Dialysis clears solute (diffusion, convection) and solvent (ultrafiltration) through extracorporeal or peritoneal circuits. HD 3x/week is standard for ESKD; CRRT for haemodynamically unstable ICU patients; PD for home-based therapy. Access is the lifeline — protect veins early.

principles

Two jobs, handled separately:

Solvent (water) clearance — ultrafiltration via pressure gradient: barometric (HD) or osmotic (PD)
Solute clearance — diffusion (concentration gradient across membrane) + convection (solute dragged with water movement)

access

Type	Details	Notes
Temporary catheter	Non-tunnelled, internal jugular or femoral	Short-term only; reassess daily
Tunnelled catheter (PermCath)	Subcutaneous cuff, internal jugular	Bridge to permanent access or when AVF/AVG not feasible
AVF	Native arteriovenous fistula	Preferred — lowest infection/thrombosis; needs 2–3 months to mature
AVG	Synthetic graft	Usable in ~2–4 weeks; higher thrombosis/infection than AVF

protect the veins

Avoid CVL/PICC lines in CKD patients whenever possible — venous stenosis/thrombosis destroys future access sites. Minimise venipuncture in dialysis patients; draw labs from the dialysis circuit 3x/week.

haemodialysis prescription

Standard chronic HD:

Parameter	Default
Frequency	3x/week (MWF or TuThSa)
Duration	4 h
Blood flow (Qb)	400 mL/min
Dialysate flow (Qd)	500 mL/min
Dialysate Na	140 mmol/L (should not exceed serum Na by >10)
Dialysate K	Rule of 7 minus pre-dialysis K (options: 1, 1.5, 3, 4 mmol/L)
Dialysate HCO3	30–40 mmol/L
Dialysate Ca	1.25 or 1.50 mmol/L
UF rate	Avoid >13 mL/kg/hr (~1 L/hr for 70 kg)
Anticoagulation	Dalteparin 2500 units (tight)

Dalteparin contraindications: HIT, pericarditis, new HD starts, recent major bleeding or surgery.

new HD start

Gradual ramp to avoid dialysis disequilibrium syndrome (cerebral oedema from rapid osmolality shifts):

	Day 1	Day 2	Day 3
Duration	2 h	3 h	4 h
Qb	200 mL/min	300 mL/min	400 mL/min
Qd	300 mL/min	400 mL/min	500 mL/min
Anticoagulation	None	None	Start as appropriate

CRRT

ICU-only modality for haemodynamically unstable patients who cannot tolerate intermittent HD.

Default mode: CVVHD (continuous venovenous haemodialysis)
Filters changed every 72 h — natural reassessment point: still need CRRT or ready for intermittent HD?
Machine taken down for off-unit transport; fresh filter on return
Anticoagulation escalation: none (default) → regional citrate (if filter clotting) → systemic heparin
Cost: ~ $1000–2000/day vs intermittent HD ~$ 250/treatment

CRRT vs intermittent HD

STARRT-AKI (2020) showed no mortality benefit from early RRT initiation. Modality choice (CRRT vs iHD) is driven by haemodynamic tolerance, not timing.

peritoneal dialysis

Home-based therapy using the peritoneal membrane as the dialysis surface. Dextrose-based dialysate creates an osmotic gradient for fluid removal.

solutions

Solution	Composition	Notes
Dianeal 1.5%	Dextrose ~8.3 mmol/L glucose	Standard
Dianeal 2.5%	Dextrose ~13.9 mmol/L glucose	More UF
Dianeal 4.25%	Dextrose ~23.6 mmol/L glucose	Maximum UF; significant glucose load
Extraneal (icodextrin)	Glucose polymer	Minimal glucose absorption — preferred for diabetics and long dwells

modalities

CAPD — continuous ambulatory PD: manual exchanges, typically 4x/day
APD/CCPD — automated/continuous cycling PD: machine performs overnight exchanges

Generally continue home PD prescription during hospital admission. Modify for volume overload (higher concentration) or hyperkalaemia.

PD and glucose

Dianeal dextrose loads can cause significant hyperglycaemia — adjust insulin accordingly. Extraneal (icodextrin) has minimal glucose effect but interferes with some glucometer readings (maltose cross-reactivity).

practical points

No need to repeat lytes post-HD unless concerned about dialysis adequacy or persistent hyperkalaemia — they will be transiently abnormal
Do not correct serum K in dialysis patients unless <2 mmol/L or symptomatic — risk of rebound hyperkalaemia
Dialysis nurses are experienced — ask them when unsure about access or prescription logistics

dialysis overview