Microcirculation of striated muscle in closed soft tissue injury: effect on tissue perfusion, inflammatory cellular response and mechanisms of cryotherapy. A study in rat by means of laser Doppler flow-measurements and intravital microscopy

The authors investigated the effects of closed soft tissue injury (CSTI) an d cryotherapy on microvascular perfusion by means of laser Doppler flowmetr y. In a different protocol interactions between leukocytes and the microvas cular endothelium of skeletal muscle, which are first steps in local inflam matory response were documented in an intravital microscopy model. Rats wer e chronically instrumented with dorsal skinfold chambers. Leukocyte rolling and adherence in postcapillary venules of striated muscle before and after standardized muscle contusion (group T: n = 6), cryotherapy following musc le contusion (TK: n = 6) or sham contusion (group N: n = 6) were quantitate d prospectively and in random order using intravital microscopy. Tissue per fusion was assessed by laser Doppler flowmetry in the microvasculature of t he flap over a period of 96 hours following CSTI (group T: n = 8), cryother apy following CSTI (group TK: n = 8), sham trauma (group N: n = 8, control 1), or cryotherapy following sham trauma (group K: n = 8, control 2). 300 m inutes after trauma the number of rolling and adherent leukocytes in striat ed muscle microvasculature was significantly reduced by cryotherapy. We fou nd an acute effect of cryotherapy on perfusion of traumatized tissue (reduc tion of perfusion around 25 %). However, there was no long-term effect (96 hours evaluation) on microvascular perfusion of cryotherapy either in the p resence or absence of CSTI. The effectiveness of ice application in reducin g edema in striated muscle following contusion may be due in part to a redu ction of the leukocyte/endothelial interactions accompanying CSTI.