8 Advances in Resuscitation
By Peter J. Kudenchuk,
MD, FACP, FACC, FAHA, FHRS
Double defibrillation, harnessing two defibrillators to administer simultaneous or double sequential shocks (sometimes called the “one-two punch”),
has seen increased use among various EMS agencies.
Though well-intentioned and considered by some as
an innovative approach to treating shock-resistant ventricular fibrillation (v fib), biphasic double defibrillation
is also controversial, off-label and poorly studied.
What Do We Actually Know?
Double defibrillation is based on the belief that a very high
energy shock (achieved by coupling two defibrillators) is
needed when v fib is unresponsive to a series of standard
shocks at maximum output. How often is this necessary?
Studies have shown that while many patients with out-of-hospital cardiac arrest require multiple shocks during the course of care, the vast majority of v fib cardiac
arrests ultimately prove to be shock-terminated, making
shock-refractory v fib a relatively rare event for the added
equipment and training double defibrillation requires.
Nonetheless, just the possibility of shock failure seem-
ingly begs the need for alternative approaches to such
patients, whether that be higher energy “double” shocks or
something else. This said, a potential problem with a high-
energy, double shock approach to v fib is that electric-
ity, like drug therapies, also has dose-dependent toxicity.
In the case of drugs, this is exemplified by the ill-effects
from high doses of antiarrhythmic drugs3 or epinephrine,
and (in the case of electricity) by the injuries sustained
from things like accidental electrocution.
Similarly, clinical and experimental studies have shown
that higher peak currents resulting from high energy defibrillation can be pro-arrhythmic. These excessively high
currents reduce rather than enhance defibrillation success and may actually promote v fib/v tach,
5–8 a concern
that could also apply when lower biphasic shock energies
are substantially increased by double defibrillation. This
approach also raises additional questions and challenges.
How Often Is Post-Shock V Fib Truly
More often than not, so-called shock-resistant v fib is a
victim of mistaken identity. In most patients with cardiac
arrest, the v fib seen after one or more shocks is the result
of its recurrence, not shock-resistance.
By definition, v fib that can’t be terminated by shock is
shock-resistant; whereas v fib that returns sometime after
Do or die?
There are substantial reasons
to question the safety, efficacy
and necessity of double
defibrillator biphasic shocks.
PHOTO COURTESY BRENDA LANAN