Slide 1: 52yo undomiciled M found down. [EKG] What’s your diagnosis and what EKG findings support it?

Slide 2: This is hypothermia. [EKG showing prolonged PR interval (can also see prolonged QT and/or QRS widening); sinus brady (can also see other bradyarrhythmias); unsteady baseline (shivering artifact); Osborn waves (aka J waves)– height is proportional to severity of hypothermia!]

Slide 3: “Osborn waves? I thought those were ST elevations!” Osborn wave: morphology – upward deflection BEFORE J-point, creating a “camel hump” appearance / location – most commonly seen in II, III, aVF, and V3-V6 / DDX most frequently seen in hypothermia, however also seen in Brugada, hypercalcemia, ischemia | ST elevation: morphology – upward deflection AFTER J-point / location – can be seen in all leads – distribution varies based on underlying etiology / DDX – ischemia, pericarditis, early repolarization (and more).

Slide 4: Hypothermia. Definition: body temperature < 95 deg F (35 deg C) + altered mental status and neuro deficits (ie ataxia). Geriatric population at increased risk. Hypothermic heart is prone to arrhythmias, including ventricular fibrillation. Pro tip: Esophageal thermometer is the most accurate way to determine a patient's temperature (better than rectal or bladder)! [diagram showing cold stress -> slowing of physiologic functions (metabolism, enzymatic reactions) -> decreased automaticity and decreased conduction ability of cardiac tissue -> conduction delay -> related EKG findings (PR prolongation, QRS widening, bradyarrhythmia)

Slide 5: Hypothermia: the major culprits. Heat loss (accidental cold exposure). Vasodilation (drugs or EtOH, sepsis). Impaired heat production (endocrine disorders, malnutrition, hypoglycemia). Iatrogenic (massive transfusion, dialysis or CRRT, intentional hypothermia protocol). Impaired thermoregulation (spinal cord injury, CVA, hypothalamic injury)

Slide 6: Hypothermia & hemodynamics. Initially: increased SVR via vasoconstriction (To prevent heat loss and maintain core temperatures) -> increased central blood volume -> inhibition of ADH release -> large quantities of dilute urine (cold-induced diuresis) -> hypotension. Keep this in mind when treating hypothermia, as cold-induced diuresis may cause: labile vital signs and possible pressor needs, underestimation of your patient’s fluid requirements!


  • Omar HR. The Osborn wave: what have we learned? Herz. 2016 Feb;41(1):48-56. Epub 2015 Aug 14. PMID 26272271.
  • Ali A, Butt N, Sheikh AS. Early repolarization syndrome: A cause of sudden cardiac death. World J Cardiol. 2015 Aug 26;7(8):466-75. PMID 26322186.
  • Duong H, Patel G. Hypothermia. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Dec 3. PMID 31424823.
  • Vassallo SU, Delaney KA. Chapter 29: Thermoregulatory Principles. In: Nelson LS, Howland M, Lewin NA, Smith SW, Goldfrank LR, Hoffman RS. eds. Goldfrank’s Toxicologic Emergencies, 11e New York, NY: McGraw-Hill.

Tags: ,