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Pediatric Hyperkalemia Workup

  • Author: Michael J Verive, MD, FAAP; Chief Editor: Timothy E Corden, MD  more...
Updated: Jan 08, 2016

Laboratory Studies

Laboratory studies depend on the etiology of hyperkalemia but may include the following:

  • Serum electrolyte tests
  • Serum BUN and creatinine tests
  • Urinalysis (UA)

Depending on the etiology or on clinical suspicion, other studies to consider include the following:

  • Arterial or free-flowing venous blood gas sampling (for acid-base disorders): Capillary blood gas sampling should not routinely be used to evaluate for hyperkalemia due to significant risks of factitious hyperkalemia.
  • Serum uric acid and phosphorous tests (for tumor lysis syndrome)
  • Serum creatinine phosphokinase (CPK) and calcium measurements (for rhabdomyolysis)
  • Urine myoglobin test (for crush injury or rhabdomyolysis; suspect if UA reveals blood in the urine but no RBCs are seen on urine microscopy)
  • Specific drug level tests for suspected toxicity (digoxin)
  • CBC count (for thrombocytosis, leukocytosis, or malignancy)
  • Urine electrolyte tests, including potassium and osmolality (osm) tests
  • Plasma osm test

When the etiology of hyperkalemia remains unclear, calculation of the transtubular potassium gradient (TTKG) using the following formula may be useful: TTKG = (K+ urine X Osm plasma)/(K+ plasma X Osm urine)

The normal TTKG varies from 5-15. In the setting of hyperkalemia with normal renal excretion of potassium, the TTKG should be greater than 10. A TTKG of less than 8 in the setting of hyperkalemia implies inadequate potassium excretion, which is usually secondary to aldosterone deficiency or unresponsiveness. Checking a serum aldosterone level may be helpful.



An ECG is essential in all children in whom hyperkalemia is suspected. ECG reveals the sequence of changes as follows:

  • Serum K + 5.5-6.5 mEq/L - Tall, peaked T waves with narrow base, best seen in precordial leads (as is shown in the image below)
    Peaked T waves. Peaked T waves.
  • Serum K + 6.5-8.0 mEq/L - Peaked T waves, prolonged PR interval, decreased or disappearing P wave, widening of QRS, amplified R wave
  • Serum K + greater than 8.0 mEq/L - Absence of P wave; progressive QRS widening, intraventricular/fascicular/bundle branch blocks; progressive widening of QRS, eventually merging with the T wave just before cardiac arrest, forming the sine wave pattern (as is shown in the image below)
    Sinusoidal wave. Sinusoidal wave.

Imaging Studies

Imaging studies are not generally indicated, except to assess the primary disease state (eg, excluding obstructive uropathy as a cause for acute renal failure).

Contributor Information and Disclosures

Michael J Verive, MD, FAAP Pediatrician, UP Health System Portage

Michael J Verive, MD, FAAP is a member of the following medical societies: American Academy of Pediatrics, Society for Pediatric Sedation

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Barry J Evans, MD Assistant Professor of Pediatrics, Temple University Medical School; Director of Pediatric Critical Care and Pulmonology, Associate Chair for Pediatric Education, Temple University Children's Medical Center

Barry J Evans, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Chest Physicians, American Thoracic Society, Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Chief Editor

Timothy E Corden, MD Associate Professor of Pediatrics, Co-Director, Policy Core, Injury Research Center, Medical College of Wisconsin; Associate Director, PICU, Children's Hospital of Wisconsin

Timothy E Corden, MD is a member of the following medical societies: American Academy of Pediatrics, Phi Beta Kappa, Society of Critical Care Medicine, Wisconsin Medical Society

Disclosure: Nothing to disclose.

Additional Contributors

G Patricia Cantwell, MD, FCCM Professor of Clinical Pediatrics, Chief, Division of Pediatric Critical Care Medicine, University of Miami Leonard M Miller School of Medicine/ Holtz Children's Hospital, Jackson Memorial Medical Center; Medical Director, Palliative Care Team, Holtz Children's Hospital; Medical Manager, FEMA, South Florida Urban Search and Rescue, Task Force 2

G Patricia Cantwell, MD, FCCM is a member of the following medical societies: American Academy of Hospice and Palliative Medicine, American Academy of Pediatrics, American Heart Association, American Trauma Society, National Association of EMS Physicians, Society of Critical Care Medicine, Wilderness Medical Society

Disclosure: Nothing to disclose.

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Peaked T waves.
Sinusoidal wave.
Hyperkalemia diagnosis and treatment flow chart.
Table. Select Factors Affecting Plasma Potassium
Factor Effect on Plasma K+ Mechanism
Aldosterone Decrease Increases sodium resorption, and increases K+ excretion
Insulin Decrease Stimulates K+ entry into cells by increasing sodium efflux (energy-dependent process)
Beta-adrenergic agents Decrease Increases skeletal muscle uptake of K+
Alpha-adrenergic agents Increase Impairs cellular K+ uptake
Acidosis (decreased pH) Increase Impairs cellular K+ uptake
Alkalosis (increased pH) Decrease Enhances cellular K+ uptake
Cell damage Increase Intracellular K+ release
Succinylcholine Increase Cell membrane depolarization
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