Hypokalemia in Emergency Medicine Workup

Updated: Apr 05, 2017
  • Author: David Garth, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Workup

Laboratory Studies

Laboratory studies include the following:

  • Serum potassium level < 3.5 mEq/L (3.5 mmol/L) [10]
  • BUN and creatinine level
  • Glucose, calcium, and/or phosphorus level if coexistent electrolyte disturbances are suspected.
  • Magnesium levels are unreliable and typically do not change management, since patients with hypokalemia almost always have coincident hypomagnesemia and should be treated empirically.
  • Consider digoxin level if the patient is on a digitalis preparation; hypokalemia can potentiate digitalis-induced arrhythmias.
  • Consider arterial blood gas (ABG): Alkalosis can cause potassium to shift from extracellular to intracellular.
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Imaging Studies

CT scan of the adrenal glands is indicated if mineralocorticoid excess is evident (rarely needed emergently).

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Other Tests

Electrocardiography

  • T-wave flattening or inverted T waves
  • Prominent U wave that appears as QT prolongation (see the image below)
    Prominent U waves after T waves in hypokalemia. Prominent U waves after T waves in hypokalemia.
  • ST-segment depression
  • Ventricular arrhythmias (eg, premature ventricular contractions [PVCs], torsade de pointes, ventricular fibrillation) [9]
  • Atrial arrhythmias (eg, premature atrial contractions [PACs], atrial fibrillation)

Thyroid screening studies - Thyroid-stimulating hormone (TSH), free T3, and free T4 in patients with tachycardia, especially Asian patients [11]

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