Pediatric Hypokalemia Workup

Updated: Nov 11, 2015
  • Author: Michael J Verive, MD, FAAP; Chief Editor: Timothy E Corden, MD  more...
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Workup

Laboratory Studies

The following studies are indicated in patients with hypokalemia:

  • Serum electrolyte tests: Screen for concurrent electrolyte abnormalities, which may affect treatment.

  • Blood gas analysis: Assess acid-base status; alkalosis may induce hypokalemia, and treatment of acidosis may worsen existing hypokalemia.

  • Drug screen (serum or urine): Amphetamines and other sympathomimetic stimulants can cause hypokalemia; other drugs that can cause hypokalemia include verapamil (with overdose), theophylline, amphotericin B, aminoglycosides, and cisplatin.

  • Serum adrenocorticotropic hormone (ACTH), cortisol, renin activity, and aldosterone tests: Evaluate for suspected Cushing, Conn, or adrenal hyperplasia syndromes, including 11-beta-hydroxylase deficiency.

  • Simultaneous serum insulin and C-peptide tests: Because hyperinsulinism can cause transient hypokalemia, elevated serum insulin without appropriately elevated C-peptide suggests exogenous insulin administration, which may represent Münchhausen-by-proxy syndrome.

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Imaging Studies

Magnetic resonance imaging

Perform brain magnetic resonance imaging (MRI) if a brain or pituitary tumor is suspected as a cause of hypercortisolism.

Ultrasonography and computed tomography scanning

Perform abdominal ultrasonography or computed tomography (CT) scanning if an adrenal tumor or hyperplasia is suspected.

Electrocardiography

Although ECG changes may be helpful if present, their absence should not be taken as reassurance of normal cardiac conduction. [12] The ECG in hypokalemia may appear normal or may have only subtle findings immediately before clinically significant dysrhythmias.

ECG findings may include the following (see the image below):

  • Ventricular dysrhythmia

  • Prolongation of QT interval

  • ST-segment depression

  • T-wave flattening

  • Appearance of U waves

    Prominent U waves after T waves in hypokalemia. Prominent U waves after T waves in hypokalemia.

During therapy, monitor for changes associated with overcorrection and hyperkalemia, including a prolonged QRS, peaked T waves, bradyarrhythmia, sinus node dysfunction, and asystole.

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