Monitoring the Patient Following Radio-Cephalic Arteriovenous Fistula Creation: Current Perspectives

Figures & data

Table 1 Risk Factors for AVF Maturation

Risk Factors for AVF Maturation
Demographic characteristics
Elderly age
Female sex
Comorbidity
Diabetes
Obesity
Chronic hypotension.
Peripheral artery disease
Ca-P metabolism alteration
Thrombophilic diathesis
Vessels inadequacy
Previous cannulations/interventions of central or peripheral vessels
Drugs or vaso-injurious factors (steroids, chemo/radio-therapy)
Insufficient arterial or venous diameters
Other factors
Surgeon inexperience

Abbreviations: AVF, arteriovenous fistula; Ca-P, calcium-phosphorus.

Table 2 Causes of AVF Early Failure

Summary Table on the Causes of Early Failure
Stenosis
-iuxta-anastomotic
-of the arterial inflow
-of the venous outflow
Thrombosis (sometimes occur immediately after surgery or resulting from the presence of a stenosis).
Central venous stenosis or thrombosis
Hematoma and pseudoaneurysm
Infection, seroma and lymphatic collection
Steal syndrome and ischemic monomelic neuropathy
Pseudo-delayed maturation

Abbreviation: AVF, arteriovenous fistula.

Table 3 Physical Examination of the Newly Created AVF

Inspection

Assesses the wound and its correct healing of the AVF anastomosis. Inspect the body of the AVF to determine if it is visible and, if so, for what length (optimal length> 6 cm). Evaluate the apparent diameter and depth to determine if it has the potential to be cannulated. Assess whether accessory veins are visible.

Palpation

Normally, the thrill of the AVF anastomosis is perceptible to the touch as a vibration. The body of the AVF should be soft and easily compressible. If the thrill is not perceived, the AVF can be thrombosed. The thrill should disappear when the outflow vein is occluded manually more proximally due to the cessation of flow. If the thrill does not go away, an accessory vein is present distal to the occlusion point. When AVF is completely occluded manually, the arterial pulse distal to the AVF anastomosis must be increased. The degree of increase is directly proportional to the flow of the AVF. If AVF is hyperpulsive (an indication of outflow stenosis), the change in pulse produced by manual occlusion reflects the severity of the stenosis that is causing hyperpulsatility. To evaluate a possible iuxta-anastomotic stenosis it is useful to palpate the vein and artery distal to the anastomosis with the finger. In case of stenosis, the impulse disappears abruptly when the site of iuxta-anastomotic stenosis is encountered. Downstream the impulse will be weak or undetectable

Auscultation

Auscultation of the bruit is useful for determining the character of the diastolic component of the flow. Normal finding is the low rumbling tone with a prominent diastolic component. In case of stenosis there is a progressive increase in resistance which makes the diastolic component disappear and the bruit becomes more acute.

Abbreviation: AVF, arteriovenous fistula.

Table 4 AVF Flow Calculation

HOW and WHEN perform the examination

The mean of three measure must be calculated but 5 is preferable in patients with cardiac arrhythmias. The examination should be performed in the interdialytic period to avoid hemodynamic instability interferences deriving from the session itself.

WHERE performs the measurement

Vascular access flow in native AVF should be measured in the brachial artery, regardless of the artery that feeds the vascular access. Irregular areas (stenosis etc.) should be kept at least 5 cm from the sample volume site.

WHICH calculation runs

The calculation of the volume flow is based on the following equation: QVA = π x r^2 x TAVM. π x r^2 is the area of the lumen assuming it in the shape of a circle. TAVM represents the average speed of blood flow through the vessel over time. It is not appropriate to use the average maximum speed to calculate the volume flow because this would overestimate the access flow since it would only describe the major blood speed central to the vessel.

Abbreviations: AVF, arteriovenous fistula, QVA, vascular access blood flow, r, radius, TAVM, time average velocity.