title: Plasma bupivacaine concentrations following orbital injections in cats.
abstract: OBJECTIVE
  To determine plasma bupivacaine concentrations after retrobulbar or peribulbar injection of bupivacaine in cats.
  
  
  METHODS
  Randomized, crossover, experimental trial with a 2 week washout period.
  
  
  METHODS
  Six adult healthy cats, aged 1-2 years, weighing 4.6 ± 0.7 kg.
  
  
  METHODS
  Cats were sedated by intramuscular injection of dexmedetomidine (36-56 μg kg-1) and were administered a retrobulbar injection of bupivacaine (0.75 mL, 0.5%; 3.75 mg) and iopamidol (0.25 mL), or a peribulbar injection of bupivacaine (1.5 mL, 0.5%; 7.5 mg), iopamidol (0.5 mL) and 0.9% saline (1 mL) via a dorsomedial approach. Blood (2 mL) was collected before and at 5, 10, 15, 22, 30, 45, 60, 120, 240 and 480 minutes after bupivacaine injection. Atipamezole was administered approximately 30 minutes after bupivacaine injection. Plasma bupivacaine and 3-hydroxybupivacaine concentrations were determined using liquid chromatography-mass spectrometry. Bupivacaine maximum plasma concentration (Cmax) and time to Cmax(Tmax) were determined from the data.
  
  
  RESULTS
  The bupivacaine median (range) Cmaxand Tmaxwere 1.4 (0.9-2.5) μg mL-1and 17 (4-60) minutes, and 1.7 (1.0-2.4) μg mL-1, and 28 (8-49) minutes, for retrobulbar and peribulbar injections, respectively. In both treatments the 3-hydroxybupivacaine peak concentration was 0.05-0.21 μg mL-1.
  
  
  CONCLUSIONS
  In healthy cats, at doses up to 2 mg kg-1, bupivacaine peak plasma concentrations were approximately half that reported to cause arrhythmias or convulsive electroencephalogram (EEG) activity in cats, and about one-sixth of that required to produce hypotension.
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California Davis, Davis, CA, USA. Electronic address: shilo.yael@gmail.com.
authors.forename: Yael
authors.initials: Y
authors.lastname: Shilo-Benjamini
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California Davis, Davis, CA, USA.
authors.forename: Bruno H
authors.initials: BH
authors.lastname: Pypendop
authors.affiliation: Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California Davis, Davis, CA, USA.
authors.forename: Georgina
authors.initials: G
authors.lastname: Newbold
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California Davis, Davis, CA, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Pascoe
mesh_terms: D018712:Analgesics, Non-Narcotic; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000097:blood*; D000818:Animals; D002045:Bupivacaine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood*; D002415:Cats; D020927:Dexmedetomidine; D005260:Female; D007267:Injections / Q000379:methods / Q000662:veterinary; D009915:Orbit
chemical_list: C121551:3-hydroxybupivacaine; D018712:Analgesics, Non-Narcotic; D000779:Anesthetics, Local; D020927:Dexmedetomidine; D002045:Bupivacaine
keywords: bupivacaine; cats; peribulbar anesthesia; plasma concentration; retrobulbar anesthesia