Dextrose 5% in Lactated Ringer’s (D5 LR) is a standard intravenous solution used in hospital settings to manage patient fluid balance. This formulation combines a balanced electrolyte solution with a small amount of sugar, providing both hydration and minimal nutritional support. Administering D5 LR replaces lost water and electrolytes while offering a modest source of calories. This prevents the body from breaking down its own proteins for energy when patients cannot take fluids or nutrition by mouth.
Understanding the Components of D5 LR
D5 LR combines Dextrose 5% and Lactated Ringer’s solution. Each liter contains 50 grams of dextrose (glucose), contributing about 170 to 180 calories. The Lactated Ringer’s component is an electrolyte mixture that closely mimics the concentrations found in the body’s plasma.
This electrolyte base includes 130 milliequivalents (mEq) of Sodium, 4 mEq of Potassium, and 3 mEq of Calcium per liter. The solution also provides 109 mEq of Chloride and 28 mEq of Lactate. These components are dissolved in sterile water, resulting in a calculated osmolarity of approximately 525 to 530 milliosmoles per liter (mOsm/L). This concentration classifies D5 LR as hypertonic while it is in the bag, meaning it has a higher solute concentration than normal body fluids.
Physiological Action After Infusion
The hypertonic nature of D5 LR changes immediately upon entering the bloodstream due to dextrose metabolism. The body rapidly utilizes the 5% dextrose as a fuel source, converting the sugar into carbon dioxide and water. This swift metabolic process removes the dextrose from circulation, causing the solution to function effectively as a hypotonic fluid in vivo.
Since the fluid is functionally hypotonic, the free water allows for fluid shifting. Water moves from the vascular space into the interstitial space and then into the intracellular space. This movement hydrates the cells, making D5 LR effective for replacing intracellular fluid deficits and providing water for metabolic processes.
The lactate component acts as a precursor to bicarbonate. The liver converts lactate ions into bicarbonate, a natural buffer that helps regulate the body’s acid-base balance. This process provides a metabolic alkalinizing effect, which can help correct mild metabolic acidosis.
Specific Clinical Uses
D5 LR is selected when a patient requires maintenance intravenous fluid that balances multiple needs. The solution provides necessary water and electrolytes to sustain normal cellular function and maintain fluid volume. Its composition is useful for patients unable to eat or drink who require modest caloric intake to prevent ketosis (the breakdown of fat for energy).
The minimal caloric contribution prevents the body from entering a fasting state without delivering a large glucose load. Healthcare providers use D5 LR for post-operative fluid maintenance following surgery. The solution replenishes fluid lost during the procedure and supports metabolic demands during initial recovery.
D5 LR is also used during the transition phase of treating diabetic ketoacidosis (DKA). Once a patient’s blood glucose level drops, the dextrose content prevents a sudden drop into hypoglycemia while insulin therapy resolves the underlying ketoacidosis. This application utilizes the combination of electrolytes, buffer, and minimal glucose.
Safety Considerations and Monitoring
Administering D5 LR requires careful consideration and monitoring due to its specific components. A primary concern is the dextrose content, which can lead to hyperglycemia (high blood sugar), especially in patients with pre-existing diabetes or those experiencing physical stress. Providers must closely monitor serum glucose levels and adjust the fluid rate or administer insulin as necessary.
The solution’s volume and sodium content pose a risk of fluid overload (hypervolemia), particularly for patients with compromised kidney or heart function. Excessive fluid can lead to complications such as pulmonary edema (fluid accumulation in the lungs). Patients with conditions like congestive heart failure or renal insufficiency require cautious administration and close monitoring of their fluid status.
The lactate component is a contraindication for patients with severe liver failure, as the liver metabolizes lactate into bicarbonate. Impaired liver function can lead to lactate accumulation, potentially causing a metabolic imbalance. Monitoring serum electrolytes, including potassium and calcium, along with acid-base balance is necessary for patients receiving D5 LR over an extended period.