Prevention of Low Blood Pressure in Persons With Tetraplegia

Despite disruption of central command of the vasculature during orthostatic maneuvers, individuals with tetraplegia are generally able to be seated in an upright position for long periods of time without developing symptoms of orthostatic intolerance. It must be appreciated however, that orthostatic hypotension may occur unpredictably in persons with chronic tetraplegia. This may result in a range of symptoms due to cerebral hypoperfusion from mild reduction in mental acuity to loss of consciousness. Nitric oxide (NO) is the most potent endogenous vasodilator which is synthesized by the enzyme NO synthase (NOS) and may be largely responsible for orthostatic hypotension in individuals with immobilizing conditions. Recent evidence suggests an up-regulation of inducible nitric oxide synthases (NOS) activity with prolonged exposure to hind limb suspension. The effects of NOS inhibition during orthostasis on blood pressure regulation in those with chronic tetraplegia may provide insight into effective pharmacological therapy to reduce or prevent pathologic orthostatic changes. Treatment with a NOS inhibitor may facilitate the process of mobilization in those with acute higher cord lesions.