Combined general anaesthesia in a horse with tricuspidal regurgitation and transthoracic sonographic monitoring of the cardiac function

A 7 years old colt was scheduled for routine castration. A 4/6 intensity holosystolic murmor was detected at thoracic auscultation during the preanesthetic examination. Transthoracic echocardiography confirmed the suspicion of tricuspidal valve regurgitation and did not reveal any other cardiac pathology. General anaesthesia was performed using a combined inhalation-intravenous protocol, with the horse in dorsal recumbency. Dobutamine was given at a low infusion rates, to maintain mean arterial blood pressure above 70 mmHg. During anaesthesia the cardiac function was repeatedly monitored using transthoracic ultrasonography. An improvement of cardiac contractility and only a small increase in the valve opening size could be detected while the horse was anaesthetized and dorsally recumbent.