A 25-year-old parturient receiving epidural bupivacaine develops sudden cardiovascular collapse with ventricular fibrillation. The MOST likely explanation is:

• A Vasovagal syncope from supine hypotension syndrome
• B Hypersensitivity reaction to the preservative in the epidural solution
• C Total spinal block from inadvertent intrathecal injection
• D Intravascular injection of bupivacaine causing sodium and potassium channel blockade in cardiomyocytes ✓

Explanation

Bupivacaine has high lipid solubility and protein binding, allowing it to penetrate cardiomyocytes readily; in toxic systemic doses (as in intravascular injection), it blocks fast sodium channels in a use-dependent manner and simultaneously blocks potassium channels, causing prolonged QRS widening, malignant arrhythmias including ventricular fibrillation, and cardiovascular collapse that is notoriously refractory to resuscitation. Lipid emulsion therapy (Intralipid 20%) is the recommended treatment. Total spinal would cause bradycardia and hypotension rather than VF as the primary event.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.