EMS Committee – Double sequential external defibrillation (DSED)

Double Sequential External Defibrillation (DSED)

BY JENNA WULFF, TORONTO FIRE FIGHTER, STATION 227-C AND EMS COMMITTEE

Out-of-hospital cardiac arrest accounts for over 350,000 unexpected deaths each year in North America. Nearly 100,000 of these deaths are specifically attributable to VF (ventricular fibrillation), which is a dangerous arrhythmia/irregular heart rate, or PVT (pulseless ventricular tachycardia), which are rapid ineffective contractions.

Video Example of DSED:

www.youtube.com/ watch?v=NmoERV9EmG0

What is Double Sequential External Defibrillation (DSED)?

Double sequential external defibrillation involves the use of two defibrillators, which are most often placed with one set of defibrillator pads placed in the standard anterior-lateral position and a second set placed in the anteriorposterior position, to deliver two shocks in rapid succession.

Image courtesy of Dr. Mark Ramzy (@MRamzyDO)

When would paramedics use DSED?

Despite high-quality cardiopulmonary resuscitation (CPR), early defibrillation, and antiarrhythmic medications, some patients remain in RVF (refractory ventricular fibrillation), which is a shock-resistant ventricular fibrillation, during out-of-hospital cardiac arrest. This method has been proposed as a viable option for patients in RVF.

Why would paramedics use DSED?

The theory suggests that more pads increase the number of vectors that the electricity can use to reach the myocardium (muscles in the heart), leading to improved current distribution and decreased shock resistance, which leads to higher delivery and increasing shock success.

Does it work?

There has been very little research done to determine if DSED is, in fact, effective. In a recent study of 152 patients in Ontario, return of spontaneous circulation was obtained in 40% of the double sequence defibrillation group. This is only a pilot study, and therefore is not designed to give us practice-changing information. Although return of spontaneous circulation was obtained at a higher rate in the double sequential defibrillation group, we should be cautious interpreting those numbers without more detailed statistics. There is a more detailed study underway that will give us clearer results in the near future.