ENVIRONMENTAL COLD INJURIES

FMST 0404

15 DEC 99

TERMINAL LEARNING OBJECTIVE(S):

1.   Given a cold casualty in a combat environment (day and night) and the standard Field Medical Service Technician supplies and equipment, manage environmental cold injuries per the references.  (FMST.04.04)

ENABLING LEARNING OBJECTIVES:

1.      Without the aid of reference materials and given a list of symptoms in hypothermia’s progression, identify the approximate body core temperature, per the student handbook.  (FMST.04.04a)

2.   Without the aid of reference materials and given the symptoms common to cold injuries, correctly identify the cold injury, per the student handbook.  (FMST.04.04b)

3.   Without the aid of reference materials and given a list of treatments for cold injuries, select the appropriate treatment for the injury, per the student handbook. (FMST.04.04c)

4.   Without the aid of reference materials and given a list of preventive measures for cold injuries, identify the measures to prevent cold injuries, per the student handbook.  (FMST.04.04d)

5.   Without the aid of reference materials and given the FMST MOLLE Medic bag and a simulated cold casualty, identify, treat and manage the casualty, per the student handbook.  (FMST.04.04e)

OUTLINE:

A.     BODY TEMPERATURE REGULATION

1.   Body temperature reflects the difference between heat production and heat loss and varies with exercise and extremes of environmental temperature.  Properly protected, the body can function in environmental conditions that range from -58 F, to 122 F.

2.   Most of the body's heat is produced by the deeper core tissues (muscle and viscera), which are insulated from the environment and protected against heat loss by the subcutaneous tissues and skin.  Adipose tissue (body fat) is a particularly good insulator.

3.   Heat loss occurs when the heat from the body's inner core is transferred to the skin surface by the circulating blood.  This heat loss occurs through radiation, conduction, and convection from the skin surface.

4.   Peripheral vasoconstriction is by far the most important mechanism of heat conservation.  The main internal temperature sensors in the body are located in the hypothalamus.  When this area senses a drop in core temperature, it initiates peripheral vasoconstriction to help retain body heat.

5.   Shivering is the body’s attempt through muscular activity to generate internal heat.  mechanism to control heat.  If heat produced by shivering does not keep up with the heat loss, the core temperature drops.  The core temperature can be approximated by noting the following symptoms:

a.       97-95F (36-35C) – Intense shivering, impaired ability to perform complex tasks.

b.      94-91F (35-32.8C) – Violent shivering.  Difficulty in speaking, sluggish thinking, amnesia.

c.       90-86F (32.2-30C) – Shivering is replaced by muscular rigidity.  Exposed skin is blue or puffy.  Movements are jerky.  Dulled sensorium, but victim still is able to maintain posture and the appearance of contact with surroundings.

d.      85-81F (29.4-27.2C) – Coma, lack of reflexes, atrial fibrillation.

e.       Below 78F (25.6C) – Failure of cardiac and respiratory centers, pulmonary edema, ventricular fibrillation.  Death.

f.        Once heat is generated, it is conserved in the body by three main mechanisms:

1.      Peripheral vasoconstriction.

2.      Sweating stops.

3.      Piloerection – erection of body hair.

B.  COLD INJURIES

      1.  Hypothermia

a.       Definition - The state in which the body's core temperature falls to 95 degrees F or less.

b.      Cause

1.      Prolonged exposure to cold and wet conditions

2.      Inadequate clothing / protection

3.      Dehydration

4.      Inadequate nutrition

5.      Poor physical condition

6.      Traumatic injuries

c.       Signs / Symptoms

1.      Pale skin, cold to the touch

2.      Core temperature of 95 degrees F or less

3.      Hypotension

4.      Slow, irregular pulse

5.      Diminished respirations

6.      Altered mental status

7.      Pupils dilated

d.      Treatment

1.      Move casualty to a warm shelter

2.      Remove wet clothing if situation allows

3.      Loosen or remove constrictive clothing

4.      Warm the casualty

a)      Sleeping Bag Rewarming

(1)   Pre-warm bag with volunteers if possible

(2)   Add insulated clothing to aid in heat loss prevention

(3)   Add heating pads / packs (avoid burns)

(4)   Monitor vital signs and rectal temperature

b)      Water Bath Rewarming

(1)   Portable / field expedient, (life raft)

(2)   Keep head and extremities out of water

(3)   Water temperature between 100 - 108 degrees F

(4)   Monitor vital signs and rectal temperature

(5)   Add heated water to maintain good temperature

c)      Warm I.V. Solutions

(1)   Pre-warm solution in warm water or between MRE heaters

(2)   Solutions can be kept warm in the field by placing them in your clothing, next to the skin

5.      Administer hot, sweet drinks if conscious

6.      Maintain the airway

7.      Monitor vital signs

      2.  Frostbite

a.       Definition - Actual freezing of tissue, due to subfreezing temperature exposure over an extended period of time. (High winds can accelerate this process)

b.      Cause

1.      Ice crystals form between the cells, their sharp points cause damage to surrounding cells as they move.

2.      Ice crystals forming inside the cells is indicative of severe frostbite with resulting tissue destruction.

c.       Signs / Symptoms

1.      Superficial Frostbite

a)      Cold, stinging and / or aching sensation progressing to numbness

b)      Red,  progressing to white skin color

c)      Skin feels cool to "frosty,"

d)      Generalized edema with a "doughy" resiliency to touch

2.      Deep Frostbite

a)      No feeling present in affected area

b)      Translucent, waxy to yellow color

c)      Solid or "wooden" feel to touch

d)      Large blisters develop

e)      Extreme edema possible

d.      Treatment

1.      Do not rewarm if there is possibility of refreezing

2.      Rapid immersion in warm water; 104 - 108 degrees F, for approximately 20 to 30 minutes

3.      CASEVAC as soon as possible

4.      Monitor vital signs and signs of hypothermia

5.      Leave blisters intact

6.      Do not use ointments

7.      Do not rub with snow

8.      Do not give alcohol or cigarettes

      3.  Immersion Foot

a.       Definition - Neurovascular damage to extremity without ice crystal formation, the result of prolonged exposure to a cold and wet environment.

b.      Cause

1.      Circulation of blood is reduced to extremity due to the body's reaction to prolonged exposure.

2.      Actual "immersion" in water is not necessary to cause Immersion Foot.

3.      Condition can occur with the hands due to damp or cold gloves

4.      Temperature does not have to be below freezing for this condition to occur.  Cool temperatures in conjunction with dampness / immersion, are sufficient to bring about Immersion Foot

c.       Signs / Symptoms

1.      Numbness and tingling sensation

2.      Reddened skin initially, turning pale to grayish-blue

3.      Blisters and edema possible

4.      Leg cramps as the condition progresses

5.      Severe cases disrupt arterial pulses in affected regions

Figure 1.  Characteristics of Immersion Foot

d.      Treatment

1.      Pat dry the extremity

2.      Gentle rewarming

3.      Elevation of affected extremity

4.      Consider tetanus booster

5.      CASEVAC severe cases

6.      Avoid placement into boots if possible

7.      Do not remove blister blebs in field environment

      4.  Frostnip

a.       Definition - A numbing of an exposed patch of skin due to the body's cold reaction of decreasing blood flow to peripheral tissues.  This is a unique condition and should not be considered a superficial frostbite.

            b.  Cause

1.      Exposure to freezing conditions

2.      Strong winds exacerbate / accelerate onset

3.      Exposed skin has diminished capillary blood supply

            c.  Signs / Symptoms

1.      Whitened patch or tip of skin / extremity

2.      Stinging sensation progressing to numbness

3.      Cold and hardened skin to the touch

            d.  Treatment

1.      Gentle rewarming

2.      Protection and / or removal from environment

3.      Should not result in serious consequences

C.  COLD WEATHER PROTECTION PRINCIPLES

1.      The Marine Corps uses the acronym “COLD” to describe the cold weather protection principles.

a.       C – Keep clothing CLEAN and free of oil and dirt.  Oily and dirty clothing quickly looses its insulating effectiveness.

b.      O – Avoid OVERHEATING.  There are more heat exhaustion cases in a cold environment because of overdressing for the type of work performed.  Over-dressing and over-exertion cause an increase in body heat production and decrease heat dissipation.  As the body temperature increases, there is a corresponding increase in perspiration, which causes saturation of clothes with sweat.  Both conditions lead to cold injuries.

c.       L – LAYER correctly.  Clothes should be loose to trap air between the layers, which produces the insulating effect necessary for survival in the cold.  Tight and constricting clothing produces cold injuries.  There can be as many as seven layers of clothing used to protect personnel in a cold environment.

d.      D – Keep clothing DRY.  If clothing becomes wet so does the skin, which will promote cooling and frostbite.  Change wet clothing at the first opportunity.

D.  OTHER CONDITIONS ASSOCIATED WITH COLD WEATHER OPERATIONS

1. Snow blindness

a.       Definition - The burning of the conjunctiva and superficial cells of the cornea by ultraviolet light.

            b.  Cause

1.      Ultraviolet light; wavelength 200 - 300 mm

2.      Exposure to the sun's ultraviolet rays in conjunction with gray, cloudy conditions, "whiteout snow conditions, or bright, sunny conditions in a snow-covered environment

            c.  Signs / Symptoms

1.      Gritty sensation in the eyes

2.      Pain in the eyes

3.      Increased lacrimation (tearing)

4.      Photophobia

5.      Blurred vision

6.      Headache

7.      Hot sensation in the eyes

            d.  Treatment

1.      Perform a fluorescent stain of the eyes to determine damage to the corneas

2.      Apply antibiotic ointment to eyes

3.      Patch both eyes

4.      Analgesics

5.      Do not put local analgesics into the eyes

6.      Do not put steroid medications into the eyes

7.      Re-examine eyes on a daily basis

8.      CASEVAC as the operational environment permits

2. Carbon Monoxide Poisoning

a.       Definition - Inhalation of carbon monoxide gas to a degree that symptoms appear.

            b.  Cause

1.      Confinement in an enclosed area with a heating unit that is inefficient or not suited for an enclosed space

2.      Carbon monoxide bonds to red blood cells at a greater rate than does oxygen, resulting in a diminished oxygen carrying capacity

3.      Carboxyhemoglobin concentrations:

a)      20% produces mild poisoning

b)      30 - 50% produces signs and symptoms of severe poisoning

c)      50% and greater are generally fatal

            c.  Signs / Symptoms

1.      Mild Cases - dizziness, headache and / or confusion

2.      Cherry-red skin color or pale to blue appearance

3.      Severe Cases - unconsciousness and / or coma with decreased respirations and rapid, thready pulse

            d.  Treatment

1.      Immediate removal from the contaminated area

2.      Mild Cases - fresh air and bed rest for a minimum of four hours

3.      Mental status verification to determine severity

4.      Severe Cases - Rescue breathing and high concentrations of oxygen

5.      CASEVAC severe cases

REFERENCE (S):                                                                             

1.  First Aid for Soldiers  (FM 21-11)

2.  Tactical Emergency Care  (FMSS-2)

3.  Emergency War Surgery  (FMSS-3)

4.  Pre-hospital Trauma Life Support  (FMSS-4)

5.  Advanced Special Operations Medical Training Course  (FMSS-7)

6.  Advanced Trauma Life Support  (FMSS-5)

7.  Cold Weather Medicine Handbook  (FMSS-8)

8.  Wilderness Medicine Handbook  (FMSS-9)

Field Medical Service School
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Operational Medicine 2001
Health Care in Military Settings

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