title: Changes in 24 h ambulatory blood pressure and effects of angiotensin II receptor blockade during acute and prolonged high-altitude exposure: a randomized clinical trial.
abstract: OBJECTIVE
  Many hypertensive subjects travel to high altitudes, but little is known on ambulatory blood pressure (ABP) changes and antihypertensive drugs' efficacy under acute and prolonged exposure to hypobaric hypoxia. In particular, the efficacy of angiotensin receptor blockers in this condition is unknown. This may be clinically relevant considering that renin-angiotensin system activity changes at altitude. The HIGHCARE-HIMALAYA study assessed changes in 24 h ABP under acute and prolonged exposure to increasing altitude and blood pressure-lowering efficacy and safety of an angiotensin receptor blockade in this setting.
  
  
  RESULTS
  Forty-seven healthy, normotensive lowlanders were randomized to telmisartan 80 mg or placebo in a double-blind, parallel group trial. Conventional and Ambulatory BPs were measured at baseline and on treatment: after 8 weeks at sea level, and under acute exposure to 3400 and 5400 m altitude, the latter upon arrival and after 12 days (Mt. Everest base camp). Blood samples were collected for plasma catecholamines, renin, angiotensin, and aldosterone. In both groups, exposure to increasing altitude was associated with: (i) significant progressive increases in conventional and 24 h blood pressure, persisting throughout the exposure to 5400 m; (ii) increased plasma noradrenaline and suppressed renin-angiotensin-aldosterone system. Telmisartan lowered 24 h ABP at the sea level and at 3400 m (between-group difference 4.0 mmHg, 95% CI: 2.2-9.5 mmHg), but not at 5400 m.
  
  
  CONCLUSIONS
  Ambulatory blood pressure increases progressively with increasing altitude, remaining elevated after 3 weeks. An angiotensin receptor blockade maintains blood pressure-lowering efficacy at 3400 m but not at 5400 m.
authors.affiliation: Department of Health Sciences, University of Milano-Bicocca, Milan, Italy Department of Cardiovascular Neural and Metabolic Sciences, S.Luca Hospital, Istituto Auxologico Italiano, IRCCS, Milan, Italy gianfranco.parati@unimib.it.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Parati
authors.affiliation: Department of Cardiovascular Neural and Metabolic Sciences, S.Luca Hospital, Istituto Auxologico Italiano, IRCCS, Milan, Italy.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Bilo
authors.affiliation: Department of Cardiovascular Neural and Metabolic Sciences, S.Luca Hospital, Istituto Auxologico Italiano, IRCCS, Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Faini
authors.affiliation: Department of Cardiovascular Neural and Metabolic Sciences, S.Luca Hospital, Istituto Auxologico Italiano, IRCCS, Milan, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Bilo
authors.affiliation: Department of Cardiovascular Neural and Metabolic Sciences, S.Luca Hospital, Istituto Auxologico Italiano, IRCCS, Milan, Italy.
authors.forename: Miriam
authors.initials: M
authors.lastname: Revera
authors.affiliation: Department of Health Sciences, University of Milano-Bicocca, Milan, Italy Department of Cardiovascular Neural and Metabolic Sciences, S.Luca Hospital, Istituto Auxologico Italiano, IRCCS, Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Giuliano
authors.affiliation: Department of Cardiovascular Neural and Metabolic Sciences, S.Luca Hospital, Istituto Auxologico Italiano, IRCCS, Milan, Italy.
authors.forename: Carolina
authors.initials: C
authors.lastname: Lombardi
authors.affiliation: Department of Cardiovascular Neural and Metabolic Sciences, S.Luca Hospital, Istituto Auxologico Italiano, IRCCS, Milan, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Caldara
authors.affiliation: Department of Cardiovascular Neural and Metabolic Sciences, S.Luca Hospital, Istituto Auxologico Italiano, IRCCS, Milan, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Gregorini
authors.affiliation: I Department of Cardiology and Hypertension, Institute of Cardiology, Jagiellonian University Medical College, Krakow, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Styczkiewicz
authors.affiliation: Department of Statistics and Quantitative Methods, University of Milano-Bicocca, Milan, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Zambon
authors.affiliation: Department of Health Sciences, University of Milano-Bicocca, Milan, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Piperno
authors.affiliation: Department of Medical and Surgical Critical Care, University of Florence, Florence, Italy.
authors.forename: Pietro Amedeo
authors.initials: PA
authors.lastname: Modesti
authors.affiliation: Centro Cardiologico Monzino, IRCCS, Milan, Italy Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
authors.forename: Piergiuseppe
authors.initials: P
authors.lastname: Agostoni
authors.affiliation: Università di Milano-Bicocca, Milan, Italy IRCCS, Center of Epidemiology and Clinical Trials, Istituto Auxologico Italiano, Milan, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mancia
mesh_terms: D000328:Adult; D000531:Altitude; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D001562:Benzimidazoles / Q000494:pharmacology*; D001565:Benzoates / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D018660:Blood Pressure Monitoring, Ambulatory; D002940:Circadian Rhythm / Q000502:physiology; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D000077333:Telmisartan; D013997:Time Factors
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D001562:Benzimidazoles; D001565:Benzoates; D000077333:Telmisartan
keywords: Ambulatory blood pressure monitoring; Angiotensin receptor blockers; Blood pressure; High altitude; Hypoxia