Heat stroke in adults

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups: see disclaimer

ACUTE

heat stroke

1st line – stabilisation

Plus – rapid active cooling

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Plus –

rapid active cooling

Treatment recommended for ALL patients in selected patient group

Start rapid active cooling immediately based on clinical suspicion (regardless of the degree of hyperthermia or measuring technique).[1]

Consider, if available:

Whole-body cold or iced water immersion in patients with exertional heat stroke, if practical and safe to do so[1][2]
- In practice, do not use water immersion in patients with an altered level of consciousness (Glasgow Coma Scale score <15), uncooperative patients, patients who require intravenous treatment, or patients who have a history of arrhythmia (e.g., atrial fibrillation, ventricular tachycardia) or a recent cardiovascular event
Wetting and fanning the skin in patients with classic heat stroke[1]
- Do not use this method in patients with exertional heat stroke, unless water immersion or wetted ice packs are not available[1]
Wetted ice packs covering the entire body as adjunctive cooling for classic heat stroke, or for exertional heat stroke if cold water immersion is unavailable[1]
- Use ice packs in preference to chemical cold packs whenever possible.[1] If using chemical cold packs, apply these to the cheeks, palms, and soles of the feet rather than the skin covering the major vessels.[1]

Aim to achieve a target temperature of no less than 39.0°C.[1] Stop cooling once this temperature is reached.[1]

Be aware that the goal of cooling is not to achieve rapid normothermia as this would result in overshoot hypothermia.[1]

Do not use dantrolene (usually used for treating malignant hyperthermia) or antipyretics.[1][2]

Discuss the patient with heat stroke with a senior colleague.

In the community:

Start rapid active cooling immediately (before the patient is transported to hospital) with available techniques (e.g., wetting and fanning the skin, cool water towels, ice packs).[1][2] In practice, avoid using aggressive cooling methods if you are unsure about the diagnosis
Arrange immediate transfer of the patient to hospital.[1][2]

Plus – supportive care and monitoring

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Plus –

supportive care and monitoring

Treatment recommended for ALL patients in selected patient group

Oxygen

Give oxygen if oxygen saturation <94% and maintain at target range.[15] In patients at risk of hypercapnia prescribe oxygen if oxygen saturation <88%.[15]

Monitor controlled oxygen therapy. An upper SpO ₂ limit of 96% is reasonable when administering supplemental oxygen to most patients with acute illness who are not at risk of hypercapnia.

Evidence suggests that liberal use of supplemental oxygen (target SpO ₂ >96%) in acutely ill adults is associated with higher mortality than more conservative oxygen therapy.[16]
A lower target SpO ₂ of 88% to 92% is appropriate if the patient is at risk of hypercapnic respiratory failure.[15]

Evidence: Target oxygen saturation in acutely ill adults

Too much supplemental oxygen increases mortality.

Evidence from a large systematic review and meta-analysis supports conservative/controlled oxygen therapy versus liberal oxygen therapy in acutely ill adults who are not at risk of hypercapnia.

Guidelines differ in their recommendations on target oxygen saturation in acutely unwell adults who are receiving supplemental oxygen.
- The 2017 British Thoracic Society (BTS) guideline recommends a target SpO ₂ range of 94% to 98% for patients not at risk of hypercapnia, whereas the 2022 Thoracic Society of Australia and New Zealand (TSANZ) guideline recommends 92% to 96%.[15][19]
- The 2022 Global Initiative For Asthma (GINA) guidelines recommend a target SpO ₂ range of 93% to 96% in the context of acute asthma exacerbations.[20]
A systematic review including a meta-analysis of data from 25 randomised controlled trials published in 2018 found that, in adults with acute illness, liberal oxygen therapy (broadly equivalent to a target saturation >96%) is associated with higher mortality than conservative oxygen therapy (broadly equivalent to a target saturation ≤96%).[16] In-hospital mortality was 11 per 1000 higher for the liberal oxygen therapy group versus the conservative therapy group (95% CI 2 to 22 per 1000 more). Mortality at 30 days was also higher in the group who had received liberal oxygen (relative risk 1.14, 95% CI 1.01 to 1.29). The trials included adults with sepsis, critical illness, stroke, trauma, myocardial infarction, or cardiac arrest, and patients who had emergency surgery. Studies that were limited to people with chronic respiratory illness or psychiatric illness, or patients on extracorporeal life support, receiving hyperbaric oxygen therapy, or having elective surgery, were all excluded from the review.
An upper SpO ₂ limit of 96% is therefore reasonable when administering supplemental oxygen to patients with acute illness who are not at risk of hypercapnia. However, a higher target may be appropriate for some specific conditions (e.g., pneumothorax, carbon monoxide poisoning, cluster headache, or sickle cell crisis).[21]
In 2019 the BTS reviewed its guidance in response to this systematic review and meta-analysis and decided an interim update was not required.[22]
- The committee noted that the systematic review supported the use of controlled oxygen therapy to a target.
- While the systematic review showed an association between higher oxygen saturations and higher mortality, the BTS committee felt the review was not definitive on what the optimal target range should be. The suggested range of 94% to 96% in the review was based on the lower 95% confidence interval and the median baseline SpO ₂ from the liberal oxygen groups, along with the earlier 2015 TSANZ guideline recommendation.
Subsequently, experience during the COVID-19 pandemic has also made clinicians more aware of the feasibility of permissive hypoxaemia.[23] The BTS guidance is due for a review in 2022.
Management of oxygen therapy in patients in intensive care is specialised and informed by further evidence (not covered in this summary) that is more specific to this setting.[24][25][26]

Intravenous fluids

Give intravenous isotonic fluids such as normal saline (0.9% sodium chloride) or hypertonic fluids (5% dextrose in normal saline) to patients with volume depletion.[1]

In practice, you can use Hartmann's solution or Ringer’s lactate solution as they only contain small amounts of potassium and the patient with heat stroke is likely to be hyperkalaemic. If the patient has exercise-associated hyponatraemia, give isotonic or hypertonic fluids with 3% sodium chloride.[1]

Practical tip

Use intravenous fluids with caution in patients with complex medical comorbidities (e.g., heart failure, renal failure). Perform a serial clinical assessment to guide fluid therapy in these patients.

Use cold (4°C) intravenous fluids whenever possible as an adjunct to active cooling.[1] Do not use intravascular cooling catheters or cold water lavage.[1]

Start intravenous fluids if possible if the patient presents in the community.[1]

Benzodiazepines

Consider giving small doses of an intravenous benzodiazepine (e.g., diazepam, midazolam) to reduce shivering, which causes heat gain (making cooling less effective).

Give an intravenous benzodiazepine (e.g., lorazepam, midazolam) to control seizures.[9] Follow your local protocol.

Monitoring

Monitor temperature regularly by measuring rectal temperature.[1] In practice, use an oesophageal probe in intubated patients.

Practical tip

Be cautious of falsely elevated rectal temperature measurements in the recovery phase resulting from the insulating effect of body mass.[1]

Monitor electrolytes levels closely in patients receiving hypertonic saline.

In practice, order and monitor serial bloods at least once daily (particularly potassium levels, renal function, arterial blood gases, clotting profile, and creatine kinase; see the Diagnosis section). If the patient is critically unwell or there is evidence of organ failure, consider repeating bloods more frequently.

Be vigilant for complications that may develop at a later stage (even after return to normothermia) including rhabdomyolysis, acute kidney injury, disseminated intravascular coagulation, and acute liver failure.[1][2] See the Complications section.

Primary options

lorazepam: consult specialist for guidance on dose

diazepam: consult specialist for guidance on dose

midazolam: consult specialist for guidance on dose

Consider – transfer to intensive care unit

heat exhaustion

1st line – supportive care and observation

Back

1st line –

supportive care and observation

Move the patient to a cooler place and remove excess clothing.[1][2][9]

Give oral isotonic fluids (0.9% sodium chloride) or hypertonic fluids.[1]

In patients with severe heat exhaustion or nausea/vomiting, give intravenous fluids (if available).[1][9] Patients with severe heat exhaustion are more volume-depleted than those with mild heat exhaustion.[1]

Do not give antipyretics.[1][2]

Antipyretics are not effective in reducing high body temperature related to heat. They work only when body temperature has been raised by pyrogens.[1]

Observe the patient for symptom resolution.[1][2]

Patients with mild heat exhaustion generally improve with the above measures.[1] Symptoms typically resolve within 2 to 3 hours.[2]

Consider – active cooling

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Heat stroke in adults

heat stroke

stabilisation

rapid active cooling

supportive care and monitoring

Oxygen

Evidence: Target oxygen saturation in acutely ill adults

Intravenous fluids

Practical tip

Benzodiazepines

Monitoring

Practical tip

Primary options

These drug options and doses relate to a patient with no comorbidities.

Primary options

Drug choice, dose and interactions may be affected by the patient's comorbidities. Check your local drug formulary.

Primary options

transfer to intensive care unit

heat exhaustion

supportive care and observation

active cooling

Heat stroke in adults

Treatment algorithm

heat stroke

stabilisation

rapid active cooling

supportive care and monitoring

Oxygen

Evidence: Target oxygen saturation in acutely ill adults

Intravenous fluids

Practical tip

Benzodiazepines

Monitoring

Practical tip

Primary options

These drug options and doses relate to a patient with no comorbidities.

Primary options

Drug choice, dose and interactions may be affected by the patient's comorbidities. Check your local drug formulary.

Primary options

transfer to intensive care unit

heat exhaustion

supportive care and observation

active cooling