title: Ultrastructure of canine meninges after repeated epidural injection of S(+)-ketamine.
abstract: BACKGROUND
  The safety of ketamine when administered by the spinal route must be confirmed in various animal species before it is approved for use in humans. This study evaluates the ultrastructure of canine meninges after repeated doses of epidural S(+)-ketamine.
  
  
  METHODS
  Five dogs received S(+)-ketamine 5%, 1 mg/kg, twice a day for 10 days through an epidural catheter with its tip located at the L5 level. One dog received the same volume of normal saline at the same times. The spinal cord and meninges were processed for histopathological and ultrastructural studies. Clinical effects were assessed after each injection.
  
  
  RESULTS
  Motor and sensory block appeared after each injection of S(+)-ketamine, but not in the dog receiving saline. No signs of clinical or neurologic alterations were observed. Using light microscopy, no meningeal layer showed alterations except focal infiltration at the catheter tip level by macrophages, lymphocytes, and a few mast cells. The cells of different layers were studied by electron microscopy and interpreted according to data from human and other animal species because no ultrastructural description of the canine meninges is currently available. There were no cellular signs of inflammation, phagocytosis, or degeneration in meningeal layers and no signs of atrophy, compression, or demyelinization in the areas of dorsal root ganglia and spinal cord around the arachnoid. These findings were common for dogs receiving S(+)-ketamine and the dog receiving saline.
  
  
  CONCLUSIONS
  Repeated doses of epidural S(+)-ketamine 5%, 1 mg/kg, twice a day for 10 days was not associated to cellular alterations in canine meninges.
authors.affiliation: Department of Anesthesia, Universitat de Barcelona, Barcelona, Spain. 38197ada@comb.es
authors.forename: Alinne
authors.initials: A
authors.lastname: Acosta
authors.forename: Carmen
authors.initials: C
authors.lastname: Gomar
authors.forename: Josep A
authors.initials: JA
authors.lastname: Bombí
authors.forename: Dominguita L
authors.initials: DL
authors.lastname: Graça
authors.forename: Marta
authors.initials: M
authors.lastname: Garrido
authors.forename: Cristina
authors.initials: C
authors.lastname: Krauspenhar
mesh_terms: D000818:Animals; D004285:Dogs; D005260:Female; D007268:Injections, Epidural; D007649:Ketamine / Q000008:administration & dosage* / Q000633:toxicity*; D008578:Meninges / Q000187:drug effects* / Q000648:ultrastructure; D013237:Stereoisomerism
chemical_list: D007649:Ketamine