Is it safe to administer Ringer's Lactate (RL) to a patient undergoing neurosurgery?

Ringer's Lactate Should Be Avoided in Neurosurgery Cases

Ringer's Lactate (RL) is not recommended for neurosurgical patients because it is hypotonic when measured by real osmolality, which can worsen cerebral edema and increase intracranial pressure. 1

Why RL is Contraindicated in Neurosurgery

Tonicity Concerns

• RL has an osmolarity of 273-277 mOsm/L, making it hypotonic compared to plasma (275-295 mOsm/L), which directly impacts water movement between plasma and brain tissue 1
• When real osmolality (mosmol.kg⁻¹) rather than theoretical osmolality (mosmol.l⁻¹) is measured, RL is definitively hypotonic and should be avoided in brain-injured patients 1
• The hypotonic nature of RL increases cerebral water content and risk of cerebral edema through rheological effects 1

Impact on Clinical Outcomes

• The primary goal of fluid therapy during neurosurgery is to maintain normal blood volume, optimize cerebral blood flow, and avoid reduction in plasma osmolarity 1
• Hypotonic solutions like RL can worsen neurological outcomes in patients with traumatic brain injury or increased intracranial pressure 1
• Research in rats with combined brain injury and hemorrhagic shock demonstrated that massive RL resuscitation (40 mL/kg) yielded the worst neurological severity scores despite better hemodynamic parameters 2

Recommended Alternative: 0.9% Saline

Normal saline (0.9% NaCl) is the crystalloid of choice for neurosurgical patients because:

• It is the only commonly available truly isotonic crystalloid solution with an osmolarity of 308 mOsm/L 1
• Guidelines provide a weak recommendation for 0.9% saline as first-line fluid therapy in patients with traumatic brain injury 1
• Saline maintains plasma osmolarity and prevents increases in brain water content 1

Important Caveat About Normal Saline

While normal saline is preferred for neurosurgery, be aware that:

• Large volumes can cause hyperchloremic metabolic acidosis 1, 3
• A comparative study in neurosurgical patients found NS caused hyperchloremic metabolic acidosis and ionic hypocalcemia, though clinical outcomes (brain relaxation, complications, hospital stay) were similar across NS, RL, and combination groups 3

Alternative Consideration: Buffered Isotonic Solutions

Buffered isotonic solutions like Plasmalyte® may be superior to normal saline because they:

• Are not associated with hyperchloremic metabolic acidosis or adverse renal effects 1
• Maintain true isotonicity without the chloride load of normal saline 1

However, the evidence base for buffered solutions in neurosurgery is limited, and guidelines do not yet strongly endorse them over saline 1.

Clinical Algorithm for Fluid Selection in Neurosurgery

For any patient undergoing neurosurgery or with brain injury:

1. First-line choice: 0.9% normal saline 1
2. Second-line choice: Buffered isotonic solutions (e.g., Plasmalyte®) if available and institutional protocols allow 1
3. Absolutely avoid: Ringer's Lactate, Ringer's Acetate, gelatins, and any hypotonic solutions 1
4. Also avoid: Albumin (strong recommendation against use in neurosurgical patients and traumatic brain injury) 1

Common Pitfalls to Avoid

• Do not assume RL is "close enough" to isotonic - even small decreases in osmolality (4 mOsm/kg) occur with RL infusion in healthy volunteers 4
• Do not use theoretical osmolarity calculations - real osmolality measurements demonstrate RL is hypotonic 1
• Do not prioritize avoiding hyperchloremia over preventing cerebral edema - in neurosurgical patients, maintaining plasma osmolarity takes precedence over acid-base concerns 1
• The transient nature of osmolality changes with RL (returning to baseline within 1 hour in healthy volunteers) 4 is irrelevant in neurosurgical patients where even brief increases in cerebral water can be catastrophic

Special Populations

For traumatic brain injury specifically:

• Hypovolemic patients must have volume status corrected before transfer, as hypotension adversely affects neurological outcomes 1
• Use 0.9% saline for resuscitation, not RL 1
• Maintain cerebral perfusion pressure while avoiding hypotonic fluids 1