20 Cold climates

Wilderness medicine in a cold or polar environment involves all the challenges of remote medicine but with additional climatic stresses that impact on all aspects of living, travelling, and surviving. In addition to being cold and windy, these regions are often extremely remote and may include dramatic high-altitude mountains and glaciers—hostile, yet beautiful environments under threat from global warming.

The characteristic feature of cold climates is that the temperature remains below freezing for lengthy periods of the year, resulting in accumulations of snow and ice. Polar environments surround both poles and extend to lower latitudes during winter, similar conditions are found at high altitude anywhere on earth. The predominance of snow in a polar climate disguises the fact that many polar environments have very little precipitation; Antarctica is one of the driest places on earth, but winds move the snow around, regularly generating blizzard conditions. Sub-Arctic continental environments such as the Yukon, Alaska, and Siberia have bitterly cold winters, but their summers can be mild or even hot, with a rich diversity of wildlife, flowers, insects, and even a significant risk of huge forest fires.

The dominant factors in polar and cold climates are air temperature, wind speed, and sunlight. Around freezing point, high humidity (freezing fog) can make conditions feel bitterly cold, but humidity falls at lower temperatures and ceases to be a significant influence.

The windchill index combines temperature and windspeed to estimate the hazards to humans of the environment. Formulated by Siple and Passal in 1945, the original calculations were based upon the rate at which plastic bags of water froze. North American studies in 2003 instead studied the rate of cooling of exposed human faces, and derived a complex mathematical formula¹ to calculate the cooling effect of the climate. In practice it is easier to use online calculators² or one of the numerous downloadable weather apps to judge the hazard of the environment. For those without communication links, Fig. 20.1 and Fig. 20.2 provide equivalent information.

Prevailing meteorological conditions may be modified by local circumstances; for instance, wind speed and therefore windchill are reduced by contour features, trees, and clothing, but increased by skiing or travelling on a skidoo. Temperatures may be lower in sheltered valleys, but travel that is safe in the valley can become dangerous when crossing an exposed and windy pass. Bright sunshine raises the apparent temperature considerably. Careless behaviour can lead to frostbite in conditions that should pose a low physical risk. (See Table 20.1.)

(See also Avalanches, p. 642.)

Novice travellers in cold environments may encounter many hazards—most of them unfamiliar:

(See also Chapter 17.)

Animal life at the two poles differs considerably. In the south, hazards are rare and can be avoided by watching animals from a sensible distance and keeping away from the sea ice edge. Research scientists are at greater risk. Killer whales and leopard seals are potential threats in or on the water and ice edge. Fur seals bite intruders in their colonies, while bull elephant seals will aggressively guard their territory. At both poles, birds, particularly terns, will attack intruders on nesting sites by flying at their heads; an umbrella or walking pole may prevent collisions.

In northern areas, bears, wolves, elk, and moose pose substantial threats. By far the commonest problem occurs on roads at night. Moose use roads as convenient thoroughfares and as salt licks, as a result are frequently hit by cars, sadly often with fatal results to both animal and humans. In Newfoundland there are about 700 moose/vehicle collisions each year, and elk create serious problems for Scandinavian drivers. Away from roads, these large animals can also be a threat. Avoid approaching male moose during the autumn rutting season, and do not stray between a mother and her calf. At other times, the animals are generally placid and can be safely observed from a distance.

Bears are a danger. In North American tourist areas national park rangers monitor bear activity and offer advice about travel, closing campsites and trails if aggressive bears have been reported. Advice on dealing with a bear encounter is widely available.³

Most bears prefer to keep away from humans and will move on if parties make noisy progress through the wilderness. Brown and grizzly bears usually hibernate in winter and are the greatest threat if early autumn snow forces them down from the mountains into tourist areas. Do not leave food where it is accessible to bears. They become accustomed to this easy source of food, threaten humans, and then have to be culled or transported to very remote areas. Travellers on back-country trails should carry pepper sprays.

Polar bears are a very serious danger, particularly in areas such as Northern Canada and Svalbard (Spitzbergen), which are increasingly popular adventure tourism destinations. Campsites can be protected by a perimeter alarm system of ropes, bells, or empty cans; sledge dog teams can be spanned around the periphery, and it may be essential to carry firearms, and clearly appropriate training is crucial ( Polar bear, p. 543). The risk of polar bear attack can reduced if visitors stay in cabins instead of tents, use trip wires that detonate explosives, use guard-dogs, and deploy someone on polar bear watch who is armed.

During the summer huge numbers of biting insects breed in the ponds and marshes of low Arctic regions; clothing with ankle and wrist elastics, and midge hoods will make life bearable.

Improvements in transport, navigation, equipment, and communications have made access to remote polar areas much easier. Using a combination of fixed and rotary winged aircraft and coastal craft, logistic companies can supply and support polar expeditions, but travel remains costly and weather restricted, sometimes making casualty evacuation very difficult.

Once at the destination, travel may involve traditional technologies such as by walking, snowshoes, dog sleds, or skis, or more modern solutions such skidoos, superjeeps, ski cats, or kite skis. Environmental hazards such as crevasses and avalanches, and meteorological variations such as diurnal temperature change or whiteout may affect route timing and choice. Navigation may utilize maps, compasses, sextants, or GPS. Modern technology greatly enhances an explorer’s ability to navigate in difficult weather and terrain, but only while the batteries last.

Whiteout is a meteorological condition where there is lack of contrast, visibility may be excellent, or masked by fog. With no visual points of reference it is easy to walk or ski over a cornice, travel in circles, or even fall over while standing still. Though sometimes necessary, travel in whiteout is undesirable and may be very hazardous.

Avalanche transceivers are essential in mountainous areas and familiarity with their expeditious use is vital if buried victims are to have a chance of being extricated alive.

Mobile phone coverage extends to fairly remote areas of Scandinavia; satellite phones are valuable, though expensive, when beyond the range of terrestrial equipment and essential if you have arranged a 24-h ‘doctor on call’ emergency service. In 2013, only the Iridium system guarantees polar coverage. Checking the adequacy of coverage of any system prior to departure is essential. Short wave radio communications can be disrupted by auroral activity. Satellite beacons (emergency position-indicating beacons; EPIRBs) are becoming increasingly useful particularly if there is a satellite phone failure (battery, damaged, or lost), but require sophisticated SAR services in the area.

Polar and cold environments are threatened by global warming, their habitats fragile and vulnerable to the increasing numbers of visitors. The concept of sustainable ecotourism needs to be championed. All visitors to these precious areas need to be aware of the impact of their visit and try to minimize the effects ( Assessing an expedition’s environmental footprint, p. 125).

Humans have little physiological ability to acclimatize to cold environments. The only proven response to chronic cold exposure is the Lewis ‘hunting response’. Fit, experienced workers who regularly expose their hands to temperatures below 5^oC can develop a cyclical vasodilatation of the skin vessels that enables them to maintain higher mean hand temperatures than new arrivals in a cold environment. At a time when hunting and fishing required hand agility at low temperatures, this mechanism had survival benefit. However, most modern polar travellers will not regularly expose their hands to such low temperatures, and those who do run the risk of suffering recurrent minor cold injury instead of acclimatizing. Native peoples in circumpolar areas have a short, stocky build, suggesting that an endomorphic body shape has survival benefits in very cold climates.

Travellers in cold dry climates encounter few problems if the temperature is above –10^oC. As temperatures fall further:

Chronic conditions that may be exacerbated by cold dry air include:

Children can be safely taken into cold climates, but must be properly dressed and closely supervised as they can lose body heat rapidly. Early signs of chilling include grumpiness and a reluctance to move. Young children should not be carried in backpacks in the cold; the parent may slip and fall, while the youngster’s legs can become constricted by the base of the pack, resulting in poor circulation and cold injury to the legs. Ski pulks—sledges for towing youngsters in the snow—are popular in Scandinavia; legislation bans their use if the air temperature is below –10°C. Parents or guides should regularly check to ensure that their charges’ hands and feet have not become numb. An exercising adult may be unaware of how cold the resting youngster has become.

Polar expeditions will usually choose a permanent building as a base camp for their work. When the camp involves several buildings, doorways should be linked by hand-lines, as it is easy to become disorientated in darkness or a blizzard. This particularly applies to latrines sited some distance from the base. Fire is a serious threat in areas where water is not available to extinguish flames. Store fuel away from the main base building, there should also be an emergency dump of clothing and food in case of a serious conflagration.

In extreme cold and at high altitude, cooking gas cylinders should be warmed (body warmth or sunlight) before use. Consider keeping the cylinder in a sleeping bag at night. When in use, raise the cylinder off the cold ground using a thin insulating board. Consider the mix of fuels being used. Pure propane has a boiling point of −42°C, but requires a heavy steel canister to safely contain it. Butane has a boiling point of −1°C, but does not vaporize well when the temperature drops well below freezing. In cold weather an appropriate cold weather blend is the best solution and usually a mix of 80–85% iso-butane and 15–20% propane is optimal (e.g. MSR IsoPro^® fuel, Snow Peak GigaPower^® fuel, or Jetboil JetPower^® fuel).

Snow holes are warmer than tents in extreme conditions, but more laborious to construct. Tents and snow holes must be positioned away from avalanche runs and trails; both should be well marked so that vehicles and skiers do not accidentally cross them, and they can be re-located in poor weather.

When camping on glaciated terrain, camps need to be carefully assessed by a roped climber using an avalanche probe to rule out hidden crevasses and mark the safe perimeter using bamboo canes or ‘wands’. Only then should the team unrope and once unroped, they should remain inside the designated safe area at all times.⁴

Carbon monoxide poisoning and dangerously low oxygen levels are both serious risks in closed areas if candles or cooking stoves are used. If a candle flame burns low or goes out, oxygen levels are dangerously low. Carbon monoxide from cooking stoves is odourless and causes insidious poisoning. Headache and nausea usually precede unconsciousness, but the cause may not be apparent to fatigued travellers, or at altitude where such symptoms are common. Tents designed for extreme conditions are very windproof, particularly if they become partially buried in drifting snow; ventilators may block with condensation and must be checked regularly. Cooking with the tent door partially open in all but the most extreme weather is strongly recommended. Deaths have occurred. Supplementary oxygen should be given to a survivor and the victim evacuated. If facilities exist in the area, hyperbaric oxygen is an effective treatment.

Fresh water can usually be obtained by melting snow, and is safe to drink unless it comes from an area frequented by animals or birds. Clear and separate designation of the latrine area and water source has to be established from the outset. Using a small volume of water at the base of a pan of snow greatly increases the speed at which the snow (mainly air) will melt. Large amounts of fuel⁵ are needed to melt snow, particularly at very low temperatures, so whenever practical dig or drill through overlying snow to obtain stream water running below. The upper layers of sea ice usually contain little salt and are potable. In the Northern hemisphere, deer and beaver may live close to apparently pristine melt streams and can contaminate the water with Giardia. Glacier outwash streams contain fine, highly abrasive rock dust in suspension; this is a powerful laxative. If in doubt, filter water and then boil or sterilize it ( Water purification, p. 102).

Because polar air is very dry, sweat evaporates quickly and fluid losses may be underestimated. Dehydration is a risk during the first days of an expedition; even if people do not feel thirsty, they should drink sufficiently to ensure that they urinate dilute, pale urine. A combination of malaise, headache, and raised body temperature is common when groups first arrive in the cold; this may be a mild form of heat exhaustion. Bathing in cold climates is a masochistic pastime. On shorter expeditions and when facilities permit, people and clothes should be washed whenever possible to prevent fungal skin infections and boils. In the field, ‘wet wipes’ can provide a practical way of maintaining hygiene. However, without washing, the Inuit and members of prolonged field expeditions develop a natural balance with their body oils and the risk of infection reduces. To avoid offence, it is wise to shower shortly after returning to heated accommodation!

Around base camp, or travelling using motorized transport, energy requirements will be similar to those of an outdoor worker in the UK (3000 kcal/ 12000 kJ per day), but man-hauling sledges and cross country skiing are extremely energetic pastimes requiring two to four times this energy intake, and eating enough is challenging. Typically a 5–10 min rest every hour to snack and rehydrate is the only way of adequately fueling during a strenuous climb. A greater proportion of the diet is likely to be made up of fatty foods, and a wide selection of high calorie snacks and foods should be available. In the past, polar expeditions have lived off the land, but nowadays most Arctic species are protected and licences are required before they are hunted. The internal organs of some polar animals contain toxic amounts of vitamin A and should never be eaten. When travelling in areas where big mammals hunt, you should ensure that food is stored appropriately. Airtight containers in rucksacks and animal-proof food dumps reduce the risk of unwanted visitors.

Polar environments are extremely fragile ecosystems in which organic matter degrades very slowly. Removing waste is your gift to future generations. In Antarctica, expeditions are required to ship out all their waste, including faeces and sanitary materials. National Parks in North America, Canada, and Greenland also have specific requirements about waste disposal, which is a ‘pack in—pack out’ policy.

Cold will affect many items, including batteries, contact lens fluids, and drugs. Aqueous drugs freeze, crystallize, and may degrade in the cold; therefore powdered preparations and plastic containers should be selected whenever possible. Critical items can be kept warm by body heat or heat packs used to maintain temperature.

Detailed advanced planning is required to accurately predict food and fuel consumption. Contingency plans and adequate reserves are required. Stoves are lifesavers in the hostile polar environment and spare parts or spare stove is essential. Optimal choice of fuel will depend upon a number of factors including the number travelling, the destination, the duration and ease of re-supply.

Just having the appropriate equipment is not enough. Familiarity with when and how to use it is often overlooked and is just as important. The ‘weekend warrior’ or the affluent but inexperienced polar traveller is a potential danger to both himself and his companions.

Careful consideration needs to be given to the range and choice of clothing taken to cold and polar regions. Active individuals will typically use a flexible layering system, with a wicking non-absorbable base-layer building up through a series of insulating layers to an outer wind/waterproof shell. Those riding on sledges or skidoos may prefer a heavily insulated overgarment, though these can restrict movement. The final choice will vary between individuals and will reflect the ambient temperature, the wind chill, the altitude, their susceptibility to cold, and the activity undertaken. Synthetic and natural fibres and fabrics have different advantages and disadvantages; these need to be understood if the benefits are to be fully utilized.

Clothing should be adequate to prevent body cooling, but excessive clothing results in a build-up of body heat and sweating, which is undesirable as perspiration condenses in clothes, reducing their insulation. Although modern breathable synthetic fabrics function adequately in cold dry climates, many experts prefer cotton ‘ventile’ shell garments. After prolonged use without washing, woollen base layers such as merino are less malodorous than synthetics. Energetic cross-country skiers often wear thin garments, but must carry windproofs in case conditions change; the groin area can become painfully cold and requires effective thermal protection, e.g. using thermal windproof underpants. If such ‘wind-pants’ are not worn, the penis is alarmingly vulnerable to frostbite. At any rest or meal break, conserve heat by putting on a belay jacket or zipping up anorak vents, and by putting on scarf, hats, and gloves.

Mittens are superior to gloves at retaining peripheral heat in very cold climates and should be used with wrist or ‘idiot loops’. Chemical hand warmers are useful when hands or feet become uncomfortably cold, and are a great morale booster for children in the snow, but should be used with caution if peripheries have become numb, as there is the risk of thermal heat injury. Loose fitting, well-insulated footwear, with gaiters to prevent snow getting onto socks, are desirable. Battery-powered heated insoles are available if feet are to be exposed to the cold for lengthy periods at low exercise levels; for instance, when travelling by skidoo, or making scientific observations. However the practicality of using any electrical or chemical technique over sustained periods is unrealistic. Whenever possible, boots should be warmed and dried; over a period of days they accumulate moisture and can freeze if taken off in a tent overnight.

Eyes must be protected from UV glare by appropriate sunglasses or goggles (see Snow blindness (photokeratitis), p. 634). For those with visual defects, contact lenses, prescription sunglasses or spectacles with photochromic lenses all work reasonably well. Wearing ordinary spectacles under goggles is cumbersome. Anyone whose vision is so poor that they always need to wear glasses or contact lenses must plan to avoid the difficulties that would arise from loss or breakage: as a minimum, a spare pair of spectacles should be taken. Below –20°C, glasses invariably mist over, and contact lenses may be preferable. However, contact lenses can adhere or even freeze to the eye. Forced or clumsy removal can then result in corneal abrasion, requiring topical treatment with antibiotics and local anaesthetic ( Contact lenses, p. 325).

Metal spectacle frames can become very cold and cause cold injury if in direct contact with the skin; opticians sell silicone sheaths that cover the side arms. Plastic-framed glasses or snow goggles are preferable, but become brittle at low temperatures. Carry spare filters for goggles as these too can crack after prolonged exposure to the cold.

In the past, imported infectious diseases such as diphtheria, measles, and TB tragically decimated circumpolar native populations, but infectious diseases are nowadays uncommon in polar areas. Some sledge dogs carry rabies, and inoculation is advisable if the expedition is visiting an endemic area. Sexually transmitted infections have a worldwide distribution. After prolonged residence in a cold climate—e.g. over-wintering on a polar base—travellers will be particularly susceptible to upper respiratory tract infections.

An increasing number of visitors are being airlifted onto the Antarctic plateau (2500 m/8000 ft+) to compete in races or personal challenges. The combination of cold and altitude with pre-existing upper respiratory tract infections has resulting in several incidents where previously fit individuals have developed severe pulmonary symptoms, possibly as a result of a combination of infection and altitude sickness.

In the field, diagnosis can be difficult, but anyone whose torso feels ‘as cold as marble’ should be treated as a cold casualty. Diagnosis can be confirmed by measuring body temperature using a low reading rectal thermometer, preferably a calibrated electronic device with the sensor inserted to 15 cm beyond the anal sphincter. Conventional oral thermometers do not measure low body temperatures, and infrared tympanic membrane thermometers can be inaccurate by several degrees, particularly when the ear has been exposed to cold, heat, or water.

Hypothermia is a drop in the victim’s core body temperature to an extent that their ability to function normally is impaired. Normal core temperature is 36.5–37^oC. Temperatures below 35^oC cause progressive symptoms similar to drunkenness and known as the ‘umbles’: the victim stumbles, grumbles, mumbles, & fumbles. They may shiver uncontrollably, but do not always do so and—rejecting help—may vehemently deny that anything is wrong. Untreated, they will eventually become comatose and die. (See Table 20.2.).

Hypothermia is uncommon in a properly clothed fit person, but develops if someone is injured, lost, short of food and/or water, or if their clothing is inadequate or wet, especially in windy conditions. Typically it develops insidiously over several hours, but death (usually from ‘cold shock’ or drowning when disabled by hypothermia) can occur within minutes if someone is immersed in cold water.

Experts disagree about the best treatment for severe hypothermia and this has led to conflicting advice in textbooks. However, the controversies are irrelevant to most expeditions as they are unlikely to carry the advanced resuscitation equipment now available to mountain rescue groups. The aim of treatment is to restore the body heat of the victim:

It may be very difficult to tell whether a hypothermic casualty is dead or alive. Breathing will be slow and shallow, while the pulse may be slow, thready, and palpable only in the neck and groin. If unsure, assume that the casualty is alive. In an isolated base camp, the best that can be done is to keep the victim as warm as possible, ensure that their breathing does not obstruct and, if possible, infuse some warmed IV fluid to maintain hydration. The patient needs to be turned regularly to ensure that they are not lying in one position for a prolonged period. Advanced life support measures such as intubation or the insertion of a laryngeal mask airway can precipitate intractable ventricular fibrillation, but may sometimes be a necessary risk. Similarly, starting external cardiac massage may tip the hypothermic heart into ventricular fibrillation. Once started, cardiac massage should be maintained until the patient has been rewarmed or delivered to a hospital: in very remote areas this makes it inadvisable to start massage because evacuation will be impractical.

If you do start CPR, it is clearly difficult to give evidence-based advice on how long to continue. Following immersion in very cold water, there have been cases of full recovery following several hours of external cardiac massage. The most effective form of rewarming from severe hypothermia is extracorporeal circulatory rewarming, but this will require rapid evacuation to a tertiary care hospital. Declaring a victim dead is more confidently done if they are warm, but the difficulty here lies in warming up someone in the wilderness enough to be able to do this.

The Scottish Mountain Safety Forum in 1997 produced guidelines to assist with decision-making (Table 20.3).

Recovery from mild hypothermia is usually uneventful, although the victim may feel exhausted for hours or a few days. Although rare, fulminating acute pancreatitis can cause rapid deterioration during or after rewarming.

Severe hypothermia, especially if the patient has been unconscious for some time, requires careful monitoring in hospital. Extracorporeal warming with warm air (e.g. Bair Hugger) is important, and whilst peritoneal lavage and bladder irrigation can be used, cardiopulmonary bypass is necessary to rewarm the profoundly hypothermic casualty. Arrhythmias, muscle damage, and kidney failure can develop. Maintaining the patient at 33°C for 48 h before fully rewarming may reduce complications.

See Fig. 20.3.

Frostnip is a superficial reversible freezing of the skin surface, which resolves completely within 30 min of starting to rewarm the frozen part. In the field, it looks as though pale wax has been dropped on the skin. Typically affecting parts of the body that are exposed to prevailing cold and wind, such as chin, cheeks, and earlobes, frostnip is rare if the environmental temperature is above –10^oC, but common in conditions below –25^oC. Strong winds, either natural, or generated by travel (running, skiing, or skidooing), increase the risk. Some experienced cold-weather travellers believe they can feel the onset of frostnip as a sudden burning ‘ping’ sensation. Once established, the lesions are numb and painless.

There is vasoconstriction of the cutaneous blood vessels endothelial cell damage, and freezing of the outermost layers of the skin. Deeper tissues are unaffected.

Novice visitors to very cold climates must be constantly aware of the dangers of the environment. Using a system of ‘buddy’ pairs is sensible if travelling in adverse conditions, with the buddies checking each other regularly for cold injuries. Simple measures to prevent cold injuries include:

For men, the protective value of beards is a hotly debated topic. In some Scandinavian countries, ointments are sold that are claimed to reduce the risk of cold injury. Evidence suggests that these are not effective and some may actually increase the risk of injury.

Frostnip should be treated as soon as possible, before permanent tissue injury develops. The skin can be gently warmed by blowing exhaled air across the affected skin, or by contact with a warm ungloved hand. Do not rubbed nipped areas. Once rewarmed, the affected area will look red and may tingle or burn. Frostnip is an indication that weather conditions are hazardous and additional skin protection is required or shelter should be sought. No additional treatment is required.

Initially the area will look red and may be slightly swollen, but the skin will return to normal rapidly. Once frostnipped, the affected areas of skin are susceptible to repeat injury. If the cold injury does not resolve within 30 min, if a zone is repeatedly injured, or if the skin blisters, the condition should be regarded as frostbite, the casualty evacuated, and treated accordingly.

Frostbite is freezing of body tissues, with extensive damage to the affected areas. This type of injury is most likely to occur in novices in polar areas who do not care for themselves properly. Serious frostbite injury is rare in experienced travellers, but develops following serious injury, immersion in cold water, or when extreme weather conditions prevent travel. Dehydration and high altitude substantially increase the risk of frostbite. The affected part will be cold, white, numb, and rigid. (See Table 20.4.)

Frostbitten tissues are seriously damaged, cell structures being disrupted through the formation of ice crystals and osmotic damage to the cells. Circulation will cease in the affected area with muscles frozen and no nerve conduction.

Consider carefully whether travel is necessary in severe weather conditions, dress appropriately, drink sufficient fluids, and pair off using the ‘buddy’ system. Avoid tight clothing and boots that may restrict circulation. Tape gloves to clothing (or use ‘idiot loops’) so that they cannot be lost in a gale, and carry spare hat, gloves, and socks. Do not ignore painfully cold hands and feet; try to rewarm affected parts as soon as possible and seek shelter urgently. Never immerse hands or feet in seawater near freezing: seawater typically freezes at temperatures below the freezing point of tissues, making severe frostbite a common result. Beware of cold fuels.

Frostbite injuries are usually serious and the casualty will usually need to be evacuated. Although undesirable, a victim can continue to travel with a frozen limb, but, once the affected area has been thawed, they will be incapacitated. Try to protect the numb area from further damage until shelter is reached.

The only reason for delaying rapid rewarming is if an arm or leg is very badly frozen. In such cases, the cellular structure of the deep tissues can be seriously damaged and the patient requires urgent transfer to hospital. As the tissues thaw, they swell, and pressures in the deep fascial compartments may exceed arterial pressure, leading to complete ischaemia of the limb. Fasciotomy prior to rewarming can prevent this disaster, but requires full investigation prior to surgery. (See Crush injuries, p. 277; Fig. 20.4.)

In individuals who have sustained a severe frostbite injury and where they can be evacuated to a major vascular or plastics unit within 24 h of the injury (this may be possible in Alaska, European Alps, Scotland, etc) it may be possible to reduce final tissue loss by the use of intra-arterial tissue-plasminogen activator or iloprost⁹. Contraindications to thrombolysis (associated major trauma, recent stroke, GI bleed, etc.) need to be ruled out.

In the early phase after rewarming, the affected area will look red, blistered, and severely swollen. Raw areas leak copious amounts of serous fluid. Later, peripheral parts of affected limbs will turn black and mummify. Systemic antibiotics and tetanus prophylaxis should be given to anyone who has significant amounts of dead or dying tissue.

The mainstay of continuing treatment is the whirlpool bath into which affected parts are placed for 30 min twice daily. An appropriate antibacterial should be added to the water. Exposure in a warm environment and early mobilization should be encouraged; smoking should be forbidden.

In temperate climates, where frostbite is very rare, vascular surgeons are familiar only with dry gangrene caused by vascular insufficiency. Such patients have deep-seated, often painful, gangrene, and require amputations. Frostbite injuries can look very similar but the damage is usually more superficial and, unless infection develops, surgical interventions should be avoided until a natural demarcation line becomes obvious between dead and healthy tissue. Better scanning techniques and anti-prostaglandin drugs are improving the outlook for patients with serious frostbite injuries.^10,11,12

A recent development that allows access to expert advice in difficult situations is the use of the Internet and satellite phones. A virtual opinion or more specialized advice can be sought from anywhere in the world using a combination of digital images and phone advice.¹³

Non-freezing cold injury is a protean condition that occurs in cold, wet conditions (‘trench foot’), shipwreck survivors (‘immersion foot’), wet jungle (‘paddy foot’), even those with dependent and immobile legs (‘shelter limb’). Common to these is a period of relative ischaemia in the feet or hands, during which there is impairment or loss of sensation, followed by hyperaemia when they are rewarmed, often accompanied by lasting and severe pain. Predisposing factors are similar to those of frostbite, but tissues do not freeze. Cold exposure is longer in duration, typically hours or days, although non-freezing cold injury can occur in less than an hour. Individuals of African ethnicity are particularly susceptible to developing the condition.

Although less understood than frostbite, current evidence suggests that cold and ischaemia damage nerves and the vascular endothelium in local tissues. Rewarming then results in further damage from free radicals and inflammation.

High standards of foot care are essential, with frequent regular replacement of wet socks with dry ones, and wiggling of toes to try to maintain local blood flow. Even assiduous care can only postpone the onset of injury, so periodic removal from cold, wet conditions is also necessary. Footwear that relies on eliminating evaporative heat loss (‘vapour barrier’) or surrounding the feet with impermeable materials leads to accumulation of sweat next to the skin, resulting in non-freezing cold injury. Foot care routines and drying are even more important when rubberized or impermeable boots are worn.

Cases that present before rewarming must be allowed to rewarm slowly, and thus non-freezing cold injury must be distinguished from frostbite, which should be rapidly rewarmed. Sometimes the only clue is that socks remained wet and did not freeze. Many cases present after rewarming, with florid redness, swelling, and pain. As this is neuropathic in origin, conventional approaches to pain management are unsuccessful, but early administration of amitriptyline in a single 25–50 mg dose a couple of hours before sleep normally brings relief. Dosage can be increased to 100 mg or greater if necessary, but patients must be cautioned about drowsiness, and must not drive, operate machinery, etc. Severe cases may develop blistering, sloughing of skin, and gangrene, which should be managed as for severe frostbite once slow rewarming has completed.

Long-term sequelae are more common following non-freezing cold injury, and include chronic pain and sensitization to the cold. Specialist advice is important, and interference with sympathetic innervation, even brief trial blocks, must be avoided, as it worsens the prognosis.

Snow blindness is sunburn of the corneal and conjunctival epithelium covering the front of the eye. Like sunburn, there is a delay between exposure and development of symptoms, usually some 6–12 h. The eye becomes red, swollen, gritty, and very painful. In serious cases victims are incapacitated, as spasm of the eyelids means that they are unable to open their eyes and they develop a severe headache.

UV light is a component of sunlight. Because light is reflected off snow, levels of UV radiation in polar areas can be several times greater than in temperate or tropical areas; additionally, in spring, thinning of the ozone layer allows increased amounts of these wavelengths to penetrate the atmosphere. The radiation causes an inflammatory response, with oedema and multiple dry areas over the superficial cornea. The whole surface epithelium of the eye may come away, a process associated with considerable lacrimation. Healing then occurs and subsequent long-term problems are very rare. The retina of the eye is unaffected.

UV rays can penetrate cloud so good quality sunglasses should be used in both clear and brightly overcast conditions. Both the front and the side of the eye should be shielded, either by suitable side flaps or by wrap-around spectacles. Some experienced polar travellers find that they rarely experience eye problems; their disregard for eye protection should not encourage novices to emulate them. Should proper sunglasses have been lost, damaged, or rendered useless by recurrent condensation, an effective emergency solution is to recreate Eskimo eye protection by cutting two thin eye slits in a piece of wood, paper, plastic, or fabric, use elastic or string to hold it to the head and use this as a shield for the eyes (Fig. 20.5).

Most cases of snow blindness will recover within 72 h. Seek help and follow up if:

Solar energy is intense in polar areas with strong reflections off the snow, and the radiation intensity may exceed that in equatorial regions. High latitude (owing to thinning of the ozone layer) and altitude increase the risk of sunburn, and a high factor (SP30+) sun cream should be applied liberally. Sunburn is particularly uncomfortable when rays reflected upwards off the snow burn the eyelids and underside of the chin and nostrils.

When persistently exposed to the cold, lips are particularly vulnerable to severe and painful chapping. They may crack and bleed. It is not certain whether this injury is due to sunburn, cold injury caused by the persistent evaporation of moisture from their surface, or the activation of herpetic cold sores. There is no guaranteed protection, but regular application of a moisturizing sunblock may reduce symptoms. The benefits of antiviral cold sore creams are unknown.

These often occur during exploration, and more recently as a result of the rise in polar racing and challenge trips where individuals or groups are exposed to long periods on the ice.