Abstract
A 13-year-old, castrated male, Shih Tzu dog with a history of acute ataxia was referred to veterinary medical teaching hospital and anesthetized for diagnostic magnetic resonance imaging of cervical intervertebral disk disease. After preanesthetic evaluation including physical examination, blood chemistry, radiography and ultrasound, the patient was premedicated with intravenous butorphanol (0.2 mg/kg). Anesthesia was induced by intravenous propofol (6 mg/kg) and maintained with isoflurane at 1.2 minimal alveolar concentrations. Because the mean arterial pressure (MAP) decreased from 70 to 58 mmHg at 70 minutes after induction, dobutamine was administered by constant rate infusion ($5{\mu}g/kg/min$) to treat hypotension. However MAP did not increase, and heart rate rapidly decreased from 100 to 55 beats per minute (bpm). To treat bradycardia, intravenous glycopyrrolate ($5{\mu}g/kg$) was administered, and heart rate increased to 165 bpm. After extubation of endotracheal tube, the patient showed normal recovery without any problems related to cardiovascular system. Unexpected dobutamine-induced bradycardia was considered as Bezold-Jarisch reflex. It is recommended that clinicians know and prepare the possibility of bradycardia during dobutamine therapy under general anesthesia.
