Background information

Aim of investigation

The aim of the investigation is to help owners, veterinary surgeons and veterinary nurses gain confidence in rabbit anaesthesia. Establishing why some rabbits during or after anaesthesia allow preventative measures to be put in place

Risk of anaesthesia in rabbits

Rabbits have a reputation as high-risk candidates for anaesthesia and two studies have supported this view. In a survey of 8209 anaesthetised or sedated pet rabbits by Brodbelt et al.,2008, the overall risk of death was 1 in 72 (1.39%) within 48 hours of the procedure. The incidence reduced to 1 in 137 (0.72%) in healthy rabbits in comparison to 0.17% in dogs and 0.24% in cats. In sick rabbits, the risk increased to 1 in 14 (7.15%). Post-operative deaths within 48 hours accounted for 64% of cases, with most cases occurring within 3 hours of sedation or anaesthesia. A recent retrospective survey of perioperative complications in 185 pet rabbits (Lee et al., 2018) reported deaths in 10/185 (4.8%) within 72 hours. Five of these rabbits died during, or recovery from, anaesthesia.A post-mortem examination was performed in only two of the ten rabbits that died. The cause of death in the remaining eight rabbits was either unknown or attributed to cardiorespiratory arrest without no confirmed details of underlying pathology. A post-mortem examination would have yielded more information. An example of the value of post-mortem examination with histopathology for an unexpected anaesthetic death in rabbits is exemplified in a case report by Romanucci et al. (2017).

Possible reasons for anaesthetic risk

Various explanations have been put forward for the higher risk of anaesthesia in rabbits in comparison with dogs and cats. These explanations include the anaesthetic protocol, stress, pre-existing disease (especially respiratory problems), problems with endotracheal intubation or post-operative gastrointestinal stasis. Without a post-mortem examination, these explanations can only be speculative. 

Benefits of a post-mortem examination

Although a post-mortem examination does not always establish a cause of death, in those cases where a diagnosis is made, knowing why the rabbit died has many benefits. If the death was due to an underlying condition that would have been difficult or impossible to diagnose during life, the diagnosis can bring relief to the veterinary staff because the death was out of their control.  Establishing a cause of death can also help bring closure to the owner. If it turns out that the death may have been prevented, measures can be put in place to prevent future rabbits from dying in similar circumstances.

Where the post-mortem examination takes place

Although a post-mortem examination is essential if a cause of death is to be established, some veterinary practitioners are reluctant to perform the examination themselves and prefer to send the body to a pathologist at a commercial laboratory instead. Despite the advantages of a veterinary pathologist performing a comprehensive post-mortem examination, cost and practicalities can cause difficulties. Transport to the laboratory poses a problem because, in rabbits, the post-mortem examination needs to be performed within six hours of death to get meaningful results. Also, the body may be unavailable for the owner to collect if they wish to arrange individual cremation or bury their pet at home. A good compromise can be made by a veterinary practitioner performing a basic post-mortem examination at the practice and collecting tissue samples to send for histopathology. At the end of the examination, the body should be available for the owner to collect if they wish to do so.

Funding

We (Frances and Nigel Harcourt-Brown) are prepared to pay the laboratory fees for histopathology providing the samples are sent to Abbey Veterinary Services. Submissions from outside the UK can be arranged. Any fees for the post-mortem examination itself are not included.

Findings of a similar investigation into sudden and unexpected death and rabbits

A similar study by Frances and Nigel Harcourt-Brown investigated  ‘Sudden and Unexpected Death’ in pet rabbits. The results showed that a simple post-mortem examination performed by a vet in practice soon after death can be extremely valuable in establishing a diagnosis. The investigation coincided with the RHDV2 epidemic in UK. Of the 300 cases that were investigated, 185 were diagnosed as RHD from but another cause of death was established from the clinical history, macroscopic findings and/or histopathology in 78/115 (88%) of the cases that were not due to RHD (88%) (Harcourt -Brown et al., 2020). We wish to continue to fund histopathological examination in cases of unexpected death but are restricting the inclusion criteria to rabbits that die during or after anaesthesia in order to exclude RHD cases.