Successful treatment of prolonged refractory ventricular fibrillation in an anesthetized dog

To describe a case of successful return of spontaneous circulation in an anesthetized dog that developed spontaneous ventricular fibrillation during CPR that was refractory to multiple defibrillation attempts by utilizing pharmacological antiarrhythmic therapy.

Cardiopulmonary arrest occurred during surgical preparation in a 1-year-old German Shepherd Dog under general anesthesia for fluoroscopic implantation of an Amplatz canine duct occluder for treatment of a patent ductus arteriosus. Pulseless electrical activity was initially diagnosed, and resuscitative efforts were immediately initiated, including basic cardiac life support, discontinuation of anesthesia with administration of reversal agents, and low-dose epinephrine administration (0.01 mg/kg, IV). After 10 minutes of CPR, the patient developed ventricular fibrillation and single-dose monophasic defibrillation attempts of escalating energy were performed. Despite these efforts, return of spontaneous circulation was unable to be achieved. However, administration of magnesium sulfate (20 mg/kg, IV) along with an additional single monophasic defibrillation attempt was successful in achieving return of spontaneous circulation.

Under current advanced cardiac life support guidelines, the best resuscitation strategy for refractory ventricular fibrillation, in which the arrhythmia persists despite multiple defibrillation attempts, remains unclear. This is especially true for veterinary patients, where refractory ventricular fibrillation is an uncommon cardiac arrest rhythm. Although guidelines for the use of antiarrhythmic therapy during cardiac arrest are well established in human medicine, evidence-based guidelines to support best practices in companion animals do not exist due to sparse data gathered through experimental studies. Only a few case reports describe successful return of spontaneous circulation following prolonged ventricular fibrillation in clinical veterinary patients. Although the use of magnesium sulfate as an antiarrhythmic agent during refractory ventricular fibrillation has been previously reported in people, this is the first case to our knowledge of refractory ventricular fibrillation in a dog that responded to magnesium sulfate.