Hemodialysis in Special Situations

1. Acute Kidney Injury (AKI) / Critically Ill Patients

• HD is performed 3–4 hours/day, 3–4 times/week as the most common renal replacement therapy (RRT) for AKI (Harrison's, p. 8473)
• Major complication: Intradialytic hypotension — especially dangerous in critically ill patients because ischemic injury can perpetuate and worsen the recovering kidney
• Continuous Renal Replacement Therapy (CRRT) is often preferred over intermittent HD (IHD) in hemodynamically unstable patients to avoid rapid fluid/solute shifts

2. Hemodialysis in Pregnancy

• Incidence: Rare but complex; occurs in women with end-stage kidney disease (ESKD) or severe AKI during pregnancy
• Intensified HD (≥20 hours/week, ideally daily nocturnal HD) is associated with markedly better fetal outcomes
• Goals:
  • Pre-dialysis BUN <50 mg/dL (reduces amniotic fluid urea, prevents osmotic shifts in the fetus)
  • Maintain euvolemia (avoid excessive ultrafiltration — reduces uterine perfusion)
  • Careful electrolyte management (K⁺, Ca²⁺, Mg²⁺, bicarbonate)
  • Avoid hypotension (fetal distress risk)
• Anticoagulation: Heparin is used; avoidance of systemic anticoagulation if bleeding risk
• Dialysate adjustments: Bicarbonate-based dialysate; avoid acetate-based
• Fetal monitoring: Regular ultrasound, non-stress testing essential

3. Pediatric Hemodialysis

• Challenges: Small body size, limited vascular access, psychological impact
• Access: Tunneled cuffed catheters more commonly used than in adults; arteriovenous (AV) fistulas preferred long-term when feasible
• Machine settings: Pediatric-specific blood lines and dialyzers required; blood volume priming often needed for neonates/infants
• Anticoagulation: Weight-based heparin dosing
• Dialysis adequacy targets (Kt/V): Similar to adults (≥1.2 per session), but frequent reassessment needed given rapid growth
• Complications: Growth retardation, neurodevelopmental issues, hypertension — warrant multidisciplinary care
• Preferred modality: Peritoneal dialysis (PD) is often preferred over HD in young children; HD reserved for those who fail PD or require urgent clearance

4. Elderly Patients

• High prevalence of ESKD in the elderly, yet outcomes are often worse than younger patients
• Vascular access: AV fistulas have poor maturation rates in the elderly due to arteriosclerosis; catheters more commonly used but carry infection risk
• Hemodynamic instability: Greater susceptibility to intradialytic hypotension due to reduced cardiac reserve and autonomic dysfunction
• Cognitive/functional decline: HD schedule can be burdensome; conservative management or home dialysis may be appropriate alternatives
• Key decision: Shared decision-making regarding dialysis initiation vs. conservative kidney management (CKM) — particularly in frail elderly with multiple comorbidities
• Incremental HD (starting with fewer sessions/week) may preserve residual renal function longer

5. Diabetic Patients on Hemodialysis

• Diabetes is the leading cause of ESKD worldwide
• Challenges:
  • Accelerated cardiovascular disease and atherosclerosis → higher CV mortality
  • Poor vascular access (AV fistula failure more common due to calcified vessels)
  • Hypoglycemia risk during HD: glucose is removed during dialysis; insulin-requiring patients may have significant hypoglycemic episodes
  • Retinopathy, peripheral neuropathy, and gastroparesis complicate management
• Dialysate glucose: Standard dialysate contains 100–200 mg/dL glucose; must be carefully matched to prevent hypo- or hyperglycemia
• Glycemic monitoring: HbA1c is unreliable in HD patients (due to hemolytic anemia and RBC transfusions); fructosamine or glycated albumin may be better markers
• Cardiovascular risk reduction: Aggressive BP control, statin therapy, aspirin

6. Patients with Cardiovascular Disease

• Intradialytic hypotension (IDH): Most common complication in HD; occurs in 20–30% of sessions
  • Causes: excessive/rapid ultrafiltration, low cardiac reserve, autonomic neuropathy, antihypertensive medications
  • Management: cool dialysate (35–36°C), sodium modeling, reduced ultrafiltration rate, midodrine, volume profiling
• Heart failure: Optimization of dry weight (euvolemia) is critical; frequent reassessment with clinical examination and biomarkers (BNP/NT-proBNP)
• Arrhythmias: Hypokalemia and hypomagnesemia during HD can precipitate arrhythmias; potassium dialysate ≥2 mEq/L generally preferred
• Coronary artery disease: HD patients have extremely high CV mortality; revascularization decisions must weigh procedural risk vs. benefit

7. Patients with Coagulopathy or Bleeding Risk

• Anticoagulation during HD is required to prevent clotting of the extracorporeal circuit
• Options in high bleeding risk:

8. Patients with Infections / Sepsis

• Sepsis-associated AKI: CRRT often preferred over HD for hemodynamic stability
• Bacteremia and catheter-related bloodstream infections (CRBSI): Major risk, especially with tunneled catheters
  • Staphylococcus aureus most common pathogen
  • Management: catheter removal + systemic antibiotics; antibiotic lock therapy for salvage
• Hepatitis B/C and HIV on HD:
  • Hepatitis B: dedicated machines and isolation rooms in many centers
  • Hepatitis C: standard infection control precautions; direct-acting antivirals (DAAs) are effective and safe in HD patients
  • HIV: no special isolation required; antiretroviral dose adjustment often needed

9. Hemodynamically Unstable / Vasopressor-Dependent Patients

• Standard HD poorly tolerated; CRRT is the modality of choice
• Slow continuous ultrafiltration (SCUF) for fluid removal when azotemia is not the primary concern
• If HD must be used: longer, slower sessions (SLED); cool dialysate; careful UF profiling

10. Poisoning and Drug Overdose

• HD is highly effective for removing dialyzable toxins:

11. Patients Requiring Surgery

• Pre-operative HD: optimize fluid status, electrolytes (especially K⁺), and acid-base balance
• Anticoagulation management: heparin withheld or dose adjusted perioperatively
• Timing: HD ideally performed the day before elective surgery
• Post-operative HD: may need to resume urgently if K⁺ rises, volume overloads, or uremia develops

12. Patients with Residual Renal Function (Incremental HD)

• Starting with 2 sessions/week (rather than 3) in patients with significant residual urine output (>500 mL/day) preserves residual kidney function
• Associated with better cardiovascular outcomes and quality of life
• Requires close monitoring of volume status, Kt/V, and electrolytes

Summary Table: Modality Selection by Clinical Scenario