Cutaneous Thermal Injury Increases Vascular Permeability of Rat Mesenteric Venules by a Reactive Oxidant‐Dependent Mechanism

Background Following major burns, edema develops in systemic organs and contributes to the development of remote organ dysfunction. The underlying mechanisms responsible for microvascular inflammation in this setting are not yet fully known. The purpose of our study was to determine if thermal injury to the skin of rats would increase vascular permeability in the mesenteric microcirculation, and if the mechanism involved generation of reactive oxidants. Methods Intravital microscopy was used to examine mesenteric venules of anesthetized rats. FITC‐albumin was used to determine a vascular permeability index (VPI) based on the ratio of extravascular to intravascular fluorescence. Thermal injury was induced by exposing skin of animals to steam for 1 min (~40% of body surface area). Control animals were not exposed to steam. Vehicle or the antioxidant lipoic acid (2 mg/kg bolus, 0.5 mg/kg/h) was administered i.v. to animals after steam injury. Results VPI significantly increased after burn (0.39±0.13 at 30 min vs 0.61±0.08 at 4 h, p<0.05, n=5), but not in non‐burned animals (0.08±0.09 at 30 min vs 0.12±0.03 at 4 h, n=5). These values for VPI were significantly different at these times in burned and non‐burned animals (p<0.05). Lipoic acid significantly attenuated VPI in burn animals (0.20±0.06 at 30 min and 0.23±0.05 at 4 h, n=5) compared to vehicle‐treated burn animals (p<0.05). Conclusions Thermal injury to the skin of rats increased vascular permeability in the mesenteric microcirculation of rats. Lipoic acid attenuated this increase which supports a role for increased generation of reactive oxidants in this mechanism. Support or Funding Information Department of Surgery Research Funds