Change Concept 9: Monitoring and Maintenance to Ensure Adequate Access Function

The health care team should establish a process for monitoring and maintenance of AV fistulae to ensure adequate access function. It is extremely important to catch problems with fistulae early. Problems must be caught within 24 hours or the fistula will fail and be irreparable. There is a 20 to 30 percent failure rate for early fistulae.

• Nephrologists and surgeons conduct post-operative physical evaluation of AVFs in 4 weeks to detect early signs of failure and refer for intervention as indicated.
• Facilities adopt standard procedures for monitoring, surveillance, and timely referral for the failing AVF.
• Nephrologists, interventional radiologists, and surgeons adopt standard criteria, and a plan for each patient, to determine the appropriate extent of intervention on an existing access before considering placing a new access.

Changes for Improvement

Conduct a Post-Operative Physical Evaluation of AVFs at 4 Weeks
Nephrologists and surgeons should conduct post-operative physical evaluations of AV fistulae at four weeks to detect early signs of failure and refer for diagnostic study and remedial intervention as indicated.

Adopt Standard Procedures for Monitoring, Surveillance, and Timely Referral for the Failing AVF
The K/DOQI has established recommendations and guidelines for monitoring and surveillance:

Monitoring, which K/DOQI defines as physical examination techniques to detect access dysfunction, has been shown in many studies to be able to identify the majority of patients with AV fistula dysfunction.

Surveillance involves the use of a variety of tests to detect access dysfunction. Intra-access blood flow measurement over time is the best surveillance method available for assessing AV fistula function and detecting dysfunction.

Two other methods offer significant value for AV fistula surveillance:

Pre-pump arterial pressure, which is measured on almost all dialysis machines, indicates the ease or difficulty with which the blood pump is able to draw blood from the access (inflow). A significant restriction of inflow will cause an excessively negative pre-pump arterial pressure. Since most causes of AV fistula dysfunction are inflow problems, an excessively negative pre-pump arterial pressure is often the earliest indication of such a problem.

Access recirculation measurement. An AV fistula may remain patent but not provide enough blood flow to meet the prescribed blood pump flow rate, resulting in under dialysis. If there is any question about adequacy of blood flow for dialysis, or if there is difficulty dialyzing the patient at the prescribed pump rate, a recirculation study will determine if the AV fistula blood flow is not sufficient to meet the prescribed blood pump flow rate.

Note: While physicians commonly use venous pressure measurement to detect access dysfunction, it is of very limited value in AV fistula surveillance. This is because most of the flow-limiting problems in AV fistulae are on the arterial of the venous needle (and often the arterial needle as well) and therefore are not detectable by pressure measurements made at the venous (or arterial) needle, which can only detect an outflow obstruction downstream of the measuring needle(s). In addition, the fistula has tributaries that can dissipate pressure in the presence of an outflow obstruction. Finally, access pressure measurements are not likely to identify centrally located venous obstructions.

Adopt Standard Criteria and a Plan for Each Patient
Nephrologists, intervention radiologists, and surgeons should adopt standard criteria, and a plan for each patient, to determine the appropriate extent of intervention on an existing access before evaluating and mapping for an AV fistula.

Resources

AV Fistula Quick Reference Guide 

An easy-to-use reference document that describes the maturation process, and guidelines for assessment and monitoring of AV fistulas.