GFR, proteinuria and circadian blood pressure

Hypertension is common, and arterial pressure rhythms are impaired in patients with chronic kidney disease (CKD). Emerging evidence suggests that consideration of excretory function together with proteinuria may provide a more holistic assessment of the extent of derangement in renal function.

To evaluate the independent relationships of estimated GFR and proteinuria with the mean level of and the circadian variation in blood pressure, we evaluated 336 patients, 184 (55%) patients with CKD (eGFR <60 or urine protein/creatinine >0.22) and 152 (45%) without CKD.

The mean level of systolic and diastolic BP increased with increasing severity of proteinuria as well as with increasing impairment in GFR. When proteinuria and eGFR were considered together in the same regression model, proteinuria-not eGFR-was related to the severity of hypertension. Non-dipping was present in 52% of those with eGFR >60 and 55% in those with no proteinuria. Non-dipping was seen early in the course of impaired GFR or proteinuria. Adjusted for proteinuria, the odds ratio for non-dipping in those with CKD was 1.71 (95% CI 1.03-2.84, P = 0.036). The odds ratio for non-dipping in those with proteinuria was 1.75 (95% CI 1.00-3.08, P = 0.049) when adjusted for CKD. A cosinor model that evaluates the midline estimating statistic of rhythm (MESOR) and circadian variation revealed that proteinuria was a stronger determinant of MESOR compared to the CKD stage; the CKD stage in addition to proteinuria did not further add to the determination of MESOR. The amplitude of variation was markedly blunted in patients with the earliest stages of derangement in kidney function whether it was assessed by proteinuria or eGFR.

These results demonstrate a graded relationship of proteinuria and eGFR with the mean level of BP and a non-graded relationship with circadian variation. Consideration of these two simple tests of renal function may better assist in gauging the severity of hypertension in patients with CKD.