Discussion
In this Prospective study of the optimal effect-site concentration of
REM and propofol to keeping proper depth of anesthesia and promote early
postoperation recover under PSI guided anesthesia. We found EC50 of REM
at 2.96ng/mL When co-adminstration with 2.5 ug/mL propofol, the PSI,
BIS, MAP and HR remained stable during anesthesia, and minimum time of
extubation and staying in PACU needed.
Previous research[1, 6, 25] described in detail the importance of
multimodal drugs and argued that coadministration of narcotic drugs with
different mechanisms usually produces a synergies effect with
theoretical advantages, multimodal medications, which can help patients
recover more quickly. Compared with propofol, REM has no opioid
accumulation effect, mainly used as an analgesic, had the advantage of
rapid action, short maintenance time, metabolism by a specific esterase.
In this study, we found that when propofol was 2.5ug/mL, the anesthesia
process of patients was more stable, that is, the depth of anesthesia,
blood pressure and heart rate were less needed to deal with measures. In
this group, EC50 of REM could be calculated as 2.96 ng/mL by sequential
method. Therefore, this can provide reference for drug concentration
collocation in clinical process.
Theoretically, according to the advantages of REM, TCI 2 ug/mL propofol,
the extubation time should be the shortest. However, our study showed,
compared with other two groups, the patients in middle concentration
group experienced the shortest extubation and PACU stay time. According
to the preceding report, awakening time from anesthesia relies on
various elements, involving age, sex, BMI, operation time, drugs
administration[26, 27] and metabolism of muscle relaxants[28,
29]. In this study, these factors make little difference. Another
research demonstrates that the increase in plasma propofol concentration
was increased by coadministration of REM due to a decreased cardiac and
hepatic blood flow[30], and there was a significant increase in REM
in the third group, which may account for the results of this study.
Although PSI appeared later than BIS, PSI has many advantages over BIS.
In this study, we found that PSI was more sensitive than BIS for the
change of anesthesia depth after skin incision, which was in keeping
with previous studies, PSI performs better than BIS in detecting
consciousness, and less impact of the shock device on the PSI value
during surgery[15]. There are several reasons account for this
advantage. Firstly, unlike BIS only equipped with 4 electrodes, the
SEDLine EEG sensor consists of 6 electrodes: 4 channels (R2, R1, L1,
L2), 1 reference channel (CT) and 1 ground channel (CB). It can collect
information from both sides of the brain to detect asymmetry in the
patient’s electrical activity. Next, this algorithm is improved by
considering individual background differences and brain responses of
different patients to different anesthetics[12, 31]. Finally, less
impact of the shock device on the PSI value during surgery.
Another advantage is that the Sedline® monitored bilateral brain
function and symmetry by DSA display. DSA converts complex EEG waveforms
into color-comparable EEG. Further, it can show how oscillations in EEG
change over time as well as changes in anesthetic drug doses or the
intensity of stimulation that could be harmful[32, 33]. A review
described three types of EEG changes caused by nociceptive stimulation
about general anesthesia: (1) beta arousal, (2) (paradoxical) delta
arousal, and (3) alpha dropout[32]. Studies have suggested that in
patients with low opioid analgesia, α activity increases, and in
patients with satisfactory analgesia, α disappears[34]. In our
study, under PSI guide, the concentration of propofol reduced with the
required concentration of REM increased in a certain range. This
phenomenon showed that sedative synergistic effect of REM was reflected
from PSI values which was similar to previous studies[1, 6]. We
compared the same group to rule out the effects of different doses of
sedative hypnotics, the change in DSA result from REM was observed in
different groups of patients. From the comparison of several groups of
patients in this study, it can be seen the minimum concentration of REM
group α activity increases; however δ wave did not change obviously. The
result performed that DSA could help anesthesiologists evaluate sedation
and analgesia level dynamically togerther with PSI value compared to BIS
applied lonely.
There are some limits to the study. The selected criterias for this
study were patients who scheduled for laparoscopic surgery with general
anesthesia, which would entail limited stimulation and a relatively
smooth operation. Most of the patients were middle-aged healthy women,
and demographics and surgery itself had little impact on the results of
the study. During the experiment, we made a more detailed choice of
patients who needed full uterus (or attachment) removal via laparoscopy,
excluding ovarian cyst removal or simple attachment removal of patients.
All patients underwent laparoscopic surgeries, but differences in
internal pain were observed. Two types of surgeries were relatively
short in duration, which could easily cause errors in the results of
data analysis. However, only patients who underwent laparoscopic surgery
were selected and patients with open abdominal disease were not selected
was the first limit of this study. Second, considering the influence of
hepatic propofol clearance in our study, the inadequacy was that no
detection of plasma concentration at the time of extubation. Besides,
the brain waves of propofol were dominated by slow δ wave and α wave
oscillations. In our study, REM and propofol were given simultaneously,
which may affect the final conclusion. Therefore, to accurately draw the
effect of REM on the EEG, further research is needed after excluding
influencing factors.