Prehospital cardioversion of cardiac dysrhythmias

Synchronized and unsynchronized electrical cardioversions are safe and effective in the prehospital environment

By Matthew Hart, Jr.

You are dispatched for chest pain in a 54-year-old male. You arrive on scene and find your patient sitting in a recliner in the living room of the residence. He appears in obvious distress. He is pale, agitated and is clutching his chest. He tells you that he was watching TV and suddenly, his heart started beating fast. He tells you that he feels like he's going to pass out and is having trouble breathing. You take his pulse and it's 180 bpm. His systolic BP is 82 mmHg. He tells you that he takes medication for high blood pressure and high cholesterol. You connect him to your monitor and recognize the rhythm as SVT. His SpO2 is 92% on room air. You administer oxygen and start an IV in his left AC. You administer adenosine per your local protocols with no conversion.

What's next? Synchronized cardioversion should be your next treatment.

Electrical cardioversion has been accepted as a safe and effective procedure to terminate certain cardiac dysrhythmias since the 1950s. Initially used only in the in-hospital setting, it is now an accepted treatment for prehospital providers. Research has shown that the use of synchronized cardioversion in the prehospital setting has been shown to be over 80% effective in terminating life-threatening cardiac dysrhythmias [1]. It has also been demonstrated that paramedic-lead electrical cardioversions have efficacy rates similar to those of physician-administered treatments [2].

Table: Initial energy requirements for commonly encountered dysrhythmias using biphasic and monophasic defibrillator cardiac monitor units

For ventricular fibrillation (V-fib) or pulseless ventricular tachycardia (V-tach), initial unsynchronized shocks of 120 J biphasic and 200 J monophasic are usually sufficient to convert. If conversion is unsuccessful, subsequent unsynchronized shocks can be delivered at 200 J for biphasic and 360 J for monophasic monitors [3].

For polymorphic V-tach with a pulse, administer unsynchronized shocks of 100 J biphasic and 100 J monophasic. Subsequent shocks can be delivered at 200 J biphasic and 360 J monophasic.

For monomorphic unstable V-tach with a pulse, use synchronized shocks at 100 J biphasic and 100 J monophasic. Subsequent shocks can be delivered at 200 J biphasic and 360 J monophasic. Synchronized cardioversion can be considered for stable patients with ventricular tachycardia with a pulse and has been proven to be successful and faster than pharmacological cardioversion [4].

For hemodynamically unstable atrial fibrillation, administer an initial synchronized shock of 120 J biphasic and 200 J monophasic. Subsequent shocks can be delivered at 200 J biphasic. Subsequent shocks using a monophasic unit should remain at 200 J. Persistent atrial fibrillation with a rate of <150 BPM is infrequently the result of hemodynamic instability. Always consider hypovolemia and hypoxia before using electrical cardioversion [5].

For unstable atrial flutter, administer an initial synchronized shock of 50 J biphasic and 100 J monophasic. Subsequent shocks can be delivered at 100 J biphasic and 200 J monophasic.

For supraventricular tachycardia, administer an initial synchronized shock of 50 J biphasic and 100 J monophasic. Subsequent shocks can be delivered at 100 J biphasic and 200 J monophasic.

Remember that electrical cardioversion, whether synchronized or unsynchronized, is only used for hemodynamically unstable patients with the exception noted above for the treatment of stable ventricular tachycardia [6]. As always, refer to your local protocols for treating cardiac dysrhythmias.

Unstable patients presenting with cardiac dysrhythmias are defined as those patients who present with ischemic chest pain, an altered level of consciousness, dyspnea and symptomatic hypotension (a systolic blood pressure of less than 90 mmHg, and fast ventricular rates close to 300 BPM, which are seen with polymorphic ventricular tachycardia and atrial fibrillation with pre-excitation). Unstable patients are at serious risk of quick deterioration, organ damage and cardiac arrest.

Procedural sedation should always be considered for patients in distress.

Remember, do not synch on the T-wave when performing cardioversion!

The following are suggested procedural guideline for electrical cardioversion:

Place pads in the anterior/posterior positions if possible. Keep the pads away from implanted devices. If you are unable to place the pads in the anterior/posterior positions, place the pads in the right upper chest and left lateral chest positions.

Electrical cardioversion is a proven safe and highly effective treatment for life-threatening dysrhythmias. Electricity is certainly one of your most powerful therapies in your toolbox. As always, know and act according to your local protocols.

Please be safe out there!

Why do we use morphine in cardiac cases?

Jon Lee joins the podcast to discuss following the evidence and pharmacology research insights

Matthew Hart, Jr., is an assistant instructor of EMT and paramedic education at Oakland Community College, in Auburn Hills, Michigan. He is also a critical care paramedic in Michigan. He is a former flight paramedic based out of Bismarck, North Dakota. He holds a bachelor's degree in chemistry from the University of Michigan and a master's degree from Brown University in electro-chemistry. He can be contacted via email at [email protected]