U curve association of blood pressure and mortality in hemodialysis patients

Background. Hypertension may play an important role in the pathogenesis of the excess cardiovascular and cerebrovascular (CV) morbidity observed in hemodialysis patients (HD). However, the optimal blood pressure (BP) range for HD patients has not been defined. We postulated that there is a "U" curve relationship between BP and CV mortality. To explore this hypothesis we studied 5,433 HD patients in Dialysis Clinic Inc., a large not-for-profit chain, over a five year period. Methods. Cox regression, with fixed and time-varying covariates. was used to assess the effect of systolic blood pressure (SBP) and diastolic blood pressure (DBP), pre- and post-dialysis, on CV mortality, while adjusting for age, gender, ethnicity, primary cause of end-stage renal disease, Kt/V, serum albumin, and antihypertensive medications. Results. The overall impact of BP on CV mortality was modest. Pre-dialysis, neither systolic nor diastolic hypertension were associated with an increase in CV mortality. Post-dialysis, SEP greater than or equal to 180 mm Hg (RR = 1.96, P < 0.015) and DBP greater than or equal to 90 mm Hg (RR = 1.73, P < 0.05) were associated with increased CV mortality. Low SEP (SBP < 110 mm Hg) was associated with increased CV mortality, pre- and post-dialysis. Conclusions. The results suggest the presence of a "U" curve relationship between SEP post-dialysis and CV mortality in HD patients.