Hypokalemia

Hypokalemia is defined as serum potassium concentration ([K⁺]) <3.5 mmol/L. The normal response to decreased plasma [K⁺] includes an immediate response (K⁺moves out of cells, H⁺moves in) and a delayed response (decreased renal excretion by suppression of aldosterone). Factors that affect K⁺distribution and transcellular shifts include acid-base status, insulin, catecholamines, aldosterone, and dietary intake.

Differential Diagnosis

• Diarrhea (very common)
  –May be related to infection
  –Other GI losses (e.g., ostomies)
  –Patients with eating disorders
  –Laxative abuse
• Vomiting (very common)
  –Potassium losses are primarily from the kidney, not the stomach
  –Loss of hydrogen ions and fluids leads to metabolic alkalosis, which causes movement of potassium into cells and aldosterone upregulation, which worsens hypokalemia and alkalosis
• Medications (causing renal K⁺wasting)
  –Diuretics
        –Loop diuretics (e.g., furosemide)
        –Thiazides (e.g., hydrochlorothiazide)
        –Diuretic abuse (eating disorder)
  –Aminoglycosides
  –Amphotericin
  –Cisplatin
  • Metabolic alkalosis from any cause stimulates potassium movement into cells in exchange for hydrogen ions
  • Medications that cause transcellular shifts
    –β-agonists (e.g., albuterol)
    –Insulin
    –Caffeine
    –Theophylline
  • Renal tubular acidosis
    –Type I, distal
    –Type II, proximal
  • Inherited tubular disorders (very rare)
    –Bartter/Gitelman syndromes
    –Liddle syndrome
  • Mineralcorticoid excess; hyperaldosteronism
    –Adrenal adenoma
    –Patients with hepatic dysfunction and decreased aldosterone metabolism
  • Familial periodic paralysis (very rare)
  • Impaired dietary intake (rare)
  • Hypomagnesemia
  • Fanconi syndrome
  • Cystic fibrosis (due to chloride depletion)
  • Licorice ingestion

  Workup and Diagnosis

  • History
    –Symptoms include weakness, fatigue, constipation, muscle cramps, hypertension, polyuria, enuresis (sign of tubular dysfunction)
    –GI losses (vomiting, diarrhea)
    –Past medical history including growth
    –History of eating disorder, laxative or diuretic use
    –History of hypertension
    –Medications
    –Family history: Kidney disease, recurrent weakness
  • Physical exam
    –Vital signs: Blood pressure, pulse
    –Assessment of hydration status (including pulse, blood pressure, skin turgor, mental status)
    –Growth parameters
    –Parotid enlargement (chronic vomiting/bulimia)
    –Abdominal masses, striae (glucocorticoid excess)
  • Labs
    –Serum chemistries, magnesium
    –Urinalysis
    –For patients with metabolic acidosis, urine chloride to distinguish GI (urine Cl^– <10 meq/L) from renal (urine Cl^– >10 meq/L) potassium losses
    –Diuretic screen
    –AM cortisol level
  • ECG
    –Findings include ST depression, flattened T waves, increased U waves

  Treatment

  • Dehydration: Rehydrate with potassium-containing IV fluids (or oral rehydration solutions)
  • Mild-moderate hypokalemia ([K⁺] >2.5 mmol/L)
    –Oral rather than IV repletion is preferred, unless patient is symptomatic or taking digoxin
  • Severe hypokalemia ([K⁺] <2.5 mmol/L)
    –IV repletion should be considered
    –Given by slow infusion at no more than 1 meq/kg over 4 hours; may require repeated infusions
    –Rapid infusion can cause life-threatening hyperkalemia
  • Adjust medications, if possible
  • Treat underlying endocrine disorders, if identified
  • Encourage consumption of high-potassium foods (bananas, tomatoes, oranges)
  • Replete magnesium if low
    –Hypokalemia may not be correctable until magnesium level is normal
  >>>

Book Source Details

• Book Title: In A Page: Pediatric Signs and Symptoms
• Author(s): Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan
• Year of Publication: 2007
• Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.

Other Book Chapters Related to Hypokalemia

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Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2008 Williams & Wilkins.

More About Causes of Hypokalemia

• Back to symptom: Hypokalemia: Introduction (review 147 causes)
• Next Book Extract About Hypokalemia: HYPOKALEMIA (Differential Diagnosis in Primary Care)
• All Book Extracts: All Online Book Extracts for Hypokalemia

More About This Book: Title: In A Page: Pediatric Signs and Symptoms Authors: Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-4051-0427-9

 » Next page: HYPOKALEMIA (Differential Diagnosis in Primary Care)

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