Extreme Weather

Apparently, a naked adult human feels most thermally comfortable in an air temperature of 30 deg C. We have complex mechanisms to thermo-regulate, so that our body temperature set point sits at about 37 deg C. In some ways, it is easier to adapt to cold than heat. The latter requires more physiological adaptation. This process is driven by the hypothalamus in the brain and the autonomic nervous system that controls sweat production and blood flow in the skin. In hot conditions, most of the heart's output is directed to the skin and blood flow can reach 8 liters a minute!  1-2 liters an hour can be lost as sweat in order to create evaporative cooling. The reverse occurs in the cold. These processes can be impaired in the very young (who also have a proportionately larger skin surface area than adults), the elderly, menopausal women and those with medical conditions such as diabetes.

Many people are taking long-term medication and don't realize that it can seriously impair thermo-regulatory processes. The following classes of drugs are all a risk.

• Antidepressants
• Anti-epileptics
• Antiparkinsons
• Antipsychotic
• Antihistamines, motion sickness and cold/flu drugs
• Diuretics and Beta Blockers used for high blood pressure
• Antispasmodics used for bladder control

These drugs either alter heat perception, the ability to change cardiac output, the ability to dilate blood vessels or the ability to sweat.

It is well established that there is increased winter mortality as well as heat wave related mortality. This can be avoided with appropriate housing, clothing and behavioural adaptations. A traveller should research the extremes they may face and prepare clothing and equipment accordingly.

Minor problems can result from arriving suddenly in a hot climate and being "unacclimatized" or from exposure to extremely hot conditions. These include rashes such as prickly heat, swollen hands and feet, cramps (from salt loss due to sweating), headache, nausea, dizziness and weakness (due to dehydration). You need to immediately adopt behaviors to prevent an escalation of symptoms. Rest, find a cool or air-conditioned place, use wet sheets/fans or ice packs, avoid coffee and alcohol, wear light, loose clothes and a wide brim hat.  Have cool showers or baths or use water spray bottles. Just resting on a cool stone seat will enable transfer of core body heat away from you to the seat. Soak your feet in a tub of cold water while resting. Have cold drinks and monitor your urine production.  Drink often, don't wait until you feel thirsty.  It is possible to drink too much water. This can result in hyponatraemia, meaning that your body's salt content is diluted, and you may become nauseated and confused. The best way to tell whether your fluid balance is right is by the amount of urine you are passing. If you are drinking too much, you will be peeing too much. If you are dehydrated, you won't be peeing.

Heat "stroke" is the term used to describe the level up from heat "exhaustion". This is the point at which the body's thermo-regulation mechanisms have failed and its temperature set point is no longer intact. When the body's temperature is over 40.5 deg C (104 F), there is no longer any sweating, heart rate and breathing are increased, and internal organs shut down. The person may be staggering, confused, unconscious or fitting. This is a medical emergency. First aid involves immediate cooling and sponging, small frequent fluid sips if the person is conscious and placing ice packs over the region of large blood vessels.

If you are planning strenuous exercise in a climate much hotter than the one you are leaving, try to undertake an acclimatization programme before you. People who are carrying more weight might need to consider adjuncts to clothing such as creams (Neat-3B Action Cream) or powder on areas of the skin that are subject to chafing. Options to use with showering include Pinetarsol. This may prevent fungal infections (mentioned previously) and skin infections (folliculitis). The benefits of extra showering (water only) cannot be overstated!

Cold dry air can cause painful skin problems for the underprepared - cracked lips, chilblains and painful Raynaud’s (for the 5% who suffer from hyperactive vasoconstriction in fingers and toes).

Simple measures such as a cold weather mask (warms and humidifies the air), and good gloves/mittens can make a huge difference to your comfort. Occasionally doctors prescribe medication for those prone to Raynaud’s. Interestingly, excess winter mortality is worse in countries with mild winters than those such as Scandinavia, where citizens are well pre-pared and stay warm. Modest cold exposure is thought to change factors in the blood that make it clot more easily. Hence there is a delayed spike in older people having strokes and heart attacks. If you have prepared well and have packed some of the wonderful layering garments now available, you should not feel the cold.

The young and fit, equipped with the latest gear, nonetheless needs to keep their wits about them when adventuring in extreme places. A small mistake or dumb decision can end in tragedy.

This begins to set in when the core body temperature drops below 35C (95 F). An early sign is uncontrolled shivering.

Stop and take shelter, especially from the wind.  Remove wet clothes and warm the body with hot drinks and energy dense foods. By 26C (78 F) body temperature, the person is usually unconscious and will die, unless found and treated. First aid involves warmed intravenous glucose containing fluids, oxygen and warming the central part of the body first.

The risk factors for this are:

• Extreme cold
• Inadequate or wet clothing
• Wind chill

Frostbite has the same risk factors plus poor circulation due to ill-fitting boots, or medical conditions such as diabetes, peripheral neuropathy, smoking and use of Beta Blockers. “Frostbite” is skin and tissue death in a local area (usually fingers and toes) due to freezing. Blood vessels will always shut down our extremities in order to preserve our central temperature and most important organs. Freezing will cause a gradual progression of damage, de-pending on the time elapsed before it is rectified. Early on there will be itching and pain, then colour change and numbness, then, finally, hardening and blackening as the tissue dies. Deeply frostbitten areas may recover over many months but, in terms of sensation, never be quite the same again. The worst cases require surgical amputation.

As soon as it is recognized as happening, the area should not be moved or rubbed, but splinted and wrapped and gradually rewarmed (out of freezing conditions).

The principles of staying warm are:

• Wearing multiple loose, light layers that can be added or subtracted to avoid wetting clothes with excess sweat. Layers also trap warm air between them. The principles of layering are: a moisture management base layer (merino wool or synthetic), middle insulating layer(s), outer shell weather protection layer. Good adventure shop staff will be able to help with choices based on your destination and planned activities.
• Fine wool is good, especially for socks, because it tends to stay warm when wet
• Hats, gloves and scarves are important. In extreme cold, waterproof outer mittens trap warm air between inner, gloved fingers
• Make sure footwear in waterproof
• Wear a waterproof shell outer jacket/pants
• Carry a space blanket for protective shelter

The best prevention for environmental health issues is to do some homework about your destination before you leave!!