Orthostatic effects of midodrine versus L-NAME on cerebral blood flow and the renin-angiotensin-aldosterone system in tetraplegia

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Abstract

Objective: To compare responses to head-up tilt (HUT) in individuals with chronic tetraplegia after midodrine hydrochloride (10mg) versus nitro-L-arginine methyl ester (L-NAME, 1mg/kg) administration. Design: Prospective comparative drug trial. Setting: Veterans Affairs medical center. Participants: Participants (N=7) were studied during 3 laboratory visits: no drug, midodrine (administered orally 30min before HUT), and L-NAME (infused over a 60-min period). Interventions: Anti-hypotensive agents, midodrine, and L-NAME. Main Outcome Measures: Mean arterial pressure (MAP), cerebral blood flow (CBF), and markers of the renin-angiotensin-aldosterone system (RAAS, plasma renin and serum aldosterone) were measured in the supine position at baseline (BL) and during a 45° HUT maneuver. Data were compared between BL and the average of 3 assessments collected during HUT. Results: Orthostatic MAP and CBF were increased with the midodrine and L-NAME groups compared with the no drug trial and the relationship between the change in MAP and CBF was significant (r=0.770; P<0.001). Both L-NAME and midodrine appeared to suppress the post-HUT RAAS response compared with no drug. Conclusions: Increasing orthostatic blood pressure with L-NAME or midodrine appears to increase CBF and suppress the RAAS during HUT in persons with tetraplegia, although more data are needed to confirm these preliminary findings.

Original languageEnglish
Pages (from-to)1789-1795
Number of pages7
JournalArchives of Physical Medicine and Rehabilitation
Volume92
Issue number11
DOIs
StatePublished - Nov 2011

Keywords

  • Blood pressure
  • Hypotension
  • Rehabilitation
  • Spinal cord injuries
  • orthostatic

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