eMedicine Specialties > Emergency Medicine > Endocrine & Metabolic

Hypokalemia: Differential Diagnoses & Workup

Author: David Garth, MD, Attending Physician, Department of Emergency Medicine, Mary Washington Hospital
Contributor Information and Disclosures

Updated: Jul 31, 2009

Differential Diagnoses

Cushing Syndrome
Hypocalcemia
Hypomagnesemia

Other Problems to Be Considered

Medication side effect
Renal tubular acidosis
Thyrotoxic hypokalemic periodic paralysis6

Workup

Laboratory Studies

  • Serum potassium level <3.5 mEq/L (3.5 mmol/L)7
  • 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.

Imaging Studies

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

Other Tests

  • Electrocardiography
    • T-wave flattening or inverted T waves
    • Prominent U wave that appears as QT prolongation (see Media file 1)


Prominent U waves after T waves in hypokalemia.

Prominent U waves after T waves in hypokalemia.

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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)5
    • 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 patients6

More on Hypokalemia

Overview: Hypokalemia
Differential Diagnoses & Workup: Hypokalemia
Treatment & Medication: Hypokalemia
Follow-up: Hypokalemia
Multimedia: Hypokalemia
References
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References

  1. ECC Committee, Subcommittees and Task Forces of the American Heart Association. 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. Dec 13 2005;112(24 Suppl):IV1-203. [Medline]. [Full Text].

  2. Latronico N, Shehu I, Seghelini E. Neuromuscular sequelae of critical illness. Curr Opin Crit Care. Aug 2005;11(4):381-90. [Medline].

  3. Ingram TC, Olsson JM. In brief: hypokalemia. Pediatr Rev. Sep 2008;29(9):e50-1. [Medline].

  4. Seigel JD, Di Palma JA. Medical treatment of constipation. Clin Colon Rectal Surg. 2005;18(2):76-80.

  5. Reactions Weekly. Dextrose: First report of ventricular arrhythmia: case report. Reactions Weekly. 2005;1046:11.

  6. Goldberger ZD. Images in cardiovascular medicine. An electrocardiogram triad in thyrotoxic hypokalemic periodic paralysis. Circulation. Feb 13 2007;115(6):e179-80. [Medline].

  7. Assadi F. Diagnosis of hypokalemia: a problem-solving approach to clinical cases. Iran J Kidney Dis. Jul 2008;2(3):115-22. [Medline].

  8. Cohn JN, Kowey PR, Whelton PK, Prisant LM. New guidelines for potassium replacement in clinical practice: a contemporary review by the National Council on Potassium in Clinical Practice. Arch Intern Med. Sep 11 2000;160(16):2429-36. [Medline].

  9. Dominiczak AF, Semple PF, Fraser R, Lever AF, Wallace AM. Hypokalaemia in alcoholics. Scott Med J. Aug 1989;34(4):489-94. [Medline].

  10. Gennari FJ. Hypokalemia. N Engl J Med. Aug 13 1998;339(7):451-8. [Medline].

  11. Halperin ML, Kamel KS. Potassium. Lancet. Jul 11 1998;352(9122):135-40. [Medline].

  12. Howes LG. Which drugs affect potassium?. Drug Saf. Apr 1995;12(4):240-4. [Medline].

  13. Kleinfeld M, Borra S, Gavani S, Corcoran A. Hypokalemia: are elderly females more vulnerable?. J Natl Med Assoc. Nov 1993;85(11):861-4. [Medline].

  14. Küng M. Parenteral adrenergic bronchodilators and potassium. Chest. Mar 1986;89(3):322-3. [Medline].

  15. Mandal AK. Hypokalemia and hyperkalemia. Med Clin North Am. May 1997;81(3):611-39. [Medline].

  16. Paice BJ, Paterson KR, Onyanga-Omara F, Donnelly T, Gray JM, Lawson DH. Record linkage study of hypokalaemia in hospitalized patients. Postgrad Med J. Mar 1986;62(725):187-91. [Medline].

  17. Singhal PC, Venkatesan J, Gibbons N, Gibbons J. Prevalence and predictors of rhabdomyolysis in patients with hypokalemia. N Engl J Med. Nov 22 1990;323(21):1488. [Medline].

  18. Walters EG, Barnes IC. A survey of hypokalaemia in patients of general practitioners. Br J Clin Pract. May 1988;42(5):192-5. [Medline].

  19. Zull DN. Disorders of potassium metabolism. Emerg Med Clin North Am. Nov 1989;7(4):771-94. [Medline].

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Further Reading

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Keywords

hypokalemia, low potassium, potassium level less than 3.5 mEq/L, potassium homeostasis, palpitations, skeletal muscle weakness, cramping, paralysis, paresthesias, abdominal cramping, ventricular arrhythmias, premature atrial beats, premature ventricular beats, respiratory distress, hypoventilation, respiratory failure, lethargy, fasciculations, tetany, hyperaldosteronism, magnesium depletion, ileal loop, diuretics, alkalosis, decreased tendon reflexes, cushingoid appearance

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Contributor Information and Disclosures

Author

David Garth, MD, Attending Physician, Department of Emergency Medicine, Mary Washington Hospital
David Garth, MD is a member of the following medical societies: American Academy of Emergency Medicine and American College of Emergency Physicians
Disclosure: Nothing to disclose.

Medical Editor

Robin R Hemphill, MD, MPH, Associate Professor, Director, Quality and Safety, Department of Emergency Medicine, Emory University
Robin R Hemphill, MD, MPH is a member of the following medical societies: American College of Emergency Physicians and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Howard A Bessen, MD, Professor of Medicine, Department of Emergency Medicine, UCLA School of Medicine; Program Director, Harbor-UCLA Medical Center
Howard A Bessen, MD is a member of the following medical societies: American College of Emergency Physicians
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Erik D Schraga, MD, Consulting Staff, Department of Emergency Medicine, Mills-Peninsula Emergency Medical Associates; Consulting Staff, Permanente Medical Group, Kaiser Permanente, Santa Clara Medical Center
Disclosure: Nothing to disclose.

 
 
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