Why is saline preferred over Hartmann's (lactated Ringer's solution) or Sterofundin in patients with traumatic brain injury (TBI) or severe brain injury?

Why Saline is Preferred Over Hartmann's/Sterofundin in Traumatic Brain Injury

In patients with traumatic brain injury or severe brain injury, normal saline (0.9% NaCl) should be used instead of Hartmann's solution (lactated Ringer's) or Sterofundin because these balanced crystalloids are hypotonic when measured by real osmolality, which can worsen cerebral edema and increase intracranial pressure, ultimately leading to increased mortality. 1, 2

The Critical Issue: Tonicity and Cerebral Edema

The fundamental problem with Hartmann's/Sterofundin in TBI relates to osmolality:

• Lactated Ringer's has an osmolarity of approximately 273-277 mOsm/L, making it hypotonic compared to plasma (275-295 mOsm/L) 2
• When real osmolality (rather than theoretical osmolality) is measured, these balanced solutions are definitively hypotonic and should be avoided in severe head trauma 2
• Hypotonic solutions can increase cerebral edema by creating an osmotic gradient that drives water into brain tissue, worsening intracranial hypertension 1, 2

Evidence of Harm in TBI Patients

The clinical evidence demonstrates actual harm from balanced crystalloids in TBI:

• A 2025 systematic review and meta-analysis of 35,207 critically ill patients found that balanced solutions increased mortality in TBI patients (OR 1.31,95% CI 1.03-1.65, P=0.03), while reducing mortality in non-TBI critical care patients (OR 0.93,95% CI 0.87-0.98) 3
• A 2024 double-blind RCT comparing Sterofundin versus normal saline in moderate-to-severe TBI found significantly higher ICP on day 3 in the Sterofundin group (18.60 ± 9.26 mmHg) compared to normal saline (12.77 ± 3.63 mmHg, p=0.037) 4
• The SAFE study demonstrated that TBI patients receiving 4% albumin (another hypotonic solution) had significantly higher mortality than those receiving 0.9% saline (24.5% vs 15.1%, RR 1.62, P=0.009) 5

Guideline Recommendations

Multiple high-quality guidelines explicitly recommend against balanced crystalloids in TBI:

• European guidelines for severe TBI management (2018) specifically state that Ringer's lactate is hypotonic when real osmolality is determined and should be avoided in brain-injured patients 5, 2
• For brain-injured patients, 0.9% saline is the recommended crystalloid of choice as it is isotonic in terms of osmolality 2
• The European Society of Intensive Care Medicine does not recommend using albumin solution after brain injury, and by extension, other hypotonic solutions should be avoided 5

Clinical Algorithm for Fluid Selection in TBI

When managing a patient with TBI or severe brain injury:

1. Use 0.9% normal saline as the primary crystalloid for resuscitation and maintenance 1, 2
2. Avoid all balanced crystalloids (Hartmann's, lactated Ringer's, Sterofundin) due to their hypotonic nature 1, 2
3. If intracranial hypertension develops, use hypertonic saline (3% or 7.5%) or mannitol as osmotherapy, not prophylactically 5, 6
4. Monitor serum sodium and osmolality, targeting sodium 145-155 mmol/L and osmolality <320 mOsm/L 6

Important Caveats and Pitfalls

Common pitfall: Assuming that because balanced crystalloids are superior in most critically ill patients (reducing hyperchloremic acidosis and acute kidney injury), they should also be used in TBI patients. This is incorrect—TBI represents a specific exception where the risk of worsening cerebral edema outweighs the metabolic benefits of balanced solutions. 3

Another pitfall: Believing that the small potassium content (4 mmol/L) in Hartmann's is the reason to avoid it in TBI. The actual contraindication is the hypotonic nature of the solution, not the potassium content. 2

Critical distinction: While prophylactic hypertonic saline administration to TBI patients without intracranial hypertension is not superior to crystalloids for outcomes 5, this does not mean hypotonic crystalloids are acceptable—it means isotonic normal saline should be the baseline fluid.

Contrast with Non-TBI Trauma Patients

In trauma patients WITHOUT severe TBI, balanced crystalloids like Hartmann's are actually preferred over normal saline because they reduce mortality and adverse renal events 1. This creates a critical decision point: the presence or absence of significant TBI fundamentally changes fluid selection strategy. 3