Daily Bolus of LR: Hyponatremia

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December 4, 2012 by dailybolusoflr

Hyponatremia
Is an inability of the body to match the intake of sodium, potassium, and water compared to its losses resulting in an abnormally low sodium level. Levels <120 are regarded as severe cases, but clinical manifestations vary widely even with similar sodium levels between patients. Acute hyponatremia results in brain swelling and intracranial hypertension leading to seizures, coma, herniation, and respiratory arrest. Chronic hyponatremia (at least 2 days) have more modest symptoms including cognitive deficits, gait disturbances, and propensity to falls. When in question, assume the hyponatremia is chronic to avoid demyelination from rapid correction.
Symptoms of demyelination (typically noted in 1-7 days after overcorrection) include:
·      hyperreflexia
·      quadriparesis
·      parkinsonism
·      locked-in syndrome
·      death
Management pearls:
·      Determining volume status is important
·      Remove potential offending agents (thiazides, SSRIs, oxytocin) and fluid restrict
·      Most will not require urgent management, treat those with severe hyponatremia and with neurologic deficits
·      Promptly but gently correct hypokalemia (K retention affects Na retention, K repletion will increase serum Na levels), potassium depletion or aggressive K repletion increases risk for demyelination
·      Correct serum Na by 4-6 mEq/L within 4-6 hours in hyponatremia encephalopathy, typically with continuous 3% normal saline infusion.
·      If seizures occur, a 100 mL bolus of 3% normal saline, up to three total doses at 10-minute intervals is the treatment of choice.
·      Do not exceed 6-8 mEq/L in 24h period to prevent demyelination (typically occurring at 9-10 mEq/L in 24h.)
·      D5W infusion and DDAVP can be used to relower sodium concentrations
·      Q2-4 hour vitals, neuro checks, serum electrolytes, and fluid balance

·      ICU admission for severe, symptomatic hyponatremia
Courtesy of Dr. Ryan Circh
Reference:
The Challenge of Hyponatremia
Adrogue HJ, Madias NE. J Am Soc Nephrol. 2012 Ju;23(7):1140-8

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