Clinical meaning
Electrolytes are minerals that carry an electrical charge when dissolved in body fluids and are essential for virtually every physiological process including nerve impulse transmission, muscle contraction, cardiac conduction, fluid balance, acid-base regulation, and enzyme activation. The body maintains electrolyte concentrations within very narrow ranges, and deviations beyond these ranges can produce life-threatening emergencies requiring immediate recognition and intervention. Potassium is the major intracellular cation (normal serum level 3.5-5.0 mEq/L) and is critical for maintaining the resting membrane potential of cardiac and skeletal muscle cells. Only 2% of total body potassium is extracellular, making the serum potassium level an imperfect reflection of total body stores. The sodium-potassium ATPase pump actively maintains the potassium gradient by pumping 3 sodium ions out and 2 potassium ions into cells, maintaining a negative intracellular charge (approximately -90 mV). Hyperkalemia (serum potassium above 5.0 mEq/L) reduces the resting membrane potential, making cardiac cells more excitable initially but eventually blocking depolarization entirely, leading to cardiac arrest. The ECG changes of progressive hyperkalemia follow a predictable sequence: peaked T waves (earliest sign, above 5.5 mEq/L), prolonged PR...