Metaraminol in the reversal of hypotension in equine anesthesia with isoflurane and dexmedetomidine: case report

Abstract

Systemic hypotension is the most frequent complication of inhalational anesthesia in horses and is directly related to increased post-anesthetic morbidity and mortality. The treatment of hypotension depends on the physiological cause and can be performed with positive chronotropic, inotropic and vasopressor drugs, alone or in combination. However, there are few drugs used in horses and the effects of these drugs on cardiovascular support in these animals during anesthesia are poorly described. For this reason, this study aimed to report the action of metaraminol (Aramin®), a vasopressor with direct and indirect action on adrenergic receptors, in the correction of hypotension in a horse anesthetized with isoflurane and continuous infusion of dexmedetomidine submitted to elective orchiectomy. Cardiovascular changes with different infusion rates of 1, 2 and 4 µg/kg/min are described. Metaraminol reversed hypotension at a rate of 4 µg/kg/min, increasing systolic blood pressure by 93 mmHg, mean blood pressure by 74 mmHg, and diastolic blood pressure by 66 mmHg, and reduced cardiac output by 7.1 L/min and heart rate at 32 bpm, in relation to mean arterial pressure of 58 mmHg, cardiac output of 13.4 L/min and heart rate of 36 bpm at the expired rate of 1.3% isoflurane. Furthermore, it improved cardiac contractility at the rate of 2 and 4 µg/kg/min and did not cause arrhythmias at all infusion rates