Relationship between arterial hypertension and renal damage in chronic kidney disease: insights from ABPM.

Background: To date, few studies have used ambulatory pressure monitoring (ABPM) in patients with chronic kidney disease (CKD) before the start of dialysis treatment. The aim of this study was therefore to ascertain the correlates of arterial hypertension assessed by ABPM in CKD patients at their first referral to a nephrologist.

Methods: We studied 244 (164 men; mean age 63 years) nondiabetic patients with CKD. Each patient had blood pres-sure (BP) measured by 24-hour ABPM, creatinine clearance (CrCl) estimated according to the Cockcroft-Gault formula, and Hgb concentration, serum lipids, iPTH, daily urinary protein (Uprot) and sodium (UNa) excretion assessed using routine methods.

Results: According to ABPM data analysis, 81 patients were normotensives, 78 were stable hypertensives, 26 had day-time hypertension and 59 had nocturnal hypertension. ANOVA showed both lower CrCl (p=0.0033), and higher Uprot (p<0.0001) in stable and nighttime hypertensives as compared with normotensives and daytime hypertensives. In the whole group each set of both systolic (SBP) and pulse pressure (PP) readings was directly associated with both age and Uprot (p<0.05), and inversely with both CrCl and Hgb (p<0.05). In multivariate analysis, however, Uprot emerged among modifiable risk factors, as the most significant predictor of both SBP and PP; the strength of this association was in the order nighttime PP > nighttime SBP > 24-hour PP > daytime PP > daytime SBP > 24-hour SBP.

Conclusion: In CKD patients, proteinuria is the strongest correlate of arterial hypertension and particularly of increased nocturnal PP, possibly as an expression of vascular damage. On the basis of these results, ABPM appears to be the most reliable tool for detecting the associations between raised BP (particularly nighttime hypertension) and renal damage in CKD patients not yet on renal replacement therapy (RRT).