Diagnostic anaesthesia of the equine lower limb: a comparison of lidocaine and lidocaine with epinephrine.

Abstract

The anaesthetic potency, onset of action, duration of action, and side effects of lidocaine and lidocaine plus epinephrine for proximal metacarpal block of the lateral and medial palmar nerves were determined. Ten horses were used and legs were injected using a cross-over model with three test solutions: 1) solvent and lidocaine (2%) plus epinephrine (SLE); 2) solvent and lidocaine (2%) without epinephrine (SL); and 3) solvent only (S). The contra-lateral leg was injected with saline (placebo; P). In both the SL and SLE groups, the onset of anaesthesia occurred between 5 and 15 minutes after injection. In the SL group the effect was short-lived, lasting 60 minutes, with a maximum effect at 15 minutes. SLE induced long-lasting anaesthesia in most animals moderate or total anesthesia lasted 6 hours, and in two horses more than 9 hours. The maximum effect was achieved at 60 and 90 minutes. Swelling, the main side effect, was seen halfway between the injection site and the fetlock joint. Swelling on day 1 was minimal in the legs injected with P (105.3%) but was progressively greater with S (129%), SL (136%), and SLE (172%). On day 1 and day 2 the differences between SLE and SL, and between SLE and S were significant (P < 0.05). The difference between S and SL was not significant. On day 3, the swelling had subsided and differences were no longer significant.