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Heat Stroke
Aka: Heat Stroke
- See Also
- Heat Illness
- Heat Edema
- Heat Cramps
- Heat Exhaustion
- Heat Stroke
- Temperature Regulation
- Heat Index
- Heat Illness Risk Factors
- Medications Predisposing to Heat Illness
- Heat Illness Prevention
- Marathon Medical Care
- Epidemiology
- Heat Stroke is the third leading cause of death among high school athletes
- Coris (2004) Sports Med 34(1): 9-16 [PubMed]
- Risk Factors
- See Temperature Regulation
- See Heat Illness Risk Factors
- See Medications Predisposing to Heat Illness
- Types
- Nonexertional (Classic) Heatstroke
- Gradual environmental exposure
- Usually seen in elderly and debilitated patients
- Exertional Heatstroke
- Rapid onset over hours
- Usually seen in young patients and in athletes or occupational heat exposure
- Pathophysiology
- Very high Body Temperatures (>105.8 F or 41 C) causes proteins to denature with secondary multisystem organ damage
- Mental status changes are a result of decreased cerebral perfusion and secondary cerebral ischemia
- Precautions
- Heat Stroke is a time-sensitive, life threatening condition (treat aggressively as a code)
- Core Temperature may have decreased below discriminatory values by the time of patient presentation
- Have a high index of suspicion with neurologic signs, even when core Temperature <104 F (40 C)
- Neurologic changes from baseline may be difficulty to assess at extremes of age (very young and very old)
- Signs
- Includes Heat Exhaustion symptoms and signs
- Hyperpyrexia (Use rectal probe)
- Core Temperature exceeds 40 C (104 F) for Heat Stroke diagnosis
- Core temps may range as high as 44 C (111 F)
- Reports of Temperatures up to 47 C (116.6 F)
- Significant neurologic changes
- Altered Level of Consciousness (Delirium to obtundation or coma)
- Slurred speech
- Ataxia
- Delirium
- Hallucinations
- Encephalopathy (associated with poor prognosis)
- Seizures (associated with poor prognosis)
- Systemic signs
- Anhidrosis
- Sinus Tachycardia
- Hypotension
- Especially common when core Temperature has exceeded 42 C (107.6 F)
- Shock results from heat-induced cardiovascular injury as well as systemic inflammatory response
- Tachypnea
- May indicate developing Acute Respiratory Distress Syndrome (ARDS)
- Imaging
- Head CT
- May demonstrate cerebral edema (although CT Head is often normal)
- Chest XRay
- Acute Respiratory Distress Syndrome (ARDS) may complicate Heat Stroke
- Labs
- Complete Blood Count (CBC) with Platelet Count
- Anemia may result from dilution and heat-induced red cell injury
- Platelet Count may decrease in first 24 hours
- Comprehensive Metabolic Panel (Chem18)
- Hyponatremia (or if no access to water, Hypernatremia)
- Renal Insufficiency is typical (due to prerenal Azotemia with BUN > Creatinine, as well as CPK in Rhabdomyolysis)
- Liver Function Test elevations (esp. AST, ALT) result from shock liver (see complications below)
- Peak at 48-72 hours after Heat Injury, and normalize by 14 days
- ProTime (PT)
- Typically elevated associated with liver dysfunction
- Partial Thromboplastin Time (PTT)
- Increased in Disseminated Intravascular Coagulation (DIC)
- Fibrinogen
- Venous Blood Gas (VBG)
- Metabolic Acidosis results from end organ ischemia and protein breakdown
- Creatine Phosphokinase (CPK)
- Increased in Rhabdomyolysis
- Urinalysis
- Myoglobinuria (dipstick orthotoluidine positive for blood, but no urine RBCs seen in freshly spun sediment)
- Diagnostics
- Electrocardiogram (EKG)
- May demonstrate coronary ischemia (ST depression, T Wave inversion) due to impaired Myocardium
- Differential Diagnosis (hyperthermia with ALOC)
- See Medications Predisposing to Heat Illness
- Sepsis
- Meningitis
- Cerebral Malaria
- Cerebrovascular Accident
- Brain Tumor
- Head Injury
- Withdrawal from abused substances
- Neuroleptic Malignant Syndrome
- Hyperthyroidism (Hyperthyroid storm)
- Pheochromocytoma
- Anticholinergic Poisoning
- Management
- Rapid cooling to Temperature under 101.4 F (38.6 C) or per some guidelines, <102.2 F (39 C)
- Best outcomes are associated when cooling is initiated within 30 minutes of heat-related injury
- See Evaporative Cooling
- Evaporative Cooling with fans and misting
- Cool saline bags applied to neck, groin and axilla
- Ice water immersion (most effective measure)
- Associated with nearly 100% survival rate when used immediately in exertional Heat Stroke
- Casa (2007) Exerc Sport Sci Rev 35(3): 141-9 [PubMed]
- Avoid prolonged cooling beyond target core Temperature
- Risk of local cold injury with tissue ischemia and inflammation
- Measures not found effective (and with risk of water Intoxication)
- Nasogastric lavage
- Peritoneal lavage
- Ice water rectal enemas
- Other measures to avoid
- Avoid antipyretics (NSAIDs and Acetaminophen) as ineffective and potentially harmful
- Same IV hydration as for Heat Exhaustion
- See Hypotension below
- Avoid Fluid Overload and observe closely for pulmonary edema
- ABC Management
- Intubation may be needed to protect airway
- Altered Level of Consciousness
- Treat as Delirium
- Check bedside Glucose
- Consider banana bag containing Thiamine
- Consider Naloxone
- Seizure
- See Status Epilepticus
- Administer Benzodiazepines
- Consider Hyponatremia, Hypoglycemia and other Seizure Causes
- Myoglobinuria
- Maintain Urine Output at 50 to 100 ml per hour
- Alkalinize urine and force diuresis with mannitol
- Hypotension
- Start by treating as distributive shock (related to peripheral vasodilation)
- Heat Stroke patients are not uniformly volume depleted
- Judicious rehydration (without overhydration)
- Permissive Hypotension allows for the fluid redistribution that occurs with cooling
- Prevents pulmonary vascular congestion that otherwise occurs with aggressive rehydration
- If refractory Hypotension, increase fluid Resuscitation and consider Vasopressors
- Disseminated Intravascular Coagulation (DIC)
- Fresh Frozen Plasma and platelets as needed
- Shivering with rapid cooling
- Consider muscle relaxants, Benzodiazepines or Neuroleptics (e.g. Chlorpromazine)
- Dantrolene is not effective in lowering core Temperature
- Bouchama (2002) N Engl J Med 346:1978-88 [PubMed]
- Disposition
- Nearly all patients will require hospitalization (typically ICU)
- Children should be admitted to pediatric ICU
- Complications
- Disseminated Intravascular Coagulation (DIC)
- Complicates 50% of Heat Stroke cases
- Rhabdomyolysis
- Acute Renal Failure
- Secondary to prerenal Azotemia, as well as Rhabdomyolysis
- Adult Respiratory Distress Syndrome (ARDS)
- Gastrointestinal Bleeding
- Hepatocellular necrosis (or shock liver)
- Liver is particularly susceptible to Heat Illness (highest heat generation and highest organ Temperature)
- Prognosis: Short-Term
- Mortality: <10% (if treated appropriately)
- Mortality higher in some groups (e.g. firefighters)
- Indicators of Poor Prognosis
- Core Temperature exceeds 42 degrees Celsius
- Aspartate Aminotransferase (AST) >1000 in first day
- Prolonged coma exceeds 2 hours
- Prognosis: Long-Term outcomes for survivors
- Increased risk of Heat Stroke under same conditions
- Test heat tolerance 8-12 weeks post-episode
- Assess for residual injury in Thermoregulation
- Long-term neurologic or behavioral deficits
- Neurologic injury is permanent in 20% of cases
- Dematte (1998) Ann Intern Med 129:173-81 [PubMed]
- Prevention
- See Heat Illness Prevention
- References
- Czerkawski (1996) Your Patient Fitness 10(4): 13-20
- Salinas and Ruttan (2017) Crit Dec Emerg Med 31(9): 3-10
- Sandor (1997) Physician SportsMed, 25(6):35-40
- Barrow (1998) Am Fam Physician 58(3):749-56 [PubMed]
- Becker (2011) Am Fam Physician 83(11): 1325-30 [PubMed]
- Hett (1998) J Postgrad Med 103(6): 107-20 [PubMed]
- Howe (2007) Am J Sports Med 35(8): 1384-95 [PubMed]
- Epstein (1990) Med Sci Sports Exerc 22(1): 29-35 [PubMed]
- Grafe (1997) Clin Sports Med 16(4):569-91 [PubMed]
- Jardine (2007) Pediatr Rev 28(7): 249-58 [PubMed]
- Wexler (2002) Am Fam Physician 65(11):2307-20 [PubMed]
- Yaqub (1998) J Neurol Sci 156(2):144-51 [PubMed]