Effects of lidocaine with epinephrine or with buffer on wound healing in rat skin

Lidocaine blocks nociceptive fibers, preventing initial wound signaling and mast cell degranulation. It is hypothesized that epinephrine and buffer affect the wound healing by potentiating lidocaine blockage. This double-blind, randomized, self-controlled study investigated this possibility using male Wistar rats, which were injected with 2 mL of different solutions into the left and right sides of the back. Then, each side was incised and sutured. Sixty rats were divided in three groups: saline solution (SS) and lidocaine; lidocaine and lidocaine with buffer; lidocaine with epinephrine and lidocaine with epinephrine and buffer. Half of each group was sacrificed 7 days after surgery and the remaining after 21 days. A sample of each wound was obtained and quantified for the level of collagen present using computer morphometry and for mast cell quantity. There were no differences between animals with regard to the collagen. However, mast cell levels in the same animal significantly differed between SS x lidocaine. Comparison of the same injected substance between animals with different healing dates showed a significant effect on collagen SS and on all mast cells, except SS. Lidocaine affected collagenization and decreased the initial quantity of mast cells at the wound site.