Dialysis and Renal Replacement Therapy
Core concepts
Know hemodialysis (HD) vs peritoneal dialysis (PD) vs continuous renal replacement therapy (CRRT). HD uses diffusion and ultrafiltration via an arteriovenous access (fistula preferred, then graft, then catheter); PD uses the peritoneum with dwell times. CRRT is preferred in hemodynamically unstable ICU patients.
Indications for urgent dialysis: AEIOU (acidosis, electrolytes-refractory hyperkalemia, intoxication, overload, uremia). Complications: hypotension, cramps, disequilibrium syndrome (cerebral edema with rapid urea removal), access infection, catheter-related thrombosis, and PD peritonitis (cloudy effluent, abdominal pain).
Adequacy: Kt/V targets; residual kidney function matters. Anemia and CKD-MBD management differ in dialysis. Drug dosing changes with dialysis-check dialyzability. Vascular access planning: preserve veins, avoid subclavian catheters if possible.
Traps
Disequilibrium syndrome is prevented by slower initial sessions. PD peritonitis is usually gram-positive (Staph) and treated with intraperitoneal antibiotics. Do not use HD for a hemodynamically unstable patient if CRRT is available. Pericarditis and encephalopathy are urgent indications.
Rule of thumb
If the patient is unstable or in the ICU with AKI, think CRRT; if chronic and stable, plan fistula and HD or PD based on preference and anatomy.
Worked example
A patient on HD develops headache, confusion, and seizures after a rapid first session. Diagnosis: dialysis disequilibrium; manage supportively and slow future sessions.