From the Guidelines
Yes, 0.9% NaCl (normal saline) can potentially worsen hypoosmolar hyponatremia in certain clinical scenarios. When treating hypoosmolar hyponatremia, the choice of fluid therapy should be guided by the patient's volume status and the underlying cause. Normal saline has a sodium concentration of 154 mEq/L, which is higher than serum sodium in hyponatremia but may still be insufficient to correct severe hyponatremia efficiently. In cases of severe symptomatic hyponatremia, 3% hypertonic saline is generally preferred as it provides more sodium per volume, as recommended by recent guidelines 1.
The problem with using normal saline occurs particularly in patients with the syndrome of inappropriate antidiuretic hormone secretion (SIADH), where it can paradoxically worsen hyponatremia. This happens because in SIADH, the kidneys excrete the water load more slowly than the sodium, potentially leading to further dilution of serum sodium. Additionally, the correction rate for hyponatremia should not exceed 8-10 mEq/L in 24 hours to avoid osmotic demyelination syndrome, as emphasized in the management of ascites in cirrhosis 1.
Key considerations in managing hypoosmolar hyponatremia include:
- Fluid restriction to 1–1.5 L/day for those who are clinically hypervolaemic with severe hyponatraemia (serum sodium <125 mmol/L) 1
- Use of hypertonic sodium chloride (3%) administration for severely symptomatic acute hyponatraemia, with careful monitoring of serum sodium correction rate 1
- Addressing the underlying cause of hyponatremia and tailoring sodium supplementation to the specific clinical context.
In practice, the management of hypoosmolar hyponatremia requires a nuanced approach, taking into account the patient's volume status, underlying cause, and potential risks of treatment, as highlighted in recent guidelines on the management of ascites in cirrhosis 1.
From the Research
Hyponatremia Treatment
- The treatment of hyponatremia depends on the underlying cause and the severity of symptoms 2, 3, 4, 5.
- For hypovolemic hyponatremia, treatment with isotonic saline (0.9% NaCl) is recommended 4, 5.
- However, for hypoosmolar hyponatremia, the use of 0.9% NaCl may not be appropriate as it can worsen the condition by increasing the amount of sodium in the body without adequately addressing the underlying cause of water retention 3, 5.
- In cases of euvolemic and hypervolemic hyponatremia, treatment options include fluid restriction, loop diuretics, and vasopressin antagonists (vaptans) 3, 4, 5.
- Hypertonic saline is reserved for the treatment of severe symptomatic hyponatremia, where rapid correction of serum sodium levels is necessary to prevent neurological complications 2, 6.
Risks of Rapid Correction
- Rapid correction of chronic hyponatremia can lead to osmotic demyelination syndrome, a rare but severe neurological condition that can result in permanent disability or death 2, 3.
- The risk of osmotic demyelination syndrome highlights the importance of careful management and monitoring of patients with hyponatremia, particularly when using hypertonic saline or other treatments that can rapidly correct serum sodium levels 6.