Is the sympathetic system involved in shock-induced gut injury?

Objective: Beta blockade (BB) has been shown to prevent bone marrow dysfunction following trauma and hemorrhagic shock (HS). The impact of the sympathetic system and the role of BB on shock-induced distant organ injury is not known. This study will determine if BB can diminish gut injury following trauma and HS. Methods: Male Sprague-Dawley rats were subjected to lung contusion (LC) followed by 45 minute HS. Animals (n=6/group) were then randomized to either receive propranolol (LCHS+BB) immediately after resuscitation or not (LCHS). Gut permeability was evaluated in vivo at 2.5 hours post resuscitation by diffusion of 4-kDa fluorescein dextran (FD4) from an isolated segment of small bowel into peripheral blood. Villous injury was graded histologically by a blinded reader. *p < 0.05 vs control and ** p < 0.05 vs. non-BB counterpart with ANOVA and Tukey-Kramer. Results: Animals undergoing LCHS had significantly higher plasma levels of FD4 compared to control animals. However, animals receiving BB had a significant reduction in plasma FD4 compared to the LCHS group and were similar to control levels (Figure). Villous injury was higher following LCHS (2.75±1) and with the use of BB villous injury score was similar to control animals (1.5±0.6 vs. 1.4±0.9). Conclusions: Propranolol can protect against the detrimental effects of trauma and HS on gut permeability and vil lous injury. This effect is l ikely due to a blunting of the exaggerated sympathetic response. Beta blockade’s reduction of both bone marrow dysfunction and gut injury further demonstrates the importance of the sympathetic nervous system and its role in potentiating end organ dysfunction following severe trauma. Gut Permeability