Hypertonic Saline as CRRT Replacement Fluid: Not Recommended
Hypertonic saline (3% or 7.5%) should not be used as CRRT replacement fluid, as it is contraindicated for this purpose and poses significant risks of rapid, uncontrolled sodium correction and osmotic complications. 1
Why Hypertonic Saline is Inappropriate for CRRT
Fundamental Incompatibility with CRRT Principles
CRRT replacement fluids must contain physiologic concentrations of electrolytes to maintain safe, gradual correction of imbalances over the continuous 24-hour treatment period 1
Hypertonic saline contains supraphysiologic sodium concentrations (513 mEq/L for 3% saline, 1283 mEq/L for 7.5% saline) that would create dangerously steep gradients when used continuously 2, 3
The continuous nature of CRRT amplifies the risk of overly rapid sodium correction, potentially causing osmotic demyelination syndrome, particularly in patients with chronic hyponatremia 2, 4
Evidence Against Hypertonic Saline in Critical Care
Multiple meta-analyses have conclusively demonstrated that hypertonic saline provides no mortality benefit in hemorrhagic shock, trauma, or critically ill patients requiring resuscitation 1
A 2017 meta-analysis of 2,932 patients found no difference in mortality, ICU length of stay, mechanical ventilation days, or renal replacement therapy requirements when comparing hypertonic saline to isotonic solutions 1
The European guidelines issued a GRADE 1- (strong) recommendation against using 3% or 7.5% hypertonic saline as first-line fluid therapy to reduce mortality in hemorrhagic shock 1
What Should Be Used Instead
Recommended CRRT Replacement Fluids
Balanced crystalloid solutions (Ringer's Lactate or Plasmalyte) are the preferred replacement fluids for CRRT, as they contain physiologic electrolyte concentrations and appropriate buffer systems 1, 5
Bicarbonate-buffered solutions are preferred over lactate-buffered solutions in patients with lactic acidosis, liver failure, or when using high-volume hemofiltration 1, 6
Replacement fluid composition should be adjusted based on the patient's specific electrolyte abnormalities, but modifications should maintain near-physiologic concentrations 1, 3
Special Considerations for Sodium Management
When treating severe hyponatremia (sodium <120 mEq/L) in patients requiring CRRT, commercially available dialysate can be diluted with sterile water to create hypotonic solutions that allow gradual, controlled sodium correction 2
The sodium concentration of replacement fluid can be customized using single-pool urea kinetic modeling and volume exchange techniques to achieve targeted correction rates of 6-8 mEq/L per 24 hours 2, 4
Post-filter infusion of dextrose 5% water can be calculated to slow sodium correction rates when pre-filter replacement fluid cannot be adequately diluted 4
Critical Pitfalls to Avoid
Never use hypertonic saline as a continuous infusion or CRRT replacement fluid due to the risk of uncontrolled hypernatremia and osmotic complications 1, 2
Avoid normal saline (0.9% NaCl) as the primary CRRT replacement fluid when large volumes are needed, as its supraphysiologic chloride content (154 mEq/L) causes hyperchloremic metabolic acidosis and increased mortality 5
Do not assume that hypertonic saline's theoretical volume-sparing properties translate to clinical benefit—all clinical trials have failed to demonstrate improved outcomes 1
Ensure sterile replacement fluids are used at all times, and consider warming fluids to prevent hypothermia below 35°C, though definitive evidence for warming is lacking 1