Updated: 6/5/2019

Hypothermia/Cold Injuries

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  • EKG - Osborn waves in hypothermiaAn 87-year-old homeless military veteran is found unconscious in an alleyway in the middle of January. He was wearing a shirt, a sweater, a pair of pants, and a peacoat. He is brought by ambulance to the ED, where vitals are quickly obtained; his blood pressure is 100/50 mmHg, pulse is 50/min, and SaO2 is 92% on RA. Rectal temperature of 87.6°F (30.8°C) is measured. Naloxone was administered enroute by paramedics with no recovery of mental status. The patient is intubated and mechanically ventilated with warm humidifed O2. IV normal saline is infused at room temperature. Initial EKG monitoring reveals sinus bradycardia with no J-point variations or ST-T wave changes. A second EKG is completed and reveals the findings above. The trauma bay temperature is increased to 82°F (27.8°C). The patient's clothing is quickly cut and replaced with a dry blanket Bair Hugger. No evidence of cold injury is observed. Rectal temperature decreases to 85°F (29.4°C). The patient is transferred to the intensive care unit.
  • Hypothermia is core temperature below 95°F (35°C)
    • mild: 90 - 95°F (32 - 35°C)
    • moderate: 82 - 90°F (28 - 32°C)
    • severe: < 82°F (< 28°C)
  • Mechanism of hypothermia depends on location
    • 4 mechanisms of heat loss
      • radiation - emission of electromagnetic energy
      • convection - transfer of heat to air or water
      • conduction - transfer of heat to solid object
      • evaporation - vaporization of water
    • radiation is main mechanism of heat loss in surgical setting (i.e. OR) due to increased exposure of body surface area
    • conduction/convection are main mechanisms of heat loss in accidental hypothermia
  • Cold-associated injuries along spectrum
    • frostnip
      • local paresthesia without permanent tissue injury
    • pernio
      • inflammatory lesion especially in cold and damp environment
    • immersion foot (nonfreezing cold injury)
      • inflammatory lesion with potential permanent tissue injury
    • frostbite (freezing cold injury)
      • inflammatory lesion due to intra- and extracellular ice crystal formation
        • requires debridement, antibiotics, tetanus vaccination
  • Predisposing factors to hypothermia
    • age (particularly very young and very old)
    • lack of housing
    • drug overdose
    • alcohol ingestion
    • trauma
    • cold water immersion/sports
  • Symptoms and signs based on hypothermia severity
    • mild: tachycardia
      • normal mental status
      • + shivering
    • moderate: bradycardia, tachycardia with Osborn (J) waves on EKG
      • altered mental status
      • - shivering
    • severe: ventricular fibrillation/asystole, unconscious
    • arrhythmia is the most common cause of death from hypothermia
Evaluation and Management
  • Primary and secondary survey with resuscitation
    • if patient presents with cardiac arrest in setting of hypothermia:
      • best initial step: rewarm body 
      • next step: ACLS algorithm based on arrhythmia (VFib / PEA )
        • however, if any pulse exists, do NOT perform CPR
        • do NOT treat new supraventricular arrhythmia pharmacologically
    • rewarming strategy is based on hypothermia severity, but goal is at least 0.9°F/hour
      • mild: passive external rewarming
        • elevate room temperature to 82°F (27.8°C)
        • remove wet clothes and replace with dry blanket
      • moderate: active external and internal rewarming 
        • active external: warm blanket, warm bath
          • warm trunk before extremities to lower risk of "afterdrop" event
            • warming of extremities -> vasodilation -> cool blood moves from extremities to core -> cardiac arrest
        • active internal: warmed IV infusion and warmed, humidified oxygen
      • severe: same as for moderate hypothermia with possible extracorporal options
        • peritoneal and pleural irrigation with warmed fluids
        • cardiopulmonary bypass
        • peritoneal dialysis with warmed fluids
    • physical exam must document cardiovascular and neurological status, and evidence of cold-assciated skin injuries
  • Investigations
    • based on major complications of hypothermia, including coagulopathy, acidosis, arrhythmia, and FEN derangements
      • coagulation: CBC, PT/INR/PTT
      • acidosis: ABG, lactate
      • arrhythmia: 12-lead EKG
        • Osborn J-waves
          • distortion of early repolarization in V2-V5 at beginning of ST segment
          • can be confused for ischemic injury
          • not sensitive, specific, or prognostic
      • FEN: electrolytes, BUN/Cr, glucose, Ca2+, Mg2+
    • radiography
      • CXR may show evidence of aspiration pneumonia/pulmonary edema
  • Frostbite-specific management
    • immersion in 98.6-102.2°F (37 - 39°C) water for 10-30 minutes every day 
      • provide pain medications!
    • cleaning and debridement
    • tetanus prophylaxis
    • NO prophylactic antibiotics



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Questions (3)
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
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
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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