What is the recommended dose of 3% (three percent) normal saline for a patient with subdural hematoma (SDH) and hyponatremia?

Recommended Dose of 3% Normal Saline in SDH Patients with Hyponatremia

For patients with subdural hematoma (SDH) and hyponatremia, administer 3% hypertonic saline at a dose of 250 mOsm in an infusion over 15-20 minutes to treat threatened intracranial hypertension or signs of brain herniation after controlling secondary brain insults. 1

Assessment and Initial Management

• Evaluate symptom severity and acuity of hyponatremia onset to determine appropriate treatment approach 2
• For severe symptomatic hyponatremia (mental status changes, seizures, coma), administer 3% hypertonic saline with an initial goal to correct sodium by 6 mmol/L over 6 hours or until severe symptoms resolve 2, 3
• For patients with SDH, hypertonic saline is effective in reducing intracranial pressure (ICP) with maximum effect observed after 10-15 minutes and lasting for 2-4 hours 1

Dosing Recommendations

• For acute treatment of threatened intracranial hypertension: 250 mOsm of 3% hypertonic saline infused over 15-20 minutes 1
• For severe symptomatic hyponatremia:
  • Initial bolus: 100-250 mL of 3% hypertonic saline 4, 5
  • A 250 mL bolus is more effective than 100 mL for achieving a rise in serum sodium ≥5 mmol/L within 4 hours (52% vs 32% success rate) 5
  • May repeat bolus up to two more times if symptoms persist, but third bolus increases risk of overcorrection 4

Correction Rate Guidelines

• Limit total correction to no more than 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 2, 3
• For patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy, use more cautious correction rates (4-6 mmol/L per day) 2
• Monitor serum sodium every 2 hours during initial correction for severe symptoms 2

Special Considerations for SDH Patients

• Subdural hematoma can cause syndrome of inappropriate ADH secretion (SIADH), leading to hyponatremia 6
• Hypertonic saline is particularly beneficial in SDH patients as it reduces cerebral edema while correcting hyponatremia 1
• Continuous infusion of 500 mL of 3% sodium chloride solution over 6 hours has been shown effective for hyponatremic encephalopathy without causing cerebral demyelination 7

Monitoring and Safety

• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 2
• Measure serum sodium within 6 hours of administration if bolus doses are given 1
• Do not re-administer hypertonic saline until serum sodium concentration is <155 mmol/L 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 2

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours can lead to osmotic demyelination syndrome 2
• Inadequate monitoring during active correction 2
• Failing to recognize and treat the underlying cause of hyponatremia 2
• Prophylactic administration of hypertonic saline to patients with no evidence of intracranial hypertension is not superior to crystalloids 1