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Free Water Deficit
Calculate free water deficit in hypernatremia to guide fluid replacement and rate of correction.
Indication
- Calculate free water deficit in hypernatremia to guide fluid replacement and rate of correction.
Criteria
- id: na; label: Serum sodium (mEq/L); type: number; placeholder: e.g. 160
- id: weight; label: Weight (kg); type: number; placeholder: e.g. 70
- id: sex; label: Sex / TBW factor; type: options; options: value: male; label: Male (0.6); value: female; label: Female (0.5); value: emale; label: Elderly male (0.5); value: efemale; label: Elderly female (0.45)
- id: desired; label: Desired sodium (mEq/L); type: number; placeholder: default 140
Clinical pearls
- Never correct chronic hypernatremia too rapidly — overcorrection causes cerebral edema, seizures, and herniation
- Acute hypernatremia (<24 h) can be corrected faster (1–2 mEq/L/hr)
- D5W is the most effective fluid for free water replacement
- Always replace ongoing losses in addition to the calculated deficit
Source and review
- Adrogue HJ and Madias NE. NEJM 2000. Last reviewed: 2025-01-01