The American Society of Anesthesiologists physical status classification system is commonly used in all fields of veterinary medicine, with higher grades correlated with increased mortality in non-avian companion animals, but little evidence is available for avian species. This study aims to investigate whether prospective ASA grade is a reliable predictor of mortality in avian species undergoing general anesthesia.
Anesthetic records for avian patients undergoing inhalational isoflurane anesthesia were retrospectively examined to assess mortality outcomes during and up to 48 hours after cessation of anesthesia. Prospective ASA grade assigned at the time of anesthesia was used to categorize anesthetized patients.
A total of 1820 anesthetic records were included over a 3-year period. A total of 81 patients (4.45%) died during anesthesia or within 48 hours of cessation of anesthesia. Patients assigned an ASA grade of 1 had a mortality rate of 0% (95% confidence interval [CI] 0.0–0.2), and patients assigned an ASA grade of 2 had a mortality rate of 0.6% (CI 0.2–1.3%). Patients assigned ASA grades 3, 4, and 5 had mortality rates of 5.9% (CI 4.3–8.0), 18.8% (CI 13.4–25.7) and 50.0% (CI 29.9–70.1) respectively. Patients assigned an ASA grade of 3 were found to have 11.5 times the odds of a mortality event (95% CI 5.0–31.8) compared to ASA grades 1 and 2. A further increase in odds of 40.0 times (CI 16.9–113.8) was identified in patients assigned an ASA grade of 4, and 185.2 (CI 57.6–668.1) identified in patients assigned an ASA grade of 5. Age, sex and weight were shown to have no statistically significant impact on odds of death. Investigation into timing of death showed that the majority of patients died following cessation of general anesthesia (81.48%), with the highest mortality rate occurring between 0 and 3 hours postgeneral anesthesia.
This study indicates that patients assigned ASA grades of 3 or greater are at higher odds of death compared to those assigned ASA grades 1 or 2. The odds of death increased with increasing ASA grades. The highest mortality rate was identified within 0–3 hours of cessation of general anesthesia.
“Mortality outcomes based on ASA grade in avian patients undergoing general anesthesia”. Ashton J. Hollwarth, et al. Journal of Exotic Pet Medicine. Volume 41, April 2022, Pages 14-19.