Influence of local anaesthetics on inflammatory activity postburn

Most studies investigating the pathophysiological processes taking place inside an experimental burn wound use in vitro techniques, which only allow for fragmented measurements of the actual and complex processes occurring inside a burn wound in vivo. In the present study, which used a recently developed in vivo technique in the rat, a full-thickness burn was induced and resulted in the formation of a subcutaneous gelatinous edema with distinct borders to the surrounding connective tissue and free communication with the systemic circulation allowing it to be easily separated for further analysis. In the present study, we investigated the effects of topical local anaesthetics (EMLA®) on the inflammatory cascade of a burn wound in vivo. Results showed significantly higher myeloperoxidase (MPO) levels in EMLA®-treated burned animals (P<0.01) versus placebo-treated burned controls. EMLA® treatment induced a significant inhibition of the synthesis of leukotrien B4 (LTB4) (P<0.001), prostaglandin E1 (PGE1) (P<0.001), prostaglandin E2 (PGE2) (P<0.001) and thromboxane B2 (TXB2) (P<0.001) versus control, while free radical formation did not differ significantly between EMLA®-treated and control animals. In conclusion, topical local anaesthetics significantly inhibit the release of several mediators known to take important part in the pathophysiological events ensuing a burn injury, such as activation of pain mechanisms (PGE), oedema formation (LTB), and postburn ischemia (TXB). The increased numbers of leukocytes (MPO) in the burn wound induced by topical local anaesthetic treatment could suggest increased influx and/or increased viability of leukocytes postburn.