Suspected venous air embolism during urinary tract endoscopy in a standing horse

Summary During cystoscopy, performed with air insufflation in a standing Argentinian gelding, the horse showed ataxia and fell to the ground with generalised muscular twitching and horizontal nystagmus, tachypnoea and tachyarrhythmia. General anaesthesia was induced. Arterial blood gas‐analysis before induction of anaesthesia revealed an increased pH, decreased partial pressure of carbon dioxide and decreased partial pressure of oxygen. Venous air embolism was suspected.