What is the preferred fluid for resuscitation in critically ill adults, balanced crystalloids (e.g. lactated Ringer's solution) or saline (sodium chloride)?

Balanced Crystalloids versus Saline in Critically Ill Adults

Balanced crystalloid solutions (e.g., lactated Ringer's) are recommended over 0.9% sodium chloride (saline) for fluid resuscitation in most critically ill adults due to lower rates of adverse kidney events and mortality. 1

Evidence-Based Comparison

Mortality and Kidney Outcomes

• A large RCT (SMART trial) with 15,802 critically ill patients demonstrated that balanced crystalloids resulted in a lower rate of the composite outcome of death, new renal replacement therapy, or persistent renal dysfunction compared to saline (14.3% vs 15.4%) 1
• In-hospital mortality at 30 days was lower with balanced crystalloids (10.3% vs 11.1%) 1
• For septic patients specifically, balanced crystalloids showed greater mortality benefit when administered from the ED through ICU care compared to ICU-only administration 2

Physiological Effects

• Saline (0.9% NaCl) can cause hyperchloremic acidosis and potentially increase risk of kidney injury due to its high chloride content 3
• Balanced solutions have electrolyte compositions closer to plasma, with more physiological sodium-to-chloride ratios 4

Clinical Algorithm for Fluid Selection

1. First-line fluid choice for most critically ill adults:

   • Use balanced crystalloid solutions (lactated Ringer's or Plasmalyte) 3, 4

2. Special considerations:

   • Traumatic brain injury patients: Use 0.9% sodium chloride instead of hypotonic solutions like Ringer's lactate to minimize cerebral edema risk 3, 4
   • Severe acidosis with hyperchloremia: Avoid saline and use balanced solutions 3
   • Hemorrhagic shock: Balanced crystalloids are probably recommended over 0.9% NaCl to reduce mortality and adverse renal events 3

3. Volume considerations:

   • If using 0.9% sodium chloride, limit to maximum of 1-1.5L to minimize hyperchloremic acidosis 3
   • For patients requiring substantial fluid volumes (e.g., hemorrhagic shock requiring >5L), the benefits of balanced solutions become more pronounced 3

Important Caveats

• Avoid hypotonic solutions in patients with traumatic brain injury 3
• Restrict use of colloids due to adverse effects on hemostasis 3
• While some meta-analyses show no significant difference in mortality between balanced crystalloids and saline 5, the most recent high-quality evidence from large RCTs supports the use of balanced solutions 1
• The European guideline on management of major bleeding and coagulopathy following trauma (2023) favors balanced electrolyte solutions as the initial crystalloid solution in trauma patients 3

Practical Implementation

• Start with balanced crystalloids for most critically ill patients requiring fluid resuscitation
• Consider early implementation (from ED through ICU) rather than ICU-only for better outcomes, particularly in sepsis 2
• Monitor electrolytes, acid-base status, and renal function during fluid resuscitation
• Adjust fluid choice based on the patient's specific condition and ongoing laboratory results