534 HEMODYNAMIC CHANGES DURING ACUTE SALT LOADING IN PATIENTS WITH RESISTANT HYPERTENSION

Abstract

Objective: To assess the changes of hemodynamic parameters during acute salt-loading (SL) in patients with resistant hypertension (RHTN) and its associations with salt-sensitivity of blood pressure (BP). Design and Methods: We studied 34 patients (17 males, 17 females; 56 ± 6 yrs) with RHTN (taking combination antihypertensive therapy (lisnopril 20 mg + amlodipine 10 mg + hydrochlorothiazide 25 mg per day and BP over 140/90 mm Hg) and 6 healthy normotensive subjects (3 males, 3 females; 54 ± 2 yrs). SL was performed via i.v. infusion of 1000 mL saline for 1 hour. Beat-to-beat BP was registered using Finometer Pro device (Amstredam). Results: Within 1 hour of SL patients with RHTN exhibited elevation of systolic (SBP) and diastolic BP (DBP) (from 188 ± 6 to 161 ± 4 mm Hg for SBP and from 104 ± 2 to 89 ± 2 mm Hg for DBP, both p < 0.01 vs baseline). In one hour after SL BP returned close to baseline level (158 ± 4 and 86 ± 2 mm Hg, respectively). At baseline total peripheral vascular resistance in RHTN was significantly higher compared to controls (1767 ± 24 vs 1212 ± 28 dyn × s × sm−5; P < 0.05). Moreover, at peak of saline infusion BRS was also higher in patients with RHTN than in controls (2212 ± 35 vs 1573 ± 44 dyn × s × sm−5; P < 0.01). In hypertensive patients total peripheral vascular resistance changes positively correlated with the magnitude of NaCl-induced elevation of SBP (r = 0.61; P = 0.01) and DBP (r = 0.52; P = 0.02) BP. Hypertensive patients were subdivided on two groups: salt-resistant (SL-induced BP elevation <20 mm Hg for both SBP and DBP (n = 15)) and salt-sensitive (SL-induced BP elevation ≥ 20 mm Hg for SBP and/or DBP (n = 19)). Total peripheral vascular resistance at baseline was similar in both groups. In salt-sensitive patients a significant correlation of total peripheral vascular resistance delta with peak SBP delta was observed (r = 0,88, P < 0.01), while in slat-resistant no relation was documented. The final BRS was higher in salt-sensitive that in salt-resistant group (2560 ± 28 vs 2030 ± 24 dyn × s × sm−5; P < 0.001). Conclusion: In patients with RHTN total peripheral vascular resistance is increased and is positively associated with the level of pressor response to SL. The increase of total peripheral vascular resistance during SL is observed only in salt-sensitive RHTN.