0.45% Saline is NOT Suitable for Fluid Resuscitation
0.45% (half-normal) saline should not be used for fluid resuscitation in any clinical scenario. This hypotonic solution is inappropriate for volume expansion and has been directly compared to isotonic solutions with inferior outcomes.
Evidence Against 0.45% Saline for Resuscitation
Direct Comparative Data
- In patients at risk for contrast-induced acute kidney injury, 0.9% saline was superior to 0.45% saline, with 0% versus 5.5% incidence of acute kidney injury (p=0.01) 1
- The KDIGO guidelines explicitly recommend isotonic volume expansion rather than hypotonic solutions for patients requiring fluid resuscitation 1
Mechanism of Harm
- Hypotonic solutions cause fluid shifts into the intracellular compartment, failing to adequately expand intravascular volume 2
- In patients with traumatic brain injury or head trauma, hypotonic solutions like 0.45% saline are contraindicated due to risk of cerebral edema from fluid shift into damaged cerebral tissue 2
- Hypotonic fluids do not provide adequate sodium delivery to maintain effective plasma volume during resuscitation 1
What Should Be Used Instead
First-Line Recommendation
Balanced crystalloid solutions (Plasma-Lyte, Lactated Ringer's) are the preferred resuscitation fluids for most clinical scenarios 1, 3
- Reduce 30-day mortality (OR 0.84,95% CI 0.74-0.95) compared to normal saline 3
- Lower rates of major adverse kidney events, particularly in sepsis 3
- Better acid-base balance without hyperchloremic acidosis 1, 3
When Isotonic Saline May Be Used
- Initial resuscitation in trauma or hemorrhagic shock requires isotonic solutions (0.9% saline or balanced crystalloids), not hypotonic 2
- In traumatic brain injury, 0.9% saline is currently recommended over buffered solutions, though this remains an area of ongoing research 1
- For contrast-induced nephropathy prevention, isotonic solutions (either 0.9% saline or sodium bicarbonate 1.26%) are indicated 1
Volume and Rate Considerations
- Limit 0.9% saline to 1-1.5 L maximum if used, then switch to balanced crystalloids to avoid chloride load 3, 4
- Large volumes of any chloride-rich solution (>5000 mL) are associated with increased mortality 3
Critical Pitfalls to Avoid
- Never use 0.45% saline for initial resuscitation in hypovolemia, sepsis, trauma, or hemorrhagic shock 1, 2
- Avoid all hypotonic solutions in neurosurgical patients or those with elevated intracranial pressure 2
- Do not confuse maintenance fluid therapy (where hypotonic solutions may occasionally have a role) with resuscitation, which always requires isotonic or hypertonic solutions 1
The historical use of 0.45% saline in some protocols for contrast nephropathy prevention has been superseded by evidence favoring isotonic solutions 1. There is no contemporary indication for 0.45% saline in fluid resuscitation.