Hold the Coroner

Could double sequential defib stop refractory v-fib?


   Your patient's in v-fib, and nothing's bringing him out. You've tried everything in the arsenal-continuous compressions, repeated shocks, all the drugs; nothing breaks it. Twenty minutes pass, then 25. The tube's fine, the EtCO2 normal, the patient takes an occasional spontaneous breath, but the heart fibs on.

   What do you do now? Is it time to call it a day?

   Not so fast. A few U.S. systems are now permitting a novel last-gasp effort to save patients like this: double sequential defibrillation, using two AEDs to deliver a final big blast of energy before writing a victim off.

   It doesn't always work. We don't know a lot about why it works when it does. There aren't many numbers to look at. But in a presentation at February's EMS State of the Sciences Conference in Dallas, former New Orleans EMS Director Jullette Saussy, MD, told of achieving several instances of return of spontaneous circulation with the measure, and even of a neurologically intact survivor to hospital discharge.

   Big Easy medics employed the double defib 16 times in a year, Saussy said. Four recipients achieved ROSC sustained to the hospital. One, a 64-year-old female, ultimately went home neurologically intact.

   The protocol actually originated with Wake County EMS in North Carolina where medical control docs kept getting calls from frustrated medics who had gone through their protocols for VF/PVT, then persistent VF/PVT, and couldn't get their patients out of it.

   "Under the old CPR," says Brent Myers, MD, MPH, medical director of Wake County's Department of EMS, "our hunch is that the perfusion was so poor, with all the breaks everybody was taking, that these patients wouldn't stay in fib-they would deteriorate into asystole. Now, with the continuous compressions and everything else, they weren't doing that, and we didn't really have a whole lot to offer our crews. We'd go through the ACLS algorithm and look at all the correctable causes, but just not be able to get these people out of fib."

   System leaders turned to local cardiologists for ideas. "The first words out of every one of their mouths," says Myers, "were, ‘Have you tried the second defibrillator yet?'"

   Turns out there are some references to this in the cardiology literature. Much of it deals with refractory atrial fibrillation, though some looks at ventricular arrhythmias too. Back in 1994, a team led by New York cardiologist David Hoch looked at sequential shocks from two defibrillators after unsuccessful single shocks for refractory VF during routine electrophysiologic studies. Refractory v-fib, Hoch's team noted, can occur in up to 0.1% of EP studies, but animal studies have shown that rapid sequential shocks may reduce its threshold. Among almost 3,000 consecutive patients, only five needed the double shocks, but all five were resuscitated successfully. "This technique of rapid double sequential external shocks may have general applicability," Hoch's team concluded, "providing a simple and potentially lifesaving approach to refractory ventricular fibrillation."1

   The shocks in Hoch's study were delivered 0.5–4.5 seconds apart. Wake's protocol directs the dual defibrillation occur "as synchronously as possible," recognizing, Myers says, the limitations of a single rescuer in the field trying to activate both defibrillators simultaneously.

   A 2005 Mexican study of 21 patients with paroxysmal or persistent atrial fibrillation saw 19 achieve sinus rhythm with double sequential shocks; its authors termed the intervention "safe and highly efficacious."2 In a 2004 Turkish study of 15 patients with refractory a-fib and heart disease, 13 achieved sinus after simultaneous shocks totaling 720 joules. Eleven of those maintained it six months later.3 Overall, Myers says, there's not a huge volume of literature, but what there is clearly suggests the double-shock gambit is safe.

Why It Works

   Why might it work? Some hypotheses:

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