What intravenous isotonic crystalloid fluid regimen should be used to maintain euvolemia and avoid hypotension in a patient with a cerebral concussion?

IV Fluid Management for Cerebral Concussion

Primary Recommendation

Use 0.9% normal saline as the sole isotonic crystalloid for maintaining euvolemia and preventing hypotension in patients with cerebral concussion. 1, 2, 3

Rationale for Normal Saline Selection

Normal saline 0.9% is the only commonly available crystalloid that is truly isotonic when measured by real osmolality (mosmol/kg) rather than theoretical osmolarity (mosmol/L). 1, 2, 3 This distinction is critical because:

• Real osmolality determines actual fluid shifts across the blood-brain barrier, and solutions that appear isotonic by calculation may be hypotonic in practice. 1, 2
• Hypotonic solutions increase brain water content, worsening cerebral edema and potentially increasing intracranial pressure. 1, 2
• The primary goal is to prevent fluid shifts into damaged cerebral tissue while maintaining adequate cerebral perfusion. 1, 2

Fluids That Must Be Avoided

Ringer's lactate and Ringer's acetate are contraindicated despite being labeled as "isotonic" because their real osmolality is hypotonic and will increase brain water. 1, 2

Albumin is absolutely contraindicated in traumatic brain injury, with the SAFE study demonstrating increased mortality (24.5% vs 15.1%, RR 1.62) in severe TBI patients receiving albumin compared to normal saline. 2, 3

Synthetic colloids (HES, gelatins) should not be used as they are associated with worse neurological outcomes and are hypotonic by real osmolality measurements. 1, 2

Hypotonic solutions (5% dextrose) are contraindicated as they reduce serum sodium and increase brain water and intracranial pressure. 4

Resuscitation Strategy

Volume Management Approach

Reverse hypovolemia aggressively with rapid fluid boluses of 500-1000 mL, reassessing after each bolus. 2 The goals are:

• Maintain euvolemia - both hypovolemia and hypervolemia are harmful in brain injury. 2, 5, 6
• Avoid hypotension at all costs - even brief episodes adversely affect neurological outcomes. 1, 2, 3
• Limit total normal saline volume to 1-1.5 L to reduce risk of hyperchloremic metabolic acidosis. 2

After Initial Resuscitation

Once euvolemia is achieved, use cautious isotonic fluid administration to maintain hydration while preventing volume overload. 1, 2 This typically involves:

• Maintenance rates rather than aggressive boluses after hemodynamic stability is restored. 1
• Continuous monitoring for signs of fluid overload including pulmonary edema and worsening neurological status. 2

Critical Pitfalls to Avoid

Permissive hypotension is absolutely contraindicated in brain injury - maintaining adequate cerebral perfusion pressure is essential to prevent secondary ischemic injury. 1, 2

In trauma patients with concussion and hypotension, assume hemorrhage until proven otherwise, and control bleeding before any transfer. 1

Do not use hypertonic saline for routine resuscitation - it is reserved for acute intracranial hypertension management, not primary fluid resuscitation. 2, 3 Large prospective studies with 2,184 patients found no survival benefit from hypertonic saline resuscitation compared to normal saline. 3

Blood Pressure Management

If hypotension persists after adequate fluid resuscitation, use small boluses of α-agonists (metaraminol) followed by infusion, or norepinephrine via central line. 1, 3

Target cerebral perfusion pressure of 60-70 mmHg to optimize outcomes while avoiding complications. 3

Monitoring Parameters

Monitor serum sodium and osmolality regularly during fluid therapy, as electrolyte imbalances can occur. 2

Watch for hyperchloremic metabolic acidosis with prolonged normal saline use, though this is preferable to the risks of hypotonic solutions. 2

Assess cardiovascular status continuously to detect fluid overload or inadequate perfusion. 2