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OVERVIEW OF HYPERKALEMIA

Hyperkalemia is defined as a plasma potassium level of 5.5 mM, occurring in up to 10% of hospitalized patients; severe hyperkalemia (>6.0 mM) occurs in ~1%, with a significantly increased risk of mortality. Although redistribution and reduced tissue uptake can acutely cause hyperkalemia, a decrease in renal K+ excretion is the most frequent underlying cause (Table 49-5). Excessive intake of K+ is a rare cause, given the adaptive capacity to increase renal secretion; however, dietary intake can have a major effect in susceptible patients, e.g., diabetics with hyporeninemic hypoaldosteronism and chronic kidney disease. Drugs that impact on the renin-angiotensin-aldosterone axis are also a major cause of hyperkalemia.

TABLE 49-5Causes of Hyperkalemia

PSEUDOHYPERKALEMIA

Hyperkalemia should be distinguished from factitious hyperkalemia or “pseudohyperkalemia,” an artifactual increase in serum K+ due to the release of K+ during or after venipuncture. Pseudohyperkalemia can occur in the setting of excessive muscle activity during venipuncture (e.g., fist clenching), a marked increase in cellular elements (thrombocytosis, leukocytosis, and/or erythrocytosis) with in vitro efflux of K+, and acute anxiety during venipuncture with respiratory alkalosis and redistributive hyperkalemia. Cooling of blood following venipuncture ...

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