What is the fluid of choice for managing head injury?

Fluid of Choice in Head Injury

Normal saline 0.9% is the crystalloid of choice for managing head injury, as it is the only commonly available truly isotonic crystalloid solution that prevents cerebral edema formation and maintains adequate cerebral perfusion. 1

Primary Fluid Selection

Isotonic crystalloids (osmolarity 280-310 mOsm/L) should be used as first-line fluid therapy in acute brain injury to reduce mortality and improve neurological prognosis. 1

Why Normal Saline 0.9%?

• Normal saline 0.9% is the only commonly available crystalloid that is truly isotonic when measured by real osmolality (mosmol/kg) rather than theoretical osmolality (mosmol/L). 1
• Ringer's Lactate and Ringer's Acetate are hypotonic when real osmolality is measured and should be avoided. 1
• A multicenter study of 300 patients with traumatic brain injury demonstrated higher mortality in patients receiving Ringer's Lactate compared to normal saline (HR 1.78,95% CI 1.04-3.04, p=0.035). 1

Alternative Isotonic Options

• Balanced isotonic crystalloids such as Plasma-Lyte and Isofundine (osmolarity 280-310 mOsm/L) are acceptable alternatives that may reduce hyperchloremia risk. 1
• However, evidence does not definitively prove superiority of balanced crystalloids over normal saline for neurological outcomes, only reduction in hyperchloremia. 1

Fluids to AVOID

Hypotonic Solutions

• All hypotonic solutions (<280 mOsm/L) must be avoided due to risk of cerebral edema formation. 1
• This includes 5% dextrose in water, which reduces serum sodium and increases brain water and intracranial pressure. 2
• Ringer's Lactate contains approximately 114 mL of free water per liter, making it mildly hypotonic and potentially harmful. 3

Colloid Solutions

• Albumin is contraindicated in traumatic brain injury. The SAFE study demonstrated increased mortality in TBI patients treated with 4% albumin (n=460; RR 1.63,95% CI 1.17-2.26, p=0.003). 1
• Synthetic colloids (gelatins, HES) are associated with worse neurological prognosis at 6 months in brain injury patients. 1
• Gelatins and other colloid preparations are hypo-osmolar when measured in vitro and may increase intracranial pressure. 4

Glucose-Containing Solutions

• Glucose-containing hypotonic solutions should be avoided as hyperglycemia is a risk factor for worsening brain injury. 3, 5

Resuscitation Strategy

Volume Management Goals

• The primary goal is to reverse hypovolemia, avoid hypotension, and maintain cerebral blood flow to limit cerebral ischemia. 1
• Euvolemia should be the target; aggressive hypervolemia has shown evidence of harm. 5
• Fluid restriction minimally affects cerebral edema and may result in hypotension, which worsens neurological outcome. 2, 3

Blood Pressure Targets

• Hypotension must be prevented or promptly corrected to maintain optimal cerebral perfusion pressure. 6
• After correcting hypovolemia, hypotension should be managed with vasopressors (small boluses of alpha-agonists like metaraminol or noradrenaline infusion). 1
• Arterial blood pressure should be measured with the transducer at the level of the tragus, including when the patient is positioned head-up. 1

Special Circumstances

Hypertonic Saline

• Hypertonic saline (3% saline, 2 ml/kg bolus) is reserved for acute management of raised intracranial pressure with impending uncal herniation. 1
• In situations combining hemorrhagic shock with severe head trauma and focal neurological signs, a hypertonic saline bolus is recommended due to its osmotic effect. 1
• However, hypertonic saline does NOT improve survival or neurological outcome when used as the primary resuscitation fluid. 1, 6
• Meta-analysis of prehospital hypertonic saline administration showed no survival benefit (RR 1.04,95% CI 0.97-1.12). 6

Mannitol

• Mannitol (0.5 g/kg) is indicated for short-term reduction of intracranial pressure with impending herniation, used alongside other ICP-lowering methods. 1, 7
• Mannitol is a therapeutic agent for ICP management, not a resuscitation fluid. 7

Critical Pitfalls to Avoid

• Never restrict fluids until hemodynamic stability is achieved, as hypovolemia and hypotension have severe consequences on neurological outcome. 3
• Do not use Ringer's Lactate despite its common availability—it is hypotonic and associated with increased mortality in TBI. 1
• Avoid albumin in all traumatic brain injury patients due to proven increased mortality. 1
• Do not administer colloids as they worsen neurological prognosis. 1
• Monitor for hyperchloremia when using large volumes of normal saline, though this is preferable to cerebral edema from hypotonic solutions. 1

Monitoring Requirements

• Continuous arterial blood pressure monitoring is mandatory. 1, 3
• Central venous pressure monitoring should be utilized. 3
• Serum sodium and osmolality should be monitored regularly to guide therapy. 5
• End-tidal CO2 should be monitored continuously with target PaCO2 of 4.5-5.0 kPa. 1