How to correct hypernatremia from 154 to 140 using 1/4 normal saline?

Correcting Hypernatremia from 154 to 140 mmol/L Using 1/4 Normal Saline

For hypernatremia correction from 154 to 140 mmol/L using 1/4 normal saline (0.225% NaCl), calculate the free water deficit and infuse at a rate that reduces sodium by no more than 10-12 mmol/L per 24 hours, monitoring serum sodium every 4-6 hours to prevent overly rapid correction and osmotic demyelination syndrome. 1, 2

Calculating the Free Water Deficit

• Use the Adrogue-Madias formula to estimate free water deficit: Free water deficit (L) = 0.6 × body weight (kg) × [(current Na ÷ desired Na) - 1] 3
• For a 70 kg patient: 0.6 × 70 × [(154 ÷ 140) - 1] = 4.2 liters of free water deficit 3
• This calculation provides the total volume needed, but correction must occur gradually over 48-72 hours 2, 3

Understanding 1/4 Normal Saline Composition

• 1/4 normal saline (0.225% NaCl) contains approximately 38.5 mEq/L of sodium with an osmolarity of ~77 mOsm/L, making it hypotonic and appropriate for hypernatremia correction 1
• This solution provides substantial free water while delivering minimal sodium, allowing gradual reduction of serum sodium 1

Critical Correction Rate Limits

• Maximum correction rate: 10-12 mmol/L per 24 hours, or approximately 0.5 mmol/L per hour 2, 4
• For your case (154 to 140 = 14 mmol/L decrease needed): plan correction over minimum 48 hours, ideally 72 hours 2, 3
• Target reduction: 6-8 mmol/L in first 24 hours, then 6 mmol/L in second 24 hours 2

Calculating Infusion Rate

• For a 70 kg patient needing to reduce sodium by 6 mmol/L in 24 hours:
  • Estimated volume needed: approximately 2-3 liters of 1/4 NS over 24 hours 3
  • Infusion rate: 80-125 mL/hour 3
• Adjust rate based on ongoing losses (urine output, insensible losses) and patient's volume status 3

Essential Monitoring Protocol

• Check serum sodium every 4-6 hours during active correction to ensure rate does not exceed 0.5 mmol/L per hour 2, 4
• Monitor serum osmolality every 6-8 hours, ensuring change does not exceed 3 mOsm/kg H₂O per hour 2
• Track urine output, vital signs, and neurological status continuously 3
• If correction rate exceeds 12 mmol/L in 24 hours, immediately slow or stop infusion 2, 5

Special Considerations and Pitfalls

• Patients with chronic hypernatremia (>48 hours duration) require slower correction at <0.5 mmol/L/hour to prevent cerebral edema from rapid osmotic shifts 4
• If patient has renal concentrating defects (diabetes insipidus), ongoing free water losses must be replaced in addition to deficit correction 1
• Never use isotonic saline (0.9% NaCl) in hypernatremia as it will worsen the condition 1
• Avoid overly rapid correction which can cause seizures, cerebral edema, and neurological damage 2, 4

Adjusting for Clinical Response

• If sodium decreases faster than expected: slow infusion rate by 25-50% and recheck sodium in 2 hours 5
• If sodium decreases too slowly: increase infusion rate by 20-30% and reassess 3
• Once sodium reaches 145 mmol/L, consider switching to maintenance fluids and slower correction for remaining deficit 3

Alternative Hypotonic Fluid Options

• 0.45% NaCl (half-normal saline) with 77 mEq/L sodium can be used for less aggressive correction if 1/4 NS unavailable 1
• D5W (5% dextrose in water) provides pure free water but risks hyperglycemia and should be reserved for severe hypernatremia 1
• The choice between 1/4 NS and 0.45% NS depends on severity: use 1/4 NS for more aggressive free water replacement 1