Fluid Selection for Patient Care

Composition and Osmolality

Half Normal Saline contains 77 mEq/L of sodium and 77 mEq/L of chloride, and is a hypotonic solution with osmolality approximately 154 mOsm/L, according to the American College of Cardiology and Circulation guidelines 1, 2, 3

D5 half normal behaves as a hypotonic solution once the glucose is metabolized, effectively becoming free water plus electrolytes, and its dextrose distributes primarily into intracellular spaces, while the remaining electrolyte solution distributes into extracellular spaces, as stated by the American Journal of Kidney Diseases 4
The dual distribution pattern of D5 half normal makes it less effective for intravascular volume expansion compared to isotonic solutions, as recommended by the American College of Cardiology 4

Neither half normal saline nor D5 half normal is appropriate for intravascular volume expansion, and isotonic crystalloids such as 0.9% saline should be used as first-line fluids, according to the American Journal of Kidney Diseases and the American College of Cardiology 4

Half Normal Saline may be used for maintenance fluid in specific clinical contexts, and has been historically used as a "gold standard" for hydration before contrast procedures, as stated by the Journal of the American College of Cardiology and Circulation 1, 2
D5 Half Normal can be used for subcutaneous rehydration in geriatric patients when combined with appropriate dextrose concentrations, and may be appropriate for treating hypernatremia in hemodynamically stable patients, as recommended by Clinical Nutrition and Praxis Medical Insights 4, 5

D5 half normal should be avoided in patients with acute ischemic stroke or risk of cerebral edema, and in patients with need for intravascular volume expansion, as stated by Praxis Medical Insights 4
Half normal saline should be avoided in patients with hemodynamic instability requiring volume expansion, as recommended by Praxis Medical Insights 4