How should hyponatremia and hypochloremia be treated?

Treatment of Hyponatremia and Hypochloremia

The most effective treatment depends on the underlying cause and volume status: hypovolemic hyponatremia requires isotonic saline for volume repletion, euvolemic hyponatremia (SIADH) requires fluid restriction as first-line therapy, and hypervolemic hyponatremia requires fluid restriction with management of the underlying condition (heart failure, cirrhosis). 1

Initial Assessment and Classification

The first critical step is determining volume status through physical examination, though this has limited accuracy (sensitivity 41%, specificity 80%) 1. Look for specific signs:

• Hypovolemic signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Euvolemic signs: absence of edema, normal blood pressure, moist mucous membranes 1
• Hypervolemic signs: peripheral edema, ascites, jugular venous distention, pulmonary congestion 1

Obtain serum and urine osmolality, urine sodium concentration, and urine electrolytes to guide diagnosis 1. A urine sodium <30 mmol/L predicts response to saline infusion with 71-100% positive predictive value in hypovolemic hyponatremia 1.

Treatment Based on Volume Status

Hypovolemic Hyponatremia

Administer isotonic saline (0.9% NaCl) for volume repletion, starting at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on clinical response 1. Discontinue any diuretics immediately if sodium is <125 mmol/L 1. For patients with cirrhosis, consider albumin infusion (6-8 g per liter of ascites drained) alongside isotonic saline 1.

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment for SIADH 1. If fluid restriction fails after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1. For resistant cases, consider:

• Urea as a pharmacological option 1
• Loop diuretics 1
• Vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrate to 30-60 mg) 1
• Demeclocycline or lithium (less commonly used due to side effects) 1

Hypervolemic Hyponatremia

Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L 1. Management focuses on treating the underlying condition:

• Heart failure: Continue diuretics despite hyponatremia, as fluid overload takes priority; only stop diuretics if sodium drops below 120 mmol/L 1
• Cirrhosis: Temporarily discontinue diuretics if sodium <125 mmol/L, consider albumin infusion, and avoid hypertonic saline unless life-threatening symptoms are present 1

Critical point: It is sodium restriction, not fluid restriction, that results in weight loss in cirrhotic patients, as fluid passively follows sodium 1.

Critical Correction Rate Guidelines

The maximum correction rate must not exceed 8 mmol/L in any 24-hour period to prevent osmotic demyelination syndrome 1. This is the single most important safety principle.

• Standard-risk patients: Target 4-8 mmol/L per day, maximum 10-12 mmol/L in 24 hours 1
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy): Limit to 4-6 mmol/L per day, absolute maximum 8 mmol/L in 24 hours 1

Severe Symptomatic Hyponatremia

For patients with seizures, coma, or altered mental status, this is a medical emergency requiring immediate intervention:

• Administer 3% hypertonic saline with initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1
• Give 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals 1
• Monitor serum sodium every 2 hours during initial correction 1
• Still respect the 8 mmol/L/24-hour limit even in emergencies 1

Management of Hypochloremia

Hypochloremia typically resolves with correction of hyponatremia when using isotonic balanced solutions that provide appropriate chloride content 1. Isotonic saline (0.9% NaCl) contains 154 mEq/L of both sodium and chloride 1. Regular monitoring of plasma electrolyte levels is essential during treatment 1.

Special Considerations for Neurosurgical Patients

Distinguish between SIADH and cerebral salt wasting (CSW), as they require opposite treatments 1:

• SIADH: Euvolemic, treat with fluid restriction 1
• CSW: Hypovolemic (CVP <6 cm H₂O), treat with volume and sodium replacement with isotonic or hypertonic saline, plus fludrocortisone 0.1-0.2 mg daily for severe cases 1

Never use fluid restriction in CSW or in subarachnoid hemorrhage patients at risk of vasospasm, as this worsens outcomes 1.

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours:

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise 1
• Target is to bring the total 24-hour correction back to ≤8 mmol/L from baseline 1

Monitoring Protocol

• Severe symptoms: Check sodium every 2 hours during initial correction 1
• Mild symptoms: Check sodium every 4 hours after symptom resolution 1
• Asymptomatic/chronic: Check sodium every 24-48 hours initially 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours – this causes osmotic demyelination syndrome 1
• Never use fluid restriction in cerebral salt wasting – this worsens outcomes and can be fatal 1
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms – it worsens edema and ascites 1
• Never ignore mild hyponatremia (130-135 mmol/L) – it increases fall risk (21% vs 5%) and mortality (60-fold increase with sodium <130 mmol/L) 1
• Inadequate monitoring during active correction is a critical error 1
• Failing to recognize and treat the underlying cause leads to recurrence 1