Dextrose 5% in Water (D5W) is a sterile intravenous fluid solution widely utilized in medical settings. It is one of the most frequently administered crystalloid solutions, serving as a fundamental tool for fluid and nutritional management. D5W is a clear, colorless liquid manufactured under sterile conditions for direct injection into a vein, providing both water and a form of sugar.
Composition and Physiological Effect
D5W contains 5 grams of dextrose (glucose) dissolved in every 100 milliliters of sterile water, equating to 50 grams per liter. This composition gives the solution an initial osmolarity of approximately 252 to 278 milliosmoles per liter (mOsm/L). Because this value is close to the osmolarity of human blood, D5W is initially considered isotonic when administered intravenously.
The physiological effect changes quickly because the body rapidly metabolizes the dextrose component. Dextrose is taken up by cells and converted into carbon dioxide and water, leaving behind only the water component. Once metabolized, the solution effectively becomes “free water” in the bloodstream, transforming it into a functionally hypotonic solution.
This hypotonic effect causes a shift in fluid dynamics within the body. Water moves via osmosis from the extracellular space, including the bloodstream, into the intracellular space. This movement allows D5W to effectively rehydrate the cells and expand the total body water volume. Each liter of D5W provides about 170 kilocalories, which is a minimal source of energy.
Primary Clinical Uses
The primary indication for D5W is the replacement of free water deficits, particularly when water loss exceeds electrolyte loss. This is the preferred treatment for hypernatremia (elevated sodium in the blood), because the free water component helps dilute the serum sodium without adding more electrolytes. The solution helps restore balance by encouraging water movement into dehydrated cells.
D5W is also frequently used as a minimal source of carbohydrate calories. Providing 50 grams of dextrose per liter helps prevent ketosis, a metabolic state occurring when the body breaks down fat for energy. This small caloric contribution also exerts a protein-sparing action, reducing the breakdown of the body’s protein stores during short periods when a patient cannot eat.
A significant application of D5W is its role as a vehicle or diluent for administering various medications. Many injectable drugs, such as certain antibiotics, are mixed with D5W before being delivered intravenously. This dilution helps ensure the medication is infused safely and slowly, and it may be necessary for drugs incompatible with saline-based solutions.
While not the primary therapy for severe acute low blood sugar, D5W helps maintain blood glucose levels in patients who are fasting or receiving other IV fluids without sugar. For significant hypoglycemia, higher concentrations like D50 (50% dextrose) are typically used. The rapid metabolism of dextrose ensures that the solution provides immediate fuel for cellular function and helps prevent glucose levels from dropping excessively.
Safety and Administration Guidelines
Despite its common use, D5W must be administered with careful consideration due to its functional hypotonic nature. The most significant concern is the risk of iatrogenic hyponatremia (low sodium levels caused by medical intervention). Rapid or excessive infusion of free water can dilute the serum sodium concentration, potentially leading to cerebral edema, or swelling of the brain.
Close monitoring of the patient’s blood glucose levels and serum electrolytes, especially sodium, is required during D5W administration. The infusion rate must be adjusted based on laboratory results and the patient’s clinical condition to prevent complications. Signs of confusion, headache, or other neurological changes may indicate a rapid shift in fluid balance.
D5W is avoided in patients with known or suspected increased intracranial pressure, such as those with acute ischemic stroke or closed head trauma. The risk of fluid moving into brain cells and exacerbating swelling makes hypotonic solutions unsafe in these situations.
The solution is also contraindicated in patients with uncontrolled diabetes or significant hyperglycemia, as the dextrose load can worsen high blood sugar. It should not be administered through the same line as a blood transfusion, as it may cause clumping of red blood cells. Caution is advised in patients with severe heart failure or kidney impairment who are susceptible to fluid overload.