Intratesticular Versus Intrafunicular Lidocaine to Reduce Perioperative Nociception and Immunological Response in Ponies Undergoing Field Castration

SIMPLE SUMMARY: Castration is a procedure performed routinely in male ponies to facilitate handling and husbandry and reduce aggression and other undesirable behaviours associated with testosterone. It can be performed in field conditions under general anaesthesia. The procedure is associated with a significant degree of pain that requires adequate analgesics, such as local anaesthetics, as an adjunct to general anaesthesia. The current study aimed to clarify the effects of two different local anaesthesia techniques with lidocaine 2% on the plasmatic concentrations of TNF-α and IL-6 in ponies submitted to field castration. The hypothesis was that the two different locoregional anaesthetic protocols could impact the immunological response and the postoperative outcome. ABSTRACT: The aim of this study was to evaluate the impact of intratesticular or intrafunicular lidocaine to reduce perioperative nociception and cytokine release in ponies undergoing field castration under total intravenous anaesthesia. Before castration, one group was injected with intrafunicular (FL) lidocaine and the other received intratesticular (TL) lidocaine. All ponies were premedicated with acepromazine (0.05 mg/kg) intramuscularly. Twenty minutes after the administration of acepromazine, xylazine (1 mg/kg) and butorphanol (0.02 mg/kg) were administered intravenously. Lidocaine 2% was given 1 mL/100 kg intrafunicularly in the FL groups or 2 mL/100 kg intratesticularly on each testicular side for TL. Surgery was performed by the same team of two experienced surgeons using Serra’s emasculator and an open technique was used for all ponies in order to promote postoperative drainage. In this study, we focused on the plasmatic levels of TNF-α and IL-6. The results from this study showed a significant difference in plasmatic concentrations of TNF-α and IL-6 between the two different locoregional anaesthetic protocols. Taken together, the results suggest that the intrafunicular lidocaine locoregional anaesthesia could be a useful technique in the anaesthesia protocol for field pony castration.