40
Participants
Start Date
June 30, 2015
Primary Completion Date
November 15, 2017
Study Completion Date
November 15, 2017
Static Handgrip
Subjects will perform static handgrip at 40% of maximum voluntary contraction until fatigue.
Dexmedetomidine
Subjects will be given dexmedetomidine to suppress sympathetic outflow to minimize sympathetic control over resting heart rate. Subjects will then be given glycopyrrolate to suppress parasympathetic tone to minimize parasympathetic control over resting heart rate. After achievement of autonomic blockade, cardiac beta receptor sensitivity will be assessed by graded infusions of isoproterenol until heart rate increases 30 beats above baseline.
Glycopyrrolate
Subjects will be given dexmedetomidine to suppress sympathetic outflow to minimize sympathetic control over resting heart rate. Subjects will then be given glycopyrrolate to suppress parasympathetic tone to minimize parasympathetic control over resting heart rate. After achievement of autonomic blockade, cardiac beta receptor sensitivity will be assessed by graded infusions of isoproterenol until heart rate increases 30 beats above baseline.
Isoproterenol
Subjects will be given dexmedetomidine to suppress sympathetic outflow to minimize sympathetic control over resting heart rate. Subjects will then be given glycopyrrolate to suppress parasympathetic tone to minimize parasympathetic control over resting heart rate. After achievement of autonomic blockade, cardiac beta receptor sensitivity will be assessed by graded infusions of isoproterenol until heart rate increases 30 beats above baseline.
The Institute for Exercise and Environmental Medicine, Dallas
University of Texas Southwestern Medical Center
OTHER