New skeletal muscle model for the longitudinal study of alterations in microcirculation following contusion and cryotherapy.

This preliminary report describes the use of a rat model developed to study in vivo the effect of anesthesia, contusion, and cryotherapy on skeletal muscle microcirculation by use of an implanted chamber. The diameters of arterioles and venules within the chamber were determined by photomicroscopy in the contusion study and by compound videomicroscopy in the anesthesia study; microvascular perfusion was determined by laser Doppler fluxmetry (LDF). Combined ketamine and xylazine anesthesia significantly reduced (P < 0.05) arteriolar and venular diameters by 32.4% and 37.8%, respectively, and average LDF measurements by 36.1%. Contusion significantly increased arteriolar diameters over baseline values (P < 0.05); cryotherapy did not alter arteriolar diameters but increased venular diameters (P < 0.05). It is hypothesized that this increase in venular diameter may, by increasing the surface area available for reabsorption, explain one mechanism by which cryotherapy decreases the edema of contusion. Use of this model should help to advance the understanding of microcirculatory dynamics following contusion and cryotherapy.