Objective—To evaluate bispectral index (BIS), spectral
edge frequency 95% (SEF), and median frequency
(MED) in relation to a visual analogue scale (VAS)
as indicators of anesthetic depth for various concentrations
of sevoflurane and isoflurane in pigs.
Procedure—Pigs were randomly allocated to 8 groups
(4 pigs/group). An electroencephalogram (EEG) was
recorded in each conscious pig. Pigs were then anesthetized
by use of sevoflurane (n = 16) or isoflurane
(16). Agents were administered in oxygen at minimum
alveolar concentrations (MACs) of 1, 1.25, 1.5, and 1.75
MAC in a randomized order. End-tidal sevoflurane and
isoflurane concentrations were maintained for 30 minutes,
after which an EEG was recorded for 5 minutes;
BIS, SEF, and MED were then calculated. Anesthetic
depth was evaluated by use of the VAS. Cardiovascular
and EEG responses to nociceptive stimuli were evaluated
for each anesthetic agent.
Results—BIS decreased significantly for the various
concentrations of each anesthetic. At equivalent
MACs, BIS values were significantly higher during
sevoflurane-induced anesthesia than during isoflurane-
induced anesthesia. Values of MED and SEF
decreased significantly from basal values to 1 MAC of
sevoflurane and isoflurane. For both agents, there
was good correlation between VAS scores and BIS
values and between VAS scores and SEF values.
Conclusions and Clinical Relevance—BIS was useful
for predicting changes in anesthetic depth at clinical
dosages of inhalant anesthetics. Values of BIS,
SEF, and MED were significantly higher during anesthesia
induced by administration of sevoflurane than
during anesthesia induced by administration of isoflurance
at equivalent MACs. (Am J Vet Res 2003;64:866–873)
Objective—To evaluate bispectral index (BIS) values
in pigs during anesthesia maintained with sevoflurane-
fentanyl or propofol-fentanyl as a predictor of
changes in hemodynamic parameters and duration of
recovery from anesthesia.
Procedure—Pigs were randomly allocated to undergo 1
of 2 anesthetic regimens. Anesthesia was induced with
propofol (2 mg/kg, IV); 6 pigs were administered sevoflurane
via inhalation (1 minimum alveolar concentration
[MAC] at a fresh gas flow rate of 3 L/min; group I), and
6 were administered propofol (11 mg/kg/h, IV; group II).
All pigs received fentanyl (2.5 mg/kg, IV, q 30 min). After
abdominal surgery, pigs were allowed to recover from
anesthesia. Cardiovascular variables and BIS values
were recorded at intervals throughout the procedure;
duration of recovery from anesthesia was noted.
Results—No correlation was established between
arterial blood pressure and BIS and between heart
rate and BIS. Mean BIS at discontinuation of administration
of the anesthetic agent was greater in group-II
pigs (65.2 ± 10.6 minutes) than in group-I pigs
(55.8 ± 2.9 minutes). However, recovery from anesthesia
was significantly longer in group II (59.80 ±
2.52 minutes) than in group I (9.80 ± 2.35 minutes).
Conclusions and Clinical Relevance—In swine
anesthetized with sevoflurane or propofol and undergoing
abdominal surgery, the BIS value derived from
an electroencephalogram at the end of anesthesia
was not useful for predicting the speed of recovery
from anesthesia. Moreover, BIS was not useful as a
predictor of clinically important changes in arterial
blood pressure and heart rate in those anesthetized
pigs. (Am J Vet Res 2004;65:409–416)
Objective—To evaluate relationships among various
techniques for monitoring anesthetic depth in sevoflurane-anesthetized dogs undergoing orthopedic
Procedure—Dogs were medicated with acepromazine
(0.05 mg/kg, IM), buprenorphine (0.01 mg/kg, IM), and
atropine (0.04 mg/kg, IM). Anesthesia was induced and
maintained with sevoflurane. Cardiovascular and respiratory
responses were monitored. Anesthetic depth
was monitored by use of the bispectral index (BIS), and
a proprietary index was used to monitor activity of the
autonomic nervous system.
Results—A significant decrease in BIS was seen
after induction but concurrent changes were not
observed for the other techniques. The proprietary
index increased significantly after intubation, but no
changes were seen for the other techniques. No significant
changes were detected during incision or
when higher nociceptive stimuli were applied. We did
not identify a correlation between BIS and the proprietary
index, the proprietary index and hemodynamic
variables, or the BIS and hemodynamic variables during
induction and maintenance. A significant increase
in the proprietary index and BIS was detected at the
time of resumption of reflexes. During anesthetic
recovery, a correlation was found between the proprietary
index and BIS but not between hemodynamic
variables and the other techniques.
Conclusions and Clinical Relevance—A significant
increase in the proprietary index, but not the BIS or
hemodynamic variables, was detected during intubation.
Anesthetic induction with sevoflurane did not
prevent the sympathetic stimulus attributable to tracheal
intubation. Monitoring of hemodynamic variables
does not provide sufficient information to allow
clinicians to evaluate stress during anesthetic recovery.
(Am J Vet Res 2004;65:1128–1135)
Objective—To determine the effects of prolonged
anesthesia with desflurane in dogs undergoing
laparotomy or abdominal laparoscopy.
Design—Randomized prospective study.
Animals—20 adult mixed-breed dogs.
Procedure—Dogs were randomly assigned to 1 of 2
groups with 10 dogs/group. Anesthesia was induced
with propofol and maintained with desflurane and fentanyl,
and pyloroplasty was performed. In 10 dogs, a
ventral midline laparotomy was performed; in the other
10, abdominal laparoscopy was performed. Dogs were
monitored for cardiovascular and respiratory responses
(ECG, oxygen saturation [SpO2], arterial blood pressure,
rectal temperature, end-tidal partial pressure of carbon
dioxide [PETCO2], and expired desflurane concentration).
Recovery times were recorded.
Results—Mean ± SD duration of anesthesia was 201
± 25 minutes for dogs undergoing laparotomy and
287 ± 15 minutes for dogs undergoing laparoscopy.
Anesthesia was accompanied by hypotension that
was less severe in dogs undergoing laparoscopy.
Heart rate did not vary significantly during anesthesia.
The SpO2 was > 97% in all dogs at all times, and
PETCO2 remained within reference limits. Recovery
times for dogs that underwent laparotomy were not
significantly different from those for dogs that underwent
laparoscopy. Mean ± SD time to standing was
13.6 ± 2.4 minutes for dogs that underwent laparotomy
and 12.5 ± 2.9 minutes for dogs that underwent
Conclusions and Clinical Relevance—Results suggest
that induction of anesthesia with propofol and
maintenance with desflurane and fentanyl is safe in
dogs undergoing abdominal surgery. (J Am Vet Med