Can hemodialysis (HD) be performed on a patient with severe hyponatremia?

Hemodialysis in Severe Hyponatremia (Sodium 110 mEq/L)

Yes, hemodialysis can be performed in patients with severe hyponatremia (sodium 110 mEq/L), but it requires specialized modifications to prevent catastrophic osmotic demyelination syndrome—specifically, using low-sodium dialysate (128 mEq/L, the lowest permissible level), reduced blood flow rates (starting at 50 mL/min), and meticulous monitoring to limit sodium correction to no more than 8 mmol/L per 24 hours. 1, 2

Critical Safety Framework

The fundamental danger is that conventional hemodialysis will correct sodium too rapidly, causing osmotic demyelination syndrome with permanent neurological damage or death. 2, 3 Standard dialysate contains 140-145 mEq/L sodium, which creates an enormous concentration gradient that will drive rapid sodium correction—exactly what must be avoided. 1, 2

Maximum Correction Rates

• Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 4
• For high-risk patients (advanced liver disease, alcoholism, malnutrition), limit correction to 4-6 mmol/L per day 4
• Target correction rate of 1 mEq/L per hour during the first HD session, then 2 mEq/L per hour in subsequent sessions 1

Modified Hemodialysis Protocol

Dialysate Modification

• Use dialysate sodium concentration of 128 mEq/L (the lowest permissible level on conventional HD machines) 1
• If conventional HD machines cannot achieve this, continuous venovenous hemofiltration (CVVH) with custom low-sodium replacement fluid is the preferred modality 2, 5

Blood Flow Rate Titration

• Start with blood flow of 50 mL/min during the first session 1
• Monitor sodium increase—should achieve approximately 1 mEq/L per hour 1
• Increase to 100 mL/min for subsequent sessions if initial correction rate is appropriate 1
• This achieves approximately 2 mEq/L per hour correction 1

Monitoring Protocol

• Check serum sodium every 2 hours during dialysis sessions 4
• Calculate total sodium correction from baseline—must not exceed 8 mmol/L in any 24-hour period 4, 1
• Continue monitoring every 4 hours between dialysis sessions 4

Alternative: Continuous Renal Replacement Therapy

CVVH with low-sodium replacement fluid is technically superior for controlling sodium correction rate in severe hyponatremia with renal failure. 2, 5

CVVH Advantages

• Allows precise control of sodium correction rate through single-pool sodium kinetic modeling 2
• Can customize replacement fluid sodium concentration to match desired correction rate 2, 5
• Provides continuous, gradual correction rather than intermittent rapid shifts 2, 5

CVVH Limitations

• Not available in most resource-limited settings 1
• Requires ICU-level care and specialized equipment 2
• When CVVH is unavailable, modified conventional HD is an acceptable alternative 1

Addressing Uremic Complications

The patient likely requires dialysis for advanced azotemia, fluid overload, and uremic symptoms (vomiting, altered mental status). 1

Balancing Competing Priorities

• Uremic symptoms require urgent dialysis, but rapid sodium correction risks osmotic demyelination 1
• The modified HD protocol addresses both: blood flow of 50-100 mL/min provides adequate uremic clearance while limiting sodium correction 1
• Complete resolution of uremic manifestations is achievable within 48 hours using this approach 1

Theoretical Protective Effect of Uremia

Uremia may provide partial protection against osmotic demyelination during rapid sodium correction. 3

Mechanism

• Urea diffuses slowly across the blood-brain barrier, acting as an effective osmole 3
• During HD, blood urea drops rapidly, potentially causing cerebral edema (dialysis disequilibrium syndrome) 3
• This cerebral edema may counteract the fluid shift out of the brain during sodium correction 3

Clinical Significance

• Case reports demonstrate successful rapid correction without neurological damage in uremic patients 3
• However, this protection is theoretical and unreliable—the standard 8 mmol/L per 24-hour limit must still be observed 4, 3

Common Pitfalls to Avoid

• Never use standard dialysate (140-145 mEq/L sodium) in severe hyponatremia—this guarantees overcorrection 1, 2
• Never prioritize rapid uremic clearance over sodium correction safety—modified protocols achieve both 1
• Never assume uremia provides complete protection against osmotic demyelination—follow correction rate limits 4, 3
• Inadequate monitoring during active correction leads to unrecognized overcorrection 4

Post-Dialysis Management

After achieving sodium >120-125 mEq/L and resolving uremic symptoms:

• Implement fluid restriction to 1-1.5 L/day if hypervolemic hyponatremia persists 4
• Discontinue diuretics until sodium normalizes 4
• Continue monitoring sodium levels daily 4
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after correction 4