Composition of Lactated Ringer's Solution
Lactated Ringer's solution contains sodium (130 mmol/L), chloride (109 mmol/L), potassium (4 mmol/L), calcium (1.4 mmol/L), and lactate (28 mmol/L) with an osmolarity of 273 mOsm/L. 1
Detailed Composition
Lactated Ringer's solution is a balanced crystalloid solution with the following components:
| Component | Concentration |
|---|---|
| Sodium (Na⁺) | 130 mmol/L |
| Chloride (Cl⁻) | 109 mmol/L |
| Potassium (K⁺) | 4 mmol/L |
| Calcium (Ca²⁺) | 1.4 mmol/L |
| Lactate | 28 mmol/L (as buffer) |
| Osmolarity | 273 mOsm/L |
| pH | 6-7.5 |
Comparison to Human Plasma
Lactated Ringer's is considered a "balanced" crystalloid because its electrolyte composition more closely resembles human plasma than other solutions like normal saline:
- Sodium: 130 mmol/L (vs. 135-145 mmol/L in plasma)
- Chloride: 109 mmol/L (vs. 95-105 mmol/L in plasma)
- Potassium: 4 mmol/L (vs. 3.5-5.3 mmol/L in plasma)
- Calcium: 1.4 mmol/L (vs. 2.2-2.6 mmol/L in plasma)
- Osmolarity: 273 mOsm/L (vs. 275-295 mOsm/L in plasma)
Lactate as a Buffer
The lactate in Lactated Ringer's (28 mmol/L) serves as a buffer that is metabolized by the liver to bicarbonate. This helps prevent the metabolic acidosis that can occur with large volumes of normal saline (0.9% NaCl) 1.
Standard Lactated Ringer's contains racemic lactate (a mixture of D- and L-stereoisomers). Research has shown that both forms are metabolized at similar rates, with both effectively increasing buffering capacity 2.
Clinical Implications
Acid-Base Balance: Lactated Ringer's causes less metabolic acidosis than normal saline due to its lower chloride content and the conversion of lactate to bicarbonate 1.
Effect on Serum Lactate: Despite containing lactate, properly administered Lactated Ringer's does not significantly increase serum lactate levels in hemodynamically stable patients. A study of healthy volunteers receiving 30 mL/kg of Lactated Ringer's showed only a modest increase in serum lactate (0.93 mmol/L) that was not statistically different from normal saline 3, 4.
Tonicity: Lactated Ringer's is slightly hypotonic (273 mOsm/L) compared to plasma (275-295 mOsm/L) 1.
Special Considerations
Hyperkalemia: Although Lactated Ringer's contains potassium (4 mmol/L), studies show it does not significantly worsen hyperkalemia, even in patients with elevated potassium levels 1.
Liver Disease: In severe liver failure, metabolism of lactate may be compromised, potentially affecting the buffering capacity of Lactated Ringer's 5.
Traumatic Brain Injury: Some guidelines suggest avoiding Lactated Ringer's in traumatic brain injury due to its slight hypotonicity 5.
Resuscitation Fluid: Lactated Ringer's is commonly used as a resuscitation fluid, with evidence suggesting improved outcomes compared to normal saline in conditions like acute pancreatitis 6.
Lactated Ringer's solution represents a balanced crystalloid option that closely mimics human plasma composition, making it suitable for a wide range of clinical applications where isotonic fluid replacement is needed.