Amide local anesthetics reduce albumin extravasation in burn injuries

Burn injury was induced in anesthetized rats by exposing the abdominal skin to a temperature of 55 degrees C by means of a hot aluminum rod. Temperature was registered on a Grass polygraph. Skin exposure was interrupted when hot rod temperature had decreased to 45 degrees C. A full-thickness burn trauma of the skin was induced as judged from histologic sections. The burned skin was dissected and extravasation of Evans blue (EB) bound plasma albumin was quantified by a spectrophotometric technique and visualized by fluorescence microscopy. In the first set of experiments, one group of rats (n = 15) was topically treated with a lidocaine-prilocaine cream 5% (25 mg of each in 1 g; EMLA) for 1.5 h starting 15 min after inducing the burn injury. In one control group (n = 14) the thermal injury was treated with placebo cream. A second control group (n = 15) was topically treated with placebo cream without being exposed to thermal trauma. Results showed a significant inhibition of EB-albumin extravasation in the skin of burned rats treated with lidocaine-prilocaine cream compared with placebo-treated burned skin (P less than 0.001). EB-albumin contents in the skin of burned rats treated with lidocaine-prilocaine cream did not differ significantly from unburned skin (P greater than 0.05). In the second set of experiments continuous iv lidocaine infusions at a rate of 5 (n = 10), 10 (n = 12), 20 (n = 10), or 30 (n = 10) micrograms.kg-1.min-1 was given.(ABSTRACT TRUNCATED AT 250 WORDS)