So how do we manage hypothermia?
One of the really important things to remember
is these very patients I was just telling you about
who appear for all intents and purposes dead?
They can actually survive in some cases.
So even patients who are stiff, blue, pulseless,
apneic, no signs of life whatsoever.
They actually can come back to life with rewarming.
Patients have survived core temperatures
as low as 14 degree celsius.
That is incredibly cold.
And the thing to remember about hypothermia
is that it's neuroprotective.
So not only have patient survived
from very severe levels of hypothermia,
patients have survived neurologically intact
which is kind of amazing.
So there’s a saying in emergency medicine
that you’re not dead until you’re warm and dead.
So basically, we should never give up
on a hypothermic patient until we’ve warmed them
up to a reasonable physiologic temperature.
And speaking of cardiac arrest in our hypothermic patients,
there are few modifications
that you wanna consider in a hypothermic patient.
One is that we normally only give ourselves 10 seconds
to decide if a pulse is present,
but in hypothermia,
we should give ourselves up to 60 seconds.
It can be much, much more difficult to detect the pulse
in a hypothermic patient because it’s gonna be slow
and it’s gonna be weak.
So give yourself enough time to decide
if the patient has a pulse or not before initiating CPR.
You actually might wanna use a hand held doppler
or an ultrasound device
to verify the presence of a pulse
if you’re having difficulty palpating.
Ultrasound is also very useful to look for cardiac motion
before you start chest compressions.
And the reason that we wanna to be a little bit circumspect
about starting chest compressions in our cardiac arrest victims
is that any kind of rough handling
or jostling of hypothermic patients
can actually precipitate dysrhythmias.
So we really wanna be sure
our patient needs CPR before we implement it.
From the airway and breathing standpoint,
we should manage the airway as normal,
just like we would for any other patient with coma
or respiratory depression.
When we give supplemental oxygen,
we wanna make sure that we warm it up.
So we wanna not give the patient cold
or room temperature oxygen
but wanna use oxygen to help warm their lungs
and hopefully raise their core temperature.
We do wanna remember that the pulse oximeter
is not typically gonna be able to detect the waveform.
So pulse oximeters rely on capillary pulsations
in your fingertips
and if you’re very vasoconstricted in the periphery
which you are if you are profoundly hypothermic,
you’re not gonna have capillary pulsations
for the machine to detect.
So this is a situation where your pulse
isn't really gonna help you
and you might need to obtain an arterial blood gas
to assess your patient’s oxygenation.
Defibrillation, if it's necessary for a ventricular dysrhythmia
should be performed as normal.
But it is important to remember
that it might actually not work
until you get the core temperature up above 30.
The heart simply is not receptive to electrical stimulation
at very low temperatures.
So as you may imagine,
the treatment of hypothermia
is gonna be to warm the patient back up
and you’ve got three options for how you rewarm your patient.
You can do passive external rewarming,
active external rewarming
or active core rewarming.
And we’ll talk about each of those.
The passive external approach basically
just involves getting rid of wet clothing
and covering the patient up
with an insulating material like a blanket.
You also wanna get him out of the cold
and get him into a warm environment.
Now, this is pretty straight forward
and it’s really only used in mild hypothermia
or in situations where active rewarming is impossible
for one reason or another.
Maybe you’re in a wilderness setting
or something like that where you can’t get the patient
to an active rewarming location.
For more severe hypothermia,
we’re always gonna use active techniques
and that’s gonna involve not just insulating the patient
but actually heating them back up.
So we’re gonna use heating pads or heated blankets.
There are forced air rewarming systems,
the one that’s commonly used in the US
it’s called the bear hugger.
But there are basically different blankets
that will blow warm air through the system
and rewarm the patient that way.
And then you can also use radiant heat lamps.
When you use active external rewarming,
one of the really important things to remember
is to try to preferentially put the warming devices
on the patient’s torso rather than the limbs.
And that’s because of phenomenon
called core temperature afterdrop.
Remember, the periphery is very vasoconstricted
and as a result of that it's very cold.
So if you warm up the extremities,
you’re gonna basically start vasodilating those extremities,
and you’re gonna allow an influx of cold blood
from cold extremities to come back
to the central circulation.
That can actually reduce your core temperature
rather than bringing it up.
So you wanna make sure
that you get the torso warm first
and don’t worry as much about the extremities
until you've reached a more reasonable core temperature.
Of course, for very severe hypothermia,
we’re gonna use active core rewarming techniques.
And that basically involves any introduction
of anything that’s warm inside of the body.
So something as simple as warm humidified oxygen
actually counts as active core rewarming.
Use of warm IV fluids is another commonly used technique.
There have been reports of use of bladder and gastric irrigation.
These are kind of questionable techniques
with a little bit of controversy around them.
It’s not clear how effective they are
and there may be some morbidity associated with them.
But it is an option that's available to you
if you don’t have other alternatives.
You can also use peritoneal dialysis with warm dialysate.
A common technique that's used in hypothermic cardiac arrest
is closed thoracic lavage.
Where you basically put two chest tubes
in the patient's two large diameter chest tubes
and you use one to put warm sterile saline in
and you use the other one to drain it back out,
and you basically just have a continuous circuit
where you introduce warm fluid into the thoracic space
in order to rewarm the heart.
Really the gold standard of active core rewarming
is extracorporeal blood rewarming
which can be conducted on a cardiac bypass circuit.
This is obviously technically challenging and difficult
but for patients with a cardiac arrest
or profound hypothermia,
it’s something that’s definitely worth pursuing.
active core rewarming is mandatory for any patient
who is unstable or has severe to profound hypothermia
and the technique that you employ
is gonna depend on what’s available in your local setting,
and how sick the patient is.
In terms of general management for patients with hypothermia,
I already mentioned this,
but you wanna minimize any kind of rough handling of the patient,
because there have been case reports
of patients developing cardiac dysrhythmias
as a result of being excessively jostled or manipulated.
You wanna make sure that you provide adequate volume resuscitation.
These patients are commonly hypovolemic
because of the cold diuresis we mentioned.
All their IV fluids should be warmed.
You may need to use vasopressors for severe shock.
However, they’re often ineffective.
Really the treatment for shock
is gonna be rewarming rather than medication or fluid.
Dysrhythmias also will typically respond to rewarming
and you really only should treat unstable rhythms
with the understanding that it may not work
until you get the patient up to a more normal body temperature.
And then of course,
all patients with severe hypothermia
should be admitted typically to an ICU setting.