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  • image Blood volume and plasma osmolality are tightly regulated in the human body because they are essential for normal cellular function. Water balance determines the serum sodium concentration, and sodium balance determines the water status.
  • image Hypovolemic hypotonic hyponatremia is relatively common in patients taking thiazide diuretics; however, thiazide-induced hyponatremia is usually mild and relatively asymptomatic.
  • image Euvolemic (isovolemic) hyponatremia is most often caused by the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Common causes of SIADH include some cancers, central nervous system (CNS) and pulmonary disorders, and certain drugs.
  • image Symptoms of hypo- or hypernatremia are usually neurologic and range from weakness, lethargy, restlessness, irritability, and confusion to twitching, seizures, coma, and death. Symptom severity depends on both the magnitude of the change in the serum sodium concentration and the rate at which it changes.
  • image Treatment goals in patients with either hypo- or hypernatremia should include cautious correction of the serum sodium concentration and, when appropriate, restoration of a normal extracellular fluid (ECF) volume. Too rapid correction of the serum sodium can result in cerebral edema, seizures, neurologic damage, osmotic demyelination syndrome, and possibly death. To minimize the risk of these complications, the serum sodium concentration should be corrected at a rate not to exceed 6 to 12 mEq/L (6 to 12 mol/L) in 24 hours, depending on the rate of change in the serum sodium concentration.
  • image Asymptomatic or mildly symptomatic hyponatremia should be managed conservatively with treatment directed at the underlying cause. IV infusion of 0.9% NaCl solution is most often used to correct the serum sodium concentration in patients with moderate to severe symptoms from hypovolemic hypotonic hyponatremia. A 3% NaCl infusion can be cautiously used in patients with moderate to severe symptoms and euvolemic or hypervolemic hypotonic hyponatremia (along with a loop diuretic).
  • image Hypernatremia is always hypertonic and most commonly occurs when increased water or hypotonic fluid losses are not offset by increased water intake or administration.
  • image Hypovolemic hypernatremia is relatively common in patients taking loop diuretics. After symptoms of hypovolemia are corrected with 0.9% NaCl solution, free water should be replaced.
  • image Patients with central diabetes insipidus (DI) can be treated with desmopressin acetate, with a goal to decrease urine volume to less than 2 L per day while maintaining the serum sodium concentration between 137 and 142 mEq/L (137 and 142 mmol/L). Patients with nephrogenic DI should be treated by correcting the underlying cause, when possible, and sodium restriction in conjunction with a thiazide diuretic to decrease the ECF volume by approximately 1 to 1.5 L.
  • image Edema develops as a primary defect in renal sodium handling or as a response to a decreased effective circulating volume. It is usually first detected in the feet or pretibial areas of ambulatory patients. Pulmonary edema, evidenced by auscultatory crackles, can be life threatening.
  • image Diuretics are the primary pharmacologic means for minimizing edema and improving organ function. Diuretic resistance often can be overcome by using an increased dose or by using a combination of a loop diuretic and a ...

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