Dialysis access procedures and complications

🩸 Anatomy - Plumbing for Purity

• Access Types & Preference:

  • Arteriovenous Fistula (AVF): Direct artery-to-vein anastomosis. Best patency, lowest infection rate.
  • Arteriovenous Graft (AVG): Synthetic tube connecting artery and vein.
  • Central Venous Catheter (CVC): Tunneled catheter (e.g., Permacath). Highest infection risk; used for immediate/temporary access.

• Common AVF Sites (Distal to Proximal):

  • Radiocephalic (Brescia-Cimino): Radial artery & cephalic vein.
  • Brachiocephalic: Brachial artery & cephalic vein.

⭐ Rule of 6s for AVF Maturation: A usable fistula should be:

• Flow > 600 mL/min
• Diameter > 6 mm
• Depth < 6 mm from skin
• Matures in ~6 weeks

📌 Mnemonic: "Fistula First" - the preferred primary access.

💉 Clinical - The Access Trinity

📌 Fistula > Graft > Catheter. Choice depends on urgency and vessel quality.

• AV Fistula (AVF): Gold standard; direct artery-vein connection (e.g., radiocephalic).
  • Pros: Best long-term patency, lowest infection/thrombosis risk.
  • Cons: Requires ~2-3 months to mature; potential for steal syndrome.
• AV Graft (AVG): Synthetic (PTFE) tube connects artery to vein.
  • Pros: Usable sooner (2-4 weeks); for patients with inadequate veins.
  • Cons: Higher thrombosis, stenosis, and infection risk than AVF.
• CVC: Tunneled catheter for temporary/bridge access.
  • Pros: Immediate use.
  • Cons: ⚠️ Highest infection risk (S. aureus bacteremia), central venous stenosis.

⭐ The most common cause of AVF/AVG failure is thrombosis, typically due to stenosis at the venous anastomosis. Loss of a palpable thrill or audible bruit is a key sign.

💔 Complications - When Lifelines Fail

• Thrombosis: Most common cause of access failure.
  • Sx: Sudden loss of thrill/bruit.
  • Tx: Pharmacomechanical thrombectomy or surgical thrombectomy.
• Stenosis: Typically at the venous anastomosis.
  • Sx: ↑ venous pressures during dialysis, prolonged bleeding post-cannulation, limb swelling.
  • Dx: Duplex US; fistulogram is gold standard.
  • Tx: Balloon angioplasty ± stenting.
• Infection: Risk: Catheter > Graft (AVG) > Fistula (AVF).
  • Pathogen: S. aureus is most common.
  • Tx: IV antibiotics; may require graft excision for AVG infection.
• Dialysis Access Steal Syndrome (DASS):
  • Patho: Ischemia distal to access due to shunting of arterial blood.
  • Sx: Pain (especially with exertion/dialysis), pallor, paresthesias, cool digits.
• Aneurysm/Pseudoaneurysm:
  • Cause: High flow, repeated needle sticks weaken the wall.
  • Tx: Surgical repair if symptomatic, rapidly expanding, or skin erosion.

⭐ New-onset hand pain, numbness, and coolness after AV fistula creation is classic for Dialysis Access Steal Syndrome (DASS).

🔧 Management - Salvage Operations

• Goal: Preserve existing access & avoid new access creation.
• Primary Interventions: Endovascular approaches are first-line.
  • Thrombectomy: For clotted access. Can be percutaneous (pharmacomechanical) or open surgical.
  • Angioplasty (PTA): Balloon dilation for stenosis. Stents used for elastic recoil or recurrent lesions.
• Surgical Revisions:
  • Anastomotic revision/Interposition graft: For complex stenosis or aneurysmal changes.
  • Banding/DRIL: For dialysis-associated steal syndrome to ↓ flow.

⭐ The most common site of stenosis in an AV fistula is the venous outflow tract, just distal to the anastomosis.

⚡ Biggest Takeaways

• AV fistula (AVF) is the preferred access: best patency, lowest infection/thrombosis rates.
• AVFs require ~6-8 weeks to mature ("Rule of 6s"); grafts are usable in ~2-3 weeks.
• Stenosis and thrombosis are the most common complications of AVF/AVG, often at the venous anastomosis.
• Central venous catheters have the highest risk of infection (S. aureus) and central vein stenosis.
• Dialysis steal syndrome causes distal limb ischemia (pain, pallor) after access creation.
• High-output heart failure is a rare complication from excessive shunting through large, proximal access.