ABSTRACT
Potassium is an essential macroelement, vital in the maintenance of normal water balance, neurotransmission, and muscle and enzymatic activity. Present in cells at high concentrations, potassium is the principal intracellular metal ion. The extracellular concentration of K is maintained at 5 mM, the intracellular at 140 mM (1). The normal homeostatic mechanism maintains steady levels of the metal ion in the body, despite wide fluctuations in intake. Absorption of excessive amounts of potassium may have toxic consequences (2), particularly if an imbalance in normal Na levels is induced. Extracellular (serum) potassium acts as an indicator of total potassium status; it rises and falls only once intracellular levels exceed or fall below capacity. Those intracellular values can be subject to major fluctuations while serum levels remain constant. It is the extracellular concentration of potassium that produces major untoward effects; a 3% increase of serum levels will cause fatal hyperkalemia, usually observed in cases of severe renal failure. The fatal dose of potassium (as K2CO3) is 15 g in the average adult. Potassium deficiency or hypokalemia (serum concentrations below 3 mEq/L) becomes manifest by muscular weakness, increased nervous irritability, disorientation, cardiac irregularities, and, ultimately paralysis and respiratory failure.
