Summer is upon us and managing heat stress and heat illness are important issues for mines. Stewart Masson writes about first responders treatment of exertional heat illness on site.
Heat Injury is a spectrum of disease that starts with heat cramps and heat exhaustion characterised by decreased performance and an elevated temperature, with many non-specific symptoms such as dizziness fatigue, cramps, nausea and vomiting. At the other end of the spectrum is a medical emergency called heat stroke. Heatstroke, by definition, consists of an elevated body temperature usually greater than 40 degrees celsius, with altered mental status.
One does not have to go through stages of heat injuries – patients can develop heatstroke without prior signs of heat exhaustion. Two forms of heat stroke are described in this article: classical and exertional. We will be focusing more on exertional heat stroke, as this type of heat stroke can be encountered in mining operations.
Classical heatstroke is caused by an increase in ambient heat. Exertional heatstroke is caused by increased metabolic production of heat due to physical exertion found typically in young and early middle-aged healthy adults. Exertional heatstroke can be found in the mining sector especially underground.
In exertional heat stroke there are some predisposing factors:
- Underlying dehydration;
- Exercise in hot and humid conditions;
- Thermogenic supplements that uncouple oxidative phosphorylation;
- Elevated body mass index (BMI);
- Poor baseline physical fitness levels;
- Lack of acclimatisation to climate;
- Sleep deprivation; and
- Prior heat injury.
Thermoregulation occurs when body heat is gained both from the environment and from cellular metabolism. Many cellular enzymes function at optimum temperatures and any significant deviation in temperature not associated with a fever can result in decreased cellular performance and ultimately, cellular death. Because of this, the body tightly regulates the temperature to keep the core temperature at approximately 37 degrees celsius.
When the core temperature rises, the hypothalamus, which is the primary regulator of body temperature, causes peripheral vasodilatation and shunts blood away from the visceral organs to the skin, thus resulting in increased heat dissipation. This process of thermoregulation specifically involves the kidneys and the intestines. Therefore, increased body temperature can predispose patients to acute renal failure and intestinal ischemia.
Given that exertional heat stroke in many instances is self-induced, significant effort should be made to mitigate and prevent the injury from happening in the first place. This can be accomplished by proper risk factor reduction and planning.
Risk factors should be identified and reduced. The workforce should ensure that workers are not taking thermogenic supplements or excessive amounts of energy drinks, have a medium level of physical fitness, and individuals should get adequate amounts of sleep. The workforce should undergo a proper acclimatisation program after arrival in hot/humid locations.
Proper planning from the emergency management department is also critical to both prevention of exertional heat stroke and if prevention is not possible, the effective treatment of exertional heat stroke. The medics need to be able to recognise work tasks that could potentially create a heat casualty. Medics should also be involved in planning in order to mitigate any risk factors that might be present. Furthermore, medics need to train for potential patients with heat injury. These training sessions should include initial treatment and then correct advanced life support techniques.
Patients with heat injury can present initially with nonspecific symptoms such as muscle cramping, as well as nausea and vomiting. However, sometimes collapsing is the first sign, and sweating often varies. As the patient’s temperature and the extent of the injury increases, altered mental status, seizures, and cardiovascular collapse can occur.
In many instances, the central nervous system (CNS) dysfunction can be subtle, presenting as inappropriate behaviour or impaired judgment. Although by definition altered mental status will be present in exertional heatstroke, loss of consciousness (LOC) cannot be used as a reliable indicator for heatstroke. When patients present with signs of heat injury, a tympanic temperature should be taken to ascertain body temperature.
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Treatment of Heat Illness
Initial treatment of heat illness should focus on the rapid reduction in core temperature. The first thirty minutes after a recognised heat illness is critical to a patient’s outcome. The rapid cooling of a patient has shown to decrease fatality rates – the longer a patient is hyperthermic, the greater the resulting damage.
According to the Australian Resuscitation Council Guidelines, the management of heat-induced illness is aimed at removing the cause and assisting the normal cooling mechanisms of evaporation, conduction, radiation and convection.
The key treatment for Heat Exhaustion:
• lie the victim down in a cool environment or in the shade
• loosen and remove excessive clothing
• moisten the skin with a moist cloth or atomizer spray
• cool by fanning
• give water to drink if fully conscious
• call for an ambulance if not quickly improving.
One can use the below quick reference or further information is available on the Australian Resuscitation Council Website
Treating Heat Stroke
The medic should get a good set of vitals, including a tympanic temperature. Activation of the evacuation plan should be done as soon as a patient with exertional heat stroke is identified. Heatstroke is a life-threatening condition and a considered approach must be undertaken:
• call for an ambulance;
• resuscitate following the Basic Life Support Flow Chart (ANZCOR Guideline 8);
• place the victim in a cool environment;
• moisten the skin with a moist cloth or atomizer spray and fan repeatedly;
• apply wrapped ice packs to neck, groin and armpits.
Where a seizure occurs
If the victim is unresponsive and not breathing normally, follow Australian Resuscitation Council and New Zealand Resuscitation Council Basic Life Support Flowchart (See Image) If the victim is unconscious and actively seizing, the rescuer should:
- follow the victim’s seizure management plan, if there is one in place;
- manage the victim;
- call an ambulance.
The rescuer should always:
- manage the victim as for any unconscious person (ARC Guideline 3);
- remove the victim from danger or remove any harmful objects which might cause secondary injury to the victim;
- note the time the seizure starts;
- protect the head;
- avoid restraining the victim during the seizure unless this is essential to avoid injury;
- lay the victim down and turn the victim on the side when practical;
- maintain an airway;
- reassure the victim who may be dazed, confused or drowsy;
- call an ambulance;
- frequently reassess the victim.
Exertional heatstroke can be encountered in mining operations and has a high rate of morbidity and mortality when unnoticed or when left untreated.
The rapid lowering of core body temperature with appropriate treatment will reduce morbidity and mortality significantly.
More information on treatment of heat Illness is available at the Australian Resuscitation Council
ABOUT STEWART MASSON
CEO SAFETY DIRECT SOLUTIONS
Stewart is the CEO of Safety Direct Solutions, which was founded in 2004. SDS is a registered training organisation and is the leading provider of fire, rescue and medical training in the Australasian region.
Stewart’s expertise lies in the emergency management space. His company is fanatical about attention to detail because they know it saves lives and they understand there may only be one chance to save a life, or minimise the negative outcomes of an emergency.
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