Orthostatic responses to nitric oxide synthase inhibition in persons with tetraplegia.
OBJECTIVE
To determine the effects of 1.0 mg/kg nitro-L-arginine methyl ester (L-NAME) on orthostatic mean arterial pressure (MAP), serum aldosterone, and plasma renin concentrations in persons with chronic tetraplegia compared with nonspinal cord-injured controls.


METHODS
Prospective placebo-controlled intervention study.


METHODS
James J. Peters Veterans Affairs Medical Center.


METHODS
Patients (n=5) with tetraplegia and controls (n=7) participated. The groups were matched for age, height, and weight; the average duration of injury in the tetraplegia group was 22+/-14 years.


METHODS
Subjects with tetraplegia visited the laboratory twice, receiving placebo on day 1 and L-NAME (1.0 mg/kg) on day 2. The agents were infused via an intravenous catheter over 60 minutes with the patient in the supine position. Data were collected during the infusion and then during head-up tilt to 45 degrees for 30 minutes. Control subjects visited the laboratory once for placebo infusion and the head-up tilt maneuver.


METHODS
Orthostatic MAP.


RESULTS
Orthostatic MAP was reduced after placebo infusion in subjects with tetraplegia compared with controls (69+/-11 vs 89+/-9 mmHg, respectively; P<.01) and compared with L-NAME infusion (90+/-16 mmHg; P<.01). Orthostatic MAP did not differ when comparing the tetraplegia group with controls after L-NAME infusion. Orthostatic aldosterone levels were increased after placebo compared with L-NAME infusion in persons with tetraplegia; plasma renin levels did not differ among the groups.


CONCLUSIONS
These data suggest that nitric oxide synthase inhibition may have clinical potential for treatment of orthostatic hypotension in persons with chronic tetraplegia.
Wecht
Jill M
JM
Center of Excellence for the Medical Consequences of Spinal Cord Injury, James J. Peters Veterans Affairs Medical Center, Bronx, NY 10468, USA. jm.wecht@VA.gov
Radulovic
Miroslav
M
Lafountaine
Michael F
MF
Rosado-Rivera
Dwindally
D
Zhang
Run-Lin
RL
Bauman
William A
WA
D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure / Q000187:drug effects*; D016022:Case-Control Studies; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007024:Hypotension, Orthostatic / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D010919:Placebos; D011446:Prospective Studies; D011782:Quadriplegia / Q000201:enzymology*; D013119:Spinal Cord Injuries / Q000188:drug therapy*; D018667:Tilt-Table Test
D010919:Placebos; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester