Browse categories and answer follow-up questions to refine your symptom profile.
Approach to the Critical Patient
Recognition and immediate priorities
Heat stroke stabilization
Core temperature threshold
Core temperature >= 40.0 C with CNS dysfunction
Heat stroke possible with lower temperature after partial cooling
Life threats
Airway compromise
Seizure
Shock
Severe electrolyte derangement
Dysrhythmia
Key immediate actions
Move to cool environment
Remove clothing and PPE
Continuous core temperature monitoring
Immediate active cooling as first priority
Cooling strategy and targets
Rapid cooling goals
Core temperature monitoring
Rectal probe preferred for accuracy
Esophageal probe acceptable if intubated
Bladder probe unreliable during oliguria or irrigation
Cooling target temperature
Stop active cooling at 38.5 C to 39.0 C to avoid overshoot hypothermia
Reassess every 5 minutes during active cooling
Cooling method selection
Exertional heat stroke
Ice water immersion preferred when feasible
Limb and trunk agitation in tub for convective flow
Classic heat stroke
Evaporative cooling with mist plus fan
Ice packs to groin, axillae, neck as adjunct
If immersion not feasible
Cold water dousing plus fan
Cooling blanket as adjunct only
Cold IV fluids as adjunct
Airway, breathing, circulation
Resuscitation bundle
Airway and ventilation
Indications for intubation
Persistent agitation preventing cooling
Inability to protect airway
Refractory seizure
Severe hypoxemia or respiratory failure
Ventilation targets
Normocapnia
Avoid permissive hyperthermia from prolonged apneic periods
Circulation
IV access
Two large bore peripheral IVs
Consider intraosseous if access delayed
Fluid strategy
Isotonic crystalloid bolus for hypotension
Reassessment with lung exam and ultrasound
Avoid fluid overload in renal failure
Vasopressors
If hypotension persists after fluids
Norepinephrine first line for distributive physiology
Monitoring
Continuous ECG
Frequent blood pressure
Pulse oximetry
Capnography if intubated
Foley for urine output if not contraindicated
Escalation and consultation triggers
Early escalation
ICU activation triggers
Persistent altered mental status
Temperature not decreasing with cooling
Hypotension requiring vasopressors
Seizure
Lactate rising or metabolic acidosis
Rhabdomyolysis with rising creatine kinase
Acute kidney injury or oliguria
Coagulopathy or bleeding
Hepatic injury with rising aminotransferases
Consultation triggers
Nephrology for severe rhabdomyolysis or hyperkalemia
Toxicology for unclear hyperthermia differential
Hematology for DIC
Obstetrics for pregnancy
Pediatrics for children
PEARLS
Heat stroke time critical principles
Cooling is the definitive therapy
Outcomes correlate with time above critical temperature
Delays to cooling increase organ failure risk
Skin findings unreliable
Diaphoresis can be present in exertional heat stroke
Hot dry skin does not exclude other hyperthermia causes
History
Exposure and timeline
Heat illness history framework
Environment and exertion
Ambient temperature and humidity
Radiant heat exposure
Duration of exposure
Physical exertion intensity and duration
Symptom timeline
Time of collapse
Preceding dizziness
Syncope
Confusion or behavior change
Seizure activity
Hydration and fueling
Fluid intake
Electrolyte replacement
Weight change during activity
Risk factors and comorbidities
Predisposing factors
Impaired heat dissipation
Lack of acclimatization
Dehydration
Heavy clothing or protective gear
Limited access to shade or cooling
Medical risk factors
Cardiovascular disease
Diabetes mellitus
Chronic kidney disease
Psychiatric illness with impaired judgment
Prior heat illness
Medications increasing risk
Anticholinergics
Diuretics
Beta blockers limiting tachycardic response
Stimulants
Antipsychotics
SSRIs and SNRIs
Alternative hyperthermia clues
Mimic flags
Infection symptoms
Recent illness
Rigors
Recent surgery or devices
Drug exposure
Serotonergic agents
Antipsychotic exposure
Sympathomimetic use
Anesthetic exposure
Neurologic symptoms before heat exposure
Headache
Focal deficits
Trauma
Physical Exam
Vitals and general appearance
Heat stroke exam priorities
Temperature method
Rectal temperature preferred
Tympanic and oral temperature underestimation risk
Hemodynamics
Tachycardia
Hypotension
Wide pulse pressure
Respiratory status
Tachypnea
Hypoxemia
Pulmonary edema signs after fluids
Neurologic and mental status
CNS dysfunction profile
Level of consciousness
Agitation
Confusion
Delirium
Coma
Seizure activity
Overt convulsions
Nonconvulsive seizure suspicion
Focal findings
Alternate diagnosis consideration if present
Skin and volume status
Thermoregulation findings
Skin temperature
Hot skin
Peripheral vasodilation
Diaphoresis
Present or absent
Not a discriminator of severity
Hydration
Dry mucous membranes
Capillary refill
Jugular venous pressure estimate
Organ system complications
Heat injury complications
Muscle tenderness
Rhabdomyolysis suspicion
Bleeding signs
Oozing at IV sites
Petechiae or ecchymoses
Abdominal findings
Hepatic tenderness
Ileus
Renal perfusion indicators
Oliguria
Dark urine
PITFALLS
Common misses
Delayed core temperature measurement
Peripheral temperatures underestimate severity
Treating as sepsis without parallel cooling
Cooling should not wait for labs or imaging
Reliance on antipyretics
No benefit in noninfectious hyperthermia
Differential Diagnosis
Life threatening hyperthermia syndromes
Critical differentials
Heat stroke
ICD-10 T67.0
SNOMED CT heat stroke concept
Sepsis with hyperthermia
ICD-10 A41.9
Serotonin syndrome
ICD-10 T43.225A
Neuroleptic malignant syndrome
ICD-10 G21.0
Malignant hyperthermia
ICD-10 T88.3
Sympathomimetic toxidrome
ICD-10 T43.621A and related
Thyroid storm
ICD-10 E05.91
Neurologic and metabolic mimics
Alternate causes of altered mental status
Hypoglycemia
ICD-10 E16.2
Hyponatremia with encephalopathy
ICD-10 E87.1
Intracranial hemorrhage
ICD-10 I61.9
Acute ischemic stroke
ICD-10 I63.9
Meningitis or encephalitis
ICD-10 G03.9
Cardiopulmonary and exertional collapse
Exertional collapse differentials
Exertional rhabdomyolysis without heat stroke
ICD-10 M62.82
Acute coronary syndrome
ICD-10 I21.9
Pulmonary embolism
ICD-10 I26.99
Heat syncope
ICD-10 T67.1
Heat exhaustion
ICD-10 T67.5
Laboratory Tests
Initial critical labs
Core heat stroke labs
Metabolic and electrolytes
Sodium for dysnatremia
Hyponatremia risk with excessive hypotonic intake
Hypernatremia risk with dehydration
Potassium for arrhythmia risk
Hyperkalemia risk with rhabdomyolysis
Hypokalemia possible with sweating and diuretics
Bicarbonate for metabolic acidosis
High anion gap from lactate
Creatinine for acute kidney injury
Rising creatinine suggests pigment nephropathy
Glucose for hypoglycemia and stress hyperglycemia
Muscle and hemolysis
Creatine kinase for rhabdomyolysis severity
Rising trend predicts renal risk
Urinalysis for heme with few RBCs
Myoglobinuria surrogate
Hepatic injury
AST and ALT
Very high values possible in severe heat stroke
Bilirubin
Coagulation and hematology
Platelets for consumption and DIC
PT and INR for coagulopathy
aPTT for coagulopathy
Fibrinogen for DIC
D dimer for DIC support
Acid base and perfusion
Venous blood gas or arterial blood gas
pH and bicarbonate for severity
PaO2 in mmHg if arterial sample
Lactate in mmol/L
Trend for shock and prognosis
Expanded evaluation and complications
Additional labs by presentation
Cardiac injury
Troponin for exertional or older patients
BNP if heart failure concern after resuscitation
Infection evaluation if unclear
Blood cultures if sepsis remains plausible
Urine culture if urinary source concern
Toxicology if suspected exposure
Acetaminophen level if altered mental status unclear
Salicylate level if acid base disturbance unexplained
Urine drug screen for contextual support
Interpretation and pitfalls
Lab interpretation pearls
Creatine kinase timing
Peak may occur 24 to 72 hours after injury
Coagulopathy progression
DIC can evolve hours after presentation
Calcium abnormalities
Early hypocalcemia possible in rhabdomyolysis
Late hypercalcemia during recovery phase
Leukocytosis
Stress leukocytosis common without infection
Diagnostic Tests
Scoring Systems
Risk stratification and organ dysfunction scores
SOFA score for multi organ dysfunction
Respiratory component
PaO2 to FiO2 ratio in mmHg
Coagulation component
Platelet count
Liver component
Bilirubin
Cardiovascular component
MAP and vasopressor requirement
CNS component
GCS
Renal component
Creatinine and urine output
JAAM heat illness severity classification
Consciousness impairment
Core temperature elevation
Organ dysfunction markers
MRI
MRI considerations
Indications
Persistent focal neurologic deficits after normothermia
Suspected alternate CNS pathology
Limitations
Time and transport delays
Not a priority over cooling
CT
CT applications
Head CT indications
Persistent altered mental status after cooling
Focal neurologic deficits
Trauma from collapse
Anticoagulation use with concern for bleed
Chest CT and angiography considerations
PE evaluation when unexplained hypoxemia persists
Abdomen and pelvis CT considerations
Alternate abdominal catastrophe concern
Ultrasound
Point of care ultrasound
Volume status assessment
IVC variability as supportive data
Cardiac filling estimates
Cardiac function
Hyperdynamic state in distributive physiology
Depressed function in cardiomyopathy or ischemia
Lung ultrasound
B lines suggesting fluid overload
Pleural effusion assessment
Renal ultrasound
Hydronephrosis exclusion in AKI
Disposition
Level of care decisions
Disposition framework
ICU admission criteria
Heat stroke diagnosis with CNS dysfunction
Ongoing altered mental status after normothermia
Hypotension requiring vasopressors
Mechanical ventilation requirement
Seizure
Creatine kinase markedly elevated or rising
Acute kidney injury or oliguria
Coagulopathy or DIC markers
Hepatic injury with rising aminotransferases
Severe metabolic acidosis
Step down or monitored bed criteria
Rapid neurologic recovery after cooling
Stable hemodynamics without vasopressors
Mild lab abnormalities with reliable trending plan
Transfer criteria
Need for ICU without local capacity
Need for renal replacement therapy
Need for advanced critical care resources
Observation and follow up planning
Monitoring requirements
Serial core temperature checks after cooling
Rebound hyperthermia monitoring for 2 to 4 hours
Serial labs
Electrolytes every 4 to 6 hours initially
Creatine kinase trend every 6 to 12 hours
Coagulation reassessment if abnormal
Creatinine and urine output trending
Neurologic reassessment
Persistent confusion triggers ICU and alternate workup
Treatment
Cooling modalities
Active cooling therapies
Ice water immersion
Indications
Exertional heat stroke with safe airway control
Practical considerations
Continuous core temperature probe
Airway monitoring with staff at head of tub
Stop at 38.5 C to 39.0 C
Evidence level
Rapid cooling associated with improved outcomes
Expert consensus strong recommendation Class I
Evaporative cooling
Indications
Classic heat stroke
When immersion not feasible
Method
Warm mist or tepid water spray
High flow fan for convection
Ice packs to groin and axilla as adjunct
Evidence level
Expert consensus recommendation Class I
Adjunct cooling
Cold IV isotonic crystalloid
4 C saline as adjunct if available
Gastric or bladder lavage
Limited evidence
Consider only in refractory hyperthermia with critical care support
Sedation, shivering, and agitation control
Pharmacologic control of agitation and shivering
Benzodiazepines
Lorazepam IV 1 mg to 2 mg
Repeat every 5 to 10 minutes as needed
Max dose individualized by respiratory status
Diazepam IV 5 mg to 10 mg
Repeat every 5 to 10 minutes as needed
Midazolam IV 2 mg to 5 mg
Repeat every 5 minutes as needed
Evidence level
Shivering reduction to facilitate cooling
Expert consensus ACEP Level C
If intubated sedation strategies
Propofol infusion
Initiate 5 mcg/kg/min
Titrate 5 mcg/kg/min to 10 mcg/kg/min every 5 minutes
Typical range 5 mcg/kg/min to 50 mcg/kg/min
Hypotension monitoring
Dexmedetomidine infusion
Initiate 0.2 mcg/kg/hour
Titrate 0.1 mcg/kg/hour every 15 to 30 minutes
Max 1.5 mcg/kg/hour
Bradycardia monitoring
Airway and ventilation management
Respiratory support
Oxygen therapy
Nasal cannula or mask to maintain saturation targets
Intubation considerations
Rapid sequence induction with hemodynamic awareness
Avoid succinylcholine if severe hyperkalemia from rhabdomyolysis suspected
Post intubation temperature monitoring with esophageal probe
Hemodynamics and fluids
Circulatory support
Isotonic crystalloid bolus
500 mL to 1000 mL initial bolus adult
Repeat based on perfusion and ultrasound
Vasopressor strategy
Norepinephrine infusion
Initiate 0.05 mcg/kg/min
Titrate every 2 to 5 minutes to MAP target
Typical range 0.05 mcg/kg/min to 0.5 mcg/kg/min
MAP target
>= 65 mmHg in shock
Higher targets individualized in chronic hypertension
Seizure management
Seizure control
Benzodiazepines first line
Lorazepam IV 0.1 mg/kg
Max single dose 4 mg
Repeat once if needed
Second line antiseizure therapy
Levetiracetam IV 60 mg/kg
Max 4500 mg
Infuse over 10 to 15 minutes
Refractory seizure escalation
Continuous infusion sedation in ICU
Rhabdomyolysis and renal protection
Rhabdomyolysis management
Fluid strategy
Isotonic crystalloid to support renal perfusion
Urine output target
1 mL/kg/hour to 2 mL/kg/hour
Electrolyte monitoring
Potassium trending
Calcium trending
Phosphate trending
Renal replacement therapy triggers
Refractory hyperkalemia
Severe acidosis
Volume overload with respiratory compromise
Uremic complications
Coagulopathy and DIC
Hemostatic management
DIC supportive care
Platelet transfusion if bleeding with thrombocytopenia
Cryoprecipitate for low fibrinogen with bleeding
Plasma for active bleeding with prolonged INR
Evidence level
Standard critical care consensus
Expert consensus ACEP Level C
Temperature adjuncts and contraindicated therapies
Adjunct and avoidance list
Antipyretics
No role in heat stroke
Hepatotoxicity risk with acetaminophen
Bleeding and renal risk with NSAIDs
Dantrolene
Not recommended for heat stroke
Reserved for malignant hyperthermia
Antibiotics
Only if infection suspected based on clinical context
Evidence levels and guideline signals
Evidence summary
Rapid active cooling
Strong recommendation Class I
Expert consensus ACEP Level C
Ice water immersion for exertional heat stroke
Preferred when feasible
Guideline supported in wilderness and sports medicine consensus
Evaporative cooling for classic heat stroke
Effective alternative when immersion not feasible
Expert consensus recommendation
Special Populations
Pregnancy
Pregnancy considerations
Maternal fetal risks
Fetal distress risk with sustained maternal hyperthermia
Preterm labor risk
Cooling priorities
Rapid maternal cooling as primary fetal therapy
Left uterine displacement after mid pregnancy to reduce aortocaval compression
Medication considerations
Benzodiazepines for seizure and agitation when needed
Avoid hypotension from sedatives
Consultation
Obstetrics for fetal monitoring and disposition
Geriatric
Geriatric considerations
Higher risk profile
Impaired thirst and thermoregulation
Chronic disease burden
Limited mobility and social isolation
Medication contributions
Anticholinergics and sedatives
Diuretics
Beta blockers
Fluid strategy nuance
Lower tolerance for large boluses
Early ultrasound guided resuscitation
Pediatrics
Pediatric considerations
Higher surface area and faster heat gain
Rapid progression risk
Weight based dosing
Lorazepam IV 0.1 mg/kg
Max single dose 4 mg
Levetiracetam IV 60 mg/kg
Max 4500 mg
Cooling approaches
Evaporative cooling and ice packs often practical
Immersion feasible with airway safety and monitoring
Safeguarding concerns
Hot car exposure evaluation
Social work involvement as indicated
Background
Epidemiology
Heat stroke population patterns
Heat stroke categories
Exertional heat stroke in athletes, military, outdoor workers
Classic heat stroke in elderly, chronically ill, socially isolated
Seasonal clustering
Heat waves and high humidity periods
Mortality drivers
Time to cooling
Multi organ failure burden
Pathophysiology
Heat stroke mechanisms
Thermoregulatory failure
Heat production exceeding heat loss
Impaired sweating and skin blood flow response
Cellular injury
Protein denaturation and enzyme dysfunction
Mitochondrial failure
Systemic inflammatory response
Cytokine mediated endothelial injury
Increased gut permeability and endotoxemia model
Coagulopathy cascade
Endothelial activation
Platelet consumption and DIC potential
Organ injury patterns
CNS edema and neurotoxicity
Hepatic necrosis
Rhabdomyolysis and pigment nephropathy
Therapeutic Considerations
Treatment rationale
Cooling as definitive therapy
Heat injury is time and temperature dependent
Faster cooling reduces organ dysfunction risk
Shivering suppression
Shivering increases heat production
Sedation improves cooling efficiency
Fluids and perfusion
Volume depletion from sweat and vasodilation
Shock may be distributive and hypovolemic mixed
Avoid ineffective therapies
Antipyretics ineffective because hypothalamic set point not elevated
Dantrolene not supported outside malignant hyperthermia
Patient Discharge Instructions
Copy discharge instructions
Discharge guidance for non heat stroke heat illness
Rest and cooling
Cool indoor environment for 24 to 48 hours
Avoid exercise and heat exposure for 48 hours
Hydration
Oral fluids with electrolytes
Avoid alcohol for 48 hours
Medication guidance
Avoid NSAIDs if kidney injury concern
Follow up
Primary care follow up within 24 to 72 hours
Repeat labs if prior abnormalities
Return to ED immediately
Confusion, fainting, seizure, or severe headache
Persistent vomiting or inability to keep fluids down
Dark urine or no urination for 8 hours
Chest pain, shortness of breath, or palpitations
Recurrent fever or overheating symptoms
Worsening weakness or muscle pain
References
Clinical guidelines and consensus statements
Guideline sources
Wilderness Medical Society practice guidelines for prevention and treatment of heat illness
Ice water immersion recommended for exertional heat stroke when feasible
Evaporative and convective methods as alternatives when immersion not feasible
Sports medicine consensus statements on exertional heat stroke management
Immediate cooling prior to transport when possible
Critical care and emergency medicine references on hyperthermia syndromes
Differentiation from serotonin syndrome and neuroleptic malignant syndrome
Evidence based sources
Evidence anchors
Observational evidence linking faster cooling to improved neurologic outcomes
Time to target temperature as prognostic factor
Comparative effectiveness data for cooling methods
Immersion fastest cooling rates in exertional settings
Evaporative cooling effective in classic presentations
Expert consensus on supportive care complications
Rhabdomyolysis management
DIC management
Renal replacement therapy triggers
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.