Efficacy of ketamine hydrochloride administered as a basilar sesamoid nerve block in alleviating foot pain in horses caused by natural disease

SummaryReasons for performing study A local anaesthetic agent capable of temporarily resolving lameness after being administered perineurally would be helpful because rapid return of lameness would allow for other analgesic techniques to be performed within a short period of time. Objectives To determine if a 3% solution of ketamine hydrochloride (HCl), administered around the palmar nerves at the level of the base of the proximal sesamoid bones, can improve naturally occurring lameness that can be improved or abolished with a basilar sesamoid nerve block performed using lidocaine HCl and to compare the change in gait produced using lidocaine to the change in gait produced using ketamine by using objective lameness assessment. Study design Experimental trial using research horses with naturally occurring lameness. Methods Seven horses, chronically lame on a thoracic limb, were chosen for the study. A wireless, inertial, sensor-based, motion analysis system was used to evaluate lameness before and after administration of 2% lidocaine and later, before and after administration of 3% ketamine over the palmar digital nerves at the base of the proximal sesamoid bones (a basilar sesamoid nerve block) at 5 min intervals for 30 min. Lameness scores obtained before and after administration of lidocaine and ketamine HCl were compared using repeated measures analysis. Results Gait significantly improved after basilar sesamoid nerve blocks using 2% lidocaine, but gait did not significantly improve after performing the same nerve block using 3% ketamine HCl. Conclusions Ketamine (3%) administered perineurally for regional anaesthesia of the digit does not desensitise the digit to the same extent as does lidocaine and thus 3% ketamine appears to have no value as a local anaesthetic agent for diagnostic regional anaesthesia.