Movement
response to skin incision: analgesia vs. EEG parameters
H. Singh, T. Sakai, A. Matsuki. Dept.
of Anaesthesiology, University of Hirosaki School of Medicine, Japan
Background and Goal of Study
Responses
to various noxious stimuli have been studied to monitor the depth of
anaesthesia. The bispectral index (BIS) and 95% spectral edge frequency (SEF)
have been studied to monitor the hypnotic effect of intravenous (i.v.)
anaesthetics (1). Fentanyl supplementation of propofol inhibits the response to
skin incision (SI) at lower propofol concentrations (2). This study determined
the effect of varying doses of fentanyl with propofol on movement response to
SI and BIS and 95% SEF values.
Materials and Methods
Following
Ethics Committee approval, 68 ASA 1-2 patients, 18-65 yr., were recruited to
participate in this study. Patients were administered fentanyl bolus, 0, 1, 2
or 3 mg.kg-1
i.v. (Groups C, F1, F2 or F3, respectively), 5-min prior to induction of
anaesthesia with propofol infusion, 1 mg.kg-1.min-1 for
2-min. Patients were intubated with succinylcholine, 1 mg.kg-1 i.v.
and anaesthesia was maintained with propofol infusion, 200 mg.kg-1.min-1
until SI. Besides routine monitoring, BIS and 95%SEF were monitored and
recorded at baseline (prior to fentanyl bolus) and at SI with A1050 EEG monitor
(Rev. 1.21, BIS algorithm 3.3, Aspect Medical Systems, Natick, USA). Movement
response to SI and total doses of propofol up to SI were noted. Sustained
tetanus was confirmed in all patients prior to SI. Data were analyzed using
unpaired t-test, multiple ANOVA and Chi-square test.
Results and Discussion
The
four treatment groups were comparable with respect to demographic data and
lengths of SI. The induction-SI durations were 29.2±7.4,
27.1±6.8,
26.3±7
and 30.1±7.7
min and doses of propofol were 454.1±142, 441.6±118.2,
424.7±100.9
and 435.6±116.8
mg, in the C, F1, F2 and F3 groups, respectively. Fentanyl boluses, 2 or 3 mg.kg-1
i.v., significantly decreased the number of patients responding to SI without
affecting the BIS or 95% SEF values (Table). There were no differences in the
BIS or 95% SEF values in four treatment groups. The hypnotic effect of propofol
with fentanyl resulted in lower BIS and 95% SEF values at SI. The hypnotic
interaction between propofol and fentanyl, 1-3 mg
i.v., was not significant to lower the BIS or 95% SEF values.
|
Treat.
Group |
BIS
Baseline |
BIS SI |
95%SEF Baseline |
95%
SEF SI |
MR |
|
C
(n=17) |
96.6±1.3 |
36.6±11.6 |
19.3±5.6 |
16±2.8 |
12 |
|
F1(n=17) |
96.5±1.3 |
32.4±9.3 |
17.9±5.9 |
14.6±2.6 |
10 |
|
F2(n=17) |
97.3±0.4 |
35±8.8 |
18.7±4.8 |
14.7±3.1 |
4* |
|
F3(n=17) |
96.7±1 |
34.8±9.4 |
20.1±4.9 |
15.9±1.4 |
4* |
* P <
0.05(F2 & F3 vs. C);MR: Movement Response
Conclusions
Though
deeper levels of hypnosis to lower the BIS and 95% SEF values may be effective
for preventing the movement response to SI, provision of adequate analgesia
rather than maintaining the clinical ranges of the BIS and 95% SEF values may
be more reliable for preventing the response to SI as BIS and 95% SEF measure the hypnotic component of
the anaesthetic effect.
References
1. Clin Pharmacol Therap 1997;61:45-58.
2. Anesthesiology 1994;81:820-828.