Why can't dialysis be done without a fistula or graft?

Why Dialysis Cannot Be Done Without a Fistula or Graft

Hemodialysis requires a reliable, high-flow vascular access that can deliver blood flow rates of at least 300-350 mL/min to achieve adequate dialysis - this cannot be safely or effectively achieved long-term through normal peripheral veins, necessitating either an arteriovenous fistula, graft, or central venous catheter. 1

Understanding Vascular Access Requirements for Hemodialysis

Hemodialysis requires:

1. High blood flow rates: Adequate dialysis delivery requires blood flow rates of at least 300-350 mL/min 2
2. Repeated access: Typically 3 times weekly for years
3. Durability: Access must withstand repeated cannulation
4. Low complication rates: Minimal infection, thrombosis, and stenosis

Why Normal Peripheral Veins Are Inadequate

Normal peripheral veins cannot meet these requirements because:

• They cannot consistently provide sufficient blood flow rates (>300 mL/min)
• They collapse under the negative pressure required for dialysis
• They cannot withstand repeated cannulation over time
• They have high rates of infiltration, thrombosis, and failure

Types of Vascular Access for Hemodialysis

1. Arteriovenous Fistula (AVF)

• Gold standard access with best long-term outcomes 2, 1
• Created by surgically connecting an artery directly to a vein
• Allows arterial pressure to enlarge the vein, creating a high-flow, durable access
• Benefits:
  • Lowest infection rates (1-4%)
  • Best long-term patency (4-5 year survival)
  • Fewer interventions needed to maintain patency
  • Reduced mortality risk compared to other access types 1

2. Arteriovenous Graft (AVG)

• Synthetic or biological conduit connecting an artery to a vein
• Used when native vessels are inadequate for fistula creation
• Higher complication rates than fistulas:
  • Infection rates of 11-20%
  • 3-7 times more access events than AVFs 1
  • Requires more interventions to maintain patency

3. Central Venous Catheters (CVC)

• Temporary access option when immediate dialysis is needed
• Associated with:
  • Highest infection rates
  • Highest mortality (2.3 times greater risk than AVFs) 1
  • Inadequate blood flow rates
  • Central venous stenosis
  • Should not be used as permanent access when possible 2

Clinical Implications of Access Choice

The type of vascular access significantly impacts:

1. Dialysis adequacy: AVFs and AVGs support higher blood flow rates with less negative pressure than catheters, leading to better dialysis delivery 3

2. Patient survival: Mortality risk is 1.47 times greater with grafts and 2.3 times greater with catheters compared to fistulas 1, 4

3. Complication rates: Fistulas have the lowest rates of infection, thrombosis, and interventions 1

4. Healthcare costs: Catheters and grafts require more interventions and hospitalizations, increasing costs 2

Transitioning Between Access Types

Converting from a catheter to either a fistula or graft is associated with significantly improved survival (HR 0.69) 4. Even when a fistula cannot be created, transitioning from a catheter to a graft provides substantial benefits over continued catheter use.

Common Pitfalls and Caveats

1. Delayed referral: Late referral for vascular access creation often results in catheter dependence and poorer outcomes 2

2. Fistula maturation issues: Not all created fistulas successfully mature for use, requiring intervention or alternative access 5

3. Catheter dependence: The ease of catheter use may lead to patient reluctance to transition to permanent access despite higher risks 2

4. Access monitoring: Failure to detect access dysfunction early can lead to thrombosis and access loss 2

In summary, the physiological requirements of hemodialysis make specialized vascular access mandatory. Normal peripheral veins simply cannot provide the sustained high blood flow rates required for effective hemodialysis without rapid failure, making arteriovenous fistulas, grafts, or central venous catheters necessary for ongoing treatment.