What is the management for hypernatremia (elevated sodium level) in a 50kg patient with a sodium level of 166 mmol/L, currently asymptomatic, due to incorrect normal saline (0.9% saline) infusion instead of half normal saline (0.45% saline)?

Management of Acute Hypernatremia (Na 166 mmol/L) in a 50kg Patient

For a 50kg patient with acute hypernatremia (Na 166 mmol/L) due to inappropriate normal saline administration, switch immediately to 0.18% saline with 4% dextrose at a rate of 60-80 mL/hour and recheck sodium levels every 4 hours until stabilized.

Assessment of the Situation

This is a case of iatrogenic hypernatremia caused by inappropriate fluid administration (normal saline instead of half-normal saline). The patient is currently asymptomatic, which is favorable, but urgent intervention is still required to prevent complications.

Key Considerations:

• Acute hypernatremia (likely <48 hours since it was iatrogenic)
• Patient weight: 50kg
• Current sodium: 166 mmol/L (severely elevated)
• Patient is asymptomatic
• Cause: Iatrogenic due to inappropriate fluid selection

Treatment Plan

1. Fluid Selection

• 0.18% saline with 4% dextrose is appropriate for this situation
• This hypotonic solution will help correct the hypernatremia without causing rapid shifts in sodium levels
• The dextrose component helps provide free water once metabolized

2. Rate of Correction

• For acute hypernatremia (<48 hours), sodium can be corrected more rapidly than chronic cases
• Target correction rate: 8-10 mmol/L per 24 hours 1, 2
• Do not exceed correction of 10 mmol/L in the first 24 hours to avoid cerebral edema

3. Initial Infusion Rate

• Calculate free water deficit:
  • Free water deficit = 0.6 × body weight (kg) × [(current Na⁺/140) - 1]
  • For 50kg patient: 0.6 × 50 × [(166/140) - 1] ≈ 5.5 liters
• Start infusion at 60-80 mL/hour of 0.18% saline with 4% dextrose
• This provides hypotonic fluid to gradually correct the hypernatremia

4. Monitoring

• Check serum sodium every 4 hours initially 1
• Adjust infusion rate based on sodium levels and clinical status
• Monitor for signs of cerebral edema (headache, altered mental status, seizures)
• Track fluid balance carefully

Cautions and Potential Complications

• Avoid overly rapid correction which can lead to cerebral edema
• If sodium decreases too rapidly (>1 mmol/L/hour), slow down the infusion rate
• Watch for signs of fluid overload, especially if the patient has cardiac or renal issues
• Hyperglycemia may occur with dextrose-containing solutions, so monitor blood glucose

Follow-up Management

• Once sodium begins to normalize, reassess fluid requirements
• Consider switching to oral fluids if the patient is alert and can drink
• Investigate the root cause of the error to prevent recurrence
• Document the incident and management plan clearly

When to Escalate Care

• If sodium levels don't respond to therapy
• If the patient develops neurological symptoms
• If there are signs of fluid overload or other complications

This approach provides a controlled correction of hypernatremia while minimizing the risk of complications from overly rapid correction.