Definition

HYPOTHERMIA: a decreased core body temperature, specifically, any temperature < 95° Fahrenheit (< 35° C).

Age is the primary statistic relevant to hypothermia-related deaths: elderly have difficulty maintaining thermoregulation (hypothalamus aging/dysfunction). 

EMS providers commonly use clinical signs to define hypothermia stages. Knowing these clinical signs and how to treat them is the most important aspect for national registry exams.

 

Clinical Signs and Stages of Hypothermia

1. Mild Hypothermia:

   • Temperature Range: 32-35°C (90-95°F)
   • Clinical Signs: Normal mental status, shivering, cold extremities. The patient may feel cold but is conscious and alert. Shivering is a key physiological response to increase body heat.

2. Moderate Hypothermia:

   • Temperature Range: 28-32°C (82-90°F)
   • Clinical Signs: Altered mental status, absence of shivering. Patients may be confused, lethargic, or disoriented. Shivering stops as the body loses its ability to generate heat, indicating a worsening condition.

3. Severe Hypothermia:

   • Temperature Range: Below 28°C (82°F)
   • Clinical Signs: Unconsciousness, potential for cardiac arrest, and severe bradycardia. The patient may appear dead but could still respond to resuscitative efforts. Muscle rigidity and dilated pupils may be present.

4. Profound Hypothermia (Apparent Death):

   • Temperature Range: 20-28°C (68-82°F)
   • Clinical Signs: Vital signs are faint or absent; the patient appears clinically dead but may be resuscitated if appropriate care is initiated.

5. Death from Hypothermia:

   • Temperature Range: Below 20°C (Below 68°F)
   • Clinical Signs: Severe metabolic and cardiovascular collapse, with little to no chance of resuscitation success.

 

Don't Write Anyone Off Just Yet. As you can see, it takes a dramatically low core temperature to kill, so always consider resuscitative measures in hypothermic patients who appear dead as end-organ damage is dramatically slowed by cold.

Patients with no circulation for upwards of 30 minutes may recover.

The Perfect Storm: Environmental factors such as low outdoor temperature, wet conditions, and wind can combine to make even seemingly "mild" conditions dangerous. In addition, your patient may be more susceptible to hypothermia based on extremes of age, preexisting medical conditions, or the influence of alcohol, drugs, or toxins.
Alcohol consumption has an effect on the user of being warmed. Even though the body is not actually warmer, the user may not take adequate shelter against the cold because he/she is not feeling cold and becomes hypothermic.

Paradoxical Undressing: Sometimes, patients with extreme hypothermia remove their clothes in an attempt to warm up. This is known as paradoxical undressing. It results when the blood vessels' vasoconstriction response fails.

As with any muscle, the small sphincters that compress the arterioles are overtaxed during prolonged hypothermia and fail. Unopposed vasodilation occurs, and the patient experiences being very hot. They disrobe to cool off.

Also, you may find these patients digging or trying to get into smaller spaces--under beds or behind wardrobes--possibly last-ditch survival instincts. Known as "terminal burrowing," it's likely an ancient, autonomous process of the brainstem triggered in the final state of hypothermia to produce a primitive and burrowing-like behavior of protection, as seen in (hibernating) animals. 

 

Special Assessment Considerations

As with all dire situations we encounter,

1. ABCs are your best initial examination. Followed by
2. an assessment of mental status

These two elements are all you need to classify and triage a patient with suspected hypothermia.

Testing a patient's temperature is best initially done by simply placing the back of your hand on the upper segment of the abdomen under the clothing.

► If this area is warm to the touch, moderate or severe hypothermia is essentially ruled out.

Formal temperature testing is best saved for transit, as clinical signs should rule out your transport decision.

 

Treatment of Hypothermia

First and foremost, REMOVE the patient from the cold area.

Any patient with mental status changes requires transport to higher level medical care. Elderly and young patients require careful monitoring as symptoms may develop or change rapidly.

MILD - MODERATE HYPOTHERMIA: can be treated with

• warmed blankets,
• warm environment, and
• removal of any wet clothing either on-site or in transit depending upon estimated transport time and the resources in your jurisdiction.

SEVERE HYPOTHERMIA: Will likely require IV administration of warmed saline and aggressive ABC management, in addition to the aforementioned measures for mild/moderate.

NOTE: As we will discuss in later sections, be cautious in the treatment of cold trauma (frostbite), as rapid rewarming may increase damage.