Glomerular Hyperfiltration Is Associated With Blood Pressure Abnormalities in Normotensive Normoalbuminuric IDDM Patients

OBJECTIVE To analyze the blood pressure patterns in normoalbuminuric IDDM patients with glomerular hyperfiltration.

RESEARCH DESIGN AND METHODS A controlled cross-sectional study of 38 normotensive normoalbuminuric (urinary albumin excretion rate <20 μg/min) IDDM patients (18 hyperfiltering [glomerular filtration rate >134 ml · min⁻¹ · 1.73 m⁻²] and 20 normofiltering) and 20 normal individuals matched for age, sex, and BMI was performed. The 24-h ambulatory blood pressure was monitored using an auscultatory technique (Pressurometer IV, Del Mar Avionics), the glomerular filtration rate was measured by ⁵¹Cr-labeled EDTA method, extracellular volume by the distribution volume of ⁵¹Cr-labeled EDTA, and the 24-h urinary albumin excretion rate by radioimmunoassay.

RESULTS Mean nocturnal diastolic blood pressure was higher in hyperfiltering IDDM patients (70.4 ± mmHg), when compared with the control group (65.1 ± 5.3 mmHg, P = 0.04). Diastolic blood pressure night:day ratio was higher in hyperfiltering IDDM patients (92.0 ± 8.6%), when compared with normofiltering IDDM patients (85.9 ± 4.8%) and control subjects (87.0 ± 6.8%, P = 0.02). In IDDM patients, the glomerular filtration rate significantly correlated with the diastolic blood pressure night:day ratio (r = 0.5, P = 0.002), extracellular volume (r = 0.04, P = 0.002), and HbA₁ (r = 0.3, P = 0.03). In stepwise multiple regression analysis, factors associated with glomerular filtration rate were diastolic blood pressure night:day ratio, extracellular volume, and HbA₁ (adjusted r² = 0.27, P = 0.003).

CONCLUSIONS Glomerular hyperfiltration is associated with higher nocturnal diastolic blood pressure and with a blunted nocturnal decrease in diastolic blood pressure levels in normotensive and normoalbuminuric IDDM patients.