How does hypertonic saline decrease Intracranial Pressure (ICP)?

From the Guidelines

Hypertonic saline is the preferred treatment for decreasing intracranial pressure (ICP) due to its ability to create an osmotic gradient across the blood-brain barrier, drawing water from brain tissue into the intravascular space, thereby reducing cerebral edema and brain volume. When administered intravenously, typically as 3% or 7.5% sodium chloride solution, it has been shown to be effective in reducing ICP in patients with traumatic brain injury and other causes of raised ICP 1. The most recent guidelines suggest that hypertonic saline may be more effective than mannitol in treating acutely elevated ICPs 1. Common dosing includes 3% saline at 0.5-1.5 mL/kg/hr as a continuous infusion or 250-500 mL boluses of 3% saline over 30 minutes for acute ICP elevations. Some key points to consider when using hypertonic saline include:

• Careful monitoring of serum sodium levels is essential, with targets typically between 145-155 mEq/L, to avoid complications like hypernatremia, central pontine myelinolysis, or rebound cerebral edema.
• Hypertonic saline has advantages over mannitol in maintaining intravascular volume and being effective even when the blood-brain barrier is disrupted.
• The duration of transient effects from hyperosmolar therapy in the setting of ICH is unclear, and further studies could determine the effective treatment durations and whether hyperosmolar agents are effective in preventing poor outcomes 1. Overall, the use of hypertonic saline is a well-established treatment for reducing ICP, and its effectiveness has been demonstrated in numerous studies, including a 2011 meta-analysis of randomized clinical trials 1.

From the Research

Mechanism of Hypertonic Saline in Decreasing ICP

• Hypertonic saline (HTS) is used to reduce intracranial pressure (ICP) after severe traumatic brain injury (TBI) by creating an osmotic gradient that pulls water out of the brain tissue, thereby decreasing ICP 2, 3.
• The use of HTS has been shown to be effective in reducing ICP while maintaining cerebral perfusion pressure (CPP) and brain tissue oxygen tension (PbtO2) 3, 4.
• HTS has been compared to mannitol, another hyperosmolar agent, in several studies, with some showing that HTS is superior to mannitol in reducing the combined burden of intracranial hypertension and associated hypoperfusion in severe TBI patients 4, 5.

Comparison of HTS and Mannitol

• Equimolar doses of 20% mannitol solution and 7.45% hypertonic saline solution (HSS) have been shown to be equally effective in reducing ICP in patients with sustained elevated ICP secondary to traumatic brain injury or stroke 5.
• A meta-analysis of randomized controlled trials found that HTS and mannitol were similar in improving functional outcome, reducing intracranial pressure, and reducing mortality, but HTS was more effective than mannitol in ICP management 6.
• HTS has been shown to increase serum sodium and osmolality, while mannitol causes a significant increase in urine output 5, 6.

Clinical Implications

• The choice between HTS and mannitol for treating elevated ICP in TBI patients should be based on individual patient factors, such as serum sodium, systemic hemodynamics, and brain hemodynamics 5, 6.
• HTS may be preferred for refractory intracranial hypertension due to its ability to reduce ICP while maintaining CPP and PbtO2 3, 4.
• Further studies are needed to determine the optimal dosing and duration of HTS treatment for elevated ICP in TBI patients 2, 6.