Importance of volume factors in dialysis related hypertension.

Abstract

Patients, classified as normotensive (n = 11) or hypertensive (n = 19), based on 24-hour blood pressure measurements, had significantly different TBW % (54.7 +/- 5.3 vs. 58.9 +/- 4.6%, p = 0.046). Ambulatory blood pressure and postdialysis blood pressure, but not predialysis blood pressure, were significantly correlated with TBW %. Acute volume changes, as reflected by interdialytic weight gain and ultrafiltration did not correlate with TBW %. These changes correlated weakly with predialysis blood pressure. Multivariate analysis showed that only TBW % and antihypertensive medication had an independent influence on 24-hour blood pressure measurements. We conclude that 24-hour blood pressure and blood pressure after dialysis are better related to total body water than blood pressure before dialysis, which was however weakly related to the acute volume overload, induced by interdialytic weight gain. We hypothesize that this could be the result of a more important chronic volume overload leading to an increase in systemic vascular resistance. On the contrary the acute but less important changes in extracellular volume between dialyses cause no hypertension after dialysis and no sustained hypertension over 24 hours, but only in some cases a temporary increase in the blood pressure just before dialysis. This volume overload can be easily determined by measurement of total body water by bioelectrical impedance analysis.