Fluid homeostasis within muscle compartments is maintained by four
pressures: capillary blood pressure, capillary blood oncotic pressure,
tissue-fluid pressure, and tissue fluid oncotic pressure. As determined in
the canine anterolateral compartment, capillary blood pressure is 25 +/- 3
millimeters of mercury; capillary blood oncotic pressure, 26 +/- 3
millimeters of mercury, tissue-pbessure, -2 +/- 2 millimeters of mercury;
and tissue-fluid oncotic pressure, 11 +/- 1 millimeters of mercury. The
wick technique allows direct measurement of tissue-fluid pressure in
skeletal muscle and, with minor modifications, is adapted to collect
microsamples of interstitial fluid for determinations of tissue-fluid
oncotic pressure. The wick technique detects very slight fluctuations in
intracompartmental pressure such as light finger compression, injection of
small volumes of fluid, and even pulsation due to adjacent arterial
pressure. Adjacent muscle compartments may contain different tissue-fluid
pressure due to impermeable osseofascial barriers. Our results obtained in
canine muscle compartments pressurized by infusion of autologous plasma
suggest that risks of muscle damage are significant at intracompartmental
pressures greater than thirty millimeters of mercury.