The following are “Know” from the syllabus
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Arterio-venous anastomosis
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Arterio venous graft access techniques
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Indications
- Haemodialysis access in patients with end-stage renal disease
- Preferred long-term access compared to catheters
- Haemodialysis access in patients with end-stage renal disease
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Principle
- Direct connection between an artery and vein
- Allows high flow, arterialised venous blood suitable for repeated cannulation
- Promotes vein maturation and wall thickening
- Direct connection between an artery and vein
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Types
- Native arteriovenous fistula (AVF)
- Radiocephalic (wrist): radial artery to cephalic vein
- Brachiocephalic (elbow): brachial artery to cephalic vein
- Brachio-basilic (transposed): brachial artery to basilic vein (requires vein mobilisation)
- Arteriovenous graft (AVG)
- Synthetic (e.g., PTFE) graft between artery and vein
- Used if veins unsuitable for AVF
- Native arteriovenous fistula (AVF)
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Preoperative considerations
- Duplex ultrasound mapping of veins and arteries
- Assess vessel diameter and flow
- Non-dominant arm preferred
- Avoid sites of prior central venous access or thrombosis
- Duplex ultrasound mapping of veins and arteries
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Surgical steps (for radiocephalic AVF)
- Local/regional anaesthesia
- Supine position with arm extended
- Longitudinal incision at wrist over radial artery and cephalic vein
- Isolate and loop artery and vein
- Heparinised saline flushes
- End to side
- Create end (vein) to side (artery) anastomosis with fine non-absorbable suture (6-0 or 7-0 prolene)
- Side to side
- Also an option
- Confirm thrill or bruit over fistula
- Close skin loosely; avoid tension or compression
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Postoperative care
- Monitor for thrill and bruit
- Elevate limb to reduce oedema
- Avoid cannulation or pressure over site
- Allow 4–8 weeks for maturation before use
- Duplex scan if poor maturation suspected
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Complications
- Thrombosis
- Most common cause of access failure
- May present as loss of bruit/thrill or inability to dialyse
- Management: urgent vascular imaging (duplex US or fistulogram), thrombectomy or thrombolysis, surgical revision if needed
- Stenosis
- Often at anastomosis or outflow vein
- Signs include high venous pressures during dialysis, arm swelling, prolonged bleeding
- Management: angioplasty (± stenting), surgical revision
- Infection
- Can affect skin, tunnel, or entire fistula
- Signs: redness, warmth, purulent discharge, systemic symptoms
- Management: antibiotics, removal of infected segment, avoid cannulation at site
- Aneurysm or pseudoaneurysm
- Due to repeated puncture or wall weakening
- Risk of rupture or skin breakdown
- Management: monitor small asymptomatic ones, surgical repair for large, painful or overlying skin thinning
- Steal syndrome
- Distal limb ischaemia from blood diversion into fistula
- Signs: pain, pallor, coolness, ulceration
- Management: flow-reducing procedures (e.g. DRIL – distal revascularisation with interval ligation), banding, ligation if severe
- High-output cardiac failure
- Excessive AV shunting increases preload
- Signs: dyspnoea, oedema, high-output signs on echocardiogram
- Management: fistula flow reduction, closure if refractory
- Haematoma
- Usually after cannulation
- Management: pressure dressing, monitor size, drain if expanding or infected
- Venous hypertension
- Due to central venous stenosis
- Signs: swelling, varicosities, skin changes
- Management: angioplasty of stenosis, surgical bypass if persistent
- Needle infiltration
- Cannulation error causing extravasation of blood
- Management: stop dialysis, apply pressure, monitor for compartment syndrome if extensive
- Thrombosis