Other cold-related conditions
Frostbite is the localised injury or death of tissue due to cold exposure. Factors which predispose to frostbite injury are:
- alcohol intake
- type of cold contact (especially contact with cold metal, water or fuels)
- duration of cold exposure
- ambient temperatures below –2°C
- high winds
- humidity and skin wetness
- inadequate protective clothing (e.g. wet clothes, poorly fitting boots or gloves)
- impaired circulation (e.g. constrictive clothing, smoking)
- fatigue, over-exertion
- previous frostbite
- long periods of immobility.
Frostbite often occurs in the setting of a sudden storm, accident, fatigue or alcohol intoxication. Avoid tight clothing and ensure that shoes and socks fit well, with no pressure areas. Keep the hands and feet dry. Wet skin is more likely to become cold or damaged, and is more susceptible to frostbite. Similarly, modify dress and activity to minimise perspiration. In extreme cold, unless dexterity is required, mittens are preferable to gloves. Take care handling equipment, particularly wet metal objects and fuel. Party members should have up-to-date tetanus immunisation.
Frostbite occurs on the extremities, such as toes, fingers, nose and ears, with the toes being the most common. The frostbitten part feels very cold and is usually numb. The area is painless until rewarming. The extremity appears pale, white or mottled blue. In superficial frostbite, tissues below the skin remain soft to touch. In deep frostbite, the deeper tissues appear frozen solid, and are hard to touch. Following thawing, there may be a few clear fluid-filled blisters in superficial frostbite and many clear or purple blisters in deep frostbite. The initial treatment of frostbite is the same regardless of the severity.
Management of frostbite
Replace wet and constrictive clothing on the affected limb with loose, dry clothes (e.g. socks and mittens). Remove jewellery or other items that are restrictive or cause pressure on the skin. Cover any blisters or wounds with dry, sterile dressings, and apply padding and a splint to the area. Remember to check for the presence of hypothermia and provide all possible shelter.
There are a number of actions that are definitely not helpful in managing frostbite:
- do not prick blisters
- avoid smoking and alcohol
- do not apply snow or cold water
- do not apply direct heat to the area
- do not rub or massage the part as this is potentially harmful.
Evacuation should be undertaken as soon as possible if blisters have formed. Self evacuation may be possible if the hands are involved but frostbite on the feet may render the patient unable to walk. If deep frostbite is suspected then medical care should be sought urgently.
Field rewarming may be precluded by adverse conditions or lack of appropriate equipment, such as an adequately sized container to provide a bath for the affected part. Rapid rewarming is undertaken by immersing the affected part in gently circulating, warm water at 40–42°C. (The rescuer should test the water with an elbow if a thermometer is not available.) Rewarming usually takes 30 minutes, and the whole of the thawed part, including the tip, should appear soft and red. Pain may be very severe, and is difficult to manage with oral medications. Blisters may appear after thawing and should be kept intact. The parts should be gently dried, sterile gauze placed between the toes or fingers, then the part padded, wrapped and insulated to prevent injury or refreezing. Elevation will help reduce swelling.
The damage caused by refreeze after the thawing of a frostbitten part is much greater than the damage caused by delayed thawing. Therefore, if the patient must evacuate by walking through snow, then that is best undertaken before thawing frostbitten feet, rather than risk refreezing after thaw. In addition, extreme pain may occur during rewarming, which may render a person previously capable of walking on frozen feet incapable of self evacuation on thawed feet. Spontaneous thawing may occur during evacuation depending on the conditions. The decision to undertake rewarming in the field needs to consider:
- the expected time until evacuation or rescue
- the likelihood of spontaneous thawing
- the rendering of an ambulatory patient incapable of walking by rewarming
- the ability to rewarm in the field, given the equipment needed.
Snow blindness is not a cold or heat injury, but is included in this chapter because it is a highly debilitating but entirely preventable injury associated with altitude and snow.
Snow blindness is the burning of the front surface of the eye (the cornea) from exposure to ultraviolet (UV) radiation, rather like sunburn damage to the skin. Exposure to UV radiation is increased with altitude and in snow conditions, and reflection of UV radiation onto the eyes from the snow can greatly increase exposure.
Although damage can occur from a short period of exposure (e.g. 60 minutes), symptoms do not occur until 8 to 12 hours after the actual injury, so will not become apparent until later in the day or the following day. Snow blinded eyes are very painful, feel irritated and gritty, and are sensitive to light. The eyes may water profusely, have swollen lids and the surface of the eye may be red and swollen. Without treatment, the eyes will usually heal themselves over the following 24–36 hours or so. However, the discomfort experienced in the meantime may be severe and render the patient quite incapacitated.
Resting with eyes closed and in a dark environment will give some relief. Cold compresses applied gently to the closed eyes may also help relieve discomfort. Contact lenses should be removed while recovery occurs, and the patient discouraged from rubbing their eyes, which may cause additional irritation. Painkillers (e.g. paracetamol) or anti-inflammatory drugs (e.g aspirin) may assist. Snow blindness is a very distressing condition for the patient and reassurance and explanation should be provided. Full recovery is normal.
Snow blindness is entirely preventable with effective eye protection. Snow goggles and sunglasses should have an Eye Protection Factor (EPF) of at least 10. Protection can be improvised by cutting narrow viewing slits in an opaque piece of foam, cardboard or cloth, and securing it around the eyes. Even on overcast days, UV exposure can be high and eye protection should be worn.