TY - JOUR
T1 - The effects of i.v. fentanyl administration on the minimum alveolar concentration of isoflurane in horses
AU - Thomasy, S. M.
AU - Steffey, E. P.
AU - Mama, K. R.
AU - Solano, A.
AU - Stanley, S. D.
PY - 2006/8
Y1 - 2006/8
N2 - Background. Fentanyl decreases the minimum alveolar concentration (MAC) of inhaled anaesthetics and has been used clinically to reduce the requirements of other anaesthetic drugs in humans and small animals. We hypothesized that i.v. fentanyl would decrease the MAC of isoflurane in horses in a dose-dependent manner. Methods. Following determination of baseline MAC of isoflurane, fentanyl was administered i.v. to target plasma concentrations of 1, 8 and 16 ng ml-1. Each horse was randomly assigned two of three target concentrations administered in ascending order. Loading and infusion doses for each horse were determined from previously derived individual pharmacokinetic values. Isoflurane MAC determination began 45 min after fentanyl administration at each target fentanyl concentration. Venous blood was collected at fixed intervals during the infusion for measurement of plasma fentanyl concentrations. Results. Mean actual fentanyl plasma concentrations were 0 (baseline), and 0.72 (sd 0.26), 8.43 (3.22), and 13.31 (6.66) ng ml-1 for the target concentrations of 1, 8 and 16 ng ml-1, respectively. The corresponding isoflurane MAC values were a baseline of 1.57 (0.23), and 1.51 (0.24), 1.41 (0.23) and 1.37 (0.09)%, respectively. The fentanyl concentrations of 0.72 and 8.43 ng ml-1 did not significantly alter the MAC of isoflurane, but an 18 (7)% ISO-MAC reduction was observed at the 13.31 ng ml-1 concentration. Conclusions. These results cautiously encourage further study of fentanyl as an opioid anaesthetic adjunct to inhalant anaesthesia in horses.
AB - Background. Fentanyl decreases the minimum alveolar concentration (MAC) of inhaled anaesthetics and has been used clinically to reduce the requirements of other anaesthetic drugs in humans and small animals. We hypothesized that i.v. fentanyl would decrease the MAC of isoflurane in horses in a dose-dependent manner. Methods. Following determination of baseline MAC of isoflurane, fentanyl was administered i.v. to target plasma concentrations of 1, 8 and 16 ng ml-1. Each horse was randomly assigned two of three target concentrations administered in ascending order. Loading and infusion doses for each horse were determined from previously derived individual pharmacokinetic values. Isoflurane MAC determination began 45 min after fentanyl administration at each target fentanyl concentration. Venous blood was collected at fixed intervals during the infusion for measurement of plasma fentanyl concentrations. Results. Mean actual fentanyl plasma concentrations were 0 (baseline), and 0.72 (sd 0.26), 8.43 (3.22), and 13.31 (6.66) ng ml-1 for the target concentrations of 1, 8 and 16 ng ml-1, respectively. The corresponding isoflurane MAC values were a baseline of 1.57 (0.23), and 1.51 (0.24), 1.41 (0.23) and 1.37 (0.09)%, respectively. The fentanyl concentrations of 0.72 and 8.43 ng ml-1 did not significantly alter the MAC of isoflurane, but an 18 (7)% ISO-MAC reduction was observed at the 13.31 ng ml-1 concentration. Conclusions. These results cautiously encourage further study of fentanyl as an opioid anaesthetic adjunct to inhalant anaesthesia in horses.
KW - Anaesthetics volatile, isoflurane
KW - Analgesics opioid, fentanyl
KW - MAC, horse
KW - Potency, anaesthetic
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U2 - 10.1093/bja/ael116
DO - 10.1093/bja/ael116
M3 - Article
C2 - 16720675
AN - SCOPUS:33747341343
SN - 0007-0912
VL - 97
SP - 232
EP - 237
JO - British Journal of Anaesthesia
JF - British Journal of Anaesthesia
IS - 2
ER -