Electrolyte & Free Water

In hypovolemic hypernatremia, the patient has a deficit in both water and sodium. Initial resuscitation should focus on volume (Normal Saline) before switching to free water (D5W) to correct tonicity.

The Free Water Deficit formula is based on the principle of conservation of mass. It assumes that total body sodium remains constant during the shift, allowing for the calculation of the volume of water needed to return the existing sodium concentration to a physiologic normal (140 mEq/L).

A giant in the field of acid-base and electrolyte physiology. His work at Tufts University provided clinicians with the mathematical framework (including the Adrogué-Madias equation) to predict how much a given liter of IV fluid will change the serum sodium concentration.