====== Hyperosmolar Therapy in Neurotrauma ======

**Purpose:** To reduce elevated intracranial pressure (ICP) and mitigate secondary brain injury in patients with traumatic brain injury (TBI), intracerebral hemorrhage, or other causes of cerebral edema.

===== Indications =====
  * Sustained ICP > 20–22 mmHg despite sedation and positioning
  * Clinical signs of herniation (e.g., unilateral mydriasis, decerebrate posturing)
  * Radiologic evidence of cerebral edema, midline shift, or compressed ventricles

===== Mechanism of Action =====
  * **Creates an osmotic gradient** across the blood-brain barrier (BBB), drawing water from brain parenchyma into the intravascular space
  * **Reduces cerebral blood volume** via plasma expansion and decreased blood viscosity

===== Main Agents =====

==== 1. Mannitol ====
  * Concentration: 20% (0.25–1.0 g/kg IV bolus)
  * Onset: 15–30 min | Duration: 2–6 h
  * Requires intact BBB to be effective
  * Monitor serum osmolality (< 320 mOsm/kg) and renal function
  * Risk: hypovolemia, renal failure, rebound ICP increase with repeated doses

==== 2. Hypertonic Saline (HTS) ====
  * Available concentrations: 3%, 7.5%, 23.4%
  * Dosing examples:
    - 3%: 250 mL over 20–30 min
    - 7.5%: 100–150 mL bolus
    - 23.4%: 30 mL bolus over 10–15 min via central line only
  * Preferred in patients with hypotension or polyuria
  * Monitor serum sodium (target: 145–155 mmol/L) and chloride
  * Can be used as continuous infusion (e.g., 3% NaCl at 30–70 mL/h)

===== Comparative Notes =====
^ Feature ^ Mannitol ^ Hypertonic Saline ^
| Volume status | Diuretic effect (↓ volume) | Volume expansion (↑ MAP) |
| Use with hypotension | Contraindicated | Preferred |
| Risk of rebound ICP | Higher | Lower |
| Monitoring | Osmolality, Cr | Na+, Cl−, fluid balance |

===== Monitoring and Safety =====
  * Frequent ICP monitoring (EVD or intraparenchymal probe)
  * Serum sodium/osmolality every 4–6 h
  * Renal function and urine output
  * Avoid prolonged or aggressive correction (>12 mEq/L/24h in chronic hyponatremia)

===== Clinical Pearls =====
  * Combine with other ICP-lowering strategies: sedation, head elevation, normocapnia
  * Avoid hypotonic fluids (e.g., D5W, 0.45% NaCl)
  * HTS may be preferred in polytrauma or hypotensive patients
  * Do not use empirically without signs of raised ICP

===== References =====
  * Neurosurg Clin N Am. 2025 Jul;36(3):387–400. doi:10.1016/j.nec.2025.03.007.
  * Brain Trauma Foundation Guidelines (2020 update)