Terminology

Preprocedure

Procedure

Definitions

• Hemodialysis (HD)
  • Patient's blood is modified by going through dialyzer
    • Certain solutes are removed
      • e.g., potassium, phosphorus, and urea
    • Dialysate solutes are added
      • e.g., bicarbonate
    • Plasma water often removed
• End-stage renal disease
  • a.k.a. chronic kidney disease (CKD) stage 5
  • Glomerular filtration rate (GFR) < 15 mL/min/1.73 m2
  • Need HD, peritoneal dialysis, or kidney transplant for medium-term survival
• Arteriovenous fistula (AVF)
  • Surgical anastomosis between artery and vein
    • Results in dilation and arterialization of vein draining fistula
    • Requires maturation period before use
      • Typically 8-12 weeks maturation
      • ~ 50% never able to be used
    • Once mature, less infections and longer lifespan than arteriovenous grafts (AVGs)
  • Common types of AVF
    • Radiocephalic (RC) fistula (forearm)
      • Preferred dialysis access
      • Problem: Low rates of maturation
      • Typical site of stenosis: Juxtaanastomotic segment
    • Brachiocephalic fistula (upper arm)
      • 2nd preferred dialysis access
      • Used when radial artery or forearm cephalic vein are unsuitable for RC creation
      • Problems: High rate of dialysis-associated steal syndrome (DASS), precludes subsequent ipsilateral forearm fistula creation
      • Typical site of stenosis: Cephalic arch
    • Brachiobasilic fistula (upper arm)
      • Used when upper arm cephalic vein unsuitable for AVF creation
      • Problems: Difficult and 2-stage surgery, high rate of steal syndrome
      • Typical site of stenosis: Proximal swing segment
• Mature fistula
  • Mature fistula is able to be repeatedly punctured and provide adequate flow for dialysis
  • Satisfies "rule of 6s"
    • Flow > 600 mL/min
    • Diameter > 0.6 cm
    • No more than 0.6 cm deep
    • Should be mature by 6 weeks
• Immature fistula
  • Occurs in > 50% of newly created AVFs
    • Inflow stenosis
      • Most common cause of nonmaturation
      • Does not allow for dilation and arterialization of fistula
    • Competing outflow veins
      • Accessory veins: Naturally occurring branches arising from venous outflow tract; treat with ligation, embolization
      • Collateral veins: Alternative drainage pathways; develop in setting of downstream stenosis; treat by addressing underlying stenosis
    • Fistula that has failed to mature at 6 weeks should trigger further evaluation
• AVG
  • Surgically created connection between artery and vein, using prosthetic conduit to provide vascular access for HD treatment
  • Used if unsuitable vascular anatomy for AVF
    • Suitable: Artery > 2 mm in diameter, vein > 2.5 mm in diameter
  • AVG has shorter lifespan than AVF
    • 6-10x greater infection risk and thrombosis
  • Polytetrafluoroethylene (PTFE) graft most frequently used AVG material
    • Can be used within 2-3 weeks of construction
    • Gore Acuseal able to be used 24 hours after creation
  • Types of AVG
    • Loop or straight configuration
      • Forearm preferred over upper arm
      • Arm preferred over groin
    • Prosthetic axillary-axillary arteriovenous straight access (necklace graft)
      • Used for patients with exhaustion of all other upper limb accesses but patent superior vena cava, subclavian and brachiocephalic veins
  • Typical site of stenosis: Graft-vein anastomosis
• Cephalic arch
  • Most central portion of cephalic vein
    • Arches through deltopectoral groove to join axillary vein
  • Most frequent site of stenosis in dysfunctional brachiocephalic fistulas (40-77%)
    • Rarely cause of dysfunction in RC fistulas
  • Etiologies of stenosis
    • Extrinsic compression by clavipectoral fascia
    • High concentration of valves in this venous segment
    • Turbulence caused by sharp turn of arch combined with high flow rate
  • Difficult to treat
    • High-pressure balloons often needed
      • Associated high rate of vessel rupture
    • Low primary patency rate at 1 year (~ 20%) with angioplasty alone
• HeRO graft (hemodialysis reliable outflow): Merit Medical
  • Arterial graft component
    • 6-mm inner diameter
    • Material: Expanded polytetrafluoroethylene (ePTFE)
  • Venous outflow component
    • 5-mm inner diameter
    • Radiopaque silicone, reinforced with braided nitinol
  • Titanium connector between arterial graft and venous outflow
  • Used for failing AVF/AVG secondary to central venous stenosis
  • Catheter dependent patients
  • Benefits
    • Lower infection compared to catheters
    • Improved HD adequacy compared to catheters
    • Higher patency rates compared to catheter
• Qa: Access flow rate
  • Varies depending on access configuration, presence of stenosis, arterial inflow
• Qb: Dialysis pump flow rate
  • Typically set at 350-400 mL/min
• Kt/V: Number quantifying dialysis treatment adequacy
  • K: Dialyzer clearance of urea
  • T: Dialysis time
  • V: Volume of distribution of urea, ~ equal to patient's total body water
• Monitoring: Periodic physical examination and review of routinely gathered data of dialysis patients performed to detect underdialysis and dysfunctional accesses prior to thrombosis
  • Weekly physical examination
  • Review of routinely gathered data collected during HD
    • Dialysis adequacy: Kt/V
      • Value < 1.2 or decrease by > 0.2 triggers referral for intervention
    • Dynamic pump pressures
      • Unreliable if taken in isolation
      • If abnormal trend or with other access abnormalities can be predictive of the side of stenosis
  • Needling problems
    • Prolonged bleeding suggests outflow stenosis
    • Difficulty with cannulation suggests inflow stenosis
• Surveillance: Instrument-based, periodic evaluation performed to detect underdialysis and dysfunctional accesses prior to thrombosis
  • Access flows
    • Measured by ultrasound dilution/conductance, dilution/thermal, dilution/Doppler
      • AVG < 600 mL/min or < 1,000 mL/min if > 25% drop → referral
      • AVF < 400 mL/min or < 1,000 mL/min if > 25% drop → referral
  • Static venous pressure
    • Useful in AVGs
      • Insensitive to detect inflow problems, which are more common in AVFs
    • Intraaccess pressure to mean arterial pressure (MAP) ratio > 0.5 triggers referral
  • Detection of recirculation
    • Occurs when Qa < Qb
      • Could be due to inflow or outflow problem
    • Recirculation > 10% triggers referral
    • Not sensitive surveillance technique AVGs
    • AVGs can thrombose with Qa < 600 mL/min
      • Recirculation occurs when flow rates are < pump rates, typically set at 350-400 mL/min
  • Doppler ultrasound
    • Can measure flow rates, detect sites of stenosis
• DASS
  • Arterial insufficiency ipsilateral to HD access
  • Risk factors
    • Diabetic patients with multiple prior shunts
    • Female gender
    • Brachial artery inflow
    • High-flow shunts/large anastomoses
    • Grafts (2.7-8.0%) more common than fistulas (< 2.0%)
  • Stages
    • Grade 1 (mild): Cool extremity but otherwise few symptoms
      • Distal flow augmentation with access occlusion
      • No treatment needed
    • Grade 2 (moderate): Intermittent ischemia
      • Pain during dialysis or with exercise
      • Treatment occasionally needed
    • Grade 3 (severe): Rest pain/tissue loss
      • Treatment mandatory, often with access ligation
• National Kidney Foundation-Kidney Disease Outcomes Quality Initiative (NKF-KDOQI)
  • Provides multidisciplinary evidence-based clinical guidelines for CKD patients
    • Includes all stages of CKD and all aspects of care
  • Vascular Access Guidelines most relevant to interventional procedures
    • Published 2006, update forthcoming January 2018

Indications

Contraindications

Preprocedure Imaging

Getting Started

Patient Position/Location

Equipment Preparation

Procedure Steps

Findings and Reporting

Alternative Procedures/Therapies

Things to Do

Things to Avoid

Complications

Expected Outcomes