What is the recommended protocol for initiating peritoneal dialysis in patients with impaired renal function?

Initiating Peritoneal Dialysis in Patients with Impaired Renal Function

Peritoneal dialysis should be initiated when weekly Kt/Vurea falls below 2.0 (equivalent to creatinine clearance 9-14 mL/min/1.73 m²), or definitively started if nutritional deterioration occurs despite optimization efforts, using either an incremental approach that maintains total Kt/Vurea ≥2.0 or full-dose therapy with four 2-L exchanges daily. 1

Timing of Initiation

Primary Threshold Criteria

• Strongly consider dialysis when weekly Kt/Vurea drops below 2.0, which corresponds to a creatinine clearance of 9-14 mL/min/1.73 m² 1
• This threshold applies regardless of whether clearance comes from residual kidney function or peritoneal dialysis, as both are considered equivalent for solute removal 1

Mandatory Initiation Triggers

Dialysis must be definitively implemented if any of the following nutritional indicators deteriorate despite vigorous attempts to optimize protein and energy intake 1:

• >6% involuntary reduction in edema-free usual body weight or decline to <90% of standard body weight (NHANES II) within 6 months 1
• Serum albumin reduction ≥0.3 g/dL to <4.0 g/dL in the absence of acute infection or inflammation, confirmed by repeat testing 1
• Deterioration in Subjective Global Assessment (SGA) by one category (normal → mild → moderate → severe) 1

The rationale is that late initiation carries known and unacceptable risks of malnutrition and uremic complications, while early initiation risks are small and justifiable 1

Initial Prescription Strategies

Two Acceptable Approaches

Option 1: Incremental Initiation 1

• Increase peritoneal Kt/Vurea (Kpt/Vurea) incrementally so that combined residual kidney Kt/Vurea (Krt/Vurea) + Kpt/Vurea maintains total ≥2.0 weekly
• Requires frequent measurement of residual kidney function to ensure total solute removal doesn't drop below target 1
• Measurements needed every 2-4 weeks initially 1

Option 2: Full-Dose Initiation 1

• Start with four 2-L exchanges per day, yielding weekly Kpt/Vurea of 1.5-2.0 depending on transport characteristics, ultrafiltration, and body size 1
• Allows less intense monitoring of residual kidney function 1
• More straightforward for most patients and clinicians 1

Pediatric Patients

• Use body surface area (BSA) for normalization rather than absolute volumes 1
• Prescribe instilled volume of at least 1,100 mL/m² BSA for most pediatric patients, adjusted for individual tolerance 1

Training and Early Monitoring Protocol

During Training Period 1

• Determine 4-hour drain volumes with 1.5%, 2.5%, or 4.25% dextrose exchanges to assess if patient's peritoneal membrane transport differs markedly from mean 1
• Monitor for catheter site leakage 1
• Perform baseline serum chemistries and complete blood count 1

At 2-4 Weeks Post-Initiation 1

• Perform 24-hour dialysate and urine collection measuring: 1
  • Kt/Vurea
  • Creatinine clearance
  • Protein nitrogen appearance (PNA)
  • Creatinine generation
  • D/P creatinine and D/P urea ratios

At 1 Month Post-Initiation 1, 2

• Perform Peritoneal Equilibration Test (PET) to establish baseline membrane transport characteristics 1, 2
• This identifies transport category (low, average, high) which guides long-term prescription 1, 2
• Repeat serum chemistries and complete blood count 1

Prescription Adjustments Based on Transport Status

Low Transporters 2

Low transporters have good ultrafiltration but may have inadequate peritoneal creatinine clearance, especially in larger patients 2

Prescription by Body Surface Area: 2

• BSA ≤1.7 m²: 2.5 L/day CAPD or 2.5 L (9 hours/night) + 2.0 L/day CCPD
• BSA 1.7-2.0 m²: 3.0 L/day CAPD or 3.0 L (9 hours/night) + 2.5 L/day CCPD
• BSA >2.0 m²: 3.0 L/day CAPD with nocturnal device or 3.0 L (10 hours/night) + 3.0 L/day CCPD

If Clearances Below Target at 1 Month 1

• First evaluate compliance and collection procedures for errors 1
• Increase instilled volume to maximize mass transfer and dwell time (most effective approach) 1
• Alternative: increase number of exchanges per day while maintaining maximum dwell time (e.g., add single nighttime exchange for 5 equal dwells/day) 1
• Consider transfer to hemodialysis if adequate clearance cannot be achieved despite maximal PD prescription 2

Critical Pitfalls to Avoid

Common Errors

• Do not confuse low drain volumes from mechanical problems or leaks with low transporter status - verify technical issues are resolved before classifying transport characteristics 2
• Do not delay initiation waiting for symptoms - the risks of late initiation (malnutrition, uremic complications) are known and unacceptable 1
• Do not use PD in patients at high risk for infections or "burn-out" - consider hemodialysis as alternative renal replacement therapy 1

Monitoring Intensity

• With incremental approach: frequent residual kidney function measurement is mandatory to prevent inadequate total clearance 1
• With full-dose approach: less frequent residual kidney function monitoring is acceptable 1

Special Populations

Diabetic Patients

• General consensus supports initiating dialysis at higher levels of residual kidney function than non-diabetic patients 1
• Apply same nutritional deterioration criteria but with lower threshold for intervention 1

Patients with Minimal Residual Function

• Those transferring from hemodialysis with minimal residual kidney function require prompt adequacy testing after PD initiation 1
• Cannot rely on residual function to meet clearance targets 1