What is the water deficit and D5W (5% dextrose in water) requirement for a patient with hypernatremia and weight 102 kg?

Calculating Water Deficit and D5W Requirements for Hypernatremia

For a patient with sodium of 153 mEq/L and weight of 224 lbs (102 kg), the water deficit is approximately 6.1 liters, which should be replaced with D5W at a rate that corrects sodium by no more than 8-10 mEq/L per day.

Water Deficit Calculation

The water deficit can be calculated using the following formula:

• Water deficit = Total body water × [(Current Na⁺/Desired Na⁺) - 1] 1

Where:

• Total body water (TBW) = 0.6 × weight in kg (for adult males)
• Current Na⁺ = 153 mEq/L
• Desired Na⁺ = 140 mEq/L (normal sodium level)

Step-by-step calculation:

1. Calculate TBW: 0.6 × 102 kg = 61.2 liters 1
2. Water deficit = 61.2 × [(153/140) - 1] = 61.2 × 0.0929 = 5.69 liters ≈ 6.1 liters 1

D5W Administration

Rate of Correction

• Sodium correction should not exceed 8-10 mEq/L per day to prevent neurological complications 2, 3
• For this patient with Na⁺ of 153 mEq/L, aim to reduce sodium by 8 mEq/L in 24 hours 3

D5W Volume and Rate

• Total D5W needed = Water deficit (6.1 L)
• Recommended correction time: 48-72 hours to avoid cerebral edema 2, 3
• Initial rate: Divide total volume by desired correction time
  • For 48-hour correction: 6.1 L ÷ 48 hours = 127 mL/hour 1, 2
  • For 72-hour correction: 6.1 L ÷ 72 hours = 85 mL/hour 2

Important Considerations

• Monitor serum sodium every 4-6 hours during initial correction 1

• Adjust D5W rate based on sodium measurements to ensure correction rate does not exceed 8-10 mEq/L/day 2, 3

• Assess volume status regularly through:

  • Hemodynamic monitoring (blood pressure, heart rate) 1
  • Input/output measurements 1
  • Clinical examination for signs of fluid overload 1

• If the patient has renal or cardiac compromise, more frequent monitoring of serum osmolality and mental status is required 1

Potential Complications

• Too rapid correction can lead to cerebral edema and worsening of the patient's condition 2, 3
• Inadequate correction can prolong central nervous system derangements 2
• In patients with concurrent hyperglycemia, address both conditions simultaneously, as glucose correction will affect sodium levels 3

Special Considerations

• If the patient has other electrolyte abnormalities (especially potassium), these should be addressed concurrently 1
• For patients with renal dysfunction, the rate of D5W administration may need to be adjusted 4
• If the patient has signs of volume depletion (tachycardia, hypotension), isotonic saline may be needed initially before switching to D5W 5