Correlation between 24-hour Urinary Sodium Excretion and the Status of Blood Pressure Control in Patients with Resistant Hypertension: A Single-center Cross-sectional Study

  Objective  To study the correlation between 24-hour urinary sodium excretion and the controlling status of office blood pressure (BP) and home blood pressure monitoring (HBPM) in patients with resistant hypertension (RH).

  Methods  A cross-sectional study was performed based on the RH patient database in Peking Union Medical College Hospital. All RH patients treated in the Cardiology Clinic, Peking Union Medical College Hospital from October 2017 to March 2018 were enrolled. Twenty-four-hour urinary sodium excretion (24h-UNa) was examined to estimate daily sodium intake. Office BP, HBPM (4 measurements daily: before medicine in the morning, 10 a.m., 4 p.m., and before sleeping at night, respectively), and the types of antihypertensive drugs were recorded. Based on the quartile method for 24h-UNa excretion, all enrolled patients were stratified into four groups: low 24h-Una, low-mid 24h-UNa, mid-high 24h-UNa, and high 24h-Una groups. Multiple Logistic regression analysis was used to analyze the correlation of independent factors with the rate of BP control.

  Results  Totally 202 subjects were recruited, 107 men, 95 women, aged (59.87±16.30) years, and the 24h-UNa was (198.92±96.59) mmol. Patients with higher urine-sodium excretion were younger and with a higher body mass index (P < 0.001). The number of antihypertensive drugs increased significantly with the increase of urinary sodium level (P=0.001). High urine sodium excretion was associated with the reduced BP control rate for HBPM in the morning and at 10 a.m.. Multivariate Logistic regression analysis showed that 24h-UNa was independently associated with the target achievement of office BP (OR=2.356, 95% CI:1.004-5.533, P=0.049), morning HBPM (OR=2.408, 95% CI:1.026-5.650, P=0.030), and 10 a.m. HBPM (OR=2.299, 95% CI:1.031-5.129, P=0.033), while not with the 4 p.m. and night HBPM.

  Conclusions  24h-UNa is an independent risk factor for the control rates of office BP and morning HBPM in RH patients. Restriction of sodium salt intake plays an important role in reducing BP fluctuation and improving BP control.