EM@3AM – Hypothermia

Author: Brit Long, MD (@long_brit, EM Attending Physician, San Antonio) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital)

Welcome to EM@3AM, an emDocs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.

A 42-year-old female presents with altered mental status after being found outside, next to an empty bottle of vodka. She is bradycardic and hypotensive, and your normal thermometer reads “Error”. You ask for a core monitor, which provides a core reading of 27C. D-Stick is 132.

What is the patient’s diagnosis? What’s the next step in your evaluation and treatment?

Answer: Hypothermia

Definition: Core temperature < 35C. Causes include increased heat loss (environmental exposure, vasodilation) and decreased heat production (endocrine, neuromuscular comorbidities, sepsis, trauma).  Majority of patients who die are greater than 65 yrs.

Classification: Mild (32-35C, shivering and awake), moderate (28-32C, depressed mental status and may not display shivering, increased risk of unstable rhythms), severe (20-28C, unconscious or depressed mental status, decreased HR/RR/BP), profound (< 20C, VS may not be obtainable).

Evaluation: Core temperature (esophageal/bladder probe better than rectal) is required, as standard thermometers record to 34C. Obtain fingerstick blood glucose, coagulation panel (may be normal due to blood warming for testing), electrolytes (K > 10 mEq/L is poor prognostic sign), CK (rhabdomyolysis common), TSH (myxedema coma), and ECG (Osborn waves, T wave inversions, prolongation of PR/QRS/QT, AV block, PVC).

Management: Includes gentle handling of patient, warm IV fluids (cold diuresis common), antibiotics if suspect infection, thiamine if considering Wernicke’s, hydrocortisone if suspecting adrenal insufficiency, thyroxine if concern for hypothyroidism.

Dysrhythmias often occur when temperature <32C. Rewarm, and most dysrhythmias do not require other treatment. A cold heart is resistant to atropine and pacing, as well as most other medications. Vtach/Vfib may be refractory until the patient is warmed. Attempt defibrillation x1 if patient is pulseless while doing CPR (evaluate for pulse for 30-60 seconds).

Treatment: Passive external warming for mild (32-35C: warm blankets), active external for moderate (28-32C: warm fluids, forced air with Bair hugger, warm water immersion), active internal for severe (20-28C: warm humidified air if intubated, peritoneal/thoracic/bladder lavage), and active internal with ACLS measures for profound (<20C). Use combination of rewarming modalities. ECMO/Bypass may be needed as last resort.

Always remove wet clothes and use warm blankets. Rewarm trunk before extremities. Warm IV fluids can be helpful.

Complications: Acid base disorders, pneumonia, bleeding, other cold injuries, dysrhythmias, DIC, rhabdomyolysis, thromboembolism, pancreatitis, multiorgan failure.

References:

Brown, et al. Accidental Hypothermia. N Engl J Med 2012; 367:1930-1938

Kempainen RR and Brunette DD. The Evaluation and Management of Accidental Hypothermia. Respir Care 2004;49(2):192-205

http://dhss.alaska.gov/dph/Emergency/Documents/ems/documents/Alaska%20DHSS%20EMS%20Cold%20Injuries%20Guidelines%20June%202014.pdf

https://lifeinthefastlane.com/ecg-library/basics/hypothermia/