What would happen if you gave IV lidocaine to a feline?

• A. Bradycardia
• B. Hypotension
• C. Arrhythmias
• D. Seizures

Answer: (C)

Lidocaine works by blocking fast sodium channels in heart muscle, which reduces excitability and slows the spread of electrical impulses. In cats, giving this drug intravenously can disrupt the heart’s conduction system, especially if it’s given too quickly or at a dose that’s too high or if there’s underlying heart disease. That disruption can manifest as arrhythmias because the normal rhythm of ventricular depolarization is altered, and ectopic beats or abnormal conduction patterns can arise. While lidocaine can cause other signs of toxicity like hypotension, bradycardia, or CNS symptoms at higher levels, the most likely cardiac effect to be watched for with IV administration is the development of arrhythmias.