Treatment of disordered blood pressure in spinal cord injury

Spinal cord injury (SCI) results in permanent paralysis and significant disability. In addition, some spinal cord injured people experience postural hypotension, a large drop in blood pressure when assuming the upright position, associated with dizziness and fainting. For someone with SCI who is wheelchair dependent, fainting can have significant consequences such as further injury from falling out of the chair, reduced independence and limited vocational outcomes, thus poorer overall physical and psychological well-being. In SCI, interruption of nervous communications, along with the loss of muscle pump in the legs, results in the impaired ability to maintain blood pressure on getting upright. Such persons have an abnormal pattern of blood pressure, whereby the blood pressure does not drop overnight, unlike the usual pattern. In some cases, there is even a higher blood pressure during the night than during the day – opposite to the normal pattern. Higher night time blood pressure leads to increased night time urine production, leaving the body with relatively less circulating blood volume in the morning, at the time that one is about to get out of bed, further contributing to postural hypotension. This study aims to examine the effects of treatment with captopril, a blood pressure lowering medication, at night, in a person with SCI who experiences symptoms of postural hypotension; we hypothesise that lowering night time blood pressure will reduce night time urine production, therefore increase blood pressure during the day, and reduce symptoms of postural hypotension, allowing the ability to stay upright during the day to carry out activities. In this placebo controlled crossover study, participants will receive either the drug treatment or a placebo (dummy pill) for 8 weeks, and then switch to the other pill to determine if there is a difference in effects between the two. Each treatment period will be separated by two weeks where the participant is not on either pill. Before and after each treatment, assessments include: measurements of blood pressure profile over 24 hours using an automatic portable monitor, recording urine volumes for 4 days, analysis of urine and blood samples. Current treatment for such blood pressure disturbances and symptoms of low blood pressure are inadequate, and this study will help to determine whether this novel treatment is effective.