Why use quarter normal saline solution (NSS) instead of half normal saline solution (NSS)?

From the Guidelines

Quarter normal saline solution (NSS) is preferred over half normal saline solution (NSS) in certain clinical situations because it provides less sodium while still delivering necessary fluids, which is crucial for maintaining optimal electrolyte balance and preventing complications such as hyperchloremia and acidosis. According to the espghan/espen/espr/cspen guidelines on pediatric parenteral nutrition: fluid and electrolytes 1, the recommended parenteral fluid and electrolyte intake for children and infants beyond the neonatal period emphasizes the importance of careful sodium and chloride management. The guidelines suggest that sodium intake should be limited to 1-3 mmol/kg/d, which can be achieved with quarter normal saline solution.

When considering the use of quarter normal saline versus half normal saline, it is essential to weigh the potential benefits and risks. Quarter normal saline provides a lower sodium concentration, which can help correct high sodium levels more effectively while minimizing the risk of cerebral edema that can occur with rapid sodium correction. Additionally, quarter normal saline may be beneficial for patients with compromised renal function who cannot excrete excess sodium efficiently.

The physiological basis for using quarter normal saline is that it creates a greater free water gradient, allowing more effective distribution of water to cells while minimizing sodium load, which is particularly important in conditions where sodium restriction is beneficial. However, it is crucial to note that the current evidence does not strictly recommend balanced solutions over the use of normal saline, and more research is needed to fully understand the implications of using different types of intravenous solutions 1.

In clinical practice, the decision to use quarter normal saline versus half normal saline should be based on individual patient needs and electrolyte status, with close monitoring of serum electrolytes and fluid status. Typical infusion rates for quarter normal saline range from 75-125 mL/hour, depending on the patient's fluid status and electrolyte needs, with close monitoring of serum electrolytes every 4-6 hours initially.

Key considerations when using quarter normal saline include:

• Patient's sodium and electrolyte status
• Renal function and ability to excrete excess sodium
• Risk of cerebral edema and hyperchloremia
• Need for free water replacement and sodium restriction
• Close monitoring of serum electrolytes and fluid status.

From the Research

Comparison of Saline Solutions

• The use of quarter normal saline solution (NSS) instead of half normal saline solution (NSS) is not directly addressed in the provided studies 2, 3, 4, 5, 6.
• However, the studies compare the effects of normal saline (NS) and half normal saline (half NS) on serum electrolytes and acid-base status in various clinical settings.
• A study on diabetic ketoacidosis found that half NS resulted in a significant decrease in corrected serum sodium and reduced hyperchloremia leading to nonanion gap acidosis compared to NS 3.
• Another study suggested that normal saline may not be the safest replacement solution due to its potential to cause metabolic acidosis, vascular and renal function changes, and abdominal pain compared to balanced crystalloids 4.
• The choice of saline solution may depend on the specific clinical context and patient population, with normal saline being a safe initial rehydration fluid in children with diarrhea-related hypernatremia 5.
• A randomized clinical trial found that normal saline, lactated Ringer's, and Plasmalyte had no significant effect on acid-base status in dehydrated patients, but normal saline may exacerbate acidosis in patients with underlying metabolic disturbances 6.

Key Findings

• Half normal saline may be preferred over normal saline in certain situations to reduce the risk of hyperchloremia and nonanion gap acidosis 3.
• Balanced crystalloids, such as Plasmalyte, may be safer than normal saline for infusion therapy, red cell washing, and salvage due to their lower toxicity 4.
• Normal saline can be used safely as an initial rehydration fluid in children with diarrhea-related hypernatremia, but judicious use and close monitoring are recommended 5.
• The choice of saline solution should be based on the individual patient's needs and clinical context, taking into account the potential risks and benefits of each solution 2, 3, 4, 5, 6.