The Journal of Trauma: Injury, Infection, and Critical Care, November 1998; Volume 45(4), pp. 715-719; doi: 10.1097/00005373-199810000-00016; Thorlacius, Henrik MD, PhD, Vollmar, Brigitte MD, PhD, Westermann, Simone MD, Torkvist, Leif MD, Menger, Michael D, MD. PhD, et al.

Abstract Content:  Cellular metabolism is dependent on the local temperature in tissues. Induced hypothermia has been shown to be protective in a number of conditions, especially traumatic, ischemic, burn, and neurological injury. However, the protective mechanisms of cold therapy remain controversial and the hemodynamic changes in the microcirculation of striated muscles in response to hypothermia have not been studied in detail previously. In this study, we investigated the microvascular response of local cooling and rewarming in the striated muscle of hamsters by use of the dorsal skinfold preparation and in vivo fluorescence microscopy. We found that reduction of the surface temperature to 8 degrees C for 30 minutes caused arteriolar vasoconstriction with a decrease in diameters by 43+/-7% while the venular and capillary diameters remained unchanged. The cooling procedure also markedly reduced the functional capillary density and the blood flow velocity and diameters in all vessel types, i.e., arterioles, venules, and capillaries. Moreover, the percentage of capillaries with no flow increased from 0.4+/-0.5% to 44+/-14% after 10 minutes of cold therapy. However, these hemodynamic changes induced by local hypothermia were completely reversed to the precooling values after termination of cooling and 30 min of rewarming. Conclusions: Taken together, our functional data demonstrate that hypothermia markedly reduces microvascular perfusion.

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