From the Research
Free water flushes lower sodium levels in the body through a process called dilution, which is crucial in treating hypernatremia, and the most recent and highest quality study 1 supports this mechanism. When a person drinks water without electrolytes (free water), it gets absorbed into the bloodstream and dilutes the concentration of sodium in the blood. This dilution effect occurs because the total amount of sodium in the body remains relatively constant while the volume of fluid increases. The kidneys then work to maintain balance by excreting excess water along with some sodium, but if free water intake exceeds the kidneys' ability to excrete it, the sodium concentration in the blood decreases further. Some key points to consider when using free water flushes to lower sodium levels include:
- The rate of sodium correction should generally not exceed 8-10 mEq/L in 24 hours to avoid complications like cerebral edema, as noted in 2 and 1.
- Careful monitoring of serum sodium levels is essential during treatment to ensure appropriate correction rates and prevent overcorrection, as emphasized in 3 and 4.
- Free water can be administered orally if the patient can drink, or intravenously as D5W (5% dextrose in water) which effectively becomes free water once the dextrose is metabolized, as mentioned in 2 and 1.
- The overall osmolality should always be considered, and overall changes in osmolality correspond to the effect on the cellular stress situation and have to be taken into account and balanced slowly, as discussed in 1.