Effects of dexmedetomidine on isoflurane requirements in healthy volunteers. 2: Auditory and somatosensory evoked responses.
The anaesthetic-sparing activity of dexmedetomidine during isoflurane anaesthesia was examined, using the end-point of lack of response to tetanic nerve stimulation. Nine subjects were given two doses of dexmedetomidine (target plasma concentrations of 0.3 ng ml-1 and 0.6 ng ml-1, respectively) and saline on separate occasions. We measured auditory (AER) and somatosensory (SER) evoked responses at end-tidal isoflurane concentrations of 0.2-1.4%. Pa and P25-N35 amplitudes increased as isoflurane concentration was reduced (P < 0.001). Dexmedetomidine had no significant effect on this relationship. In contrast, P15-N20 (SER) amplitude increased (P < 0.001) as isoflurane concentration was reduced. The dose of dexmedetomidine had a significant interaction with this trend (P < 0.002). Decreasing the concentration of isoflurane at the high dose of dexmedetomidine had less impact on P15-N20 amplitude than decreasing isoflurane at the low dose or with saline. The mechanism by which dexmedetomidine spares isoflurane is discussed in the light of these evoked response changes.
Thornton
C
C
Academic Department of Anaesthetics, Imperial College School of Medicine, St Mary's, Northwick Park Hospital, Harrow, London, UK.
Lucas
M A
MA
Newton
D E
DE
Doré
C J
CJ
Jones
R M
RM
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000328:Adult; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D020927:Dexmedetomidine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005071:Evoked Potentials / Q000187:drug effects*; D005072:Evoked Potentials, Auditory / Q000187:drug effects; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects; D006801:Humans; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male
D000316:Adrenergic alpha-Agonists; D018685:Anesthetics, Inhalation; D020927:Dexmedetomidine; D007530:Isoflurane