AV Grafts and the Tunneled

The contract between this chapter and the reader.

1. 1. State when an AV graft is chosen over a fistula or a catheter.
2. 2. Describe graft configurations and the venous-anastomosis stenosis problem.
3. 3. Compare graft and fistula by time-to-use, patency, and complications.
4. 4. Choose a tunneled catheter site and explain why the subclavian is avoided.
5. 5. Distinguish tunneled-cuffed from non-tunneled temporary catheters.
6. 6. Manage catheter dysfunction — thrombosis, fibrin sheath, and malposition.
7. 7. Use catheter locking solutions appropriately.
8. 8. Cannulate a graft safely.

A sixty-second reading. Each bullet stands alone.

• An AV graft is a synthetic conduit joining an artery to a vein when the veins are inadequate for a fistula.
• A graft is usable sooner than a fistula and needs no maturation, but it clots and stenoses more and needs more interventions.
• Graft stenosis classically forms at the venous anastomosis from neointimal hyperplasia.
• A graft's infection risk sits between a fistula (lowest) and a catheter (highest).
• A tunneled cuffed catheter is used when a fistula or graft is not possible or not yet ready, or as a bridge.
• The right internal jugular is the preferred catheter site; the subclavian is avoided because it causes central stenosis.
• Tunneling and a Dacron cuff reduce catheter infection and dislodgement compared with a temporary line.
• The catheter tip sits at the cavoatrial junction for reliable flow.
• Between sessions the catheter is locked — with heparin or citrate — to prevent thrombosis.
• Poor catheter flow is usually thrombosis, a fibrin sheath, or malposition; a thrombolytic lock often restores it.
• Reversing the catheter lines restores flow but causes recirculation and is only a temporary measure.
• Cannulate grafts by rope-ladder and not before they are incorporated.

The medical core. An expert should agree grafts and catheters are fully covered here.

Why it matters at the bedside

When a fistula is not possible, the choice is a graft or a catheter — and the two could not be more different. A graft is a durable, cannulatable conduit that clots; a catheter works the instant it is placed and quietly drives infection and central stenosis. Knowing the technique and the failure modes of each is what keeps a patient dialysing safely.

The AV graft: when and what

• An AV graft — usually expanded PTFE — bridges an artery to a vein when the native veins are too small or poor for a fistula but the inflow artery and outflow vein are adequate. It is chosen over a catheter whenever feasible, because its infection and mortality risk are lower.
• Common configurations are a forearm loop, an upper-arm straight or loop graft, and — as a last resort — a thigh graft, which carries a higher infection risk.

Graft patency and the venous-anastomosis problem

• A graft needs no maturation — it is a tube — so it is usable within about two weeks (early-cannulation grafts within days). The trade-off is durability: grafts clot and stenose more than fistulae and need more interventions.
• The characteristic lesion is neointimal hyperplasia at the venous anastomosis, which narrows over time, lowers flow, and eventually thromboses unless found and treated. Falling flow is the warning, and it is surveilled.

Graft cannulation

• Do not cannulate a standard graft before it has incorporated into the surrounding tissue — about two weeks — or a haematoma will form; early-cannulation grafts are the exception. Once usable, rope-ladder the punctures along the graft; repeated area puncture causes pseudoaneurysm.

The tunneled catheter: when and where

• A tunneled cuffed catheter is the access when a fistula or graft is impossible or not yet ready, or as a deliberate bridge. Site matters: the right internal jugular is preferred for its straight path and lowest stenosis and thrombosis; the left internal jugular is second; the femoral vein is for temporary use and is infection-prone.
• The subclavian vein is avoided for chronic access because it causes central venous stenosis that can ruin the entire arm for a future fistula or graft.

Catheter type and tip

• A tunnel and a Dacron cuff anchor the catheter and lower infection and dislodgement, which is why a tunneled cuffed catheter is used for anything beyond short-term needs; a non-tunneled temporary catheter is acceptable only for acute, brief use. The tip is positioned at the cavoatrial junction for reliable high flow.

Locking the catheter

• Between sessions the lumens are filled with a locking solution — heparin or citrate — to prevent thrombosis, with an antimicrobial lock reserved for selected high-risk patients.

Catheter dysfunction and its management

• Poor flow is the common problem. The usual causes are an intraluminal thrombus, a fibrin sheath at the tip, or malposition or kinking. A thrombolytic (alteplase) lock often restores flow; recurrent dysfunction from a fibrin sheath is managed by stripping or exchanging the catheter over a guidewire, and malposition by repositioning. Reversing the lines restores numbers but causes recirculation and is only a stopgap.

Insertion technique and confirmation

• Catheters are placed under ultrasound guidance for the venous puncture and fluoroscopy for tip position, tunneled with the cuff in the subcutaneous track, and confirmed by flow and a chest radiograph for tip position and to exclude pneumothorax.

Complications

• Beyond dysfunction, the dominant catheter hazards are bloodstream infection (covered in the access-infection chapter), thrombosis, and central venous stenosis; grafts add thrombosis, pseudoaneurysm, and steal. These are why a graft is preferred to a catheter, and a fistula to both.

Five fully-built tables.

Table A — Graft versus fistula

Table B — Graft configurations

Table C — Tunneled catheter sites

Table D — Catheter dysfunction

Table E — Locking and care

Visualise & Map

Numbered rules. These numbers are the cross-reference handle for the cases and flowcharts.

Clinical Reasoning

Four cases. Each stops you at a decision before it answers it.

Exhaustive. Every rule in the chapter is here.

Safety & Evidence

Panel A — Red flags

Panel B — NEVER DO

Anti-patterns clinicians fall into. Each becomes a Level 22 distractor.

The grade reflects strength of evidence, not importance.

Apply & Test

Copy-paste chart notes that map to the real procedures in this chapter.

Template 1 — Tunneled catheter insertion note

• Indication: bridge / no fistula or graft / by choice; consent obtained.
• Site: right IJ / left IJ / femoral (subclavian avoided); ultrasound-guided puncture.
• Catheter: tunneled cuffed / temporary; tip confirmed at cavoatrial junction (fluoroscopy).
• Flow confirmed: yes/no; chest radiograph (tip / pneumothorax): ___.
• Lock instilled: heparin / citrate; complications: none / ___.

Template 2 — Catheter dysfunction management note

• Problem: poor flow at ___; positional? yes/no.
• Imaging: tip position ___; kink ___.
• Working cause: thrombus / fibrin sheath / malposition.
• Action: thrombolytic lock / reposition / strip or exchange over wire.
• Outcome and plan if recurrent: ___.

Pre-rounds compression. Rules only.

Active recall. At least one card per objective.

Micro-teaching for rounds. Two scenarios, five steps each.

Eight items, each anchored in this chapter. At least one per objective.