Paradoxical Association Between Intradialytic Blood Pressure Change and Long-Term Mortality with Different Levels of Interdialytic Weight Gain

BACKGROUND: A greater interdialytic weight gain (IDWG) implies a greater ultrafiltration rate, which might lead to hemodynamic instability and intradialytic blood pressure (BP) change in hemodialysis patients. However, current studies have not explicated the impact of IDWG on the association between intradialytic BP changes and prognosis, especially in patients without cardiac dysfunction and diabetes. In this study, we aimed to explore the relationship between absolute intradialytic BP changes and mortality with different IDWG levels. METHODS: A total of 204 hemodialysis patients (without cardiac dysfunction and diabetes) were included in this prospective observation study, with a mean follow-up of 55.32±20.99 months. Initially, we collected IDWG, IDWG% (percentages according to dry weight), and pre-/post-BPs of 36 consecutive dialysis sessions during three months enrollment. And the average value of them was defined as baseline value. Patients were divided into 3 cohorts according to IDWG% tertiles (<3.3%, 3.3%–4.6%, ≥4.6%). Comparisons between different tertiles were analyzed. RESULTS: Compared to the low IDWG% group (tertile 1, T1), patients of high IDWG% group (tertile 3, T3) were younger, had higher ultrafiltration rate, less residual kidney function, lower BMI and dry weight, longer dialysis vintage and higher N terminal pro B type natriuretic peptide levels (P<0.05). Correlations were found between IDWG% and intradialytic BP changes. Kaplan–Meier analysis and multivariate Cox regression model adjusted for demographic data, dialysis information and predialysis BPs indicated that greater absolute intradialytic BP changes were associated with worse prognosis in T1 group (P<0.05). While in T3 group, less absolute intradialytic BP changes were associated with higher mortality (P<0.05). CONCLUSION: There is a paradoxical association between absolute intradialytic BP changes and long-term mortality with different IDWG levels. Both BP stability and volume balance are crucial to patients’ prognosis.