What is the recommended way to correct symptomatic hyponatremia with hypertonic 3% sodium chloride in a patient with a subdural hematoma?

3% Hypertonic Saline Correction in Subdural Hematoma with Hyponatremia

For a patient with subdural hematoma (SDH) and symptomatic hyponatremia, administer 3% hypertonic saline in 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals, targeting an initial correction of 6 mmol/L over 6 hours or until symptoms resolve, while never exceeding 8 mmol/L rise in any 24-hour period. 1, 2

Immediate Assessment and Indications

Determine symptom severity first. Severe symptoms (seizures, altered mental status, coma) mandate immediate hypertonic saline regardless of absolute sodium level. 2 Subdural hematoma patients may develop hyponatremia through SIADH or cerebral salt wasting (CSW), and distinguishing between these is critical because they require opposite fluid management strategies. 2

Key Diagnostic Distinctions

• SIADH presents with euvolemia: normal to slightly elevated central venous pressure, no orthostatic hypotension, moist mucous membranes, urine sodium >20-40 mmol/L, and urine osmolality >300 mOsm/kg. 2
• CSW presents with true hypovolemia: orthostatic hypotension, dry mucous membranes, flat neck veins, CVP <6 cm H₂O, yet paradoxically elevated urine sodium >20 mmol/L despite volume depletion. 2
• Physical examination alone has poor accuracy (sensitivity 41%, specificity 80%) for volume assessment, so incorporate urine studies and clinical context. 2

Hypertonic Saline Protocol for SDH Patients

Dosing Strategy

Administer 100 mL of 3% NaCl intravenously over 10 minutes as the initial bolus. 1, 2 This dose can be repeated up to three times at 10-minute intervals if severe symptoms persist or intracranial pressure remains elevated. 1, 2

• Target correction: 6 mmol/L over the first 6 hours or until severe neurological symptoms resolve (not normalization of sodium). 2
• Absolute maximum: 8 mmol/L rise in any 24-hour period to prevent osmotic demyelination syndrome. 1, 2, 3
• Check serum sodium 4-6 hours after each bolus to guide further dosing and avoid overcorrection. 1, 2

Continuous Infusion Alternative

For sustained intracranial pressure control in SDH, continuous 3% saline infusion may be employed, particularly when prolonged therapy is anticipated. 1, 2 Some head injury protocols safely target serum sodium of 145-155 mmol/L during continuous infusion, though this exceeds typical hyponatremia correction targets. 1

Critical Safety Considerations

Osmotic Demyelination Prevention

Never exceed 8 mmol/L correction in 24 hours. 1, 2, 3 Patients with subdural hematoma may have additional risk factors that mandate even slower correction:

• Advanced liver disease, chronic alcoholism, or malnutrition: limit to 4-6 mmol/L per day (maximum 8 mmol/L in 24 hours). 2, 3
• Risk of osmotic demyelination syndrome is 0.5-1.5% even with careful correction in high-risk populations. 2
• ODS symptoms appear 2-7 days after overcorrection: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis, locked-in syndrome. 2, 3

Monitoring Requirements

• Serum sodium every 2 hours during initial correction of severe symptoms. 2, 3
• Every 4-6 hours after symptom resolution until stable. 2, 3
• Intracranial pressure monitoring (if device present): target ICP <20 mmHg. 2
• Cerebral perfusion pressure: maintain >60 mmHg. 2
• Daily neurological examination using Glasgow Coma Scale, pupillary response, motor function. 3

Volume Status-Specific Management

If SIADH (Euvolemic)

After acute correction with hypertonic saline, transition to fluid restriction (1 L/day) as definitive management. 2 Do not continue aggressive saline infusion in euvolemic patients, as this worsens hyponatremia. 2

• Add oral sodium chloride 100 mEq three times daily if fluid restriction fails. 2
• Pharmacologic options for resistant SIADH: urea, loop diuretics, demeclocycline, lithium. 2

If Cerebral Salt Wasting (Hypovolemic)

Fluid restriction is absolutely contraindicated in CSW—it worsens outcomes and precipitates cerebral ischemia. 2 After initial hypertonic saline boluses:

• Continue aggressive volume replacement with isotonic saline (0.9% NaCl) at 50-100 mL/kg/day. 2
• Add fludrocortisone 0.1-0.2 mg daily to reduce renal sodium losses in severe or refractory CSW. 2
• Hydrocortisone may prevent natriuresis in subarachnoid hemorrhage patients with CSW. 2

Special Considerations for Subdural Hematoma

Intracranial Pressure Management

3% hypertonic saline reduces ICP, improves cerebral perfusion pressure, and shortens duration of intracranial hypertension in SDH patients. 1, 2, 4 This dual benefit makes it particularly valuable when both elevated ICP and hyponatremia coexist. 1, 4

• Hypertonic saline increases regional cerebral blood flow, brain tissue oxygen, and pH in patients with acute brain injury. 2
• Bolus administration is preferred over continuous infusion for acute ICP crises or severe symptomatic hyponatremia. 1, 2

Fluid Selection After Acute Phase

Once mental status normalizes and sodium reaches 120-125 mmol/L, switch from 3% saline to isotonic 0.9% NaCl for maintenance. 2

• Avoid all hypotonic solutions (0.45% saline, lactated Ringer's, D5W) as they worsen cerebral edema and hyponatremia. 2
• Never use fluid restriction in SDH patients at risk for vasospasm (particularly subarachnoid hemorrhage), as this increases ischemic complications. 2

Management of Overcorrection

If sodium rises >8 mmol/L in 24 hours or patient develops unexplained neurological deterioration:

• Immediately stop all hypertonic and isotonic saline. 2, 3
• Switch to D5W (5% dextrose in water) to prevent further sodium rise. 2, 3
• Administer desmopressin to slow or reverse the rapid increase, targeting total 24-hour correction ≤8 mmol/L from baseline. 2, 3, 5
• Obtain urgent brain MRI to evaluate for pontine and extrapontine myelinolysis, though MRI changes may lag clinical symptoms by several days. 3, 6

Common Pitfalls to Avoid

• Misdiagnosing CSW as SIADH and applying fluid restriction worsens cerebral ischemia and can be fatal in neurosurgical patients. 2
• Correcting to normal sodium (135-145 mmol/L) acutely is unnecessary and dangerous—target 125-130 mmol/L for severe symptomatic hyponatremia. 2
• Relying on physical examination alone for volume status without urine sodium, urine osmolality, and clinical context leads to misdiagnosis. 2
• Continuing aggressive saline after symptoms resolve in SIADH patients perpetuates the problem rather than correcting it. 2
• Using central venous access unnecessarily—peripheral administration of 3% saline has low complication rates (infiltration 3.3%, phlebitis 6.2%) and is less invasive. 7

Peripheral vs. Central Administration

Peripheral intravenous administration of 3% hypertonic saline is safe and preferred when central access is not already established. 7 The overall complication rate is low: infiltration 3.3%, phlebitis 6.2%, erythema 2.3%, edema 1.8%, venous thrombosis 1%. 7 Central venous catheter placement carries its own risks (pneumothorax, infection, thrombosis) that often exceed peripheral 3% saline complications. 7