Rosen & Barkin's 5-Minute Emergency Medicine Consult (370 page)

• Classic triad: Hyperthermia, CNS dysfunction, hot skin (often with anhidrosis)
  
• Core temp: >105°F (40.5°C)
  
• CNS:
  
  • Severe confusion/delirium
    
  • Lethargy or coma
    
  • Seizure
    
  • Ataxia
    
• CV:
  
  • Tachycardia
    
  • Wide pulse pressure
    
  • Low peripheral vascular resistance
    
  • Hypotension
    
  • Conduction disturbances
    
• Pulmonary:
  
  • Tachypnea
    
  • Rales due to noncardiac pulmonary edema
    
  • Respiratory alkalosis (may be substantial enough to cause tetany)
    
  • Hypoxemia (due to aspiration, pneumonitis, pulmonary edema, and high metabolic demand)
    
• GI:
  
  • Nausea/vomiting
    
  • Diarrhea
    
• Skin:
  
  • Cutaneous vasodilation → Hot skin
    
  • Usually dry, though sweating may be present if not dehydrated
    
• Acute oliguric renal failure due to dehydration +/- rhabdomyolysis
  
• Hepatic failure with elevation of transaminases in the tens of thousands
  
• Coagulopathy, including DIC (poor prognostic sign) → purpura, melena, hematochezia, hematuria, CNS hemorrhage
  

• Core temp moderately elevated, usually <104°F (40°C) and never >40.5°C
  
• CNS:
  
  • Frontal headache
    
  • Fatigue/malaise
    
  • Impaired judgment
    
  • Vertigo
    
  • Agitation
    
  • No severe CNS dysfunction
    
• CV:
  
  • Mild tachycardia
    
  • Dehydration
    
• Pulmonary: Tachypnea
  
• GI: Nausea, vomiting
  
• Skin: Perspiration present, often profuse
  

• Cramps in heavily worked muscles after exercise
  
• Occurs after profuse sweating and rehydration with hypotonic fluid (i.e., water)
  
• Results in hyponatremia and hypochloremia without rhabdomyolysis or renal damage
  
• Treat with oral salt solutions if minor or NS IV if severe
  

• Swelling of feet/ankles from environmental heat in nonacclimatized people
  
• Due to vasodilatation and orthostatic pooling and increased aldosterone
  
• Resolves after acclimatization. Treatment with elevation or compression stockings.
  

• Unexplained syncope during heat exposure with prolonged standing, especially in elderly
  
• Cutaneous vessels dilate in an effort to dissipate heat → decreased central blood volume → syncope
  
• Self-limited illness. Resolves when the patient lays flat.
  

• Pruritic maculopapular/vesicular rash over clothed areas after profuse sweating in tight clothing
  
• Due to blockage of pores and secondary staphylococcus infection
  

• Accurate core temperature
  
• History of heat exposure
  
• Heat exhaustion is a diagnosis of exclusion
  
• Core temperature >105°F (40.5°C) and CNS dysfunction required to make diagnosis of heat stroke
  

• CBC
  
  • Leukocytosis, hemoconcentration
    
• Electrolytes, BUN, Cr, glucose
  
  • Hypernatremia with severe dehydration
    
  • Hyponatremia can occur if drinking copious free water
    
  • Acute renal failure
    
• UA
  
  • Myoglobin present in rhabdomyolysis
    
• Blood and urine cultures to rule out septic etiology
  
• Toxicology screen
  
• Serum creatinine kinase to rule out rhabdomyolysis
  
• ABG
  
  • Acidosis is common with exertional heat stroke, and lactate is usually elevated
    

• PT/PTT/DIC panel – coagulopathy implies poor prognosis
  
• Liver function tests
  
• Troponin I – poor prognosis if elevated
  
• Consider lumbar puncture to distinguish from meningitis/encephalitis
  

• EKG in elderly or patients at cardiac risk
  
• CT head for altered mental status
  
• CXR for ARDS, aspiration pneumonia, and to rule out septic etiology
  

• Febrile illness/sepsis
  
• Thyroid storm
  
• Pheochromocytoma
  
• Cocaine/PCP
  
• Anticholinergics
  
• MAO inhibitors
  
• Meningitis/encephalitis
  
• Cerebral falciparum malaria
  
• Delirium tremens
  
• Neuroleptic malignant syndrome
  
• Malignant hyperthermia
  
• Serotonin syndrome
  

TREATMENT

• Initiate cooling measures for severe heat illness
  
  • Remove from heat stress
    
  • Disrobe patient
    
  • Cover body with wet sheet
    

• ABCs
  
• Continuous core temperature monitoring with a rectal or esophageal probe
  
• Rapid cooling if temperature >104°F (40°C)
  
• Start with IV 0.9% NS 500 cc fluid bolus if hypotensive
  
• If altered mental status, administer glucose (or Accu-Chek), thiamine, naloxone
  

• Initiate for body temperature >104°F (40°C)
  
• Evaporative cooling
  
  • Extremely effective (0.05–0.3°C/min)
    
  • Spray disrobed patient with fine mist of warm water (prevents shivering)
    
  • Airflow with fans blowing over patient
    
• Conductive cooling
  
  • Ice packs to groin/axilla. Combine with evaporative cooling treatment above
    
  • Iced or cold water immersion—effective but impractical
    
• Iced peritoneal lavage, cardiopulmonary bypass, or HD with cold dialysate for refractory cases – not well studied
  
• Stop cooling therapy at 102°F (39°C) to avoid overshooting and hypothermia
  
• Antipyretic agents are not helpful because underlying mechanism does not involve a change in the hypothalamus set point
  
• Avoid alcohol sponge baths. Toxicity can occur due to dilated cutaneous vessels.
  

• Rehydration for heat stroke/heat exhaustion
  
  • Initial rehydration with 0.5–1.0 L 0.9% NS
    
  • Aggressive fluid resuscitation until BP >90/60 or central venous pressure (CVP) >12 mL H
    ₂
    O
    
  • Avoid overhydration, which can contribute to pulmonary edema and ARDS
    
  • Peds: Start with 20 cc/kg bolus
    
  • Place Foley catheter to monitor urine output for heat stroke victims and CVP monitor if feasible. Maintain UOP >2 mL/kg/hr if rhabdomyolysis is present
    
  • Rehydrate to hemodynamic stability with NS then slowly administer free water if needed for correction of hypernatremia
    
• Benzodiazepines for seizure, agitation, or to stop shivering
  
• Tachyarrhythmias can develop, which usually resolve with cooling. Avoid electricity or α-adrenergics until after the myocardium is cooled
  
• Heat cramps: Analgesics and oral or IV hydration with electrolyte-containing fluid
  
• Heat edema: Lower extremity elevation + compression stockings
  
• Prickly heat: Chlorhexidine cream/lotion +/- salicylic acid 1% TID
  

• Diazepam: 5–10 mg (peds: 0.2–0.4 mg/kg) IVP
  
• Lorazepam: 1–2 mg (peds 0.05–0.1 mg/kg) IVP
  
• Naloxone (Narcan): 2 mg (peds: 0.1 mg/kg) IVP
  

FOLLOW-UP

• Heat stroke – admit to the ICU
  
• Heat exhaustion – admit to general or monitored floor if:
  
  • Severe electrolyte abnormalities
    
  • Renal failure or evidence of rhabdomyolysis
    
  • Elderly
    

All patients except those with heat stroke or severe heat exhaustion may be discharged

• Cannot make diagnosis of heat stroke without temp >40.5°C and severe CNS dysfunction.
  
• Management of heat stroke requires management of ABCs and rapid cooling.
  
• Continuous core monitoring with a rectal or esophageal probe is standard of care.
  
• Evaporative cooling is the cooling method of choice.
  

• Hausfater P, Doumenc B, Chopin S, et al. Elevation of cardiac troponin I during non-exertional heat-related illness in the context of a heatwave.
  Crit Care
  . 2010;14(3):R99.
  
• LoVecchio F, Pizon AF, Berrett C, et al. Outcomes after environmental hyperthermia.
  Am J Emerg Med
  . 2007;25(4):442–444.
  
• Martin-Latry K, Gourmy MP, Latry P, et al. Psychotropic drugs use and risk of heat-related hospitalization.
  Eur Psychiatry.
  2007;22(6):335–338.
  
• Marx JA, Hockberger RS, Walls RM. Heat Illness.
  Rosen’s Emergency Medicine: Concepts and Clinical Practice
  . 7th ed., Vol 2. Philadelphia, PA: Mosby Elsevier; 2010:1882–1892.
  
• Smith JE. Cooling methods used in the treatment of exertional heat illness.
  Br J Sports Med.
  2005;39(8):503–507.
  
• Varghese GM, John G, Thomas K, et al. Predictors of multi-organ dysfunction in heatstroke.
  Emerg Med J
  . 2005;22(3):185–187.
  

CODES

• 992.0 Heat stroke and sunstroke
  
• 992.2 Heat cramps
  
• 992.5 Heat exhaustion, unspecified