During ACLS, a patient in cardiac arrest has a rhythm strip showing fine ventricular fibrillation (low-amplitude). The FIRST intervention before attempting defibrillation should be:

• A Intubate immediately to ensure oxygenation before defibrillation
• B Administer amiodarone to convert fine VF to coarse VF before shocking
• C Continue high-quality CPR to improve VF amplitude and coronary perfusion pressure ✓
• D Administer magnesium sulfate to increase myocardial membrane excitability

Explanation

Fine VF has a very low amplitude because myocardial cells are severely ischaemic and lack sufficient energy substrate for organised electrical activity. Continued high-quality CPR restores coronary perfusion pressure, delivering oxygen and glucose to the myocardium, which converts fine VF to coarse (high-amplitude) VF. Coarse VF is more likely to respond to defibrillation. Amiodarone does not convert fine to coarse VF; intubation should not delay defibrillation. Importantly, no drug should delay defibrillation in VF — shocks are delivered as soon as the defibrillator is ready regardless of VF amplitude.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.