title: Partial angiotensin-converting enzyme inhibition during acute orthostatic stress in persons with tetraplegia.
abstract: BACKGROUND
  Individuals with tetraplegia rely on the renin-angiotensin system for orthostatic blood pressure control.
  
  
  OBJECTIVE
  To determine the effect of partial angiotensin-converting enzyme (ACE) inhibition on heart rate (HR), active plasma renin (PR), and mean arterial blood pressure (MAP) during acute orthostasis in subjects with tetraplegia (n = 7) and nondisabled persons (n = 8).
  
  
  METHODS
  Subjects were instructed to avoid caffeine and alcohol for 24 hours before testing and to report to the laboratory between 10 AM and 1 PM. Progressive head-up tilt (15 degrees, 25 degrees, 35 degrees, and 45 degrees) was performed on 2 separate days; Day 1: without ACE inhibition; Day 2: after intravenous (IV) infusion of enalaprilat (0.625 mg).
  
  
  RESULTS
  HR was reduced during orthostasis in the tetraplegia compared with the nondisabled group (P < 0.0001), and was unaffected by ACE inhibition in either group. PR was not increased with orthostasis in either group, but was increased after ACE inhibition in both groups (P < 0.001). MAP was not affected by orthostasis in either group, but was reduced with ACE inhibition in both groups (P < 0.01). In the tetraplegia group, MAP was initially reduced after ACE inhibition, but was maintained thereafter with increasing angles of tilt, and no subject complained of symptomatic orthostatic hypotension.
  
  
  CONCLUSIONS
  Subjects with tetraplegia were tolerant of an acute bout of orthostatic stress after partial ACE inhibition. This may have clinical relevance because of the increased prevalence of type 2 diabetes mellitus in this population and the use of ACE inhibitors for the treatment of progressive renal and cardiovascular disease.
authors.affiliation: Spinal Cord Damage Research Center, Veterans Affairs Medical Center, Bronx, New York 10468, USA. jill.wecht@med.va.gov
authors.forename: Jill M
authors.initials: JM
authors.lastname: Wecht
authors.forename: Miroslav
authors.initials: M
authors.lastname: Radulovic
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Weir
authors.forename: Joanah
authors.initials: J
authors.lastname: Lessey
authors.forename: Ann M
authors.initials: AM
authors.lastname: Spungen
authors.forename: William A
authors.initials: WA
authors.lastname: Bauman
mesh_terms: D000328:Adult; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D002574:Cervical Vertebrae; D004244:Dizziness / Q000503:physiopathology*; D015773:Enalaprilat / Q000494:pharmacology*; D006801:Humans; D008875:Middle Aged; D011782:Quadriplegia / Q000209:etiology / Q000503:physiopathology*; D012084:Renin-Angiotensin System / Q000187:drug effects*; D013119:Spinal Cord Injuries / Q000150:complications / Q000503:physiopathology; D018667:Tilt-Table Test
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D015773:Enalaprilat