Impaired aldosterone response to the saline infusion test in patients with resistant hypertension and obstructive sleep apnea

Abstract

Background In this cross-sectional study, we sought associations among severity of obstructive sleep apnea (OSA), renin-angiotensin-aldosterone system and blood pressure patterns in patients with resistant hypertension.
Material and methods In 65 patients with resistant hypertension we measured the apnea-hypopnea index (AHI) by a portable sleep recorded system and aldosterone and plasma renin activity (PRA) in response to saline infusion test. We also collected data on cardiovascular events, dyslipidemia, chronic kidney disease, and diabetes and performed 24-hour blood pressure monitoring (ABPM).
Results Baseline PRA, aldosterone and aldosterone-to-renin ratio were within normal range but aldosterone level in response to saline infusion was increased above normal upper limit. In ABPM, 68% of patients had an altered pattern of blood pressure (non-dipping or reverse dipping). AHI was inversely correlated with PRA and positively with weight, BMI, plasma aldosterone, aldosterone to renin ratio, and aldosterone after saline load but not with blood pressure. Patients with severe OSA (AHI > 30) in comparison to those with mild OSA (AHI 5–15) had significantly higher PRA and aldosterone (baseline and after saline load) but comparable values of blood pressure. We did not find significant impact of OSA severity on the frequency of abnormal blood pressure patterns. Frequencies of diabetes, abnormal lipid profiles, ischemic heart disease, myocardial infarction, and stroke increased with increases in severity of OSA.
Conclusions Despite of normal basal PRA and aldosterone concentration, patients with resistant hypertension and OSA had impaired response to saline load and a rate of this impairment depended on the severity of OSA.