An in vivo microanalytical technique for measuring the local biochemical milieu of human skeletal muscle

1 Rehabilitation Medicine Department, Clinical Research Center, National Institutes of Health; 2 Ultramicro Analytical Immunochemistry Resource, Division of Bioengineering and Physical Science, Office of Research Services, National Institutes of Health, Bethesda, Maryland; and 3 Department of Exercise Science, George Washington University, Washington, DC Submitted 14 April 2005 ; accepted in final form 11 July 2005 Myofascial pain associated with myofascial trigger points (MTrPs) is a common cause of nonarticular musculoskeletal pain. Although the presence of MTrPs can be determined by soft tissue palpation, little is known about the mechanisms and biochemical milieu associated with persistent muscle pain. A microanalytical system was developed to measure the in vivo biochemical milieu of muscle in near real time at the subnanogram level of concentration. The system includes a microdialysis needle capable of continuously collecting extremely small samples ( 0.5 µl) of physiological saline after exposure to the internal tissue milieu across a 105-µm-thick semi-permeable membrane. This membrane is positioned 200 µm from the tip of the needle and permits solutes of