Hypertonic Saline: Hypertonic saline is a crystalloid intravenous fluid composed of NaCl dissolved in water with a higher concentration of sodium compared to normal blood serum. Both 3% and 5% hypertonic saline (HS) is currently FDA-approved for use in hyponatremia and increased intracranial pressure (ICP). Patients with hyponatremia with severe features should have their serum sodium gradually corrected with boluses of hypertonic saline. Patients should have their serum sodium monitored at regular intervals and can receive multiple boluses a day. Hypertonic saline should be discontinued once the patient’s symptoms improve or they have an adequate increase in serum sodium. Cerebral edema and elevated intracranial pressure (ICP) are significant causes of morbidity and mortality in patients with intracranial tumors, cerebral hematomas, traumatic brain injuries, cerebral infarcts, and intracranial hemorrhages. Hypertonic saline increases the osmolarity of the blood, which allows fluid from the extravascular space to enter the intravascular space, which leads to decreases in brain edema, improved cerebral blood flow, and decreased CSF production. Research shows that 3% hypertonic saline decreases ICP similarly to 20% mannitol. Both hypertonic fluids have similar effects on hemodynamics. Hypertonic saline leads to increases in serum sodium and has less of a diuretic effect than mannitol likely due to the increased serum sodium causing ADH release. Hypertonic saline administered after mannitol in traumatic brain injury has also been shown to improve cerebral oxygenation in addition to lowering ICP. Due to there being no guidelines regarding the administration of hypertonic saline for increased ICP, various studies have used concentrations of 3% to 23.5% NaCl.. While not FDA-approved, small doses of hypertonic saline are thought to be effective in hypovolemia and shock due to the movement of fluid from the intracellular to intravascular spaces, increasing intravascular fluid volume and improving capillary blood flow.
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