with less invasive means are exposed to increased
morbidity because of the invasive nature of introducing extracorporeal support.
So, how should refractory cardiac arrest be
defined? Contemporary reports in the literature
have generally used one of two methods. The first
approach is to simply limit the time spent in the
field attempting resuscitation. Three published
reports have suggested three different time intervals in this regard: One using 5–10 minutes of
resuscitation effort; the second using 10 minutes;
and the third using 10-15 minutes.
Using the passage of time to determine refractoriness of the cardiac arrest is complicated by
the need to ensure that standard treatments are
completed within that time period and by the difficulty of keeping track of time during the complex
task of emergency cardiac care and resuscitation.
An alternate approach is to define a cardiac arrest
as refractory if standard treatments are completed
but cardiac arrest persists. One study used the completion of three defibrillation shocks without ROSC;
another used three shocks and administration of IV
or intraosseous (IO) amiodarone.
15, 17 If cardiac arrest
continued they then transported to the hospital.
This completion of treatment approach may still
be impacted by the need for accurate time measurement. These therapies need to occur quickly and not
be drawn out beyond reasonable expectations, or the
intervention will again be adversely impacted and
ineffective secondary to the extent of injury to both
the central nervous system and the myocardium.
As these examples show, there’s currently no
consensus on how to best define refractory cardiac
provider (e.g., limited rescuers available, prolonged
CPR, during hypothermic cardiac arrest, in a mov-
ing ambulance, in the angiography suite, during
preparation for extracorporeal CPR [ECPR]), pro-
vided that rescuers strictly limit interruptions in
CPR during deployment and removal of the devices
(Class IIb, LOE C-EO).”
Certainly, manual chest compressions in the
patient compartment of a moving ambulance are
problematic. Several reports suggest that allowing
unrestrained rescuers to attempt manual CPR during transport is a definite safety hazard and puts
the rescuer at risk.
Others have shown that manual chest compressions during transport are frequently interrupted
and often more shallow than recommended. However, mechanical compressions in a moving ambulance achieved the recommended rate and depth,
while improving the CPR fraction compared to
Determining When to Transport
When to load the patient and transport to the
hospital with ongoing resuscitation efforts is an
important question, and one that’s not yet fully
answered. It’s clear that waiting until a lengthy
resuscitation effort has failed in the field before
transporting typically leaves a non-viable patient.
One study highlighted the importance of starting
extracorporeal membrane oxygenation (ECMO)
within 60 minutes of cardiac arrest onset, if meaningful survival is to be realized.
On the other hand, transporting too early means
some patients who would have been resuscitated
Table 1: Demographics and outcomes from the TROICA trial5
Placebo TNK p-value
Number of patients 525 525 1.00
Age 64.7± 13. 7 64.9± 13. 2 0.82
Male 78.6% 79.2% 0.89
White 96.4% 97.8% 0.25
Presumed AMI etiology 68.5% 74.8% 0.01
Bystander CPR 29.2% 30.4% 0.09
V fib 52.9% 54.8% 0.79
ROSC 54.6% 55.0% 0.96
Hospital admission 55.0% 53.5% 0.67
24-hour survival 33.3% 30.6% 0.39
Survival to discharge 17.5% 15.1% 0.33
30-day survival (prespecified primary endpoint) 17.0% 14.7% 0.36
Neurological outcome CPC 1 or 2 56.3% 62.8% 0.69
Intracranial hemorrhage 0.4% 2.7% 0.006