title: Effect of intravenous lidocaine and ketamine on the minimum alveolar concentration of isoflurane in goats.
abstract: OBJECTIVE
  To evaluate the effects of i.v. lidocaine (L) and ketamine (K), alone and in combination (LK), on the minimum alveolar concentration (MAC) of isoflurane (ISO) in goats.
  
  
  METHODS
  Randomized crossover design.
  
  
  METHODS
  Eight, adult mixed breed castrated male goats, aged 1-2 years weighing 24-51 kg.
  
  
  METHODS
  Anesthesia was induced with ISO that was delivered via a mask. The tracheas were intubated and the animals ventilated to maintain an end-tidal carbon dioxide partial pressure between 25 and 30 mmHg (3.3-4 kPa). Baseline MAC (MAC(B)) that prevented purposeful movement in response to clamping a claw was determined in triplicate. After MAC(B) determination, each goat received one of the following treatments, which were administered as a loading (LD) dose followed by a constant rate infusion, IV: L (2.5 mg kg(-1); 100 microg kg(-1) minute(-1)), K (1.5 mg kg(-1); 50 microg kg(-1) minute(-1)), L and K combination or saline, and the MAC (MAC(T)) was re-determined in triplicate. Plasma concentrations of L and K were measured around each MAC point and the values averaged.
  
  
  RESULTS
  The least-squares mean MAC(B) for all treatments was 1.13 +/- 0.03%. L, K, and LK reduced (p < 0.05) MAC(B) by 18.3%, 49.6% and 69.4%, respectively. Plasma concentrations for L, K, and LK were 1617 +/- 385, 1535 +/- 251 and 1865 +/- 317/1467 +/- 185 ng mL(-1), respectively. No change (p > 0.05) occurred with saline.
  
  
  CONCLUSIONS
  Lidocaine and K caused significant decreases in the MAC of ISO. The combination (LK) had an additive effect. However, the plasma L concentrations were less than predicted, as was the MAC reduction with L.
  
  
  CONCLUSIONS
  The use of L, K and the combination, at the doses studied, will allow a clinically important reduction in the concentration of ISO required to maintain general anesthesia in goats.
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA. tdoherty@utk.edu
authors.forename: Tom
authors.initials: T
authors.lastname: Doherty
authors.forename: Marcia A
authors.initials: MA
authors.lastname: Redua
authors.forename: Patricia
authors.initials: P
authors.lastname: Queiroz-Castro
authors.forename: Christine
authors.initials: C
authors.lastname: Egger
authors.forename: Sherry K
authors.initials: SK
authors.lastname: Cox
authors.forename: Barton W
authors.initials: BW
authors.lastname: Rohrbach
mesh_terms: D000768:Anesthesia, General / Q000662:veterinary*; D019162:Anesthetics, Combined / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D018592:Cross-Over Studies; D006041:Goats / Q000378:metabolism / Q000502:physiology*; D007262:Infusions, Intravenous / Q000662:veterinary; D007530:Isoflurane / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D007649:Ketamine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D008012:Lidocaine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D008297:Male; D011650:Pulmonary Alveoli / Q000378:metabolism*
chemical_list: D019162:Anesthetics, Combined; D018685:Anesthetics, Inhalation; D000779:Anesthetics, Local; D007649:Ketamine; D008012:Lidocaine; D007530:Isoflurane