From the Guidelines
Normal saline (NS) contains a higher sodium concentration than Ringer's lactate (RL), with 154 mmol/L of sodium in NS compared to 130 mmol/L in RL, as reported in the most recent study 1. This difference of 24 mmol/L is clinically significant when considering fluid replacement therapy.
- Normal saline is isotonic but contains only sodium and chloride ions, making it slightly more acidic due to its high chloride content.
- Ringer's lactate, on the other hand, has a more physiologic electrolyte composition that includes potassium, calcium, and lactate in addition to sodium and chloride. The lactate in RL is metabolized to bicarbonate in the liver, giving it a mild alkalinizing effect compared to NS. When choosing between these fluids, consider that NS may be preferred in patients with hyperkalemia or severe liver dysfunction, while RL may be better for patients at risk for acidosis or those requiring large volume resuscitation, as it's less likely to cause hyperchloremic metabolic acidosis, as suggested by the guidelines for the choice of intravenous fluids for vascular filling in critically ill patients 1. The most recent study 1 provides the most up-to-date information on the composition of NS and RL, and its findings should be prioritized when making clinical decisions. Key points to consider when choosing between NS and RL include the patient's electrolyte balance, acid-base status, and the potential for large volume resuscitation, as well as the presence of any underlying conditions that may affect the choice of fluid, such as hyperkalemia or liver dysfunction 1.
From the Research
Sodium Levels in Normal Saline and Ringer's Lactate
- Normal saline (NS) contains 154 mEq/L of sodium, whereas Ringer's lactate (RL) contains 130 mEq/L of sodium 2.
- The difference in sodium levels between NS and RL can affect the choice of fluid for rehydration in various clinical settings.
Comparison of Sodium Levels in Studies
- A study comparing RL and NS for rehydration in children with acute diarrhea and severe dehydration found that both fluids were equivalent in terms of change in serum sodium levels from baseline 2.
- Another study found that the improvement in pH from baseline was not significant between RL and NS groups, but children in the RL group required less fluids and had shorter hospital stays 3.
- A study on healthy volunteers found that changes in serum electrolyte concentrations and acid-base status after rapid infusion of 2 liters of either isotonic sodium chloride or Ringer lactate solution were small and statistically insignificant 4.
Clinical Implications
- The choice of fluid for rehydration may depend on various factors, including the patient's underlying condition, serum electrolyte levels, and acid-base status 5, 6.
- The measurement of urine sodium (UNa) may not be a reliable indicator of saline responsiveness in patients with severe hyponatremia, and clinical evaluation of volume status is important 6.