Blood pressure and mortality among hemodialysis patients

Abstract

Blood pressure measured before and after dialysis does not agree well with those recorded outside the dialysis unit. Whether recordings obtained outside the dialysis unit are of greater prognostic value than blood pressure obtained just before and after dialysis remains incompletely understood. Among 326 patients on long-term hemodialysis, blood pressure was self-measured at home for 1 week, over an interdialytic interval by ambulatory recording and before and after dialysis over 2 weeks. Over a mean follow-up of 32 (SD 20) months, 102 patients died (31%), yielding a crude mortality rate of 118/1000 patient years. Systolic but not diastolic blood pressure was found to be of prognostic importance. Adjusted and unadjusted multivariate analyses showed increasing quartiles of ambulatory and home systolic blood pressure to be associated with all-cause mortality (adjusted hazard ratios for increasing quartiles of ambulatory: 2.51, 3.43, 2.62; and for home blood pressure: 2.15, 1.7, 1.44). Mortality was lowest when home systolic blood pressure was between 120 to 130 mm Hg and ambulatory systolic blood pressure was between 110 to 120 mm Hg. Blood pressure recorded before and after dialysis was not statistically significant (P=0.17 for predialysis, and P=0.997 for postdialysis) in predicting mortality. Out-of-dialysis unit blood pressure measurement provided superior prognostic information compared to blood pressure within the dialysis unit (likelihood ratio test, P<0.05). Out-of-dialysis unit blood pressure among hemodialysis patients is prognostically more informative than that recorded just before and after dialysis. Therefore, the management of hypertension among these patients should focus on blood pressure recordings outside the dialysis unit.

Figure 1

Study flow diagram.

Figure 2

Kaplan Meier survival curves for ambulatory systolic BP and mortality. The log rank test demonstrated a significant difference in survival between quartiles of ambulatory systolic BP.

Figure 3

Kaplan Meier survival curves for home systolic BP and mortality. The log rank test demonstrated a significant difference in survival between quartiles of ambulatory systolic BP.

Figure 4

Non-linear relationship of systolic BP obtained outside the dialysis unit and subsequent mortality over up to 6 years. The best outcome was seen when ambulatory systolic BP was between 110–120 mmHg and home systolic BP was between 120–130 mmHg. The splines are calculated at the average age of this cohort which was 55 years.