Effects of epidural administration of dexmedetomidine on the minimum alveolar concentration of isoflurane in dogs.
Objective-To evaluate the effects of epidural administration of 3 doses of dexmedetomidine on isoflurane minimum alveolar concentration (MAC) and characterize changes in bispectral index (BIS) induced by nociceptive stimulation used for MAC determination in dogs. Animals-6 adult dogs. Procedures-Isoflurane-anesthetized dogs received physiologic saline (0.9% NaCl) solution (control treatment) or dexmedetomidine (1.5 [DEX1.5], 3.0 [DEX3], or 6.0 [DEX6] mug/kg) epidurally in a crossover study. Isoflurane MAC (determined by use of electrical nociceptive stimulation of the hind limb) was targeted to be accomplished at 2 and 4.5 hours. Changes in BIS attributable to nociceptive stimulation and cardiopulmonary data were recorded at each MAC determination. Results-With the control treatment, mean +/- SD MAC values did not change over time (1.57 +/- 0.23% and 1.55 +/- 0.25% at 2 and 4.5 hours, respectively). Compared with the control treatment, MAC was significantly lower at 2 hours (13% reduction) but not at 4.5 hours (7% reduction) in DEX1.5-treated dogs and significantly lower at 2 hours (29% reduction) and 4.5 hours (13% reduction) in DEX3-treated dogs. The DEX6 treatment yielded the greatest MAC reduction (31% and 22% at 2 and 4.5 hours, respectively). During all treatments, noxious stimulation increased BIS; but changes in BIS were correlated with increases in electromyographic activity. Conclusions and Clinical Relevance-In dogs, epidural administration of dexmedetomidine resulted in dose-dependent decreases in isoflurane MAC and that effect decreased over time. Changes in BIS during MAC determinations may not represent increased awareness because of the possible interference of electromyographic activity.
Campagnol
Daniela
D
Department of Veterinary Surgery and Anesthesiology, Faculdade de Medicina Veterinária e Zootecnia, Universidade Estadual Paulista (UNESP), Botucatu, São Paulo, Brazil.
Teixeira Neto
Francisco J
FJ
Giordano
Tatiana
T
Ferreira
Tatiana H
TH
Monteiro
Eduardo R
ER
D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000494:pharmacology; D000769:Anesthesia, Inhalation / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000493:pharmacokinetics; D000818:Animals; D020927:Dexmedetomidine / Q000008:administration & dosage* / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D007268:Injections, Epidural; D007530:Isoflurane / Q000493:pharmacokinetics*; D008297:Male; D011650:Pulmonary Alveoli / Q000378:metabolism*
D018712:Analgesics, Non-Narcotic; D018685:Anesthetics, Inhalation; D020927:Dexmedetomidine; D007530:Isoflurane