Cardiac Arrest Algorithms: VF/pVT, PEA, Asystole
Two branches, two priorities
The arrest algorithm splits at the rhythm check. Shockable (VF/pVT): start CPR, charge while compressions continue, deliver one shock, resume compressions immediately for 2 minutes, then recheck. Give epinephrine 1 mg IV/IO every 3–5 minutes after the second shock, and an antiarrhythmic - amiodarone 300 mg bolus, then 150 mg - after the second or third shock. Lidocaine is an acceptable alternative. Non-shockable (PEA/asystole): CPR, epinephrine 1 mg as soon as feasible and every 3–5 minutes, rhythm check every 2 minutes, and an aggressive search for reversible causes. Never defibrillate asystole or PEA.
Reversible causes
H's: hypovolemia, hypoxia, hydrogen ion (acidosis), hypo-/hyperkalemia, hypothermia. T's: tension pneumothorax, cardiac tamponade, toxins, thrombosis (pulmonary or coronary). Bedside ultrasound, a 12-lead, and a quick history (dialysis, overdose, recent surgery) drive these decisions.
Traps
Giving epinephrine before the first shock in VF - defibrillation takes priority. Prolonged rhythm checks that interrupt compressions. Forgetting that PEA requires a documented organized rhythm and an absent pulse, so a patient with a pulse but no blood pressure reading is not PEA. Assuming asystole is a terminal rhythm without checking leads and gain. Terminating resuscitation without considering a reversible cause or extracorporeal options.
Rule of thumb
Shockable gets shocked first; non-shockable gets epinephrine first. The sequence is shock → CPR 2 min → check → shock → CPR 2 min → epinephrine.