Polymorphic tachycardia in an anaesthetised horse with an undiagnosed pheochromocytoma undergoing emergency coeliotomy

29 Jan 2020

Ranninger, E., Bettschart-Wolfensberger, R.

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A 17-year-old, 550-kg, neutered male Oldenburger horse was referred for an exploratory coeliotomy after acute collapse, profuse sweating and abdominal pain refractory to conventional analgesics. Clinical evaluation was only possible under sedation and revealed pale mucous membranes, tachypnoea, tachycardia with irregular heart rhythm and distended small intestines with decreased motility. Preoperative blood testing revealed severe hyperlactataemia and hyperglycaemia, whereas an abdominocentesis showed evidence of haemoperitoneum. Under general anaesthesia, polymorphic tachyarrhythmias, hypotension, peripheral oedema, persistent hyperlactataemia, electrolyte imbalances and haemorrhage complicated the anaesthetic management of this case. Despite cardiovascular support, including administration of fluid therapy, inotropes, 3.5 litres of fresh whole blood and 5 litres of fresh frozen plasma, the horse did not recover from general anaesthesia. A pheochromocytoma of the left adrenal gland with parenchymal rupture and haemorrhage was diagnosed postmortem. The present report describes the anaesthetic challenges of an undiagnosed pheochromocytoma in a horse with colic.