 control dogs and was most commonly achieved with a combination including medetomidine; specific drugs were not listed. Anesthesia was induced in the remaining 140 dogs that died and 451 control dogs. Most dogs were premedicated before anesthesia with combinations of acepromazine, medetomidine, or a benzodiazepine or opioid. Anesthesia was induced with propofol or thiopentone or by administering inhalant anesthetic through a face mask. Anesthesia was maintained with isoflurane, halothane, sevoflurane, or injectable drugs (not listed).

Results revealed that a higher risk of an anesthetic-related death was related to increased American Society of Anesthesiologists physical status, increased urgency and duration of the procedure, and patient age (≥ 12 years). Decreased body weight (< 5 kg), anesthesia for a major procedure, injectable induction agents and halothane, and inhalant anesthetics alone were also all associated with an increased risk of death. The authors concluded that knowledge of these factors should encourage better perioperative patient management and anesthetic monitoring and help reduce the risk of mortality associated with sedation and anesthesia.


This study reviews cases from numerous clinics and statistically evaluates newer sedatives and anesthetics such as medetomidine, propofol, sevoflurane, and isoflurane. Unfortunately, not all of the injectable sedatives and anesthetic drug combinations used in the animals are listed. The data reveal useful information for veterinarians and their clients about risk factors for an anesthetic-related death. Undoubtedly, this information will serve as an important reminder—and lawsuit deterrent—that hospital admission and the use of sedative and anesthetic drugs in veterinary patients always carry a potential for a life-threatening complication.

Brodbelt DC, Pfeiffer DU, Young LE, et al. Results of the confidential enquiry into perioperative small animal fatalities regarding risk factors for anesthetic-related death in dogs. J Am Vet Med Assoc 2008;233(7):1096-1103.

The information in "Research Updates" was provided by Veterinary Medicine Editorial Advisory Board member Joseph Harari, MS, DVM, DACVS, Veterinary Surgical Specialists, 21 E. Mission Ave., Spokane, WA 99202.