Vascular access for hemodialysis: postoperative evaluation and function monitoring.

Vascular access (VA) survival is a crucial issue associated with morbidity and mortality of patients undergoing maintenance hemodialysis. The development of stenosis is the major factor that leads to VA failure. Strategies for early detection of lesions within a VA system before serious complications arise are therefore crucial. The implementation of a VA surveillance program could lead to timely detection of VA dysfunction and referral for correction, reduction in central venous catheter use and decrease in hospitalization and VA-related cost. Suggested methods for arteriovenous fistulae and grafts surveillance include blood flow measurement, static pressure evaluation and duplex ultrasonography. Physical examination is an accepted method in contrast to nonstandardized dynamic pressure measurement for grafts. Access recirculation (not urea based) and dynamic pressure measurements are accepted methods for fistulae. Decreasing URR or Kt/V (otherwise unexplained) and increased (negative) arterial pressure in the dialysis machine are methods of limited sensitivity and specificity for both fistulae and grafts. Measurement of access blood flow has been proposed as the gold standard for the screening of all types of VA. Access flow can be measured by various techniques which are direct or indirect. Several studies about VA surveillance programs have demonstrated conflicting results. Larger, randomized controlled trials need to be carried out in order to clarify whether surveillance programs are necessary and which is the best surveillance strategy for each type of VA.