Fentanyl-induced asystole in two dogs

Area of Science:

• Veterinary Anesthesiology
• Small Animal Medicine
• Pharmacology

Background:

• Fentanyl is a common analgesic for perioperative pain management in small animals.
• Isoflurane is a widely used inhalant anesthetic in veterinary medicine.

Observation:

• Two dogs experienced severe bradycardia and asystole following a 3 µg/kg fentanyl bolus during isoflurane anesthesia.
• Pre-administration of glycopyrrolate did not prevent asystole in one dog.
• Intravenous glycopyrrolate failed to reverse the progressive bradycardia and subsequent asystole in the second dog.

Findings:

• Fentanyl administration can induce life-threatening bradycardia and asystole in dogs under isoflurane anesthesia.
• Atropine demonstrated superior efficacy in rapidly reversing fentanyl-induced asystole compared to glycopyrrolate.
• Closed chest compressions were necessary in both cases alongside pharmacological intervention.

Implications:

• Veterinarians should exercise caution when administering fentanyl boluses to isoflurane-anesthetized dogs.
• Atropine should be considered the primary treatment for fentanyl-induced bradycardia and asystole.
• This case report highlights potential drug interactions and adverse cardiovascular events in veterinary anesthesia.