Which blood pressure readings better predicted mortality in people on hemodialysis?

Details

Blood pressure readings taken before and after dialysis do not agree well with readings taken outside the dialysis unit. The researchers investigated whether outside readings had greater prognostic value, a question that remained incompletely understood.

Among 326 patients on long-term hemodialysis, blood pressure was self-measured at home for 1 week, recorded by ambulatory monitoring over an interdialytic interval, and measured before and after dialysis over 2 weeks. During a mean follow-up of 32 months (SD 20), 102 patients died (31%), giving a crude mortality rate of 118 per 1,000 patient-years.

Systolic, but not diastolic, blood pressure was prognostically important. Adjusted and unadjusted multivariate analyses found associations between increasing quartiles of ambulatory and home systolic blood pressure and all-cause mortality; adjusted hazard ratios for increasing quartiles were 2.51, 3.43 and 2.62 for ambulatory readings and 2.15, 1.7 and 1.44 for home readings. Mortality was lowest when home systolic blood pressure was 120–130 mm Hg and ambulatory systolic blood pressure was 110–120 mm Hg.

Blood pressure measured before and after dialysis was not statistically significant in predicting mortality (P=0.17 before dialysis and P=0.997 after dialysis). Measurements outside the dialysis unit provided better prognostic information than those inside it (likelihood ratio test, P<0.05). The researchers concluded that outside readings are more informative than readings taken just before and after dialysis, and that hypertension management in these patients should focus on readings outside the dialysis unit.