Updated: 4/1/2020

Hyperthermia/Heat Injuries

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Snapshot
  • A 16-year-old football player is brought to the school nurse by his teammates with extreme fatigue and altered mental status in early August. He refuses to be evaluated by his sports coach. Temporal temperature is 103°F (39.4°C). With restraining support from the teammates, the nurse records a rectal temperature of 105°F (40.5°C). The nurse informs the coach and quickly removes the athlete's equipment and clothing to facilitate cooling. The nurse then calls the ambulance to transfer the patient to the local hospital. His pretransfer rectal temperature is 102°F.
Introduction
  • Hyperthermia
    • elevation of core body temperature 96.8 - 99.5 °F (> 36 - 37.5 °C) due to failure of thermoregulation
  • Hyperthermia is NOT fever
    • fever is induced by cytokine activation during inflammation
    • regulated at hypothalamus
    • however, difficult to distinguish hyperthermia from fever
  • Heat-related illnesses can be multifactorial
    • can be exertional (e.g., athlete overexertion)
    • can be nonexertional (e.g., elderly person with dementia; immobile patient)
    • can be medication-induced (e.g., anticholinergic/neuroleptic medications)
Presentation
  •  Heat exhaustion and heat stroke definitions overlap
    • heat exhaustion (HE)
      • ≤ to 104°F
      • non-specific malaise, headache, fatigue
      • no coma/seizures
      • symptoms due to loss of circulating volume caused by heat exposure
        • water depletion
          • symptoms due to inadequate replacement of fluids
        • salt depletion
          • symptoms due to inappropriate replacement with hypotonic fluids
          • e.g., water, juice
    • heat stroke (HS) 
      • > 104°F
        • exertional HS 
          • usually younger, more active demographic
          • diaphoretic skin
          • may have DIC, AKI, rhabdomyolysis, lactic acidosis
        • nonexertional HS 
          • usually older, poor, sedentary, immobile demographic
          • hot, dry skin
          • altered mental status, delirium, coma, and seizures
    • heat syncope 
      • no specific temperature
      • syncope due to poor CNS perfusion
        • cutaneous and skeletal muscle vasodilation shunts blood from CNS to periphery
        • worsened by dehydration
 Evaluation and Management
  • Primary and secondary survey with resuscitation  
    • secure airway if seizure/aspiration risk is high
    • fluid resuscitation with intravenous isotonic fluids (NS/LR) 
  • Best diagnostic test: rectal temperature
  • Best initial step: anything that cools patient rapidly
    • remove any layers of equipment/clothing
    • cold water and ice water immersion therapy
    • goal is to cool core temperature 0.3-0.5°F/min to 100-102°F
  • Avoid antipyretics (e.g., aspirin, Tylenol)
  • Transfer patient to medical facility for definitive care
  • If etiology is exertional, American College Sports Medicine guidelines recommends no exercise for 7 days after event
 Complications
  • If patient does not respond quickly to cooling treatment, consider other etiologies of hyperthermia
    • infection/meningitis
    • thyroid storm
    • anticholinergic poisoning
    • delirium tremens

References

 

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Questions (4)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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