Hypothermia

Elderly male patient with history of mental illness, homelessness, alcoholism, hypopituitarism, hypothyroidism, hypoadrenalism, CVA presents with hypothermia. Patient found submerged in water with head trauma. Received aggressive fluid resuscitation en route. Temperature < 35 C on exam.

• Severity

  • Mild (32.2-35 C): Hypertension, tachycardia, tachypnea, hypovolemia, shivering, ataxia, apathy, increased urine output.

  • Moderate (28-32.2 C): Bradycardia, bradypnea, hypotension, decreased level of consciousness, pupillary dilation, hyporeflexia. No shivering noted.

  • Severe (< 28 C): Non-responsive with non-reactive pupils, apnea, crackles on lung exam, oliguria. EKG shows ventricular arrhythmia, J-waves. Decreased activity on EEG.

• Labs

  • Measure temperature with low-read rectal thermometer

  • Obtain fingerstick glucose, CBC, CMP q4h, PT/PTT/INR, TSH, Free T4, EtOH level, urine drug screen

  • Consider scheduling cosyntropin stimulation test after resuscitation if hypoadrenalism suspected

• Treatment: Do not abandon resuscitation efforts until core temperature > 32.2 C

  • Mild hypothermia and hemodynamically stable moderate hypothermia

    • Remove wet clothing

    • Passive rewarming: Move to warm environment, insulate, administer warmed liquids PO

  • Hemodynamically unstable due to moderate/severe hypothermia

    • Insulate with Bair Hugger, start D5NS at 40 C

    • Avoid NG tube placement due to risk for precipitating AFib

    • Consider surgical c/s for active rewarming via closed thoracic lavage

  • Cardiac arrest

    • Follow AHA resuscitation guidelines, but do not defibrillate unless VFib is present.

    • VFib on EKG: One time trial of defibrillation. If unsuccessful, do not repeat until core temperature > 30 C.

  • Comorbidities

    • Monitor for hemorrhage

    • Replete glucose, electrolytes PRN

    • Suspected alcoholism and/or positive EtOH: Administer empiric thiamine 250 mg IV x 3 days followed by 100 mg PO x 1 month

    • Confirmed adrenal insufficiency: Administer empiric steroid therapy

• Patient advised to prevent future episodes by wearing layers and carrying a winter survival kit

Notes

• Etiology

  • Cold exposure (e.g. homelessness) +/- concomitant alcohol use is the most common cause of hypothermia

  • Hypopituitarism, hypothyroidism, hypoadrenalism, and CVA may result in temperature dysregulation

  • Aggressive hydration is a common cause of iatrogenic hypothermia

• Physiology

  • Severe hypothermia is associated with pulmonary edema (crackles)

  • Cold diuresis: Kidneys lose concentrating ability

  • Hypothermia may disrupt enzymatic reactions in clotting cascade despite normal PT/PTT/INR results

  • Electrolyte levels may change rapidly during resuscitation; this is especially true for potassium

  • J waves are positive deflections occurring at the junction between the QRS complex and the ST segment

• Treatment

  • Most clinical thermometers only measure as low as 34.4C (94F)

  • Core temperature afterdrop: Phenomenon in which pt clinically worsens when circulation resumes and cold blood returns to heart; minimize by utilizing passive rewarming when possible

  • Closed thoracic lavage: Two thoracostomy tubes placed and warmed saline circulated through thoracic cavity