Serum Sodium of 135 mEq/L: Management
No Active Treatment Required
A serum sodium of 135 mEq/L is at the lower limit of normal and does not require specific treatment for hyponatremia. 1
Clinical Context and Monitoring
- Hyponatremia is defined as serum sodium <135 mEq/L, making 135 mEq/L technically normal 1, 2, 3
- However, this borderline value warrants closer monitoring in certain clinical contexts, as even mild reductions below 135 mEq/L are associated with increased fall risk (21% vs 5% in normonatremic patients) and mortality 1
- The American Association for the Study of Liver Diseases recommends further investigation and treatment when serum sodium falls below 131 mmol/L 1
Risk Assessment Based on Clinical Context
High-Risk Populations Requiring Closer Monitoring
- Neurosurgical patients: Even mild hyponatremia requires closer monitoring as it may indicate cerebral salt wasting or SIADH 1
- Cirrhotic patients: Sodium levels approaching 130 mmol/L indicate worsening hemodynamic status and increased risk of complications including spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
- Patients on diuretics: Continue diuretic therapy with close monitoring of serum electrolytes, as sodium 135 mmol/L does not require water restriction or medication adjustment 1
- Elderly patients: The hyponatremic group tends to be significantly older and at higher risk for complications 4
When to Discontinue Fluid Restriction
- For patients previously on fluid restriction for hyponatremia, restriction can be safely discontinued when serum sodium rises above 130 mmol/L in cirrhotic patients 5
- For neurosurgical patients, fluid restriction can be discontinued when serum sodium reaches 131 mmol/L 5
- After discontinuing fluid restriction, reduce monitoring frequency from every 2-4 hours to daily 5
Recommended Monitoring Strategy
- For patients with cirrhosis and sodium 126-135 mmol/L with normal renal function: No fluid restriction is needed, and diuretics can be safely continued 5
- For patients on diuretics: Continue to observe serum electrolytes without intervention 1
- Monitor for underlying causes if sodium begins to trend downward, including medication review (particularly diuretics, carbamazepine, SSRIs), assessment of fluid intake, and evaluation for heart failure, cirrhosis, or SIADH 2, 3
Common Pitfalls to Avoid
- Do not ignore borderline values (135 mmol/L) as clinically insignificant, particularly in high-risk populations 1
- Do not implement fluid restriction at sodium 135 mmol/L, as this is reserved for sodium <125-130 mmol/L depending on volume status 1, 5
- Do not discontinue diuretics at this sodium level unless there are other clinical indications 1
- Failing to recognize that sodium restriction (not fluid restriction) results in weight loss in cirrhotic patients, as fluid passively follows sodium 1