Insufficient effect of sedation followed by difficulties inducing a colicking Shetland pony

Abstract

AbstractA Shetland pony suspected of large intestinal displacement was presented for exploratory laparotomy. The pony was extremely agitated with refractory pain despite repeated intravenous administration of detomidine and morphine. As the pony became unmanageable and recumbent, it was decided to induce general anaesthesia as soon as possible to prevent further harm. However, it subsequently proved impossible to obtain adequate anaesthetic depth despite intravenous administration of ketamine/midazolam, propofol and thiopental. Only after endotracheal intubation and administration of isoflurane was a surgical plane of anaesthesia achieved. An anaesthetist may be faced with an unexpected lack of effect of administered anaesthetic drugs, which in equine anaesthesia may lead to dangerous situations for patients and personnel. Possible explanations for the observed events and recommendations for prevention are offered.