What is the initial management for a patient with a cardiac rhythm disturbance, differentiating between shockable and non-shockable rhythms, such as ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) versus pulseless electrical activity (PEA) and asystole?

Management of Shockable vs Non-Shockable Cardiac Arrest Rhythms

For cardiac arrest, immediate defibrillation is the priority for shockable rhythms (VF/pulseless VT), while high-quality CPR with early epinephrine administration is the cornerstone for non-shockable rhythms (PEA/asystole). 1

Initial Rhythm Classification

Shockable rhythms include ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT), while non-shockable rhythms encompass pulseless electrical activity (PEA) and asystole. 1 This distinction is critical because shockable rhythms have significantly better survival outcomes—patients with initial shockable rhythms demonstrate 4-9 times higher survival rates compared to non-shockable rhythms. 1

Management of Shockable Rhythms (VF/Pulseless VT)

Immediate Defibrillation Protocol

• Deliver the first shock immediately (2 J/kg in pediatrics; 120-200 J biphasic or 360 J monophasic in adults) with minimal interruption to CPR. 1
• Resume CPR immediately after shock delivery, beginning with chest compressions, without pausing for pulse or rhythm checks. 1
• Continue CPR for approximately 2 minutes before the next rhythm check. 1

Subsequent Shock Sequence

• If VF/pVT persists after the first shock, deliver a second shock at the same or increased energy (4 J/kg in pediatrics, 360 J in adults). 1
• Minimize interruptions: ideally, the first three shocks should be delivered within 60 seconds when possible, as over 80% of successful defibrillations occur within the first three attempts. 1
• Charge the defibrillator during chest compressions when a shockable rhythm persists to minimize hands-off time. 1

Medication Administration for Refractory VF/pVT

• Administer epinephrine 1 mg IV/IO after initial defibrillation attempts have failed (typically after the second or third shock), then repeat every 3-5 minutes. 1, 2
• Give amiodarone 300 mg IV/IO (or lidocaine if amiodarone unavailable) after continued unsuccessful shocks. 1
• Critical timing consideration: For shockable rhythms, epinephrine is given AFTER defibrillation attempts, unlike non-shockable rhythms where it should be given immediately. 2

Management of Non-Shockable Rhythms (PEA/Asystole)

Immediate CPR and Epinephrine

• Begin high-quality CPR immediately with chest compressions at a rate of at least 100-120 per minute. 3
• Administer epinephrine 1 mg IV/IO as soon as feasible after establishing vascular access—this is a strong recommendation for non-shockable rhythms. 2, 3
• Repeat epinephrine every 3-5 minutes throughout the resuscitation. 1, 3
• Do NOT delay epinephrine administration in non-shockable rhythms, as earlier administration is associated with improved outcomes. 2

Ongoing Management

• Continue CPR for 2-minute cycles before reassessing rhythm. 1, 3
• Secure advanced airway and establish IV/IO access during CPR without interrupting compressions. 1, 3
• If rhythm converts to VF/pVT, immediately switch to the shockable rhythm algorithm and deliver defibrillation. 3

Search for Reversible Causes

Systematically evaluate and treat the "5 H's and 4 T's": 3

• 5 H's: Hypoxia, Hypovolemia, Hydrogen ion (acidosis), Hypo/hyperkalemia, Hypothermia
• 4 T's: Tension pneumothorax, Tamponade (cardiac), Thrombosis (coronary/pulmonary), Toxins

Prognostic Considerations

Rhythm Conversion Patterns

• Patients who progress from non-shockable to shockable rhythms have improved survival (7% vs 2% survival to discharge) compared to those remaining in non-shockable rhythms. 4
• However, patients with refractory cardiac arrest and initial non-shockable rhythms have poor prognosis (5% favorable neurological outcome) even with advanced interventions like ECPR, compared to 40% with initial shockable rhythms. 5

Epinephrine Effects

• Epinephrine significantly increases return of spontaneous circulation (ROSC) across all rhythms (high certainty evidence). 2
• For non-shockable rhythms specifically, epinephrine improves survival to discharge (RR 2.56,95% CI 1.37-4.80). 2
• Caution: More frequent epinephrine administration (every 3.1-3.4 minutes vs standard 5 minutes) is associated with development of secondary VF/VT, which paradoxically increases mortality. 6

Common Pitfalls to Avoid

• Never delay defibrillation in shockable rhythms to establish IV access or administer medications—defibrillation is the only rhythm-specific therapy proven to increase survival. 7
• Do not interrupt chest compressions for prolonged periods—hands-off time should be minimized to <10 seconds for rhythm checks and shock delivery. 1
• Avoid delaying epinephrine in non-shockable rhythms—it should be given as soon as vascular access is obtained. 2
• Do not give epinephrine before attempting defibrillation in shockable rhythms—shock first, then epinephrine if unsuccessful. 2