Ambulatory blood pressure monitoring in nephrology: focus on BP variability.

As accurate assessment of hypertension in renal patients must be the cornerstone of better prevention of its deleterious effects, ambulatory blood pressure monitoring (ABPM) has become an essential clinical and research procedure in day to day nephrological practice. However, despite numerous studies in the renal literature, a consensus is needed for normal (desirable?!) ambulatory daytime and nighttime BP levels and for defining normal sleep BP dipping. Nevertheless, blunted sleep BP fall appears to be a ubiquitous finding in renal disease (primary renal conditions, chronic renal failure pre-dialysis, peritoneal and hemodialysis, and renal transplantation). Abnormal diurnal variability should be considered as an important contributor to cardiac and general morbidity as it is clearly associated with a faster decline in renal function and also with more cardiac structural and functional abnormalities - especially left ventricular dilatation. Several mechanisms have been proposed to explain the reduced BP circadian rhythm, but the majority of the supporting evidence is still contradictory. A novel, unifying hypothesis to be tested in future studies, is linking the common diurnal rhythm abnormalities with functional disturbances in aortic and carotid baroreflexes caused by uraemia-related large arterial structural changes (arterial intima and media thickening, arterial calcifications and increased arterial stiffness).