title: Drug Residues after Intravenous Anesthesia and Intrathecal Lidocaine Hydrochloride Euthanasia in Horses.
abstract: BACKGROUND
  Intrathecal lidocaine hydrochloride under general anesthesia has been used as an alternative method of euthanasia in equids. Carnivore, scavenger, and even human consumption of horse meat from carcasses have been anecdotally reported in rural areas after this method of euthanasia. The presence of drug residues in horse meat has not been investigated.
  
  
  OBJECTIVE
  To investigate if drug residues are found in horse tissues and determine their concentrations.
  
  
  METHODS
  Of 11 horses requiring euthanasia for medical reasons.
  
  
  METHODS
  Prospective descriptive study. Horses were anesthetized with total IV dose of xylazine (mean, 2.5 mg/kg), midazolam (0.1 mg/kg), and ketamine hydrochloride (mean, 5.8 mg/kg). An atlanto-occipital cisterna centesis for the collection of cerebrospinal fluid (CSF) and administration of lidocaine hydrochloride (4 mg/kg) was performed. Blood samples for both serum and plasma, skeletal muscle (triceps brachii, gluteus medius), and CSF were collected for the determination of drug residues. Frozen skeletal muscle available from 5 additional horses that received standard dosages of drugs for short-term anesthesia (xylazine 1.1 mg/kg, midazolam 0.1 mg/kg, and ketamine 2.2 mg/kg) also were analyzed.
  
  
  RESULTS
  Drug residues were found in the tissues of all horses, but at extremely low concentrations.
  
  
  CONCLUSIONS
  Euthanasia by administration of lidocaine intrathecally to horses under IV anesthesia poses a low risk of toxicity to carnivores and scavengers that might consume muscle tissue from a carcass in which this protocol has been used.
authors.affiliation: Departments of Medicine and Epidemiology, University of California, Davis, CA.
authors.forename: M
authors.initials: M
authors.lastname: Aleman
authors.affiliation: International Animal Welfare Training Institute, University of California, Davis, CA.
authors.forename: E
authors.initials: E
authors.lastname: Davis
authors.affiliation: K. L. Maddy Equine Analytical Chemistry Laboratory, University of California, Davis, CA.
authors.forename: H
authors.initials: H
authors.lastname: Knych
authors.affiliation: Surgical and Radiological Sciences, University of California, Davis, CA.
authors.forename: A
authors.initials: A
authors.lastname: Guedes
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, CA.
authors.forename: F
authors.initials: F
authors.lastname: Smith
authors.affiliation: Departments of Medicine and Epidemiology, University of California, Davis, CA.
authors.forename: J E
authors.initials: JE
authors.lastname: Madigan
mesh_terms: D000771:Anesthesia, Intravenous / Q000662:veterinary*; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D002102:Cadaver; D004350:Drug Residues / Q000032:analysis*; D037901:Euthanasia, Animal / Q000379:methods*; D006736:Horses; D007278:Injections, Spinal; D008012:Lidocaine / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine
keywords: Death; Equine; Pharmacology; Toxicology