Immediate Questions

A. Is patient symptomatic? Symptoms of hypokalemia include muscular weakness, gastric hypomotility, and cardiac disturbances (arrhythmia, premature atrial contractions [PACs], premature ventricular contractions [PVCs], flattened T waves, ST segment changes, U waves).

B. What medication(s) does child take? p-Agonists, penicillins, loop diuretics, steroids, laxatives, aminoglycosides, and amphotericin B may all contribute to hypokalemia. Hypokalemia can potentiate digitalis toxicity.

C. Is there a history of hypokalemia? A history of hypokalemia in the patient or a family member may point to associated syndromes or tumor.

III. Differential Diagnosis. To determine the etiology of hypokalemia, one must first decide which of five primary mechanisms exists: redistribution, renal loss, GI loss, other loss (sweating), or inadequate intake. A. Redistribution Hypokalemia. Potassium is primarily an intracellular ion; hence a small shift of this ion into the cell can cause a large change in plasma potassium concentration. Extracellular potassium can shift into the intracellular space in the setting of alkalosis, 0-agonist use, catecholamine excess, insulin administration, hypothermia, and familial periodic paralysis (autosomal dominant).

B. Renal Potassium Loss. Can be differentiated based on child's acid-base status.

1. With metabolic acidosis. Includes such disorders as type 1 and type 2 renal tubular acidosis, and diabetic ketoacidosis.

2. With metabolic alkalosis. Bartter syndrome, Gitelman syndrome, diuretic therapy, and mineralocorticoid excess (hyperal-dosteronism, Cushing syndrome, adrenal tumor, exogenous steroid administration).

3. Variable. Renal losses not associated with a specific acid-base imbalance occur with hypomagnesemia, some penicillins, aminoglycosides, amphotericin B, cisplatin, and osmotic diuresis.

C. GI Loss. The major source for extrarenal potassium loss occurs in the setting of colonic fluid loss, seen with diarrhea and laxative abuse. Severe vomiting can produce hypokalemia in patients with contraction alkalosis.

D. Other Loss. Copious sweating is the primary cause of potassium loss other than from kidney and GI tract.

E. Inadequate Intake. Produces hypokalemia over time as total body stores become depleted.

IV. Database. Data collection for hypokalemia serves two purposes. First, one must use data to determine the source of potassium depletion. Second, one must obtain data to assist in diagnosis of related disorders and to detect adverse consequences of hypokalemia. Most of the appropriate studies to perform will be based on information obtained by taking a thorough history. Review all medications child may be taking, including any home remedies administered.

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