International travellers encounter extremes of climate to which they are not accustomed. Exposure to heat and cold can result in serious injury or death. Travellers should investigate the climate extremes they will face during their journey and prepare with proper clothing, equipment, and knowledge.
Travellers who sit on the beach or by the pool and do only short walking tours incur a minimal risk of heat illness. Those participating in strenuous hiking, biking, or work in the heat are at risk, especially travellers coming from cool or temperate climates who are not in good physical condition and not acclimatised to the heat.
Cardiovascular status and conditioning are the major physiologic variables affecting the response to heat stress at all ages. Many chronic illnesses (in particular, those involving the cardiovascular system or the skin) limit tolerance to heat and predispose to heat illness; these include cardiovascular disease, diabetes, renal disease, and extensive skin disorders or scarring that limits sweating.
Apart from environmental conditions and intensity of exercise, dehydration is the most important predisposing factor in heat illness. Dehydration reduces exercise performance, decreases time to exhaustion, and increases internal heat load.
Temperature and heart rate increase in direct proportion to the level of dehydration. Sweat is a hypotonic fluid containing sodium and chloride. Sweat rates commonly reach 1 L per hour or more, resulting in substantial fluid and sodium loss.
Minor heat disorders could be in the form of heat cramps, Heat syncope, Heat edema and Prickly heat. Water with a salty snack is usually enough to take care of heat cramps. But travellers can also make a simple oral salt solution by adding one-fourth to one-half teaspoon of table salt (or two 1-g salt tablets) to 1 L of water.
Heat syncope—sudden fainting caused by vasodilatation—occurs in acclimatized people standing in the heat or after 15–20 minutes of exercise. They can lose consciousness, but this can rapidly return when the patient is supine. Rest, relief from the heat, and oral rehydration are adequate treatment. Heat edema is another minor heat disorder. It occurs more frequently in women than in men. Characterised by mild swelling of the hands and feet during the first few days of heat exposure, this condition typically resolves spontaneously.
Travellers should not treat heat oedema with diuretics, which can both delay heat acclimatization and cause dehydration. Prickly heat (malaria or heat rash) manifests as small, red, raised itchy bumps on the skin caused by obstruction of the sweat ducts. It resolves spontaneously, aided by relief from the heat and avoiding continued sweating. Travellers can best prevent prickly heat by wearing light, loose clothing and avoiding heavy, continuous sweating.
Life-threatening heat disorders can be in the form of heatstroke, heat exhaustion, and exercise-associated hyponatremia. Heat exhaustion can be relieved by rest and drinking of salt solution while heat stroke is an emergency requiring more aggressive treatment including hospital care. It is important to be able to recognise it. Heat Disorders can be prevented by heat acclimatisation. This requires 1–2 hours of exercise in the heat each day. With a suitable amount of daily exercise, most acclimatization changes occur within 10 days. If possible, all travellers should acclimatize before departing for hot climates by exercising ≥1 hour daily in the heat.
Physically fit travellers have improved exercise tolerance and capacity but still benefit from acclimatisation. If this is not possible, advise travellers to limit exercise intensity and duration during their first week of travel. It is a good idea to conform to the local practice in most hot regions and avoid strenuous activity during the hottest part of the day.
Ade Alakija, medical director Q-Life Family Clinic & Bukola Adeniyi, Consultant Family physician and travel medicine physician Q-Life Family Clinic.
