Approach for Correcting Hyponatremia
The correction of hyponatremia must be guided by symptom severity and chronicity, with the absolute priority being prevention of osmotic demyelination syndrome by limiting correction to 8 mmol/L in 24 hours for most patients, while ensuring severe symptomatic cases receive immediate hypertonic saline to prevent death from cerebral edema. 1
Initial Assessment Framework
Before initiating treatment, rapidly determine three critical factors:
- Symptom severity: Severe symptoms (seizures, coma, altered consciousness, respiratory distress) versus mild symptoms (nausea, headache, confusion) versus asymptomatic 1, 2
- Chronicity: Acute (<48 hours) versus chronic (>48 hours) onset—this fundamentally changes your correction rate safety profile 1, 3
- Volume status: Hypovolemic (orthostatic hypotension, dry mucous membranes, decreased skin turgor), euvolemic (normal volume status), or hypervolemic (edema, ascites, jugular venous distention) 1
Essential initial workup includes serum and urine osmolality, urine sodium, urine electrolytes, serum uric acid, and assessment of extracellular fluid volume 1. A urine sodium <30 mmol/L predicts response to saline with 71-100% positive predictive value in hypovolemic states 1.
Treatment Algorithm Based on Symptom Severity
Severe Symptomatic Hyponatremia (Medical Emergency)
For patients with seizures, coma, or altered mental status, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve. 1, 4
- Administer 100 mL boluses of 3% saline over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms improve 1
- Monitor serum sodium every 2 hours during initial correction 1
- Critical safety limit: Total correction must not exceed 8 mmol/L in 24 hours 1, 5
- After achieving 6 mmol/L correction in the first 6 hours, only 2 mmol/L additional correction is permitted in the remaining 18 hours 1
- Transition to mild symptom protocol once severe symptoms resolve 6
Mild Symptomatic or Asymptomatic Hyponatremia
Treatment depends entirely on volume status:
Hypovolemic hyponatremia: Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1. This addresses the underlying cause while safely correcting sodium.
Euvolemic hyponatremia (SIADH): Fluid restriction to 1 L/day is the cornerstone of treatment 1. If no response after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1. For resistant cases, consider vasopressin receptor antagonists (tolvaptan 15 mg once daily) 1, 5.
Hypervolemic hyponatremia (heart failure, cirrhosis): Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1. In cirrhotic patients, consider albumin infusion alongside fluid restriction 1. Avoid hypertonic saline unless life-threatening symptoms are present, as it worsens edema and ascites 1.
Critical Correction Rate Guidelines
The maximum safe correction rate is 8 mmol/L per 24 hours for most patients 1, 5. However, high-risk populations require even slower correction:
High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy, severe hyponatremia <120 mmol/L): Limit correction to 4-6 mmol/L per day 1, 3. These patients have dramatically increased risk of osmotic demyelination syndrome.
For acute hyponatremia (<48 hours), rapid correction at 1 mmol/L/hour is safe because brain adaptation has not yet occurred 1, 3. For chronic hyponatremia (>48 hours), the brain has completed osmotic adaptation, making rapid correction dangerous 3.
Management of Overcorrection
If sodium correction exceeds 8 mmol/L in 24 hours:
- Immediately discontinue all current fluids and switch to D5W (5% dextrose in water) 1
- Administer desmopressin to slow or reverse the rapid rise in serum sodium 1
- The goal is to bring total 24-hour correction back to ≤8 mmol/L from the starting point 1
Osmotic demyelination syndrome typically manifests 2-7 days after overcorrection with dysarthria, dysphagia, oculomotor dysfunction, and quadriparesis 1, 5.
Special Population Considerations
Neurosurgical patients: Distinguish between SIADH and cerebral salt wasting (CSW), as treatments are opposite 1. CSW requires volume and sodium replacement with isotonic or hypertonic saline plus fludrocortisone for severe cases 1. Never use fluid restriction in CSW or subarachnoid hemorrhage patients at risk of vasospasm—this worsens outcomes 1.
Cirrhotic patients: These patients have hypervolemic hyponatremia in ~60% of cases 1. Sodium <130 mmol/L increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1. Tolvaptan carries higher risk of gastrointestinal bleeding in cirrhosis (10% vs 2% placebo) 5.
Common Pitfalls to Avoid
- Ignoring mild hyponatremia (130-135 mmol/L): Even mild chronic hyponatremia increases fall risk (21% vs 5%), hospital mortality (60-fold increase), and causes cognitive impairment 1, 2, 7
- Using normal saline in SIADH: This worsens hyponatremia through dilution 1
- Inadequate monitoring during active correction: Check sodium every 2 hours for severe symptoms, every 4 hours after symptom resolution 1
- Failing to recognize the underlying cause: Treatment must address etiology, not just the number 1
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms: This exacerbates fluid overload 1