Extracorporeal pressure monitoring and the detection of vascular access stenosis

Prospective monitoring of static venous pressure is an established tool to detect outflow stenoses in a vascular access. However, with this method it is not possible to identify vascular stenoses which are localized between the arterial and venous dialysis needle. We describe a new approach based on both static arterial and venous extracorporeal pressures. Pressure data of 9 dialysis patients with normal vascular access function and 9 patients with stenotic access were analyzed. Extracorporeal pressure was found to depend on the position of the heart relative to the extracorporeal blood circuit. All patients with venous outflow stenoses had an elevated ratio of arterial and venous intra-access pressure to mean arterial pressure. In case of access stenosis between arterial and venous needle the ratio of venous pressure to mean arterial pressure was normal, and only the arterial pressure ratio was elevated. We conclude that combined arterial and venous intraaccess pressure measurement normalized by mean blood pressure detects venous stenosis as well as stenosis between the arterial and venous dialysis needle. To minimize the rate of access thrombosis both arterial and venous intra-access pressure should be monitored.