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.
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.
Hypokalemia may be due to a total body deficiency of potassium, which may result from prolonged inadequate intake or excessive losses (including but not limited to, long-term diuretic or laxative use, and chronic diarrhea, hypomagnesemia, or hyperhidrosis). Acute causes of potassium depletion include diabetic ketoacidosis,  severe GI losses due to vomiting and diarrhea, dialysis, and diuretic therapy.
Hypokalemia may also be the manifestation of large potassium shifts from the extracellular to intracellular space, as seen with alkalosis, insulin, catecholamines (including albuterol and other commonly-used beta2-adrenergic agonists), sympathomimetics, and hypothermia.
Other recognizable causes include renal tubular disorders, such as distal renal tubular acidosis, Bartter syndrome,  and Gitelman syndrome, periodic hypokalemic paralysis, hyperthyroidism, and hyperaldosteronism.
Other mineralocorticoid excess states that may cause hypokalemia include cystic fibrosis (with hyperaldosteronism from severe chloride and volume depletion), Cushing syndrome, and exogenous steroid administration. Excessive natural licorice consumption can also cause or exacerbate potassium loss due to inhibition of 11-betahydoxysteroid dehydrogenase, which leads to elevated endogenous mineralocorticoid activity. 
With adequate control of potassium levels and resolution of any predisposing condition, the prognosis is excellent.
Mortality is rare, except when hypokalemia is severe or occurs following cardiac surgery, when accompanied by arrhythmia, or in patients who have underlying heart disease and require digoxin therapy.
Short-term morbidity is common and may include GI hypomotility or ileus; cardiac dysrhythmia; QT prolongation; appearance of U waves that may mimic atrial flutter, T-wave flattening, or ST-segment depression; and muscle weakness or cramping.
Mortality and morbidity can also be related to treatment for hypokalemia with potassium supplementation, particularly if potassium is given in large doses or rapidly. Because of the risk associated with potassium replacement, alleviation of the cause of hypokalemia may be preferable to treatment, especially if hypokalemia is mild, asymptomatic, or transient and is likely to resolve without treatment.
Complications of hypokalemia include the following:
Hyperkalemia due to excessive/rapid potassium replacement
Racial differences may be present in predisposing conditions such as Bartter syndrome, Gitelman syndrome, Conn syndrome (ie, hyperaldosteronism), Cushing syndrome, and familial hypokalemic paralysis. In addition, significant hypokalemia and hypokalemic paralysis develop in 2-8% of Asians with hyperthyroidism.
No known sex predilection has been noted.
Viral GI infections tend to be more common in infants and younger children. Younger children with emesis or diarrhea are at an increased risk of hypokalemia because the depletion of fluid volume and electrolytes from GI loss is relatively higher than that found in older children and adults.
Insulin-dependent diabetes mellitus that results in diabetic ketoacidosis (with its inherent fluid and potassium loss) is more common in children. Excessive corticosteroid and mineralocorticoid secretion, as in Cushing syndrome and Conn syndrome, is a less common cause of hypokalemia in the pediatric patient. Periodic hypokalemic paralysis may appear in childhood or young adulthood, precipitated by rest after strenuous exercise, physical or metabolic stress (eg, exposure to cold, alcohol ingestion), a high-carbohydrate meal, or exposure to exogenous insulin or catecholamines (eg, epinephrine and albuterol). Hypokalemia due to hyperthyroidism is generally observed in adults.
What would you like to print?