Intrathecal morphine overdose in a dog

Area of Science:

• Veterinary Anesthesiology
• Neurology
• Pharmacology

Background:

• A 6-year-old spayed female Boxer underwent surgery for a ruptured cranial cruciate ligament.
• The patient inadvertently received an overdose of morphine (1.3 mg/kg) via subarachnoid injection.

Observation:

• Fifty minutes post-injection, multifocal myoclonic contractions began in the tail and progressed cranially.
• These seizures intensified throughout the surgery and were refractory to midazolam, naloxone, phenobarbital, and pentobarbital.

Findings:

• Atracurium was the only effective treatment for the myoclonus.
• The patient developed hypertension, dysphoria, hyperthermia, and hypercapnia.
• Intensive supportive care included propofol, diazepam, atracurium, and naloxone infusions.

Implications:

• Intrathecal morphine overdose can cause severe, potentially fatal complications in dogs.
• Complete recovery is possible with immediate and extensive supportive care.
• This case highlights the critical need for careful drug administration and preparedness for adverse events.