Ringer's Lactate Composition Compared to 0.9% Normal Saline
Ringer's lactate (also called Lactated Ringer's solution) contains 130 mmol/L of sodium and 109 mmol/L of chloride, making it a balanced crystalloid solution, whereas 0.9% normal saline contains 154 mmol/L of both sodium and chloride. 1
Detailed Composition Comparison
Sodium Chloride 0.9% (Normal Saline)
- Sodium: 154 mmol/L 1
- Chloride: 154 mmol/L 1
- Na+:Cl- ratio: 1:1 (equal concentrations) 1
- Osmolarity: 308 mOsm/L 1
- pH: 4.5-7 1
- Contains no other electrolytes, buffers, or glucose 1
Lactated Ringer's Solution
- Sodium: 130 mmol/L 1
- Chloride: 109 mmol/L 1
- Potassium: 4 mmol/L 1, 2
- Calcium: 1.4 mmol/L 1
- Lactate (as buffer): 28 mmol/L 1
- Na+:Cl- ratio: 1.19:1 (more physiologic) 1
- Osmolarity: 273 mOsm/L 1, 2
- pH: 6-7.5 1
Key Clinical Differences
Tonicity
- Normal saline is isotonic with an osmolarity of 308 mOsm/L 1
- Lactated Ringer's is slightly hypotonic with an osmolarity of 273-277 mOsm/L compared to plasma (275-295 mOsm/L) 1, 2
Electrolyte Balance
- Lactated Ringer's has a more physiologic electrolyte composition that closely resembles plasma, with a balanced Na+:Cl- ratio of 1.19:1 versus the non-physiologic 1:1 ratio in normal saline 1, 2
- The lactate in Ringer's solution is metabolized to bicarbonate, providing buffering capacity 2, 3
Clinical Implications
- Lactated Ringer's is preferred over normal saline for most fluid resuscitation scenarios because it avoids hyperchloremic metabolic acidosis associated with large volumes of 0.9% saline 1, 2, 4
- In sepsis-induced hypotension, lactated Ringer's is associated with improved survival compared to normal saline (adjusted HR 0.71,95% CI 0.51-0.99) 5
- Normal saline should be avoided or limited to maximum 1-1.5L when possible due to risk of salt and fluid overload 1, 4
Important Contraindications for Lactated Ringer's
- Severe traumatic brain injury or head trauma: The hypotonic nature of Lactated Ringer's can worsen cerebral edema; use 0.9% saline instead 2, 4
- Rhabdomyolysis or crush syndrome: Avoid due to potassium content (4 mmol/L) which poses additional risk in these conditions 2
Common Pitfall to Avoid
The presence of 4 mmol/L potassium in Lactated Ringer's should not be considered a contraindication in patients with mild-to-moderate hyperkalemia or renal dysfunction, as this concentration is similar to normal plasma levels and large studies have shown no increased hyperkalemia risk 2, 4