Prevalence of detectable venous pressure drops expected with venous needle dislodgement

Venous needle dislodgement (VND) is a potentially fatal complication during hemodialysis (HD) treatment and the venous pressure monitor is the most widely used device for its detection. VND can only be detected by the venous sensor if the resulting pressure drop exceeds the difference between the actual venous pressure and the lower alarm limit. In clinical practice, the lower alarm limit is usually set 30-40 mmHg below the actual venous pressure to avoid a disproportionate high number of nuisance alarms. The aim of this study was to quantify the number of fistulas and grafts in a group of HD patients where venous pressure monitoring can be expected to detect VND. We determined intra-access pressures in 99 chronic HD patients. Sixty-five (65.7%) had a fistula and 34 (34.3%) had a prosthetic graft as a vascular access. Mean intra-access pressure (Pa ) in fistulas was 32.6 ± 23.5 mmHg, whereas in grafts mean Pa was 60.9 ± 19.5 mmHg. Nineteen (29.2%) of the fistulas and 32 (94.1%) of the grafts exhibited an intra-access pressure above 40 mmHg. Therefore, in our study nearly all grafts but only 29% of fistulas would fulfill the requirement for venous pressure monitoring to detect VND.