Causes of hypokalemia

Spurious hypokalemia: high number of metabolically active cells present in blood absorb the ECF potassium.

Decreased net intake

• GI or renal losses

Shift into cells

• Alkalemia

• Insulin

• Catecholamines

• Hypokalemic periodic paralysis

Increased net loss

• Nonrenal loss:

  • Lower GI tract losses.

  • Hypokalemia from vomiting is due to renal K secretion from secondary hyperaldosteronism. Diaphoresis

• Renal loss: Accounts for most cases of chronic hypokalemia.

  • Augmented distal urine flow rate: diuretic use and osmotic diuresis (glucosuria). Bartter's and Gitelman's syndromes mimic diuretic use.

  • Disorder that promote K+ loss by increasing the lumen-negative gradient, which drives K+ secretion. This can be achieved with reabsorption of a cation (Na+) or presence of a nonreabsorbed anion (HCO3 - metabolic alkalosis or type 2 RTA, ketones, and hippurate from toulene intoxication or glue sniffing).

  • Distal Na+ reabsorption is influences by mineralocorticoid activity.

  • Primary mineralocorticoid excess seen in primary hyperaldosteronism due to an adenoma or adrenocortical hyperplasia.

  • Cushing's syndrome (excess cortisol)

  • Secondary hyperaldosteronism can be seen in any situation with a decreased effective circulating volume

  • Liddle's synd.