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Dialysis in theTreatment of Kidney Failure

Chapter 323 | Part 9: Disorders of the Kidney and Urinary Tract · Part 9 – Renal & Urinary Tract Disorders · Chapter 323

Key Clinical Points

  1. ESKD prevalence in the US exceeds 800,000 patients; prevalence increased 65% since 2000 due to improved survival.
  2. Primary causes of ESKD in the US: Diabetes mellitus (~45%) and hypertension (~30%).
  3. Criteria for initiating maintenance dialysis: uremic symptoms, hyperkalemia (unresponsive to conservative measures), persistent volume expansion, acidosis (refractory to therapy), bleeding diathesis, and GFR <10 mL/min per 1.73 m².
  4. Hemodialysis adequacy targets: Urea Reduction Ratio (URR) >65–70% and Kt/V >1.2 or 1.05 (depending on equilibration).
  5. Peritoneal dialysis peritonitis definition: peritoneal fluid leukocyte count >100/mm³ with ≥50% polymorphonuclear neutrophils.
  6. Cardiovascular disease is the leading cause of death in ESKD patients; mortality is highest in the developing world due to limited access.
  7. The 'fistula first' initiative prioritizes arteriovenous fistulas for superior long-term patency and lower infection rates.
  8. High peritoneal transporters (rapid equilibration) absorb more glucose and lose albumin, requiring more frequent, shorter dwell-time exchanges.
  9. Midodrine has been advocated for hypotension but lacks sufficient evidence for routine use; rapid fluid removal (>13 mL/kg per h) is associated with adverse outcomes.

1. DEFINITION & OVERVIEW

• Overview: Dialysis is required for both acute and even chronic kidney disease (CKD). The focus here is on end-stage kidney disease (ESKD). • ESKD Prevalence: ◦ Over 800,000 patients in the US; prevalence increased 65% since 2000 due to improved survival. ◦ Crude incidence rate: 363 cases per million population per year. • Demographics: Higher incidence in African Americans (partially linked to high-risk alleles for the APOL1 gene). • Primary Causes of ESKD: ◦ Diabetes Mellitus: ~45% of new cases. ◦ Hypertension: ~30% of cases (cause vs. consequence of vascular disease is unclear). ◦ Other causes: Glomerulonephritis, polycystic kidney disease, and obstructive uropathy. • Treatment Modalities: ◦ Hemodialysis (HD): Most common (>80%); performed in-center or at home. ◦ Peritoneal Dialysis (PD): Continuous; less efficient solute clearance than HD; rarely used for AKI/CKD due to infection risk and lower efficiency per unit of time. ◦ Transplantation: Alternative treatment (see Chap. 325).

2. EPIDEMIOLOGY

• Global Mortality: Lowest in Europe and Japan; very high in the developing world due to limited dialysis availability. • US Trends: Mortality rates remained high prior to COVID-19; significant increase noted during the pandemic (point estimates removed). • Predictors of Death: ◦ Older age ◦ Male sex ◦ Nonblack race ◦ Diabetes mellitus ◦ Malnutrition ◦ Underlying heart disease

3. ETIOLOGY & PATHOPHYSIOLOGY

• Dialysis Principles: ◦ Hemodialysis: Relies on solute diffusion across a semipermeable membrane. ◦ Diffusion Factors: Concentration gradient, membrane surface area, and mass transfer coefficient (function of porosity, thickness, molecule size, and flow). ◦ Molecule Size Effect: Small molecules (e.g., urea, 60 Da) clear well; larger molecules (e.g., creatinine, 113 Da) clear less efficiently. ◦ Convective Clearance: Solutes swept along with water across the membrane due to solvent drag. ◦ Peritoneal Dialysis: ◦ 1.5–3 L of a dextrose-containing solution is infused into the peritoneal cavity; dwell time 2–4 h. ◦ Clearance depends on balance between movement of solute/water into the cavity vs. absorption from the cavity via capillary and lymphatic circulation. ◦ High Peritoneal Transporters: Patients with rapid equilibration tend to absorb more glucose and lose albumin; they require more frequent, shorter dwell-time exchanges. • Hemodialysis Components: ◦ Dialyzer: Hollow-fiber dialyzer is standard; uses biocompatible synthetic membranes (e.g., polysulfone). ◦ Dialysate Composition (Table 1): ◦ Potassium: 0–4 mmol/L (Note: <1 mmol/L increases risk of sudden death/arrhythmias). ◦ Calcium: 1.25 mmol/L (2.5 mEq/L) (Higher levels used for hypocalcemia or 'hungry bone' syndrome). ◦ Sodium: 135–140 mmol/L (Standard); 145–155 mmol/L (Sodium modeling to counter urea-related osmotic gradients). ◦ Water Treatment: Filtration, softening, deionization, and reverse osmosis. • Blood Delivery System & Access: ◦ Circuit: Blood pump moves blood from access site through dialyzer at 250–450 mL/min. ◦ Ultrafiltration: Controlled by negative hydrostatic pressure on the dialysate side. ◦ Vascular Access Types: ◦ Arteriovenous Fistula: Preferred; results in arterialization of veins. → Risk: Subclavian stenosis (can preclude permanent access in that limb). ◦ Tunneled Catheters: Used when fistula/graft fails or is not feasible. → Advantage: Reduced bacterial translocation from skin. → Risks: Infection, venous thrombosis, and superior vena cava syndrome. ◦ Note: Subclavian veins are generally avoided by specialists due to high risk of stenosis.

4. CLINICAL FEATURES

• Initiation Criteria: ◦ Uremic symptoms. ◦ Hyperkalemia (unresponsive to conservative measures). ◦ Persistent volume expansion (despite diuretics). ◦ Acidosis (refractory to medical therapy). ◦ Bleeding diathesis. ◦ GFR <10 mL/min per 1.73 m². • Hemodialysis Complications: ◦ Hypotension: Most common acute complication; risk factors include excessive ultrafiltration, impaired vasoactive response, and use of antihypertensives. ◦ Muscle Cramps: Often due to rapid volume removal or removal below dry weight. ◦ Anaphylactoid Reactions: ◦ Type A: IgE-mediated; occurs within minutes of first use; can lead to full anaphylaxis. ◦ Type B: Complement activation/cytokine release; causes chest/back pain; resolves over time. • Peritoneal Dialysis Complications: ◦ Peritonitis: ◦ Definition: Peritoneal fluid leukocyte count >100/mm³ with ≥50% polymorphonuclear neutrophils. ◦ Presentation: Pain, cloudy dialysate, fever. ◦ Organisms: Gram-positive cocci (most common); Gram-negative rods (less common). ◦ Tunnel Infections: Nonperitonitis infections; may require local treatment or catheter removal. ◦ Metabolic Issues: Albumin loss, hyperglycemia, weight gain, and hypertriglyceridemia (in diabetics)."

5. INVESTIGATIONS & DIAGNOSIS

  1. Assess Dialysis Adequacy:
  2. Target Urea Reduction Ratio (URR) >65–70%.
  3. Target Kt/V >1.2 or 1.05 (depending on equilibration).
  4. Monitor Ultrafiltration Rate:
  5. Ensure rate is <13 mL/kg per h to avoid cardiovascular complications.
  6. Evaluate Peritoneal Dialysis Safety:
  7. Monitor for peritonitis using leukocyte count (>100/mm³) and % polymorphonuclear neutrophils (≥50%).

6. MANAGEMENT & TREATMENT

  1. Hemodialysis Protocol:
  2. Hypotension Management: → Stop ultrafiltration. → Administer 100–250 mL isotonic saline. → Administer salt-poor albumin (if available).
  3. Prevention of Hypotension: → Perform ultrafiltration modeling (more fluid removed at start of session). → Use sodium modeling (dialysate Na 145–155 mmol/L). → Cool dialysate. → Avoid heavy meals during treatment. → Note: Midodrine has been advocated but lacks sufficient evidence for routine use.
  4. Cramp Management: → Reduce volume removal. → Utilize ultrafiltration profiling. → Implement sodium modeling.
  5. Peritoneal Dialysis Protocol:
  6. Peritonitis Treatment: → Intraperitoneal or oral antibiotics (depending on organism). → Catheter removal if infection is due to Gram-negative rods (e.g., Pseudomonas) or yeast.
  7. Vascular Access Management:
  8. Strategy: "Fistula first" initiative.
  9. Action: Create arteriovenous fistulas as primary choice for highest patency and lowest infection rates.
  10. Avoidance: Limit use of catheters to minimize risk of infection, thrombosis, and stenosis (especially in subclavian veins)."

7. PROGNOSIS & COMPLICATIONS

• Cardiovascular Disease: Primary cause of death in ESKD patients. • Technique Failure: ◦ Catheter complications: Infection, venous thrombosis, and venous stenosis (leading to superior vena cava syndrome). ◦ Fistula/Graft issues: High-output cardiac failure from excessive shunting. ◦ Subclavian Stenosis: Common complication of subclavian access; can preclude permanent access in that limb.

8. SPECIAL CONSIDERATIONS

• Predictors of Death: ◦ Older age. ◦ Male sex. ◦ Nonblack race. ◦ Diabetes mellitus. ◦ Malnutrition. ◦ Underlying heart disease.

9. KEY PEARLS & CLINICAL TRAPS

• Safety Threshold: Ultrafiltration >13 mL/kg per h is linked to increased cardiovascular mortality. • Sodium Modeling: Used for patients with frequent hypotension; however, it may cause sodium balance and thirst (avoid in hypertensive patients). • Peritonitis Definition: Leukocytes >100/mm³ and ≥50% PMN are the specific thresholds for diagnosis. • Fistula First: This is the standard of care for long-term vascular access due to superior durability compared to catheters. • High Peritoneal Transporters: These patients require more frequent, shorter dwell-time exchanges because they lose more albumin and absorb more glucose.