Management of Subdural Hematoma with Hyponatremia

Introduction to Hyperosmolar Therapy

The American Society of Anesthesiologists recommends using hypertonic saline as the sole hyperosmolar agent rather than mannitol in patients with subdural hematoma and hyponatremia, and these two agents should NOT be used simultaneously 1, 2, 3

Hypertonic saline is preferred over mannitol for correcting hyponatremia and reducing intracranial pressure, providing dual therapeutic benefit 3, 2, 3
Hypertonic saline expands intravascular volume while reducing ICP, unlike mannitol which induces osmotic diuresis and can worsen hypovolemia 2, 3
At equiosmolar doses, hypertonic saline demonstrates superior or equivalent ICP reduction compared to mannitol, with the added benefit of improving cerebral perfusion pressure more effectively 4

The initial concentration of hypertonic saline should be 3% for most patients 3
The dosing of hypertonic saline should be 1.4 mL/kg as initial bolus dose, given over 15-20 minutes 2
Serum sodium should be checked every 4-6 hours initially, with a target gradual correction to avoid central pontine myelinolysis 3
Serum osmolality should be maintained <320 mOsm/L 2, 3
ICP monitoring should target ICP <20-22 mm Hg 4
Cerebral perfusion pressure should be maintained at 60-70 mm Hg 2, 3

The recommendation against simultaneous use of hypertonic saline and mannitol is based on Grade A evidence from the 2009 Anaesthesia guidelines 1
The 2022 AHA/ASA Stroke guidelines confirm hypertonic saline superiority over mannitol for ICP reduction 4, 5