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Heat exhaustion while trekking at low altitude in the monsoon in the Himalayas

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Staying Safe Outdoors – hot weather problems

1 Sep , 2017  

Any form of exercise in hot weather can cause a wide range of problems (dehydration, heat stress, heat exhaustion, heat stroke, hyponatraemia etc) that can be avoided by careful preparation and prevention. This guide to staying safe in hot weather will help you recognise and treat common problems. Recognition of early symptoms is essential, as they are not painful and therefore easy to ignore. This is an excerpt from First Aid and Wilderness Medicine, a pocket sized book written by Drs Jim Duff and Ross Anderson.

Heat related syncopy (fainting) while travelling by bus between Kathmandu and Pokhara

Heat related syncopy (fainting) while travelling by bus between Kathmandu and Pokhara

Hot weather problems

The problems mentioned above are caused by exertion in hot climates, and are made more likely by lack of preparation, acclimatization and appropriate clothing. The elderly, children and the less fit are more vulnerable. The most common problem is heat stress, progressing to the less common but more serious heat exhaustion and deadly heat stroke. These problems can be thought of as a spectrum of related complaints from mild to life-threatening. There is always an element of dehydration and salt loss.

Heat stress, heat exhaustion and heat stroke


Heat stress

It is vital to recognize and treat early symptoms of heat stress as it is not painful, easy to ignore and can quickly progress to heat exhaustion or life-threatening heat stroke.

Symptoms and signs

  • Weakness, dizziness, nausea, feeling faint; may faint briefly.

Treatment

  • Provide shade
  • fan them
  • rest and rehydrate until recovered.

Heat exhaustion

If heat exhaustion is not recognized/treated, heat stroke may develop.

Symptoms and signs

  • Tiredness, dizziness, nausea, vomiting, thirst, headache or muscle cramps
  • Victim is still sweating and their skin is still elastic
  • Temperature is usually normal but may be up to 40°C
  • Rapid pulse, low blood pressure (respiratory rate normal)
  • Feeling faint or even fainting briefly but with NO reduced level of consciousness before or after a brief faint

Treatment

  • Provide shelter from the sun in cool shade with fanning and good ventilation. Insulate from hot ground and rehydrate.
  • Lay the victim flat on their back with legs raised if they feel faint, or on their side if they do faint.
  • Cool them if their temperature is above normal: fan them while spraying, wiping, sponging or splashing with water.
  • Rehydrate (see this article on ‘Dehydration’ for type and rate of liquid replacement).
  • If there is any loss of consciousness (other than brief fainting) or persistent reduced level of consciousness, treat urgently as heat stroke.
  • Recovery in mild cases of heat exhaustion can be rapid but weakness may persist for days. If the illness is moderate to severe, the victim may be unwell for days and evacuation may be needed.
Hot weather leads to heat stress while walking in to Everest expedition during the monsoon

Hot weather leads to heat stress while walking in to Everest expedition during the monsoon


Heat stroke

This is an emergency. Heat stroke causes death by overheating of the brain and other vital organs. The heat loss mechanisms of the body fail and there is a rapid rise in body temperature. High humidity and exertion are contributing factors. Environmental awareness and early symptoms detection are vital.

Symptoms and signs

Signs and symptoms of heat exhaustion may have been present but now the distinguishing features are:

  • persistent reduced level of consciousness or unconsciousness
  • there may be sweating or not, with loss of skin elasticity
  • raised core temperature (40°C or more)
  • fitting and/or shivering may occur
  • raised respiratory rate, rapid pulse, low blood pressure.

Treatment

  • Evacuate, while cooling the victim aggressively:
  • fan them while spraying, wiping, sponging or splashing with water: the victim may be semi-naked or covered with a wet sheet
  • apply cold wet cloths or ice to the neck, armpits, groin and upper abdomen while continuing to fan and spray the victim
  • if available, use ice cold water, an electric fan or even immerse the victim in cold water
  • measuring core temperature rectally is helpful to monitor progress
  • give oxygen (6 to 8L/min).
Heat exhaustion while trekking at low altitude in the monsoon in the Himalayas

Heat exhaustion while trekking at low altitude in the monsoon in the Himalayas

Other heat and hot weather problems


Dilutional (exertional) hyponatraemia (water intoxication)

This dangerously low blood sodium level is much less common than heat stroke It usually occurs in elite athletes in endurance events and requires hospital treatment. In a wilderness setting it is difficult to differentiate from heat stroke and is untreatable so prevention is vital. It occurs after long periods of sweating exercise when no food has been eaten but lots of plain water has been drunk. As a result, sodium concentration in the blood drops too low, with little or no dehydration.

Symptoms and signs

  • Symptoms are similar to heat stroke.
  • Fits are more common than in heat stroke.
  • Core temperature may be raised but not as high as heat stroke.
  • There is typically no thirst, and urine is still being passed.

Treatment

In a wilderness setting, hyponatraemia is difficult to tell from heat stroke so treat all cases of impaired consciousness as heat stroke (unless able to measure blood sodium level).


Heat edema

Swelling of fingers and ankles may occur in the first few days in a hot environment. It usually settles without treatment.


Prickly heat

This happens when the sweat glands in the groin, under the breasts, around the waist, chest or back get blocked in hot and humid conditions. Itchy areas of redness with spots and blisters appear in the affected areas. If this is widespread, it may predispose to heat exhaustion.

Keep cool, wear loose cotton clothes and avoid scratching. Wash with water only, no soap, and dry the skin. Antihistamines, calamine lotion and/or hydrocortisone cream help settle itching.


Heat cramps

This is a common problem, solved by gently stretching out and massaging the cramping muscle and drinking salted water.


More First Aid Advice

This is an excerpt from First Aid and Wilderness Medicine, a pocket sized book written by Drs Jim Duff and Ross Anderson. More information can be found in  First Aid and Wilderness Medicine, a pocket sized book written by Drs Jim Duff and Ross Anderson.

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