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The sodium correction calculator uses a formula presented by Adrogue and Madias to help estimate the effects of different IV fluids in the treatment of hyponatremia or hypernatremia. It predicts the change in serum sodium based on the administration of one liter of the described fluid.
expected change in Na = (infusate sodium concentration - serum sodium concentration)/(total body water + 1)
total body water = correction factor * weight
The correction factor is 0.6 for men, 0.5 for women and elderly men, and 0.45 for elderly women.
It does not take into account ongoing losses and complex physiology that may underly these conditions. Repeated, frequent monitoring of serum sodium during therapy is needed to ensure the treatment is achieving the desired effect.
nephromatic expands on this calculation by suggesting a flow rate and treatment duration that would be expected to correct the sodium to the goal level at a rate of 0.5 meq/L each hour. This rate is recommended to minimize risk of central pontine myelinolysis (in the case of hyponatremia) or cerebral edema (in the case of hypernatremia) due to excessively rapid correction.
liters infusate = |(serum sodium-goal sodium)|/expected change in Na per liter infusate
hours to correct = |(serum sodium-goal sodium)|/0.5
infusion rate = liters infusate/hours to correct
- Adrogué HJ and Madias NE. Hypernatremia. New Engl J Med 342(20): 1493-9, 2000.