What is the recommended prefilter D5W (5% dextrose in water) rate for a 95kg patient with hyponatremia (sodium 122 mEq/L) on Continuous Renal Replacement Therapy (CRRT) with a sodium bath of 140 mEq/L?

Calculating Prefilter D5W Rate for Hyponatremic Patient on CRRT

For a 95kg patient with hyponatremia (sodium 122 mEq/L) on CRRT with a sodium bath of 140 mEq/L, the recommended prefilter D5W rate is approximately 1000-1200 mL/hour to prevent overcorrection of hyponatremia.

Rationale for Prefilter D5W in Hyponatremia

• Patients with hyponatremia on CRRT are at risk for overcorrection due to preformulated isotonic replacement or dialysate fluids (typically 140 mEq/L sodium) 1
• Rapid correction of hyponatremia can lead to osmotic demyelination syndrome (ODS), a serious neurologic complication 1, 2
• Adding calculated amounts of D5W prefilter can prevent overcorrection while still delivering recommended CRRT effluent volumes 1

Calculation Method

For a 95kg patient with sodium of 122 mEq/L on CRRT with sodium bath of 140 mEq/L:

1. Determine target sodium correction rate:

   • For patients with chronic hyponatremia, the goal rate of increase should be 4-6 mEq/L per 24-hour period, not exceeding 8 mEq/L per 24-hour period 2
   • This patient has moderate hyponatremia (120-125 mEq/L) requiring careful correction 2, 3

2. Calculate prefilter D5W rate:

   • Using the mixing paradigm approach to balance sodium concentration 4
   • D5W rate = Blood flow rate × [(Bath sodium - Target sodium) ÷ Target sodium]
   • For typical CRRT settings with blood flow of 150-200 mL/min and targeting a correction of 6 mEq/L/day:
     • D5W rate ≈ 1000-1200 mL/hour 1, 4

Implementation Guidelines

• Monitor serum sodium every 4-6 hours to ensure correction rate does not exceed 8 mEq/L in 24 hours 2
• Adjust D5W rate based on measured sodium levels and correction rate 1, 4
• Continue D5W infusion until serum sodium reaches 130-132 mEq/L, then reassess 3

Special Considerations

• If sodium correction exceeds target rate, increase D5W rate to slow correction 1
• Warming the dialysate helps maintain hemodynamic stability during CRRT 2
• For CRRT with regional citrate anticoagulation, sodium adjustment can still be performed without compromising anticoagulation efficacy 5

Potential Complications and Monitoring

• Watch for signs of ODS: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 2
• Risk factors for ODS include advanced liver disease, alcoholism, severe hyponatremia, malnutrition, and metabolic derangements 2
• Monitor for other electrolyte abnormalities that may develop during CRRT 5

Alternative Approaches

• If D5W prefilter is not feasible, consider:
  • Custom sodium-diluted dialysate/replacement fluids 6
  • Reduced effluent volume (though this may compromise clearance of other solutes) 1
  • Post-filter D5W infusion 4

Remember that the goal is to prevent rapid correction while still providing adequate renal replacement therapy. The prefilter D5W approach allows for safe sodium correction while maintaining recommended CRRT effluent volumes.