What is the recommended dose and frequency of urea (Urea) administration?

Urea Dosing and Administration Guidelines

For hemodialysis patients, the target dose for urea clearance should be a single-pool Kt/V (spKt/V) of 1.4 per dialysis session when administered three times per week, with a minimally adequate dose of spKt/V of 1.2 per session. 1

Hemodialysis Dosing Parameters

Standard Three-Times Weekly Hemodialysis

• The minimally adequate dose of hemodialysis given 3 times per week to patients with residual kidney function (Kr) less than 2 mL/min/1.73 m² should be an spKt/V of 1.2 per dialysis 1
• For treatment times less than 5 hours, an alternative minimum dose is a urea reduction ratio (URR) of 65% 1
• The target dose should be an spKt/V of 1.4 per dialysis or URR of 70% 1

Patients with Residual Kidney Function

• In patients with residual urea clearance (Kr) greater than or equal to 2 mL/min/1.73 m², the minimum session spKt/V can be reduced 1
• For these patients, the target spKt/V should be at least 15% greater than the minimum dose 1

Peritoneal Dialysis Dosing

CAPD (Continuous Ambulatory Peritoneal Dialysis)

• The minimal "delivered" dose of total small-solute clearance should be a total (peritoneal and kidney) Kt/V urea of at least 1.7 per week 1
• This is a revision from previous guidelines that recommended a weekly Kt/V urea of 2.0 1
• Total solute clearance should be measured within the first month after initiating dialysis therapy and at least once every 4 months thereafter 1

Residual Kidney Function Monitoring

• If the patient has greater than 100 mL/d of residual kidney volume, a 24-hour urine collection for urine volume and solute clearance determinations should be obtained at minimum every 2 months 1

Monitoring and Compliance

Frequency of Measurement

• Kt/V urea should be measured within the first month after initiating dialysis therapy and at least once every 4 months thereafter 1
• Efforts should be made to monitor and minimize the occurrence of missed or shortened treatments, as these significantly impact outcomes 1

Sampling Methods

• When using the stop-dialysate-flow method for blood sampling, blood flow must not be reduced as dialysate needs to equilibrate with blood quickly 1
• A 3-minute waiting period after stopping dialysate flow is sufficient for equilibration 1

Special Considerations

Alternative Dialysis Schedules

• For twice-weekly hemodialysis schedules, patients should have substantial residual kidney function 1
• The same minimum levels of spKt/V are recommended for hemofiltration and hemodiafiltration as for standard hemodialysis 1

Urea for Hyponatremia Treatment

• For hyponatremia treatment, particularly in SIADH, urea is typically administered at doses of 0.25-0.50 g/kg/day 2
• A median dose of 30 g/day has been shown to effectively increase serum sodium levels 3, 4
• Patient tolerance may be an issue, with distaste being a common side effect, though it rarely leads to treatment discontinuation 2, 4

Pitfalls and Caveats

• Overcorrection of serum sodium (increase >8 mEq/L in 24 hours) can occur in approximately 8% of patients treated with urea for hyponatremia 3
• The stop-dialysate-flow method has not been validated during pediatric dialysis 1
• With large dialyzers used at relatively lower blood flow rates, dialyzer outlet blood may still have substantially lower urea concentration than inlet blood after 3 minutes of stopping dialysate flow 1
• Patient compliance with dialysis schedules significantly impacts outcomes, with missed treatments being an important predictor of mortality and hospitalizations 1