The relationship between blood pressure variabilityand renal progress in chronic kidney patients

BACKGROUND and OBJECTIVES: Elevated blood pressure (BP) (hypertension; HT) is known to cause of chronic kidney disease (CKD), as well as accelerate renal progression and progression to end-stage renal failure (ESRF). Variations in BP are called variability. Current studies have shown that blood pressure variability (BPV) is associated with increased target organ damage and cardiovascular events. However, there are also studies in the literature with different results. In this study, we aimed to evaluate the effect of 24 hour sistolic and diastolic BPV on renal progression in patients with CKD and HT. METHODS: In our study, a descriptive and retrospective data collection method was used between the dates 01.01.2013 and 31.12.2017 in Recep Tayyip Erdoğan University, Faculty of Medicine, Education and Research Hospital, Nephrology Department outpatient clinic. Fifty nine (59) patients which is older than 18 years of age and who had been followed up for CKD and HT for more than 3 months and underwent 24 hours ambulatory blood pressure measurement (ABPM) were included in the study. Patients who refused to participate in the study, did not follow consecutive day and night ABPM, who were not diagnosed with CKD and/or HT and who were not followed up for more than 3 months were excluded. Systolic and diastolic blood pressure (SBP and DBP) values (day, night, mean and standard deviation) of all patients were recorded. Blood pressure variability (BPV) coefficients (VC) were calculated separately for both systolic (SBP-CV) and diastolic (DBP -CV) blood pressures. Estimated glomerular filtration (e-GFR) values of the patients were calculated with CKD-EPI formula. A decrease in e-GFR of <5 ml/min/year was accepted as normal progression and a decrease in ≥5 ml/min/year was considered as rapid renal progression. The presence of rapid renal progression was determined as the primary endpoint. RESULTS: Of the 59 patients (mean age: 54.2±14.6 years, 50.8% male), 39% were diabetic. 40.6% of the patients had uncontrolled HT, while 45.8% had non-dipper pattern. SBP values are considered; mean daytime SBP was 135.3±17.9 (min:104max:184) mmHg, mean day SBP-VC was 11.7±2.8 (min:5.8-max:18.9), night SBP average 128.6±23.0 (min:89-max:195) mmHg, night SBP-VC average of 9.5±3.6 (min:4.1-max:23.2), the total SBP mean was 134.0±18.4 (min:101-max:175) mmHg and the total SBP-VC was 12.0±2.7 (min:6.1-max:17.6) detected. Diastolic blood pressure (DBP) values are considered; mean DBP at daytime 84.5±13.4 (min:50max:110) mmHg, mean DBP-VC at daytime was 13.8±3.8 (min:5.7-max:26.1), the mean night DBP was 77.2±16.1 (min:45-max:109) mmHg, the average night DBP-VC was 12.0±3.7 (min:4.1-max:23.1) total DBP mean was 82.9±13.9 (min:49-max:109) mmHg and total DBP-VC was 14.3±3.6 (min:7.1-max:25.7). Serum creatinine levels of all patients at the beginning of the study were 1.9±1.8 mg/dl, e-GFR: 64.6±38.1 ml/min, and proteinuria: 1419.9±1973.3 mg/g. Serum creatinine: 2.2±2.2 mg/dl, e-GFR: 61.3±38.0 ml/min and proteinuria: 1488.2±2009.3 mg/g were determined after a mean follow-up period of 15.4±8.0 months. Rapid renal progression was detected in 15 of 59 patients (25.4%). There was no significant difference between daytime, nighttime and total SBP, SBP-VC, DBP and DBP-VC values between patients with rapid renal progression and those with natural progression (p> 0.05). Independent effect of SBPVC and DBP-VC in predicting rapid renal progression was examined with regression analysis by controlling the parameters such as age, gender, presence of DM, baseline eGFR value and dipping status. Accordingly, both SBP-VC and DBP-VC were not effective in predicting rapid progression (p> 0.05). CONCLUSIONS: In our study, we found no relationship between BPV and renal progression in CKD and HT patients. We believe that prospective, randomized controlled trials with more patients and longer follow-up are needed to clarify this issue.