“Thermoregulation and Cognition During Cool Ambient Exposure in Tetraplegia”
The ability to maintain normal core body temperature (Tcore = 98.6A?F) is impaired in persons with a cervical spinal cord injury (tetraplegia). Despite the known deficits in the ability of persons with spinal cord injury (SCI) to maintain Tcore, and the effects of hypothermia to impair mental function in able-bodied (AB) persons, there has been no work to date addressing these issues in persons with tetraplegia. Primary Aim: To determine if exposure of up to 2 hours to cool temperatures (64A?F) causes Tcore to decrease in persons with tetraplegia, and if that decrease is associated with a decrease in cognitive function. Primary Hypotheses: Based on our pilot data: (1) 66% of persons with tetraplegia and none of the matched controls will demonstrate a decline of 1.8A?F in Tcore; (2) 80% of persons with tetraplegia and 30% of controls will have a decline of at least one T-score in Stroop Interference scores (a measure of executive function). Secondary Aim: To determine the change in: (1) distal skin temperature, (2) metabolic rate, and (3) thermal sensitivity. Secondary Hypothesis: Persons with tetraplegia will have less of a percent change in average distal skin temperatures and metabolic rate, and report lower thermal sensitivity ratings compared with AB controls. Tertiary Aim: To determine if a 10 mg dose of an approved blood pressure-raising medicine (midodrine hydrochloride) will (1) reduce the decrease in Tcore and (2) prevent or delay the decline in cognitive performance in the group with tetraplegia compared to the exact same procedures performed on the day with no medicine (Visit 1) in that same group. Tertiary Hypothesis: Through administering a one-time dose of midodrine, the medicine-induced decreased blood flow to the skin will lessen the decline in Tcore and prevent or delay the associated decline in cognitive performance compared to the changes in Tcore and cognitive performance during cool temperature exposure without midodrine in the same group with tetraplegia.
Drug - Midodrine Hydrochloride
Midodrine hydrochloride is an approved medication used to treat low blood pressure. We are using a standard dose of 10 mg (tablet) only one time to determine if the vascular-constricting effects of this drug will help keep warm blood closer to the body's core and improve the ability to maintain Tcore in a cool environment (off-label use). A physician will administer the drug once before the cool thermal challenge in subjects with tetraplegia only (Visit 2).
Subjects will be exposed to a routinely encountered cool temperature (64Â° F) for up to to 2 hours depending on the vital signs (BP, HR, Tcore) and tolerance (comfort).
Thermoregulation and Cognition During Cool Ambient Exposure in Tetraplegia