Analogous to the variety of beverages in your supermarket’s soda aisle, there exist numerous choices for fluids for patients. What is best for your patient’s needs? What fluid is appropriate for specific situations? How much fluid should be administered? Although these questions may seem trivial, the kneejerk reflex for most residents is to use a fluid that they feel most comfortable administering. Let us wade out of the “normal saline” pool and explore the clinical uses of hypertonic saline.

Fluids became the focus of prehospital resuscitation research more than 75 years ago. The same clinical problems encountered with fluid resuscitation efforts then remain the focus of today’s research. The search continues for an “ideal” fluid, i.e., one that is inexpensive, generates sustained hemodynamic effects with minimal peripheral or pulmonary edema, and is effective even in small volumes.

Traditionally, isotonic crystalloids such as lactated Ringer’s solution and normal saline have been considered first-line treatment for trauma patients. Although these fluids are inexpensive, readily available, nonallergenic, noninfectious, and efficacious in restoring total body fluid, they lack oxygen-carrying capacity and coagulation capability, and they have limited intravascular half-life. A proposed solution to the “solution problem” is to augment the osmotic properties of traditional resuscitation fluids. In theory, this would extend the intravascular half-life and reduce the amount of third spacing. The “ideal” fluid search then focused on osmotic properties, and hypertonic saline (with and without colloid) became a prime subject of research.

Hypertonic saline already had a role in the trauma setting, as it was used for patients with increased intracranial pressure secondary to traumatic head injury. Of note, mannitol (an osmotic diuretic and cerebral arteriolar vasoconstrictor) was traditionally used as first-line therapy in this patient population, but it was associated with rebound intracranial hypertension. It was believed that this effect was due to intravascular dehydration and an inability to maintain cerebral perfusion pressure when diuresis was not matched by appropriate fluid administration. Hypertonic saline became the agent of choice, as it served a dual purpose as a diuretic and a resuscitative agent.