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Hypokalemia

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Movement of K+ into cells may transiently decrease the plasma [K+] without altering total body K+ content. These shifts can result from alkalemia, insulin, and catecholamine release, periodic paralysis | Hypokalemia Definition Hypokalemia is defined as a plasma K 3.5 mEq L. Etiology decreased net intake is seldom the sole cause of K depletion because urinary excretion can be effectively decreased to 15 mEq d. shift into cells Movement of K into cells may transiently decrease the plasma K without altering total body K content. These shifts can result from alkalemia insulin and catecholamine release periodic paralysis increased net loss nonrenal Kali loss and renal kali loss Nonrenal K loss. Hypokalemia may result from the loss of potassium-rich fluids from the lower GI tract from the loss of upper GI contents is typically more attributable to renal K secretion from secondary hyperaldosteronism.excessive sweating Renal K loss accounts for most cases of chronic hypokalemia Augmented distal urine flow rate occurs commonly with diuretic use and osmotic diuresis Bartter s and Gitelman s syndromes Promote K loss by increasing the lumen-negative gradient Distal Na reabsorption Primary mineralocorticoid excess Secondary hyperaldosteronism Liddle s syndrome. DIAGNOSIS Clinical Presentation The clinical features of K depletion vary greatly and their severity depends in part on the degree of hypokalemia. Symptoms seldom occur unless the plasma K is 3.0 mEq L. Fatigue myalgias and muscular weakness or cramps of the lower extremities are common. Smooth muscle function may also be affected and may manifest with complaints of constipation or frank paralytic ileus. Severe hypokalemia may lead to complete paralysis hypoventilation or rhabdomyolysis. Diagnostic Testing renal K excretion and the acid-base status can help identify the cause Urine K . The appropriate response to hypokalemia is to excrete 25 mEq d of K in the urine. A transtubular potassium gradient TTKG can be calculated as follows TTKG Urine K Serum K Urine Osmolality Serum Osmolality A TTKG 2 suggests a nonrenal source while a TTKG 4 suggests inappropriate renal K secretion Acid-Base status. Intracellular shifting and