Effects of lidocaine on lipopolysaccharide-induced synovitis in horses

Lidocaine (100mg 2%) injected into the carpal joint was used to evaluate the inflammatory response induced by injection (1.5ng) of intra-articular E. coli lipopolysaccharide (LPS) endotoxin. Seventeen male Mangalarga horses aged two to three years were divided into three groups and in all animals was injected 0.9% saline (SAL) in the left carpus (LC), and in the right carpus (RC) one of the following combinations were injected: group A (n=6) LPS plus SAL; group B (n=6) LPS plus lidocaine; group C (n=5) lidocaine plus SAL. Synovial fluid and blood samples were collected immediately before the injection of LPS (T0), and at 1.5 (T1), 3 (T2), 6 (T3), 12 (T4) and 36 hours (T5) after the injection. Clinical and physical variables and cellular and biochemical characteristics of the synovial fluid were evaluated at the same time. The local and systemic inflammatory response was evaluated by measurement of mean serum and synovial fluid TNF-alpha concentration. A rise in TNF-alpha concentration in LPS injected joints at 3h in group A and from 1.5h to 3h in group B was observed. It is concluded that LPS triggered an inflammatory process and that lidocaine did not inhibit or attenuate the LPS-induced synovitis nor the synthesis and release of TNF-alpha