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Potassium disorders encompass hypokalemia (serum K+ <3.5 mEq/L) and hyperkalemia (serum K+ >5.0 mEq/L), representing critical electrolyte imbalances with potentially life-threatening consequences. These conditions affect cellular membrane potential and can lead to severe cardiac arrhythmias, muscle weakness, and paralysis if left untreated.
Potassium is primarily an intracellular cation maintained by the Na+/K+-ATPase pump, with normal serum levels tightly regulated between 3.5-5.0 mEq/L through renal excretion and cellular uptake mechanisms. Hypokalemia results from inadequate intake, excessive losses (diarrhea, diuretics), or transcellular shifts, while hyperkalemia occurs due to impaired renal excretion, tissue breakdown, or transcellular shifts from cells to extracellular space.
Clinical presentation varies with severity and rate of change, with hypokalemia causing muscle weakness, cramping, and potentially fatal arrhythmias, while hyperkalemia presents with similar neuromuscular symptoms but carries higher risk of sudden cardiac death. ECG changes serve as crucial diagnostic markers, showing U-waves and ST depression in hypokalemia, and peaked T-waves progressing to wide QRS complexes in hyperkalemia, guiding urgent treatment decisions.