Estimate the volume of free water required to correct hypernatremia based on serum sodium levels and total body water.
Total Body Water (TBW):
0 Liters
Free Water Deficit (FWD):
Note: Correction should typically not exceed 10-12 mEq/L per 24 hours to avoid cerebral edema.
The Free Water Deficit calculation determines the volume of pure water required to return a high serum sodium level back to a specified normal target level. This is crucial in managing hypernatremia safely.
Formula: FWD = TBW × [(Current Na / Target Na) - 1]
FWD = TBW × [(Current Na / Target Na) - 1]
Example: A 70kg adult male with a current sodium of 160 mEq/L and a target of 140 mEq/L.
This calculation helps clinicians estimate the volume of hypotonic fluids needed to correct electrolyte imbalances while monitoring patient response closely.
What is a safe rate of sodium correction?Generally, aim for a decrease of no more than 0.5 mEq/L per hour or 10-12 mEq/L per day to avoid cerebral edema.
Does this include maintenance fluids?No, this only calculates the static deficit; maintenance requirements and ongoing losses must be calculated and added separately.
Which water factor should I use?Factors depend on age, biological sex, and muscle mass, as muscle tissue contains significantly more water than adipose tissue.
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