Peri-anaesthetic and anaesthetic-related mortality risks in great apes (Hominidae) in zoological collections in the UK and Ireland.

Objective: To estimate the risk of death and identify the major risk factors for peri-anaesthetic mortality in great apes (Hominidae) that underwent anaesthesia in zoological collections in the UK and Ireland between 1 January 1990 and 30 June 2005.
Study Design: confidential, retrospective cohort study.
Animal Population: The study population comprised all great apes from 16 zoological collections in the UK and Ireland that were anaesthetised during that period.
Methods: All available anaesthetic records were collected. Outcome at 7 days post-anaesthesia was recorded as alive, dead or euthanased. The risk of peri-anaesthetic mortality was calculated. Multivariable analysis of potential risk factors was performed.
Results: A total of 1182 anaesthetic records were collected and analysed. Sixteen peri-anaesthetic deaths occurred, resulting in a peri-anaesthetic mortality risk of 1.35%. Twenty percent of deaths (3/15) occurred during maintenance and 80% (12/15) occurred post-anaesthetic but within 7 days. A subjective assessment suggests at least five anaesthetic-related deaths occurred; in other words an anaesthetic-related mortality risk of 0.42% (5/1182) or above. In the multivariable analysis, health status and age were significantly associated with peri-anaesthetic mortality. Animals assessed as 'sick' pre-anaesthetic were associated with a 26-fold (95% CI 5.55-122.32) increased risk of death compared with animals with a good health status. Animals aged over 30 years were associated with a 30-fold (95% CI 3.44-261.85) increased risk of death, compared with adults aged between 10 and 30 years.
Conclusions and Clinical Relevance: This study has shown that great ape anaesthesia appears to carry a high risk of mortality. Sick and aged patients are at an increased risk of death and particular care should be exercised during their anaesthesia. Standardisation and completeness of anaesthetic records across zoological collections would assist greatly in further studies.