What is the immediate treatment for a patient in ventricular fibrillation?

Immediate Treatment for Ventricular Fibrillation

Deliver immediate unsynchronized defibrillation followed by high-quality CPR starting with chest compressions—this is the only intervention proven to terminate VF and restore perfusing rhythm. 1, 2

Initial Defibrillation Protocol

Shock immediately upon VF recognition:

• Use 200J for monophasic defibrillators or manufacturer-recommended dose for biphasic devices (typically 120-200J) 1, 2
• The shock must be unsynchronized—never use synchronized cardioversion for VF 2
• Resume CPR immediately after shock delivery without pausing to check rhythm or pulse 3, 2

The probability of successful defibrillation decreases 7-10% per minute without CPR, but only 3-4% per minute when bystander CPR is provided. 3 This underscores why immediate action is critical—every second counts.

High-Quality CPR Technique

Begin chest compressions immediately after each shock:

• Rate: At least 100 compressions per minute 1, 2
• Depth: 2/3 of the anteroposterior chest diameter 1, 2
• Minimize all interruptions—chest compressions should comprise at least 60% of total resuscitation time 3
• Continue for 2 minutes (5 cycles of 30:2 compression-to-ventilation ratio) before rechecking rhythm 3, 4

Critical pitfall: Post-shock asystole or pulseless electrical activity persists for a median of 20 seconds, with 25% of patients remaining pulseless beyond 2 minutes. 4 Pausing to check rhythm prematurely wastes precious perfusion time.

Medication Administration for Shock-Refractory VF

If VF persists after initial defibrillation attempts:

Epinephrine:

• 1 mg IV/IO every 3-5 minutes throughout resuscitation 2
• Improves coronary perfusion pressure during CPR 5

Antiarrhythmic therapy (after ≥1 failed shock):

• Amiodarone 150 mg IV over 10 minutes is the preferred agent 3, 2, 6
• Alternative: Lidocaine may be considered if amiodarone unavailable 3
• The 2018 AHA guidelines clarify that while these drugs increase ROSC and hospital admission rates, neither has demonstrated improved long-term survival or neurological outcomes 3

Important caveat: Establishing IV access should never delay CPR or defibrillation—both are more strongly associated with survival than any medication. 3

Subsequent Shocks

For persistent VF after initial CPR cycle:

• Deliver second shock at 200-300J (monophasic) or per manufacturer (biphasic) 1
• Third shock at 360J if needed 1
• Resume CPR immediately after each shock 3, 2
• Modern biphasic defibrillators achieve >90% first-shock efficacy, making prolonged shock sequences obsolete 3

Post-Resuscitation Priorities

Once ROSC achieved:

• Correct electrolyte abnormalities immediately, particularly potassium and magnesium 2
• Search for reversible causes (Hs and Ts): hypovolemia, hypoxia, acidosis, hypo/hyperkalemia, hypothermia, tension pneumothorax, cardiac tamponade, toxins, thrombosis (pulmonary/coronary) 1, 2
• Maintain adequate ventilation and oxygenation 1

Special Considerations

For witnessed arrest with AED immediately available:

• Start CPR and use AED as soon as possible 3
• Do not delay defibrillation for prolonged CPR in witnessed arrests with immediate defibrillator access 3

For prolonged VF (>5 minutes):

• Brief CPR before defibrillation may improve outcomes by delivering oxygen and metabolic substrates to depleted myocardium 3, 5
• However, two randomized trials showed no survival benefit from 1.5-3 minutes of pre-shock CPR by EMS 3

Avoid these critical errors:

• Never use synchronized cardioversion for VF 2
• Never delay defibrillation to establish IV access 3
• Never give AV nodal blockers (beta-blockers, calcium channel blockers, digoxin) if pre-excitation syndrome suspected—this can precipitate VF 2