Bezold-Jarisch reflex induced by dopamine during isoflurane anesthesia in small dogs

ABSTRACT

Background: Unlike other major reflexes contributing to hemodynamic homeostasis, the Bezold-Jarisch reflex (BJR)paradoxically decreases heart rate (HR) and mean arterial pressure (MAP) despite hypotension. In the veterinary field,there are few reported cases of BJR induced by dopamine, which is often used to manage hypotension. Herein, 2 casesinvolving small dogs exhibiting BJR due to dopamine infusion during general anesthesia are described.Cases Case 1 A 7-year-old, 7 kg, mongrel was referred for external skeletal fixator removal. The patient was premedicatedwith 0.3 mg/kg midazolam and 0.2 mg/kg butorphanol intravenously (IV). General anesthesia was induced with 6 mg/kgpropofol and maintained with 1.6% isoflurane in oxygen. The patient was given 5 mL/kg/h of Hartmann’s solution IV. Therespiratory rate (RR) was set to 9 breaths/min with a ventilator. The HR and MAP values were initially 120 bpm and 76mmHg and gradually decreased to 70 bpm and 40 mmHg, respectively. The end-tidal CO2 partial pressure (ETCO2) was 39mmHg, and the patient was administered 2.5 μg/kg glycopyrrolate IV. Then, 5 μg/kg/min dopamine was administered IVsince the MAP did not improve. The HR, MAP, and ETCO2 increased to 113 bpm, 72 mmHg, and 47 mmHg, respectively.Subsequently, HR and MAP dramatically decreased to 50 bpm and 43 mmHg, respectively. A second-degree atrioventricularblock was detected, prompting dopamine infusion discontinuation, and 2.5 μg/kg glycopyrrolate was again administeredIV. Within 5 min, HR and MAP values normalized, and postoperative patient recovery was typical. Case 2 A 2-year-old,8.6 kg, mongrel underwent surgery to correct a medial luxating patella of the right leg. The patient was premedicated with0.3 mg/kg midazolam and 0.2 mg/kg butorphanol IV. Anesthesia was induced with 4 mg/kg propofol IV and maintained...