Hyperthermia is a life-threatening emergency that requires immediate and aggressive treatment to lower body temperature. Untreated, heat stroke leads to multiorgan failure and death, and the single greatest contributor to patient morbidity and mortality is the duration of the elevated core body temperature. 

First responders, emergency medical responders, and paramedics can expect an increase in frequency and intensity of extreme heat events as climate destruction worsens these phenomena.

This guideline provides clinicians with the knowledge necessary to quickly recognize environmental heat injury, identify environmental and population-based risk factors, and to perform critical rapid cooling techniques.

• Rapid recognition of environmental factors and patient risk factors for heat illness is key to management. Be aware of the diversity of the clinical manifestations of heat illness.
• Cooling should be initiated on scene wherever possible, and continued throughout patient transport.
• Recognize and treat concurrent dehydration if present.

Warning:

Hyperthermia as a result of increased environmental temperature is not equivalent to hyperthermia produced because of fever or medication use.  Use clinical observation to differentiate the primary cause of heat, and treat environmental heat exhaustion/heat stroke according to this protocol.

• DO NOT treat environmental heat exhaustion/heat stroke with anti-pyretics. There is no role for antipyretic agents such as acetaminophen or aspirin in the management of heat stroke, since the underlying mechanism does not involve a change in the hypothalamic set-point and these medications may worsen complications such as hepatic injury or disseminated intravascular coagulation (DIC).
• IV Fluid should not be routinely administered to patients suffering from heat stress unless signs of dehydration, hypotension, or shock are present, in which case it should be started after initiating full-body cooling and given with caution with the goal of correcting hypoperfusion.  Ensure that saline solution is NOT WARM to the touch.
• Oral hydration is not an effective cooling technique. Dehydration can be a concomitant pathology that demands attention, as mentioned above. Patients who are dehydrated and able to ingest liquids should self-administer oral rehydration solution (electrolytes) if available without delaying transport.

• Induced hypothermia is an unwarranted concern for paramedic care of heat-injured patients.
• Consultation with CliniCall may help to guide care planning in call cases of hyperthermia. Pre-arrival notification to receiving facilities can improve transition of care and initiation of core temperature monitoring and management.
• The basic treatments for heat emergencies are the same across all license levels and vary only in the case of critically ill patients suspected of heat stroke.
• The management of classic heat stroke consists of ensuring adequate airway protection, breathing, circulation, rapid active cooling, and treatment of complications.

• In-hospital treatment consists of full-body ice-water immersion in a dedicated tank or in body bags with core temperature monitoring and management of end-organ complications. Full-body cooling is continued until core temperature drops to 38.3–39°C; manifestations of organ damage are managed specifically and separately (e.g. coma, adult respiratory distress syndrome, disseminated intravascular coagulation, hepatic failure, renal failure, rhabdomyolysis).

• Be sure to differentiate shaking and tremors from seizures.  Manage seizures in accordance with F02: Seizures.

ASTaR for heat emergencies - includes alternative destination and access to cooling centres and advice for home

Heat stroke has a remarkably high mortality rate, between 21-63% in heat stroke patients who arrive to hospital. The first cells affected by core body temperature ≥ 40º C are: neurons, hepatocytes (liver cells) and vascular endothelial cells (the inner lining of all blood vessels), yet all body organs will be injured by hyperthermia.

It can be hard to fully recognize the threat of heat stroke because the damage is at a cellular/tissue level. It is therefore critical that the paramedics identify abnormalities in any body system during their initial and ongoing assessments, and record and report their findings during patient handover in hospital.

The importance of initiating cooling on-scene cannot be overstated.  All heat illness patients should receive immediate cooling on-scene and during transport, regardless of proximity of higher level of care or predicted time of conveyance.

Environmental risk factors for development of heat illness include:

• Hot weather, with or without high environmental humidity
• Enclosed spaces with poor ventilation
• Outdoor spaces with no shade
• Lack of access to water

Patient-specific risk factors for the development of heat illness include:

• Elderly individuals: the body has a lower water content in older age, which predisposes elders to severe heat injury compared to younger people
• Mental illness, specifically schizophrenia, can predispose individuals to severe heat injury.

Caution: These two groups are considered the highest-risk cohorts for the development of lethal heat injuries.  Exercise extreme care while developing patient care plans, consult with CliniCall as required, and convey patients to appropriate destinations if safety cannot be assured.

• Obesity: adipose tissue insulates the body and retains heat; it may also generate additional heat
• Physical exertion
• Concomitant or chronic illnesses
• Use of alcohol, drugs, or other medications (including anticholinergics, antidopaminergics, antihistamines, antipsychotics, beta- and calcium channel blockers, diuretics, antidepressants, and lithium).
• Pregnancy
• Socioeconomic and/or Occupational vulnerability

Signs and Symptoms of Heat illness and Injury:

The formal definition of heat stroke – either exertional or classic heat illness from high environmental temperatures, with or without physical activity – is a core temperature above 40°C with central nervous system dysfunction.  Measurement of core temperature is only authorized for CCP providers, meaning that other providers must use clinical findings as part of their assessment.  History is critically important.  Use observations of the environment as well as patient signs and symptoms to guide treatment planning.

Differentiating between heat exhaustion and heat stroke can be difficult.  The key element is the degree of central nervous system impairment.  The treatment for both is the same.

Heat exhaustion and heat stroke can mimic or present concurrently with many other illnesses.  Paramedics must consider the possibility of sepsis, ischemic strokes, hypoglycemia, toxic ingestion, or drug misuse. 

Prevention is critical and can save lives. Patients with stable vital signs, fully intact level of consciousness and orientation and no signs of heat exhaustion or heat stroke can be moved to a cool environment and encouraged to rest and stay hydrated.  When providing on-scene guidance and support to patients, remember that fans alone are insufficient for cooling purposes, and may exacerbate heat exposure due to convective air movement in areas where ambient temperatures exceed 35°C. 

“Heat cramps” are localized and painful muscle spasms most often due to electrolyte loss from strenuous activity in a hot environment, cramp onset is usually at rest immediately after activity. Heat cramp patients have no evidence of dehydration. Paramedics, emergency medical responders, and first responders can encourage heat cramp patients to self-administer oral electrolyte drinks.

Heat stroke or heat exhaustion should be assumed in any patient exposed to extreme environmental heat with any of the following signs and symptoms:

• Extreme weakness
• Flushed, hot skin; pale, cold skin; with or without sweating
• Shivering
• Pallor
• “Prickly heat” sensation
• Dehydration
• Fatigue
• Headache
• Light-headedness
• Altered mental status
• Confusion
• Behavioural changes
• Imbalance (ataxia)
• Unresponsive
• Seizure
• Tachycardia
• Hypotension
• Dysrhythmia
• Tachypnea or bradypnea
• Low SpO2
• Abdominal cramps, nausea, vomiting, or diarrhea
• Persistent muscle cramps

Hyperthermia

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7. Wasserman, D, [et al]. EMS Methods To Cool A Patient In The Field. 2022. StatPearls Publishing.
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10. Belval, L. [et al]. Consensus Statement- Prehospital Care of Exertional Heat Stroke. 2018. [Link]
11. Monseau, A J, [et al]. Status of US Emergency Medical Service Protocols Regarding Pre-Transfer Cooling for Exertional Heat Stroke. 2021. [Link]

• 2022-09-22: Typographical corrections.
• 2022-06-04: Revised and re-published. The previous version archived, no longer publicly available. 
• 2022-07-29 - Addition of Heat Emergency ASTaR Pathway in the referral section.