Return of spontaneous circulation after cardiopulmonary arrest in an adult horse recovering from anaesthesia

This report describes successful cardiopulmonary resuscitation of a healthy, 525 kg, 8 years 9 months-old Quarter horse gelding. After successful pelvic limb orthopaedic surgery to excise a metatarsal bone under general anaesthesia, with the horse in left lateral recumbency, the horse was hoisted into recovery. After the horse was positioned in recovery, a routine cardiac check by thoracic auscultation was performed. Cardiopulmonary arrest (CPA) was identified by absence of cardiac sounds and pulse, as evaluated by digital palpation of the facial artery, absence of the right palpebral reflex, mydriasis and pale coloration of the tongue. Chest compressions were started immediately, using the knee-drop technique, at 40–53 compressions minute⁻¹. Compressions were performed by four people (body masses ranging from 61 to 100 kg) with a different person taking a turn every 2 minutes. Intermittent positive pressure ventilation continued at 4–6 breaths minute⁻¹ using oxygen delivered via demand valve. Following two intravenous doses of epinephrine (0.002 mg kg⁻¹ per dose) and four compression cycles, end-tidal carbon dioxide varied between 10 and 21 mmHg (1.3–2.8 kPa), increasing during the fifth cycle to 31 mmHg (4.1 kPa), suggesting return of spontaneous circulation (ROSC). A sixth cycle was started and stopped after 28 seconds for thoracic auscultation, when heart sounds were audible and a pulse present on palpation of the facial artery, indicating ROSC. After standing, the horse showed signs of distress (shaking and sweating) and was non-weight bearing on its right thoracic limb. A grade 3/6 left-sided systolic heart murmur and tachycardia (56 beats minute⁻¹) were present. Two days post-CPA, the heart murmur was undetectable, and the horse was weight bearing on all limbs. This case describes successful ROSC in an adult horse with low compression rates and highlights the importance of capnography to assess compression quality and ROSC.