Vascular Access for Haemodialysis and Critical Care
AVF creation and maturation · central venous access · IVC filters · complications · dialysis catheter management
Haemodialysis Access Overview and AVF Creation
Introduction to Renal Failure and Access Hierarchy
Chronic kidney disease (CKD) affects millions globally, progressing from CKD stage 1 (GFR >90) through stage 5 (GFR <15) where renal replacement therapy becomes necessary. Patients requiring haemodialysis need vascular access providing adequate flow (target 400–500 mL/min, ideally >600 mL/min) for efficient solute removal. Three main dialysis modalities exist: in-centre haemodialysis (HD), peritoneal dialysis (PD), and transplantation. The “Fistula First, Catheter Last” initiative by KDIGO encourages arteriovenous fistula (AVF) creation as the gold standard vascular access due to superior longevity, lower infection rates, and cost-effectiveness compared to grafts or catheters.
AVF Hierarchy: The Five-Tier Access Strategy
Vascular access selection follows a strict hierarchy based on vessel quality, anatomy, and predicted longevity. This hierarchy should be offered in sequence to maximise access survival and limit revision surgery:
Pre-Operative Assessment for AVF Creation
Optimal outcomes require careful pre-operative vascular mapping and patient selection. Allen’s test assesses collateral hand perfusion: patient makes a fist, examiner compresses both radial and ulnar arteries, patient opens hand (should be pale), examiner releases one artery — normal flush within 5–7 seconds indicates patency. Modified Allen’s test with plethysmography or duplex provides objective assessment.
Vascular duplex ultrasound should map: radial and ulnar artery diameters (>2.0 mm ideal for radiocephalic AVF), patency, and flow velocities; cephalic and basilic vein diameters (>2.5 mm ideal) and compressibility; and absence of central venous stenosis. CKD staging guides referral timing: GFR <25–30 mL/min/1.73 m² warrants referral for access evaluation, allowing adequate maturation time before dialysis initiation (minimum 6 weeks, ideally 3–6 months in advance).
AVF Maturation: The Rule of 6s
The classic “Rule of 6s” serves as a useful bedside guide to predict fistula readiness: diameter ≥6 mm, flow ≥600 mL/min, depth ≤6 mm from skin surface, assessed at 6 weeks post-creation. A fistula meeting all three criteria is typically ready for dialysis cannulation. Radiocephalic fistulae may mature more slowly (8–12 weeks). Pre-maturation cannulation risks irreversible thrombosis.
Surgical Technique: Basic AVF Construction
Radiocephalic AVF technique: performed under local anaesthesia (1% lidocaine infiltration) or regional wrist block. Two small incisions are made — one at the snuffbox for radial artery identification and one on the volar wrist for cephalic vein. The cephalic vein is mobilised for 2–3 cm and the radial artery dissected free. An end-to-side anastomosis (cephalic vein end to radial artery side) is the most common configuration, preserving distal radial perfusion. Anastomosis is performed with 6-0 or 7-0 polypropylene interrupted or continuous sutures. An audible thrill and visible vein engorgement confirm success. CXR is not required post-operatively for a peripheral fistula.
AVF Maturation: Key MRCS Points
Refer when GFR <25–30 mL/min/1.73 m² to allow adequate maturation time. Radiocephalic requires 8–12 weeks; brachiocephalic 4–8 weeks; brachiobasilic 12+ weeks (two-stage). Pre-operative duplex with vein diameter >2.5 mm strongly predicts success. Monitor maturation at 6 weeks — if the Rule of 6s is not met, duplex assessment for juxta-anastomotic stenosis or inadequate inflow should be performed, as early PTA can salvage a failing fistula before it thromboses.