Monitoring interposition graft venous pressures at higher blood-flow rates improves sensitivity in predicting graft failure.

Abstract

Monitoring the patency of hemodialysis interposition grafts is recommended to improve graft survival. Which blood flows best predict graft survival is not known. We monitored venous pressures in 32 dialysis patients over a median of 252 days at variable flow rates of the blood pump (Qb). Venous pressure trends (VPTs), maximum venous pressure (MVP), and the variability of venous pressure (percent coefficient of variation) were calculated. Kaplan-Meier curves were constructed from the time of the end of VPT monitoring to time to failure, defined as angioplasty, clotting, or surgical revision. Risk for graft failure for each 10-mm Hg increase in venous pressure was calculated by the Cox proportional hazards model. There were 12 graft failures, but no failures in 12 fistulas over the course of the study. The variability in venous pressure was less at greater Qbs. For grafts, VPTs were predictive of event only when calculated for Qbs greater than 100 mL/min. At Qbs of 400 mL/min, there was a 70% risk for graft failure with each 10-mm Hg increase in VPT. The risk for graft failure increased between 28% and 44% for each 10-mm Hg increase in MVP at all Qbs. MVP of 230 mm Hg at a Qb of 400 mL/min provided the best efficiency of test performance. Dialysis venous chamber pressure monitoring is a useful test to predict graft stenosis or thrombosis. There is a substantial variability in venous pressures in the same patient that reduces with increasing Qbs. Venous pressure monitoring at greater Qbs provides a more sensitive method for predicting access failure.