KEEPING IT COOL
CASE REPORT
A 56-year-old male was walking into his
place of work when he suddenly collapsed
in the parking lot. He was found by a co-worker who happened to be a registered
nurse. She initiated bystander compressions while the public access automatic
external defibrillator (AED) was obtained
from the place of business.
Prior to the arrival of the AED at the
patient’s side, firefighter BLS first response
and a paramedic level ambulance were
on the scene (with a 9-1-1 phone ring
to arrival interval of five minutes and 11
seconds). An advanced practice paramedic
arrived two minutes later, carrying normal
saline IV fluids chilled at 2° C.
The airway was managed with a bag-valve mask (BVM). Bilateral tibial intraosseous (IO) needles were placed via an EZ-IO
device and infused with chilled saline, and
the defibrillator applied during continuous
chest compressions (see Figure 1, below).
The patient had return of spontaneous
circulation (ROSC) after the first defibrillation with a total estimated down time of
less than 10 minutes. Airway management
was continued with the BVM, and the post-resuscitation 12-lead ECG demonstrated
an obvious ST-elevation myocardial
infarction (STEMI) (See Figure 2, p. 58).
The patient was emergently transported to a post-resuscitation center 30
minutes from the scene. While en route,
Figure 1: Pre-Resuscitation ECG
LEARNING Objectives
>> Provide a rationale for the use of
early hypothermia
>> Describe effective prehospital cooling
methods and procedures
>> Describe the benefits and harm
associated with prehospital induction
of therapeutic hypothermia
he became combative but non-purpose-ful in his movements. He received 10 mg
of midazolam and 1,700 mL of chilled
saline, and was discovered to have thermal
burns on his back and posterior arms from
the hot asphalt of the parking lot where
he collapsed.
deficits. 1, 2 Brain-specific strategies that go
beyond cardiac arrest prevention and limitation of brain insult with effective CPR
are needed. Many cooling methods have
been proposed for use in the field by paramedics: The use of cold 4o C IV fluid, cold
metal cooling plates, and a cooling helmet.
The development of new cooling methods
and technology to augment or improve
cooling are currently under way and are
an area of commercial interest. This article
will focus primarily on the use of cold fluid
and briefly discuss the use of other surface
cooling methods.
RATIONALE FOR EARLY
HYPOTHERMIA
Prior to implementing any new therapy,
medical providers first seek to do no
harm. Both animal and human studies
have consistently demonstrated that early
implementation of hypothermia—either
during resuscitation or after ROSC—does
not cause harm and may even improve
effectiveness of such traditional therapies
as defibrillation. 4–7
In considering the optimal timing of
mild hypothermia as it relates to neurological outcome, several animal studies
suggest that cooling earlier rather than
cooling later results in more protection.
In a recent study of cardiac arrest in mice,
application of hypothermia (using cooling blankets) during CPR was shown to
enhance outcomes compared with application after ROSC. 8
However, these animal studies must be
In a dog model of ventricular fibrillation (v fib) arrest, early application of mild
hypothermia with cold normal saline infusion during CPR enables intact survival;
however, delay in the induction of mild
hypothermia reduces its efficacy, which
suggests that mild hypothermia should be
applied as early as possible. 9
IMAGE COURTESY WAKE COUNTY EMS
In another study, researchers demonstrated that mild hypothermia induced
immediately after cardiac arrest improves
cerebral function and morphologic
outcome, whereas delays of 15 minutes in the
initiation of cooling after reperfusion
doesn’t improve outcomes. 10 Thus, these
animal studies suggest that intra-arrest
cooling or cooling within 15 minutes
after ROSC offers the best chance for neurologic recovery.
INTRODUCTION
Cardiac arrest occurs commonly and
causes substantial morbidity and mortality. The incidence of out-of-hospital
cardiac arrest ranges from 0.04–0.13% of
the total population per year. 1–3 Despite
advances in prevention and treatments,
including external chest compression with
ventilation, defibrillation and advanced life
support, most patients whom paramedics
resuscitate in the field remain unconscious.
Survival with good neurologic recovery
has been reported achieved in 11–48% of
resuscitated patients; the remaining number either die during their hospital stay
or remain alive with severe neurologic
