An investigation of the effect of advancing uraemia, renal replacement therapy and renal transplantation on blood pressure diurnal variability.

BACKGROUND Ambulatory blood pressure recordings have been shown to correlate better with target organ damage than have isolated clinic blood pressure readings. There have been some small studies demonstrating that abnormal blood pressure diurnal rhythm is common in uraemia and in patients on renal replacement therapy. Abnormal blood pressure diurnal rhythm itself may be a risk factor for accelerated target organ damage. METHODS We retrospectively studied 480 ambulatory blood pressure recordings in 380 patients with essential hypertension, secondary hypertension, and on renal replacement therapy. We examined diurnal blood pressure rhythm in each group. RESULTS Abnormal blood pressure diurnal rhythm (non-dipping) is significantly more prevalent in patients with underlying renal disease, even with normal excretory renal function (53%) than in age-, sex-, and race-matched controls with essential hypertension ((30%), P < 0.01). In patients with renal disease the prevalence of non-dipping rose with worsening renal function, reaching statistical significance once plasma creatinine was greater than 400 mumol/l. There was a direct correlation between plasma creatinine and percent decline in blood pressure at night for both systolic (r = 0.23) and diastolic (r = 0.24) blood pressure in patients with underlying renal disease and impaired excretory renal function. High prevalences of abnormal diurnal BP rhythm are seen in patients on haemodialysis (82%), peritoneal dialysis (78%), patients with plasma creatinine > 600 mumol/l (75%), and in renal transplant recipients (74%). CONCLUSIONS Abnormal blood pressure diurnal rhythm ('non-dipping') is significantly more common in secondary than in primary hypertension, even with normal renal function. Abnormal blood pressure diurnal rhythm becomes increasingly common with advancing uraemia. Once the plasma creatinine is greater than 600 mumol/l the prevalence of non-dipping is the same as that seen with renal replacement therapy. This phenomenon is not modulated by successful renal transplantation.