Electrophysiologic Study of a Method of Euthanasia Using Intrathecal Lidocaine Hydrochloride Administered during Intravenous Anesthesia in Horses

Abstract

BackgroundAn intravenous (IV) overdose of pentobarbital sodium is the most commonly used method of euthanasia in veterinary medicine. However, this compound is not available in many countries or rural areas resulting in usage of alternative methods such as intrathecal lidocaine administration after IV anesthesia. Its safety and efficacy as a method of euthanasia have not been investigated in the horse.Hypothesis/ObjectivesTo investigate changes in mean arterial blood pressure and electrical activity of the cerebral cortex, brainstem, and heart during intrathecal administration of lidocaine. Our hypothesis was that intrathecal lidocaine affects the cerebral cortex and brainstem before affecting cardiovascular function.AnimalsEleven horses requiring euthanasia for medical reasons.MethodsProspective observational study. Horses were anesthetized with xylazine, midazolam, and ketamine; and instrumented for recording of electroencephalogram (EEG), electrooculogram (EOG), brainstem auditory evoked response (BAER), and electrocardiogram (ECG). Physical and neurological (brainstem reflexes) variables were monitored. Mean arterial blood pressure was recorded throughout the study.ResultsLoss of cerebro‐cortical electrical activity occurred up to 226 seconds after the end of the infusion of lidocaine solution. Cessation of brainstem function as evidenced by a lack of brainstem reflexes and disappearance of BAER occurred subsequently. Undetectable heart sounds, nonpalpable arterial pulse, and extremely low mean arterial blood pressure supported cardiac death; a recordable ECG was the last variable to disappear after the infusion (300–1,279 seconds).Conclusions and Clinical ImportanceIntrathecal administration of lidocaine is an effective alternative method of euthanasia in anesthetized horses, during which brain death occurs before cardiac death.

Cardiovascular, respiratory and metabolic responses to apnea induced by atlanto‐occipital intrathecal lidocaine injection in anesthetized horses

“…The times from the end of lidocaine injection to an isoelectric electroencephalogram, loss of brainstem reflexes and loss of brainstem auditory evoked responses were 0.7–3.8 minutes, 0.7–4.7 minutes and 2.9–7.4 minutes, respectively, as reported elsewhere (Aleman et al. ).…”

“…After lidocaine injection, no horses required additional xylazine-ketamine based on clinical signs of anesthesia and neurophysiologic data. The times from the end of lidocaine injection to an isoelectric electroencephalogram, loss of brainstem reflexes and loss of brainstem auditory evoked responses were 0.7-3.8 minutes, 0.7-4.7 minutes and 2.9-7.4 minutes, respectively, as reported elsewhere (Aleman et al 2015).…”

Investigation of Known Genetic Mutations of Arabian Horses in Egyptian Arabian Foals with Juvenile Idiopathic Epilepsy

“…In brief, clinical and neurologic examinations were determined to be normal between seizures in Egyptian Arabian foals. Paroxysmal activity consisting of sharp waves (70–200 ms), and spikes (<70 ms) and waves on central and parietal cortical areas of the brain based on electroencephalography were part of the inclusion criteria. The central cortical area of the brain was defined as the area between the frontal and parietal cortical areas as described previously .…”

Drug Residues after Intravenous Anesthesia and Intrathecal Lidocaine Hydrochloride Euthanasia in Horses

“…Lidocaine hydrochloride is widely available and inexpensive. However, because the efficacy, safety, and welfare aspects of using this method of euthanasia in equids remain unknown, we recently investigated if this method induced loss of electroencephalographic activity, and cardiac and respiratory arrest . This method of euthanasia proved to be an effective alternative if barbiturates are not available .…”

“…8 This method of euthanasia proved to be an effective alternative if barbiturates are not available. 8 In countries in which this method has been used, animals are premedicated with xylazine hydrochloride and ketamine hydrochloride is used to induce anesthesia before intrathecal administration of lidocaine. a Therefore, the purpose of this study was to investigate if drug residues (those used for intravenous anesthesia and lidocaine) are found in various tissues of horses undergoing euthanasia.…”