Effects of constant rate infusions of dexmedetomidine or MK-467 on the minimum alveolar concentration of sevoflurane in dogs

Rachel C. Hector, Marlis L. Rezende, Khursheed R. Mama, Eugene Steffey, Heather K Knych, Ann M. Hess, Juhana M. Honkavaara, Marja R. Raekallio, Outi M. Vainio

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Abstract

Objective To determine the effects of low and high dose infusions of dexmedetomidine and a peripheral α2-adrenoceptor antagonist, MK-467, on sevoflurane minimum alveolar concentration (MAC) in dogs. Study design Crossover experimental study. Animals Six healthy, adult Beagle dogs weighing 12.6 ± 0.9 kg (mean ± standard deviation). Methods Dogs were anesthetized with sevoflurane in oxygen. After a 60-minute instrumentation and equilibration period, the MAC of sevoflurane was determined in triplicate using the tail clamp technique. PaCO2 and temperature were maintained at 40 ± 5 mmHg (5.3 ± 0.7 kPa) and 38 ± 0.5 ºC, respectively. After baseline MAC determination, dogs were administered two incremental loading and infusion doses of either dexmedetomidine (1.5 μg kg−1 then 1.5 μg kg−1 hour−1 and 4.5 μg kg−1 then 4.5 μg kg−1 hour−1) or MK-467 (90 μg kg−1 then 90 μg kg−1 hour−1 and 180 μg kg−1 then 180 μg kg−1 hour−1); loading doses were administered over 10 minutes. MAC was redetermined in duplicate starting 30 minutes after the start of drug administration at each dose. End-tidal sevoflurane concentrations were corrected for calibration and adjusted to sea level. A repeated-measures analysis was performed and comparisons between doses were conducted using Tukey's method. Statistical significance was considered at p < 0.05. Results Sevoflurane MAC decreased significantly from 1.86 ± 0.3% to 1.04 ± 0.1% and 0.57 ± 0.1% with incremental doses of dexmedetomidine. Sevoflurane MAC significantly increased with high dose MK-467, from 1.93 ± 0.3% to 2.29 ± 0.5%. Conclusions and clinical relevance Dexmedetomidine caused a dose-dependent decrease in sevoflurane MAC, whereas MK-467 caused an increase in MAC at the higher infusion dose. Further studies evaluating the combined effects of dexmedetomidine and MK-467 on MAC and cardiovascular function may elucidate potential benefits of the addition of a peripheral α2-adrenergic antagonist to inhalation anesthesia in dogs.

Original languageEnglish (US)
Pages (from-to)755-765
Number of pages11
JournalVeterinary Anaesthesia and Analgesia
Volume44
Issue number4
DOIs
StatePublished - Jul 1 2017

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Keywords

  • adrenergic α-receptor antagonist
  • dexmedetomidine
  • dog
  • minimum alveolar concentration
  • MK-467

ASJC Scopus subject areas

  • veterinary(all)

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