Timing of KRT Initiation
The IDEAL Trial: Paradigm Shift
The IDEAL trial (2010) randomized 828 patients: early initiation (eGFR 10–14) vs. late initiation (eGFR 5–7 or uremic symptoms). Results: no significant difference in survival, cardiovascular events, or quality of life. The early group experienced longer exposure to dialysis-related complications without measurable benefit.
Subsequent meta-analyses consistently confirm the absence of survival benefit from early dialysis initiation. Evidence supports symptom-driven initiation rather than arbitrary eGFR thresholds.
Lead Time Bias
Many observational studies reporting survival advantages with early initiation failed to account for lead time bias — earlier detection creates the appearance of improved survival due to extended observation periods, not genuine clinical improvement. RCTs eliminate this bias.
Clinical Indicators for Initiation
- Uremic symptoms: Decreased appetite, nausea, vomiting, altered mental status, sleep disturbances, reduced functional capacity
- Refractory fluid overload: When optimal medical therapy fails to maintain euvolemia
- Metabolic acidosis: Serum bicarbonate consistently <15 mEq/L despite medical management
- Severe electrolyte abnormalities
- Uremic complications: Pericarditis, neuropathy
Peritoneal Dialysis
Principles
Peritoneal membrane (~1–2 m² surface area) serves as natural dialyzing surface. Dialysate creates concentration and osmotic gradients for solute removal and ultrafiltration. Small solutes move via diffusion; larger molecules via convection.
Catheter and Access
- Tenckhoff catheter: Most common; multiple side holes with curled tip
- Placement: Surgical, laparoscopic, or percutaneous
- Break-in period: 2–4 weeks for tunnel maturation; gradual volume escalation
Dialysate Solutions
| Solution | Glucose | UF Capacity | Use |
|---|---|---|---|
| Low | 1.5% | Minimal | Solute clearance when UF not needed |
| Intermediate | 2.5% | Moderate | Routine fluid management |
| High | 4.25% | Maximal | Significant fluid retention; limit frequent use |
| Icodextrin | Corn starch polymer | Sustained | Long dwells; patients with rapid glucose absorption |
Peritoneal Equilibration Testing (PET)
D/P creatinine ratio at 4 hours classifies transport status:
| Transport | D/P Cr Ratio | Characteristics | Best Modality |
|---|---|---|---|
| High | >0.81 | Rapid equilibration; good clearance but rapid glucose absorption, poor UF with long dwells | APD with short, frequent cycles |
| Low | <0.50 | Slow equilibration; maintains UF throughout long dwells | CAPD with longer exchanges |
PD Modalities
- CAPD: 4 manual exchanges daily (4–6 hr dwells, 2–3 L volumes). Freedom from machines; requires dexterity and visual acuity.
- APD: Cycler performs 3–6 cycles over 8–10 hours overnight. May add daytime exchange with icodextrin.
- Tidal PD: Maintains tidal volume (50–85%) in abdomen; may reduce inflow pain. Higher dialysate consumption.
Hemodialysis
Circuit Design
- Blood flow rates: 300–450 mL/min; curvilinear clearance relationship with diminishing returns at higher flows
- Dialysate flow: 500–800 mL/min, counter-current direction; proportioned from acid + bicarbonate concentrates + treated water
- Temperature: 36–37°C standard; cooler dialysate improves hemodynamic stability
- Access recirculation: >10–15% indicates access dysfunction requiring intervention
Post-Dialysis Potassium Rebound
Post-dialysis K+ measurements taken within 15–30 minutes of treatment completion may underestimate true values by 0.5–1.0 mEq/L. Administering potassium supplements based on immediately post-dialysis levels can cause life-threatening hyperkalemia.
Mechanism
Rapid dialytic K+ removal from the intravascular compartment outpaces equilibration with intracellular stores (95% of total body K+ is intracellular). Potassium rebound occurs over 30 minutes to 2 hours as intracellular K+ redistributes to extracellular space.
Evidence-Based Management
- Use pre-dialysis K+ as the primary guide for dialysate K+ prescription and supplementation decisions
- If post-dialysis measurement needed, obtain ≥30–60 minutes after treatment (ideally 2 hours)
- Adjust dialysate K+ concentration rather than supplementing post-treatment
- If supplementation necessary, use oral K+ during the interdialytic period, not IV immediately post-dialysis
Implement standardized protocols that discourage routine post-dialysis K+ measurement and emphasize pre-dialysis values. Track post-dialysis K+ supplementation rates as a quality metric — high rates indicate suboptimal practice patterns.
Vascular Access
| Access Type | Maturation | Advantages | Disadvantages |
|---|---|---|---|
| AV Fistula | 6–12 weeks | Superior longevity; lowest complication rates; highest flow rates | Long maturation; not all patients have suitable anatomy |
| AV Graft | 2–4 weeks | Shorter maturation; when native fistula not possible | Higher infection and thrombosis rates; reduced lifespan |
| CVC | Immediate | Immediate access | Infection, thrombosis, central venous stenosis; minimize use |
Dialysis Adequacy
Kt/V
- K = dialyzer clearance, T = treatment time, V = urea distribution volume
- Target: spKt/V >1.2 per session for thrice-weekly HD
- Equilibrated Kt/V: typically 10–15% lower than single-pool (accounts for urea rebound)
- URR alternative: target >65%
PD Adequacy
- Weekly Kt/V >1.7 (peritoneal + residual renal clearance)
- Creatinine clearance >50 L/week/1.73 m²
- Monthly monitoring of residual renal function
Key Determinants of Adequacy
- Treatment time: Most powerful determinant; linear relationship with solute clearance
- Blood flow rate: Access flow must exceed prescribed Qb by ≥300–400 mL/min
- Dialyzer selection: Larger surface area = increased clearance; high-flux for middle molecule removal
- Vascular access type: AVF > graft > catheter for achievable flow rates
Technique Survival
- PD: 15–20% annual technique failure (inadequacy, complications, preference changes)
- HD: ~90% annual technique survival, limited primarily by access complications
Key References
- Cooper BA, et al. Early versus late initiation of dialysis (IDEAL). N Engl J Med. 2010;363(7):609–619. PubMed
- Rosansky S, et al. Early start of dialysis: a critical review. Clin J Am Soc Nephrol. 2011;6(5):1222–1228. PubMed
- Li PK, et al. ISPD peritonitis guideline 2022 update. Perit Dial Int. 2022;42(2):110–153. PubMed
- Hecking M, et al. Predialysis serum sodium and mortality (DOPPS). Am J Kidney Dis. 2012;59(2):238–248. PubMed