Effects of intravenous lidocaine, ketamine, and the combination on the minimum alveolar concentration of sevoflurane in dogs.
OBJECTIVE
To evaluate the effects of intravenous lidocaine (L) and ketamine (K) alone and their combination (LK) on the minimum alveolar concentration (MAC) of sevoflurane (SEVO) in dogs.


METHODS
Prospective randomized, Latin-square experimental study.


METHODS
Six, healthy, adult Beagles, 2 males, 4 females, weighing 7.8 - 12.8 kg.


METHODS
Anesthesia was induced with SEVO in oxygen delivered by face mask. The tracheas were intubated and the lungs ventilated to maintain normocapnia. Baseline minimum alveolar concentration of SEVO (MAC(B)) was determined in duplicate for each dog using an electrical stimulus and then the treatment was initiated. Each dog received each of the following treatments, intravenously as a loading dose (LD) followed by a constant rate infusion (CRI): lidocaine (LD 2 mg kg(-1), CRI 50 microg kg(-1)minute(-1)), lidocaine (LD 2 mg kg(-1), CRI 100 microg kg(-1) minute(-1)), lidocaine (LD 2 mg kg(-1), CRI 200 microg kg(-1) minute(-1)), ketamine (LD 3 mg kg(-1), CRI 50 microg kg(-1) minute(-1)), ketamine (LD 3 mgkg(-1), CRI 100 microg kg(-1) minute(-1)), or lidocaine (LD 2 mg kg(-1), CRI 100 microg kg(-1) minute(-1)) + ketamine (LD 3 mg kg(-1), CRI 100 microg kg(-1) minute(-1)) in combination. Post-treatment MAC (MAC(T)) determination started 30 minutes after initiation of treatment.


RESULTS
Least squares mean +/- SEM MAC(B) of all groups was 1.9 +/- 0.2%. Lidocaine infusions of 50, 100, and 200 microg kg(-1) minute(-1) significantly reduced MAC(B) by 22.6%, 29.0%, and 39.6%, respectively. Ketamine infusions of 50 and 100 microg kg(-1) minute(-1) significantly reduced MAC(B) by 40.0% and 44.7%, respectively. The combination of K and L significantly reduced MAC(B) by 62.8%.


CONCLUSIONS
Lidocaine and K, alone and in combination, decrease SEVO MAC in dogs. Their use, at the doses studied, provides a clinically important reduction in the concentration of SEVO during anesthesia in dogs.
Wilson
Jeffrey
J
Department of Small Animal Clinical Sciences, University of Tennessee, Knoxville, TN 37996, USA. jwilso62@utk.edu
Doherty
Thomas J
TJ
Egger
Christine M
CM
Fidler
Andrew
A
Cox
Sherry
S
Rohrbach
Barton
B
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; D004285:Dogs / Q000378:metabolism / Q000502:physiology*; D005260:Female; D007262:Infusions, Intravenous / Q000662:veterinary; D007649:Ketamine / Q000008:administration & dosage / Q000494:pharmacology; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D011650:Pulmonary Alveoli / Q000378:metabolism*; D000077149:Sevoflurane
D019162:Anesthetics, Combined; D018685:Anesthetics, Inhalation; D000779:Anesthetics, Local; D008738:Methyl Ethers; D000077149:Sevoflurane; D007649:Ketamine; D008012:Lidocaine