Hypokalemia is generally defined as a serum potassium level of less than 3.5 mEq/L in children, although exact values for reference ranges of serum potassium are age-dependent, and vary among laboratories. It is frequently present in pediatric patients who are critically ill and reflects a total body deficiency of potassium or, more commonly, reflects conditions that promote the shift of extracellular potassium into the intracellular space.Potassium is the most abundant intracellular cation and is necessary for maintaining a normal charge difference between intracellular and extracellular environments. Potassium homeostasis is integral to normal cellular function and is tightly regulated by specific ion-exchange pumps, primarily by cellular, membrane-bound, sodium-potassium adenosine triphosphatase (ATPase) pumps. Derangements of potassium regulation may lead to neuromuscular, GI, and cardiac conduction abnormalities.
Definition and Etiology
- Hypokalemia is defined as a serum potassium <3.5 mEq/L.
- It is a result of potassium losses in excess of replacement. Potassium can be lost through the GI tract as well as the kidneys.
- Hypokalemia may be due to a total body deficit of potassium, which may occur chronically with the following:
- Prolonged diuretic use
- Inadequate potassium intake
- Laxative use
- Diarrhea
- Hyperhidrosis
- Hypomagnesemia
- Acute causes of potassium depletion include the following:
- Diabetic ketoacidosis
- Severe GI losses from vomiting and diarrhea
- Dialysis and diuretic therapy
- Hypokalemia may also be due to excessive potassium shifts from the extracellular to the intracellular space, as seen with the following:
- Alkalosis
- Insulin use
- Catecholamine use
- Sympathomimetic use
- Hypothermia
- Other recognizable causes of hypokalemia include the following:
- Renal tubular disorders, such as Bartter syndrome and Gitelman syndrome
- Type I or classic distal tubular acidosis
- Periodic hypokalemic paralysis
- Hyperaldosteronism
- Other states of mineralocorticoid excess that may cause hypokalemia include the following:
- Cystic fibrosis with hyperaldosteronism from severe chloride and volume depletion
- Cushing syndrome
- Exogenous steroid administration, including fludrocortisone and other mineralocorticoids
- Excessive licorice consumption
- Other conditions that may cause hypokalemia include acute myelogenous, monomyeloblastic, or lymphoblastic leukemia.
- Drugs that may commonly cause hypokalemia include the following:
- Furosemide, bumetanide, and other loop diuretics
- Methylxanthines (theophylline, aminophylline, caffeine)
- Verapamil (with overdose)
- Amphotericin B
- Quetiapine (particularly in overdose)
- Ampicillin, carbenicillin, high-dose penicillin
- Drugs associated with magnesium depletion, such as aminoglycosides, amphotericin B, and cisplatin
Clinical Presentation and Physical Examination
- Symptoms: constipation, fatigue, muscle weakness, and paralysis
- Physical examination
- Check for possible irregular heartbeat.
- Evaluate for signs of muscle weakness/paralysis.
-
Differential Diagnosis
- Decreased intake as a result of low dietary intake or IV fluids without potassium
- Increased GI losses from vomiting, nasogastric suction, or diarrhea
- Increased urinary losses because of loop and thiazide diuretics
- Mineralocorticoid excess
- Liddle syndrome (autosomal dominant with increased sodium resorption)
- Bartter or Gitelman syndromes
- Amphotericin
- Hypomagnesemia
Treatment
- Administer oral or IV potassium supplements.
- Correct hypomagnesemia.
- Stop diuretics and amphotericin if possible.source:http://emedicine.medscape.com/article/907757-overview#a0199
Subscribe to email feed
