Intrathecal mepivacaine after general anesthesia is an effective method of equine euthanasia when compared to intravenous pentobarbital.

Abstract

This study aims to assess intrathecal mepivacaine for euthanasia in anesthetized horses and compare it to a traditional euthanasia method using a single intravenous injection of pentobarbital in sedated horses. Client-owned horses and horses requiring euthanasia due to involvement in concurrent research projects were used. Horses were randomly assigned to 1 of 2 groups: intrathecal mepivacaine after anesthesia or intravenous pentobarbital after sedation. All horses had normal vital parameters and no signs of infectious disease at the time of euthanasia. The intrathecal mepivacaine group was anesthetized before the intrathecal injection of mepivacaine. The pentobarbital group was sedated, concurrently anesthetized and euthanized using intravenous pentobarbital, then received an intrathecal saline (0.9% NaCl) solution injection to a blind observer. Both groups were sedated with detomidine and the time from sedation to the cessation of vital parameters (respirations, pulse, corneal reflex, and ECG) was recorded. Euthanasias were recorded for review by a blinded anesthesiologist, using an independent scale to assess the quality of sedation, anesthesia induction, and lateral recumbency. Time from detomidine administration to cessation of each vital parameter was significantly longer in the intrathecal mepivacaine group. There was no statistically significant difference in qualitative scores between groups for sedation or induction, but lateral recumbency was subjectively superior in the anesthetized intrathecal mepivacaine group. Intrathecal mepivacaine provided a safe, effective, alternative method of euthanasia to intravenous pentobarbital and addresses concerns about barbiturate availability. This study also informs practitioners of what to expect (ie, longer cessation of vital parameters) when using the intrathecal mepivacaine method.