Modalities and Prescription
The Modalities and Prescription domain tests matching hemodialysis, hemodiafiltration, peritoneal dialysis and CRRT to patient needs, and setting Qb, Qd, duration, frequency, dialysate composition and UF goal.
Core rules
- Conventional HD uses diffusion; HDF adds convective volume; PD uses the peritoneum; CRRT provides slow continuous clearance for unstable patients.
- A typical HD prescription is Qb 200–500 mL/min, Qd 500–800 mL/min, 3–5 hours, three sessions weekly; target single-pool Kt/V 1.2–1.4 and URR ≥65%.
- Dialysate sodium, potassium, calcium and bicarbonate are individualized; the UF goal equals fluid removal plus rinseback, not just weight change.
- PD prescription includes dwell volume, dwell time and dextrose concentration; CRRT dose is often 20–25 mL/kg/h.
Worked example
Remove 2.4 L over 4 hours. UF rate = 2400 mL ÷ 240 min = 10 mL/min, about 600 mL/h. If the patient develops cramps or hypotension, reduce the rate, adjust sodium modeling or reassess dry weight rather than simply increasing time.
Traps
Do not prescribe UF from weight alone without assessing refill and hemodynamics; do not ignore residual kidney function in PD; do not confuse URR with Kt/V.