Surveillance of access function by the blood temperature monitor.

Low access blood flow is considered the most important cause of peripheral vascular access thrombosis, particularly with grafts. The measurement of access flow is time consuming, operator dependent, and may affect the efficiency of dialysis so that it cannot be done with every treatment. The measurement of recirculation, however, is possible with every treatment and can be done automatically when using the thermodilution offered by the blood temperature monitor (BTM). Since BTM recirculation always includes a component related to cardiopulmonary recirculation, the threshold to detect access recirculation in peripheral arteriovenous grafts and native fistulas must be shifted from zero recirculation applicable for bolus techniques to 15% for the slow thermodilution technique. In one study, recirculation in native arteriovenous fistulas was measured with every treatment in 80 patients over a period of 6 months. Nine of 11 interventions performed during the entire observation period were triggered by a BTM recirculation above the threshold. Two fistulas thrombosed in spite of a BTM recirculation below the threshold. BTM recirculation to detect fistulas for revision is sensitive (81.8%) and specific (98.6%) in the presence of cardiopulmonary recirculation and can be done with minimum intervention and without loss of efficient treatment time.