So063pre-Dialysis Fluid Status Modifies the Relation Between Pre-Dialysis Systolic Blood Pressure and Outcome in Prevalent Hemodialysis Patients

INTRODUCTION AND AIMS: Pre-dialysis fluid overload (FO) is a risk factor for mortality and the most frequent cause of elevated pre-dialysis systolic blood pressure (SBP). However, especially low pre-dialysis SBP is associated with increased mortality in hemodialysis (HD) patients. Whether the combination of pre-dialysis SBP and fluid status (FS) modifies the association with mortality has not yet been investigated. The objective of this study was to investigate the interaction between pre-dialysis FS and pre-dialysis SBP in the association with mortality. METHODS: We included all patients from the MONDO database who had a pre-dialysis multifrequency bioimpedance spectroscopy (MF-BIS) measurement in the year 2011. BP was measured pre- and post-dialysis by the oscillometric method incorporated in the dialysis machine. We used all parameters available for the 90-day baseline period before the last MF-BIS of 2011 for descriptive and regression analysis. All cause-mortality was recorded during 1-year follow up. Associations with outcome were assessed with Cox-models with different levels of adjustment and with a smoothing spline Cox analysis. RESULTS: We included 8883 patients and found that in patients with pre-dialysis FO (>+1.1 to +2.5L), low pre-dialysis SBP (<110 mmHg) was associated with an increased risk of death (HR 1.52 (95% CI 1.06-2.17)), as compared to normovolemic (-1.1L to +1.1L)(NV) and normotensive (110-140 mmHg)(NT) patients. An increased risk of death, compared to pre-dialysis NV and NT patients, was also observed in patients with pre-dialysis fluid depletion ((FD)< -1.1L)) and a pre-dialysis SBP <140 mmHg. In NV patients, low pre-dialysis SBP (<110mmHg) associated with a survival benefit (HR 0.46 (95% CI 0.23-0.91)). Post-dialysis FD was associated with a survival benefit. Results were similar but more pronounced when inflammation was present. High ultrafiltration rates could not solely explain the higher mortality rates observed in the FO groups.