Defibrillation, cardioversion and transcutaneous pacing — branching viva

Branching viva — defibrillation, cardioversion and pacing

The examiner releases the stem and then branches into five probes. A strong candidate answers the mode and dose first, defends the physiology, places the pads correctly, runs the drug sequence, and contrasts the two other electrical therapies without prompting. ^{[1] [6]}

Opening (examiner)

"An eight-year-old collapses in the waiting room. Cardiopulmonary resuscitation is in progress. The rhythm strip shows ventricular fibrillation. There is no pulse. Walk me through what you do." ^[1]

Branch 1 — Mode, dose and delivery (expected answer)

This is a shockable arrest rhythm, so deliver an unsynchronised shock — SYNC off — at 4 joules per kilogram, biphasic. The synchronisation function is not used because ventricular fibrillation has no organised R wave; leaving SYNC on would stop the machine from firing. Apply pads anterolateral or anteroposterior, charge while compressions continue, call stand clear, deliver, and resume compressions immediately without a pulse check. ^{[1] [2]}

Probe. "Why 4 joules per kilogram?" — The dose is weight-based because transthoracic impedance, the resistance the shock must overcome, scales with chest size relative to mass; 4 joules per kilogram is the biphasic standard taught by the European Resuscitation Council and APLS, and the American Heart Association accepts an initial 2 to 4 joules per kilogram. ^{[1] [3]}

Branch 2 — The shockable-arrest algorithm (expected answer)

After the shock, resume cardiopulmonary resuscitation for two minutes and reassess. If ventricular fibrillation persists, deliver a second shock at 4 joules per kilogram, then give adrenaline 10 micrograms per kilogram and repeat it every three to five minutes. If a third shock is needed, give amiodarone 5 milligrams per kilogram after the shock and flush. Continue cycles of shock, two minutes of compressions, and reassessment, treating reversible causes throughout. ^[1]