The influence of high versus low sodium intake on blood pressure and haemodynamics in patients with morbid obesity

摘要

Background: Many patients with morbid obesity (BMIa??> a??40a??kg/m) have hypertension. The complex pathophysiological abnormalities linking hypertension to obesity have not been fully clarified, but abnormal sodium handling could be an important mechanism.Method: Therefore, we examined changes in body fluid compartments and haemodynamic responses (at rest and during exercise) after 5 days of a low-sodium diet (90a??mmol/day) and 5 days of a high-sodium diet (250a??mmol/day) in 12 morbidly obese, hypertensive patients; 12 morbidly obese, normotensive patients and 12 nonobese controls.Results: High sodium intake as compared to low sodium intake was associated with an increase in plasma volume (obese, hypertensive patients: 5a??±a??4%; obese, normotensive patients: 10a??±a??11%; nonobese controls: 7a??±a??6%), cardiac output (CO) (obese, hypertensive patients: 17a??±a ??12%; obese, normotensive patients: 20a??± a??16%; nonobese controls: 13a??± a??14%) and stroke volume (SV) (obese, hypertensive patients: 27a??±a??26%; obese, normotensive patients: 27a??±a??24%; nonobese controls: 18a??±a??27%) in all three groups with no differences between the groups. Despite an increase in CO during high salt intake, 24-h blood pressure (BP) was unchanged in patients and controls as a result of a reduction in total peripheral resistance (obese, hypertensive patients: -11a??±a??11%; obese, normotensive patients: - 10a??±a??12%; nonobese controls: -5a??±a??14%). Similar changes were observed during an incremental bicycle exercise test wherein CO and SV were higher, whereas mean arterial BP was unchanged at each exercise level during high sodium intake.Conclusion: Despite substantial increases in CO and SV, we did not observe any significant change in BP during high sodium intake, neither in morbid obese patients nor in lean individuals.