Is saline really normal?

The question

When a newborn needs a fluid bolus, should it be 0.9% sodium chloride ("normal" saline) or a balanced crystalloid such as lactated Ringer's?

The study

A perspective in the Journal of Perinatology (open access) from UC Davis. It reviews the physiology and the mostly pediatric and adult evidence, then proposes a practical approach for the NICU.

What they found

• "Normal" saline is neither physiologically normal nor chemically a 1 N solution. It contains 154 mmol/L each of sodium and chloride.
• Saline is associated with hyperchloremic metabolic acidosis and acute kidney injury. Using Stewart's strong ion difference, excess chloride pushes bicarbonate and pH down.
• Balanced crystalloids (lactated Ringer's, Plasma-Lyte, Normosol-R) sit closer to plasma and carry buffers such as lactate, acetate or gluconate.
• Practical trade-offs: lactated Ringer's contains calcium, so it can clot citrated blood products and risks precipitation with TPN, ceftriaxone and other drugs. Plasma-Lyte and Normosol-R contain no calcium but cost more, and Normosol-R's magnesium content may rule it out for babies with known or suspected hypermagnesemia.
• The NRP textbook (9th edition) recommends saline for acute hypovolemia, with lactated Ringer's acceptable.
• The authors' suggested approach: consider a balanced crystalloid for hypoperfusion with known or suspected fluid loss, or for existing metabolic acidosis with high chloride or low bicarbonate. Saline may be preferred when IV access is limited and calcium-, phosphate- or citrate-containing fluids are running, or in the delivery room when a balanced fluid isn't at hand.

Where the evidence stops

• Most of the supporting data come from adults and older children. Many studies exclude neonates, use larger volumes, or look at maintenance fluids rather than boluses.
• Benefits of balanced crystalloids in those populations have been modest and inconsistent.
• There is no strong neonatal evidence yet for any one bolus fluid. The authors call for targeted studies.

References

1. Carrigan K, Lakshminrusimha S. Balanced fluid bolus: Should we prefer balanced crystalloids over “normal” saline? J Perinatol. 2026;46(11):2216–2219. doi:10.1038/s41372-026-02622-z · PubMed 41826663

Independent educational content, not medical advice. Not affiliated with or endorsed by the AAP. Summaries reflect the published papers; read the originals before changing practice.