Hypertonic Saline Initiation Based on Midline Shift
Hypertonic saline should be initiated when midline shift exceeds 5 mm on CT imaging, as this threshold indicates significant mass effect and risk of elevated intracranial pressure requiring osmotic therapy. 1
Imaging Criteria for Treatment Initiation
The decision to start hypertonic saline is based on severity signs on cerebral imaging, specifically:
- Midline shift > 5 mm is a key threshold that warrants ICP monitoring and consideration for osmotic therapy 1
- Compressed basal cisterns on CT scan 1
- Presence of other intracranial lesions 1
- Intracerebral hematoma volume > 25 mL 2
These imaging findings indicate threatened intracranial hypertension even before ICP is directly measured.
Clinical Context for Treatment
Do not wait for measured ICP values if clinical signs of herniation are present. Hypertonic saline should be administered immediately for: 1
- Anisocoria or mydriasis (pupillary changes suggesting herniation) 1
- Neurological deterioration not attributable to systemic causes 1
- Signs of brain herniation in the prehospital or emergency setting 1
Dosing Protocol
When midline shift > 5 mm is identified, administer: 1, 3
- 250 mL of 7.5% hypertonic saline (approximately 250 mOsm) 1
- Infuse over 15-20 minutes 1, 3
- Maximum effect occurs at 10-15 minutes with duration of 2-4 hours 1, 3
Alternative regimen: 30 mL of 23.4% hypertonic saline over 15 minutes for more concentrated dosing 4
Monitoring Requirements
After initiating therapy for midline shift: 3
- Measure serum sodium within 6 hours of bolus administration 3
- Target serum sodium concentration of 145-155 mmol/L 1, 3
- Do not re-administer until serum sodium < 155 mmol/L 3
- Monitor for complications including hypernatremia and hyperchloremia 1
Comparison to Mannitol
At equiosmotic doses (250 mOsm), hypertonic saline and mannitol have comparable efficacy, but hypertonic saline may be preferred when: 1
- Patient has hypovolemia (mannitol causes osmotic diuresis) 1
- More rapid ICP reduction is needed 3
- Greater cerebral perfusion pressure increase is desired 3
Critical Pitfall
Midline shift > 5 mm with clinical deterioration requires immediate osmotic therapy—do not delay for formal ICP monitoring. 1 The presence of significant midline shift on imaging is itself an indication for treatment, as it represents mass effect and impending herniation risk. Waiting for invasive ICP monitoring in this setting can result in irreversible brain injury. 1
Evidence Limitations
Despite robust evidence that hypertonic saline reduces ICP (Grade A), there is no evidence it improves neurological outcomes (Grade B) or survival (Grade A) in patients with raised intracranial pressure. 3 However, it remains standard of care for managing threatened herniation and elevated ICP based on physiologic endpoints. 1