Low systolic blood pressure values, renal resistive index measurement and glomerular filtration rate in a non-dialysis dependent chronic kidney disease population

A longitudinal prospective case control study was organized to explore the relationships between glomerular filtration rate (GFR), renal resistive index (RRI) and blood pressure values in a non-dialysis dependent adult population affected by chronic kidney disease and exposed to low systolic blood pressure (SBP) values. The study sample (54 patients: 31 males and 23 females with an average age of 61.7 ± 19.2 years) was randomly selected from a population of adult non-dialysis dependent patients that scored a SBP < 100 mmHg at the medical examination. The patients were equally divided in two groups defined by the presence and absence of chronic kidney disease, (i.e. a GFR less or greater than 60 ml/min/1.73 m2, respectively). Patients were submitted to a full therapeutic and dietetic intervention to correct the hypotension until reaching a steady SBP > 100 mmHg. In the group with chronic renal disease, the comparison between the data recorded with SBP < 100 mmHg (t0) and those detected with SBP ≥ 100 mmHg (t1) showed a statistically significant decrease of serum creatinine as well as an increase of GFR (mean serum creatinine t0 - serum creatinine t1: 0.194 ± 0.35, p < 0.01; mean GFR t0 - GFR t1: -4.615 ± 8.8, p < 0.013). There was also a statistically significant reduction of the RRI (mean right kidney RRI t0 - mean right kidney RRI t1: + 0.082 ± 0.03, p < 0; mean left kidney RRI t0 - mean left kidney RRI t1: 0.076 ± 0.03, p < 0). We concluded that, in CKD, when aorta is stiffed, a decrease of SBP can limit the renal perfusion that, in this condition, is mostly dependent by stroke volume, causing an increase of RRI and a decrease of GFR that we suppose as reversible with the restoration of SBP.