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Approximately 19 million adults in the United States have chronic kidney disease (CKD) and the prevalence of CKD continues to increase. Patients with CKD have an increased risk of cardiovascular (CV) disease and most CKD patients die before reaching the need for dialysis.1 There is constant debate about optimal BP goals for the nondialysis CKD population with ongoing studies in this area (Systolic Blood Pressure Intervention Trial [SPRINT]).2 The current guidelines advocate a goal blood pressure (BP) of ≤130/80 mm Hg with even tighter BP control in patients with significant proteinuria. These guidelines are based on office BP measurements. A recently published study questions the validity of these office BP guidelines in the nondialysis CKD population.

Minutolo and colleagues3 evaluated the prognostic role of ambulatory BP monitoring (ABPM) in patients with nondialysis CKD stages 2 to 4. This was a prospective cohort study of 436 patients at 4 Italian nephrology units seen between January 2003 until December 2005. Patients were followed for a median of 4.2 years. All patients had 24-hour ABPM performed. All patients were repeatedly seen by the same physician. Patients were followed until they reached a prespecified renal or cardiovascular end point or until September 30, 2010. Primary end points were time to renal death (end-stage renal disease or death) and time to fatal or nonfatal CV events. The mean age of patients was 65 (13.6) years with a mean glomerular filtration rate of 42.9 (19.7) mL/min/1.73m2. All the patients were Caucasian and approximately one third had diabetes and preexisting CV disease. Quintiles of BP were used to classify patients. Mean office BP was 146/82 mm Hg, daytime systolic BP (SBP) was 131/75 mm Hg, and nighttime BP was 122/66 mm Hg. A total of 155 patients reached the renal end point and 103 patients reached the CV end point.

There are some noteworthy findings associated with this study.

  •  Office BP values except for the highest quartile were not predictive of either renal or CV end points.
  •  Nighttime SBP was a stronger predictor for both end points than daytime SBP readings. There was an increased risk for renal end point with a daytime SBP >135 mm Hg and increased CV end point with nighttime SBP >124 mm Hg. Nighttime DBP better predicted risk of fatal and nonfatal CV end points.
  •  Dipping status was evaluated in all patients and results showed a 2-fold increased risk of CV end points in nondippers and reverse dippers with risk of renal death increased by 62% in nondippers and by 72% in reverse dippers.

From this study one can conclude that ABPM is prognostically superior to office BP measurements in nondialysis CKD patients, confirming the few other studies in CKD such as those of Agarwal and the participants in the African American Study of Kidney Disease and Hypertension (AASK) trial.4,5 Abnormal nighttime BP as observed on ABPM and dipping status predicted increased renal and CV risk. Office BP was not predictive for these events. Office BP also had a poor predictive role in discriminating risk profile for dipping status. All of the patients in the study were Caucasian, which may not be generalizable to the US population of CKD patients.

The size of this study, the follow-up period, and the outcomes in this thought-provoking report move us a step closer to finding the optimal way to manage BP in the nondialysis CKD population. What we think is needed next are two things. First, what underlies the failure of BP to dip or even to rise during the night, and can we alter the nocturnal component of the BP profile? Second, and perhaps most importantly, can we show that management of BP using the wealth of information obtained from 24 hours in the patients environs as compared with 5 to 10 minutes in an office setting? The Effect of Strict Blood Pressure Control and ACE Inhibition on CKD Progression in Pediatric Nephropathies (ESCAPE)6 trial experience suggests that the answer is “perhaps” in CKD. When you weigh the costs of dialysis/transplantation against the costs of ABPM, admittedly a contrived comparison, it would seem that the question is worthy of further study and is ready for clinical trial evaluation.

References

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  2. References
  • 1
    Matsushita K, van der Velde M, Astor BC, et al. Chronic Kidney Disease Prognosis Consortium. Association of estimated glomerular filtration rate and albuminuria with all-cause and cardiovascular mortality in general population cohorts: a collaborative meta-analysis. Lancet 2010;375(9731):273281.
  • 2
    Systolic Blood Pressure Intervention Trial (SPRINT). (http://clinicaltrials.gov/ct2/show/NCT01206062). Accessed December 6, 2010.
  • 3
    Minutolo R, Agarwal R, Borrelli S, et al. Prognostic role of ambulatory blood pressure measurement in patients with nondialysis chronic kidney disease. Arch Intern Med 2011;171(12):10901098.
  • 4
    Agarwal R, Andersen MJ. Prognostic importance of ambulatory blood pressure recordings in patients with chronic kidney disease. Kidney Int 2006;69(7):11751180.
  • 5
    Sika M, Lewis J, Douglas J, et al. Baseline characteristics of participants in the African American Study of Kidney Disease and Hypertension (AASK) Clinical Trial and Cohort Study. Am J Kidney Dis 2007;50(1):7889, e1.
  • 6
    ESCAPE Trial Group, Wühl E, Trivelli A, Picca S, et al. Strict blood-pressure control and progression of renal failure in children. N Engl J Med 2009;361:16391650.