Severe intraoperative hypoxaemia in a horse due to failure of an oxygen concentrator and auxiliary oxygen supply

06 Dec 2018

Kropf, J., Hughes, J. M. L.

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A horse with acute colic underwent exploratory laparotomy. Following anaesthetic induction, the inspired fraction of oxygen (FiO2) was found to be 0.23 and severe hypoxaemia (PaO2: 4.12 kPa [30.9 mmHg]) was detected. The terminal oxygen outlet was delivering mostly pressurised room air due to a mechanical fault within the oxygen concentrator, with subsequent failure of the auxiliary oxygen manifold. The oxygen supply in the operating room was switched to a cylinder (FiO2: 0.95) but PaO2 increased to only 12.3 kPa [92.3 mmHg], indicating probable ventilation/perfusion mismatch. Anaesthetic recovery was uneventful, but signs of abdominal pain returned four days later. A second laparotomy revealed perforation of the jejunum and generalised peritonitis, and the horse was euthanased. Failure of both an oxygen concentrator and the backup supply is rare but potentially disastrous. A thorough preanaesthetic equipment check, including the FiO2, and detailed knowledge of all equipment components are essential for the anaesthetist.