The use of cold IV fluid for prehospital
cooling requires additional training and
equipment, such as portable refrigeration
for cooling the IV fluid and ability to measure central body temperature in the field.
In Wake County (N.C.), a district chief or
advanced practice paramedic is dispatched
to all cardiac arrests. Their vehicles are
equipped with portable refrigeration units
that maintain the normal saline at 2–4° C.
Temperatures are obtained via the tympanic
route and infusion of chilled saline is initiated during resuscitation for all patients
with an initial temperature greater than
34°. Paralysis with vecuronium and sedation with etomidate is available for use at
the discretion of the paramedics, should
In Seattle, each of the paramedic units
is equipped with portable refrigerators
capable of storing several 1 L bags of
normal saline at 4o C. Paramedics are placing esophageal temperature probes after
tracheal intubation in all resuscitated
out-of-hospital cardiac arrest patients.
Paramedics record temperatures using a
portable temperature recorder and other
temperature recorders, which are directly
integrated into the ALS monitors.
During a Seattle/King County pilot field
study, paramedics administered up to 2 L
of 4o C normal saline, pancuronium (0.1
mg/kg), and diazepam ( 1–2 mg) via IV.
Similar to the previously mentioned pilot
study of patients treated in hospital, the use
of pancuronium appears to augment the
cooling effect of the infusion of cold fluid.
Seattle Medic One paramedics were
already using IV pancuronium and diazepam in the field but not for this indication.
Not all EMS systems use these drugs routinely, and this could limit the applicability
of this cooling protocol to other systems.
The use of cold fluid alone is enough to
lower patients’ temperatures in the field.
However, in these patients, skeletal muscle
relaxation needs to be administered on
arrival at the ED.
In the Seattle pilot study, the saline
was infused through a peripheral IV line,
18-gauge or larger, using a pressure bag
inflated to 300 mmHg. The Seattle research
protocol didn’t adjust the amount of 4o C
normal saline to body weight.
EXTERNAL COOLING DEVICES
External cooling devices, such as cooling
helmets and cooling plates, have also been
proposed for use in the prehospital setting.
Cooling helmets are an attractive alternative and have been used in an in-hospital
cardiac arrest pilot study. 14 The investigators used a helmet device containing a
solution of aqueous glycerol and placed it
around the head and neck in order to
Before its application, the helmet device
was kept in the refrigerator to maintain
a temperature at -4o C. Using this device,
cooling to 34o C took a median time of
180 minutes as measured by bladder thermometer and 60 minutes as measured by
Another external cooling device
developed in Vienna, Austria, known as
Emcools, consists of multiple metal cooling plates. The plates are pre-cooled to
20o C until shortly before use. The efficacy
of these cooling plates has been demonstrated in a swine model of cardiac arrest.
The main advantage is the very rapid
cooling rates compared with infusion of
cold fluid. The cooling plates are also less
invasive because an infusion of fluid isn’t
needed. In this animal model, no evidence
of skin trauma was detected after the appli-
cation of the cooling plates.
intubated. He was taken emergently to
the cardiac catheterization lab, where he
was found to have 100% occlusion of his
right coronary artery. He then received
successful percutaneous intervention with
a door-to-balloon time of 46 minutes. The
patient was continued on the hypother-
mia protocol for 24 hours, rewarmed, and
transferred to the regional burn center for
continued care of his third-degree burns.
On hospital day number 13, the patient
was successfully weaned from the ventilator. On day 20, he was moved from
the intensive care unit and was
subsequently discharged with good neurological function.
Many systems use adult intraosseous infusion in at least one body location to administer cooled
saline during therapeutic hypothermia treatment of patient’s in cardiac arrest.
CASE REPORT CONTINUED
On arrival at the post-resuscitation center,
the patient was paralyzed, sedated and
Experimental animal work demonstrates
that early cooling or even intra-arrest cooling offers the best chance or neurologic
recovery following cardiac arrest. Because
the majority of cardiac arrests occur
outside the hospital, the application of
therapeutic hypothermia presents numerous challenges.
The use of cold 4o C IV fluid has been
shown to be effective and safe for use
in the field by paramedics, while the use
of other techniques, such as cold metal
plates and helmets, awaits further testing.
Whether field cooling improves neurologic outcomes and survival in resuscitated
cardiac arrest patients needs to be tested in
a large clinical trial before final conclusions
can be made.