Cold Illness
Frostnip/Chilblain
Frostnip is the mildest form of cold injury. It is caused by cold-induced constriction of the blood vessels. Symptoms include pain and altered sensation. Frostnip resolves with rewarming without causing damage to the skin. It especially affects the fingers, toes and ears.
Chilblains are caused by chronic intermittent exposure to cool (above freezing), wet conditions. Tissue damage is caused by constriction and inflammation of the blood vessels. Symptoms include itching, burning, tingling, swelling and redness. Ulcers and nodules are occasionally seen. Symptoms usually resolve in 1 - 3 weeks. Again, the common sites are hands, feet and ears.
Trench Foot
Trench foot is caused by prolonged exposure to cold (temperature 0 - 20 degrees) and wet environment. Tissue injury is caused by swelling of the skin and damage to the small blood vessels due to water absorption at cold temperatures. It is characterised by numbness, pain, leg cramping, pale and wrinkled soles, blisters, ulcers and gangrene in severe cases. Tissue loss can take months to heal.
- Frostnip, chilblains and trenchfoot respond well to rewarming with dry heat. Treatment also consists of elevating the affected part and avoiding manipulation or pressure. Topical antibiotic cream is also useful.
Frostbite
Frostbite is caused by destruction of the tissues secondary to freezing. It usually occurs at temperatures less than 2 degrees Celcius.
It can be divided into two phases.
- Cooling Injury: Initial response of dilation and constriction of blood vessels in the tissues, followed by formation of tissue ice crystals. The tissue temperature continues to fall, forming ice crystals within the cells and leading to cell death.
- Rewarming Injury: Thawing of the limb leads to small blood vessel damage and formation of clots.
The tissue injury is effectively like a burn, ranging from first to fourth degree in severity. Fourth degree injuries involve muscle and bone and later become black and mummified. Commonly affected areas include fingers, toes, nose, ears and cheek.
Management of frostbite commences with removing affected areas from cold environment if possible. Splint the extremity to minimise motion. Provide adequate analgesia and give anti-inflammatories. Commence rapid rethawing in water at 40 - 42 degrees (dry heat rewarming leads to increased tissue loss) over approximately 15 minutes. Do not rub the affected part. Avoid refreezing as this can worsen tissue damage. Release large, non-haemorrhagic blisters. NO SMOKING. After rapid thaw, bed rest with dry air warming.
Hypothermia
Hypothermia is defined as core body temperature of less than 35 degrees Celsius. It can be divided into mild (temp 32 - 35), moderate (temp 28 - 32) and severe (< 28). It can also be classified as either Primary (exposure hypothermia) or Secondary. The latter is seen in the elderly, ill or intoxicated and will not be discussed here.
Risks for hypothermia in the adventure or wilderness setting include exposure (low temperatures, wind chill, wet clothing, immersion), trauma (head injuries, immobility), malnutrition, and alcohol.
Patients with mild hypothermia experience uncontrollable shivering, lethargy, confusion or unusual behaviour, urinary frequency and loss of coordination. Moderate hypothermia presents with slow breathing and pulse, loss of shivering, decreased level of consciousness and delerium. Patients with severe hypothermia are unconscious, cold to touch, have difficulty breathing and abnormal heart rhythms and may appear dead.
Treatment of hypothermia starts with prevention of further cooling. Remove wet clothes, apply warm blankets and avoid further exposure to cold environment. Warmed sweet drinks may be helpful. Avoid alcohol. Apply hot water bottles or commercial heat packs to the head, neck, armpits and groin. If severe, place the patient in a pre-warmed sleeping bag with another person. Use skin to skin contact to promote head transfer. Patients with moderate or severe hypothermia need urgent hospital care.
