Cardiovascular complications during anaesthesia for surgical correction of an aberrant right subclavian artery in a dog

A six-month-old neutered male German shepherd dog with aberrant right subclavian artery (ARSA) was premedicated with methadone, medetomidine and then fentanyl; anaesthesia was induced with propofol and maintained with infusions of medetomidine and fentanyl and isoflurane in oxygen. Hartmann's solution and noradrenaline were administered for cardiovascular support. Arterial pressure was measured using Doppler technique in both metacarpal arteries and invasive technique in both dorsal pedal arteries. During ARSA occlusion test, severe hypotension (30 mmHg) in the right forelimb, bradycardia (45 bpm) and advanced atrioventricular blocks (AVB) were observed. The occlusion test was interrupted; atropine was administered; cardiovascular parameters, except AVB, were normalised; medetomidine and noradrenaline were interrupted. Other two attempts of ARSA occlusion generated similar cardiovascular side effects. The surgical correction was precluded and the animal was recovered from anaesthesia. This case indicates that ARSA occlusion can be followed by severe arrhythmias and focus on the management of these alterations.