A 28-year-old male presents to the emergency department 2 hours after a motor vehicle accident with a GCS of 8. CT head shows acute subdural hematoma with 8 mm midline shift. He is intubated for airway protection. Which agent is the drug of choice for acute management of raised intracranial pressure in this patient?

Question

Accepted Answer

A. Mannitol. ## Osmotic Agents in Acute Head Injury

**Key Point:** Mannitol is the first-line osmotic agent for acute management of raised intracranial pressure (ICP) in traumatic brain injury with GCS ≤8.

### Mechanism of Action
Mannitol works via:
1. **Osmotic gradient** — creates an osmotic gradient across the blood–brain barrier, drawing fluid from the brain parenchyma into the intravascular space
2. **Rapid onset** — peak effect within 15–30 minutes
3. **ICP reduction** — can reduce ICP by 30–50% acutely

### Dosing & Administration
- **Dose:** 0.25–1 g/kg IV bolus
- **Repeat:** Every 4–6 hours as needed
- **Monitoring:** Check serum osmolality (keep <320 mOsm/L to avoid renal toxicity)

### Comparison with Other Osmotic Agents

| Agent | Onset | Duration | Renal Toxicity | Use in TBI |
| --- | --- | --- | --- | --- |
| **Mannitol** | 15–30 min | 4–6 hrs | Low (if osmol <320) | **First-line** |
| **Hypertonic saline (3%)** | 5–10 min | 4–8 hrs | Minimal | Alternative/adjunct |
| **Hypertonic saline (7.5%)** | Rapid | Longer | Minimal | Prehospital/resuscitation |

**Clinical Pearl:** Mannitol is preferred in acute traumatic brain injury because it has the longest track record of evidence in ATLS protocols and reduces ICP reliably in the acute phase. Hypertonic saline is increasingly used as an adjunct or alternative, especially in hypotensive patients.

**High-Yield:** In a patient with GCS ≤8 and imaging evidence of mass effect (midline shift, subdural hematoma), osmotic therapy + head elevation (30°) + normothermia + sedation form the cornerstone of ICP management pending neurosurgical intervention.

**Warning:** Do not delay neurosurgical consultation while optimizing medical ICP management. This patient requires urgent surgical evacuation of the subdural hematoma.

Answer

B. Hypertonic saline (3%)

Answer

C. Dexamethasone

Answer

D. Propofol

Explanation

Osmotic Agents in Acute Head Injury

Mechanism of Action

Dosing & Administration

Comparison with Other Osmotic Agents

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Agent	Onset	Duration	Renal Toxicity	Use in TBI
Mannitol	15–30 min	4–6 hrs	Low (if osmol <320)	First-line
Hypertonic saline (3%)	5–10 min	4–8 hrs	Minimal	Alternative/adjunct
Hypertonic saline (7.5%)	Rapid	Longer	Minimal	Prehospital/resuscitation