What is Potassium Imbalance ?
Potassium - a cation and the dominant cellular electrolyte-facilitates contraction of both skeletal and smooth muscles, including myocardial contraction. It figures prominently in nerve impulse conduction, acid-base balance, enzyme action, and cell membrane function. Because serum potassium level has such a narrow range (3.5 to 5 mEq/L), a slight deviation in either direction can produce profound consequences.
Causes of Potassium Imbalance
Hypokalemia rarely results from a dietary deficiency because many foods contain potassium. Instead, potassium loss results from:
Hyperkalemia usually results from reduced excretion by the kidneys. This may be due to acute or severe chronic renal failure, oliguria due to shock or severe dehydration, or the use of potassium-sparing diuretics such as triamterene by patients with renal disease. Inadequate potassium excretion may also be due to hyperaldosteronism or Addison's disease.Hyperkalemia may also result from failure to excrete excessive amounts of potassium infused l.V. or administered orally. Another cause is massive release of intracellular potassium, such as can occur with burns, crushing injuries, severe infection, or acidosis.
Signs & Symptoms of Potassium Imbalance
Signs of potassium deficiency include:
Electrocardiograph changes accompanying hypokalemia are ST depression, flat T waves, U waves and dysrhythmias. The pulse will be fast, then slow. If digitalized, monitor for digitalis toxicity.
Serum potassium levels allow definitive diagnosis of a porassium abnormality. In hypokalemia, potassium levels are less than 3.5 mEq/L. In hyperkalemia, levels are more than 5 mEq/L.
Additional tests may be necessary to determine the underlying cause of the imbalance.
Hypokalemia treatment should involve increased dietary intake of potassium or oral supplements with potassium salts. Potassium chloride is the preferred choice. Edematous patients with diuretic-induced hypokalemia should receive a potassium-sparing diuretic such as spironolactone.
Patients with GI potassium loss or severe potassium depletion require I.V. potassium replacement therapy. If hypocalcemia is also present, treatment should include calcium replacement.
For patients with hyperkalemia, treatment consists of withholding potassium and administering a carion exchange resin orally or by enema. Sodium polystyrene sulfonate (Kayexalate) with 70% sorbitol exchanges sodium ions for potassium ions in the intestine.
In an emergency, rapid infusion of 10% calcium gluconate decreases myocardial irritability and temporarily prevents cardiac arrest but doesn't correct serum potassium excess; it's also contraindicated in patients receiving digoxin.Also as an emergency measure, sodium bicarbonate I.V. increases pH and causes potassium to shift back into the cells. Insulin and 10% to 50% glucose I.V. also move potassium back into cells. Infusions should be followed by dextrose 5% in water because infusion of 10% to 15% glucose stimulates secretion of endogenous insulin. Hemodialysis or peritoneal dialysis also helps remove excess potassium, but these are slow techniques.
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