What is the recommended treatment approach for a patient with water intoxication, considering serum sodium levels and potential underlying conditions such as heart, liver, or kidney disease?

Management of Water Intoxication

For water intoxication, immediately restrict fluid intake and administer hypertonic saline (3% NaCl) if the patient has severe symptoms (seizures, altered mental status, coma), targeting a sodium correction of 6 mmol/L over the first 6 hours, with total correction not exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Diagnosis

Water intoxication presents as hypotonic hyponatremia caused by excessive water intake overwhelming the kidney's dilutional capacity 2, 3. The median volume consumed is approximately 8 L/day, with serum sodium typically around 118 mmol/L at presentation 2.

Key diagnostic steps:

• Obtain serum sodium, serum osmolality, urine osmolality, and urine sodium to confirm hypotonic hyponatremia 1
• Assess volume status through physical examination (looking for signs of euvolemia or hypervolemia, as water intoxication typically presents without hypovolemia) 1
• Evaluate for underlying psychiatric conditions (present in 52% of cases), iatrogenic causes (13%), or exercise-related polydipsia (12%) 2
• Rule out SIADH, cerebral salt wasting, and other causes of hyponatremia through clinical context and laboratory findings 1, 4

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Seizures, Coma, Altered Mental Status)

Immediate intervention with hypertonic saline is required:

• Administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve 1, 5
• Total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 6
• Monitor serum sodium every 2 hours during initial correction 1
• Consider ICU admission for close monitoring 1

The rationale for this aggressive approach is that severe symptoms (present in 53% of water intoxication cases) carry significant mortality risk (13% death rate) 2.

Moderate Symptoms (Confusion, Vomiting, Agitation)

• Implement strict fluid restriction (typically <1 L/day) 1, 5
• Consider isotonic saline (0.9% NaCl) for supportive care if needed 2
• Monitor serum sodium every 4 hours initially 1
• Target slower correction rate of 4-8 mmol/L per day 1

Mild or Asymptomatic Cases

• Immediate fluid restriction is the cornerstone of treatment 5, 4
• Supportive care with treatment of underlying cause 2
• Monitor serum sodium every 24 hours initially 1

Critical Correction Rate Guidelines

The sodium correction rate is directly associated with complications, particularly rhabdomyolysis:

• Rapid sodium correction (>1.02 mEq/L/h) significantly increases rhabdomyolysis risk (adjusted OR 1.53 per 0.1 mEq/L/h increase) 6
• Maximum correction should not exceed 8 mmol/L in 24 hours for any patient 1, 6
• For high-risk patients (those with chronic psychiatric conditions, malnutrition, or liver disease), limit correction to 4-6 mmol/L per day 1

Monitoring for Complications

Water intoxication carries significant complication risks:

• Rhabdomyolysis occurs in 62.5% of cases and should be monitored with serial creatine kinase levels 6
• Osmotic demyelination syndrome occurs in 3% of cases, typically 2-7 days after rapid correction 1, 2
• Watch for signs including dysarthria, dysphagia, oculomotor dysfunction, and quadriparesis 1

Management of Underlying Causes

Address the motivator for excessive water intake:

• For psychogenic polydipsia (55% of cases): behavioral interventions, psychiatric consultation, and medications that oppose ADH action 5, 2
• For iatrogenic causes (13%): discontinue offending medications or practices 2
• For exercise-related polydipsia (12%): education on appropriate hydration strategies 2

Common Pitfalls to Avoid

• Never use hypotonic fluids (such as 0.45% NaCl or D5W) in water intoxication, as this will worsen hyponatremia 1
• Avoid overly rapid correction exceeding 8 mmol/L in 24 hours, which causes osmotic demyelination syndrome 1, 6
• Do not delay treatment in symptomatic patients while awaiting complete diagnostic workup 2
• Never use fluid restriction alone for severe symptomatic hyponatremia—hypertonic saline is required 1, 5

Special Considerations

For patients with underlying conditions:

• Heart, liver, or kidney disease: Use even more cautious correction rates (4-6 mmol/L per day maximum) due to higher risk of osmotic demyelination 1
• Chronic psychiatric patients: Consider long-term behavioral interventions and medications that oppose ADH (such as demeclocycline or lithium) to prevent recurrence 5
• Post-correction management: Continue fluid restriction until serum sodium normalizes and address underlying psychiatric or behavioral causes 5, 2