Hyponatremia

First Things First (assess & treat for the following)

  • Hyponatremia is defined as a plasma sodium concentration < 135 MEq/L.
  • It is present in 6-22% of general hospital patients but in as many as 30% of ICU patients and is a significant predictor of mortality.
  • Is the hyponatremia real?
    • Laboratory error: repeat test
    • Spurious hyponatremia: blood drawn from vein w/ infusing hypotonic IV solution
  • Is pt symptomatic?
    • Most pts are asymptomatic.
    • Severity of signs & symptoms depends on rapidity of onset and absolute decrease in plasma sodium concentration. Major clinical manifestations are neurologic and are due to acute brain swelling or cerebral edema.
    • Symptoms of hyponatremia: Headache, lethargy, apathy, confusion, disorientation, muscle cramps, anorexia, nausea, agitation
    • Signs of hyponatremia: abnormal sensorium, depressed deep tendon reflexes, Cheyne-Stokes respiration, hypothermia, pathologic reflexes, seizures, stupor, coma
  • What is the pt’s volume status?
  • DIAGNOSIS: Hyponatremia is not a disease but a manifestation of variety of disorders. The underlying cause can often be ascertained from a careful history and physical examination, including the assessment of ECF volume and effective intravascular volume status.

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Last updated: May 5, 2010