Heat Stroke

Aka: Heat Stroke

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