Development of equine post anaesthetic myelopathy: Thirty cases (1979-2010)

Abstract

Summary Post anaesthetic myelopathy is a rare but devastating complication of equine anaesthesia and there is a need for better understanding of the condition and to raise veterinary awareness. The aim of this study was to collect data on unreported cases and combine those with reported cases to better identify possible risk factors and early clinical signs and outcomes of horses developing post anaesthetic myelopathy (PAM). A survey was conducted to identify cases of equine PAM. Records were also requested via the American College of Veterinary Anaesthesiologists listserve. Additional cases of PAM were located through review of the literature. Eighteen new cases and 12 published cases were identified. Large‐framed breeds between 6–24 months of age were more commonly affected (23/30). The majority of horses were positioned in dorsal recumbency during anaesthesia. Lack of movement and deep pain of the rear limbs, loss of anal tone and lack of panniculus response from the mid to caudal thorax distally were the most common clinical findings. Reported treatments resulted in no improvement of clinical signs and all horses died or were subjected to euthanasia from a few hours to 8 days post operatively. Poliomyelomalacia of the caudal spinal cord is the most common histopathological finding. Although a rare complication it is a catastrophic risk that can be eliminated by performing a standing operation. Hopefully in the future better understanding of this condition will lead to prevention and treatment strategies.

Post anaesthetic myelopathy in the horse: a case report

“…Although there are some exceptions in age and weight distribution in the group of affected horses, it appears that immature heavily muscled or large breed horses are prone to the development of post anaesthetic myelopathy. No breed predisposition has been described, although in an earlier report six Friesians and seven draught horses were found from a total of 30 cases (Ragle et al 2011). The horse described here was also young and well-muscled and was considered healthy except for a granuloma in the ventral sternal region.…”

“…To date 30 cases of post anaesthetic myelopathy have been described, with the first case reported in 1979 (Schatzmann et al 1979;Blakemore et al 1984;Zink 1985;Brearley et al 1986;Yovich et al 1986;Lerche et al 1993;Lam et al 1995;Raidal et al 1997;Joubert et al 2005;van Loon et al 2010;Ragle et al 2011). Most commonly the affected horses were young, up to 24 months old, males and heavily muscled breeds.…”

“…Median weight was 381 kg (range 214-650 kg). Horses were admitted mostly for elective surgery (orthopaedic or soft tissue surgery) and, according to the preoperative examination, were considered to be healthy (Ragle et al 2011). Lam et al (1995) described this disorder in a seven month old Connemara pony presented as an emergency with herniation of abdominal content following castration.…”

“…All but one horse were positioned in dorsal recumbency and underwent surgery with inhalation anaesthesia (Ragle et al 2011). The one exception was a two year old Thoroughbred colt which underwent castration in right lateral recumbency with total intravenous anaesthesia (Raidal et al 1997).…”

“…Median anaesthetic time was 90 min (range 25 to 205 min) (Ragle et al 2011). In our case anaesthesia duration was 85 min.…”