Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

1 39

Section V: Environmental Medicine

General Principles

Mild Hypothermia: Sub Acute • Slow onset, hours to days • Dehydrated and calorie depleted • Will not rewarm spontaneously

Low Risk !

High Risk

©2018WMA

Hypothermia is a dangerous complication in trauma cases where patients may lay immobile for hours awaiting evacuation. In rapid onset cases such as cold water immer- sion, there is often a marked difference in tem- perature between the cold body shell and the still relatively warm body core. People often become incapacitated by cooling of extremity muscles before they become severely hypother- mic. Generally, the patient has not had time to become significantly dehydrated or glycogen depleted. This is called acute hypothermia, and spontaneous rewarming is usually possible once the patient has been removed from the water, dried, and insulated. In slow onset cases, called subacute hypother- mia, glycogen stores and blood sugar have been depleted. The patient is usually dehydrated. The temperature difference between shell and core is not as dramatic. These patients are not able to rewarm without help. In fact, rewarming efforts can be lethal without hydration and food.

The most obvious signs of mild hypothermia are mental status changes and shivering. The patient may be lethargic, withdrawn, confused, or exhibit other personality changes. The skin is pale and cool, and there may be some loss of dexterity in the extremities as the shell/core compensa- tion reduces blood flow. Body core temperature measures below 35°C. Shivering can be mild to severe. If the patient is not already dehydrated, cold diuresis may continue with the patient pro- ducing relatively dilute urine.

Vital Signs in Mild Hypothermia: • Pulse: Normal to slightly elevated • Blood pressure: Normal • Respirations: Normal • Temperature: Between 32° and 35°C • Consciousness: A to V on AVPU; mild to moderate mental status changes • Skin: Shell/core compensation

General Principles

Mild Hypothermia: Acute • Rapid onset, minutes to hours (cold water) • Usually not dehydrated or calorie depleted • Spontaneous rewarming is usually possible

The most accurate body core temperature mea- surements are made by esophageal probe, which is not usually available for field rescue. Rectal measurements would be the next most useful. A special low-reading clinical thermometer is required for measuring core temperature below 34°C. Oral, ear, and skin surface measurements are frequently inaccurate in hypothermia.

Low Risk

High Risk

©2018WMA