Discussion
In our study, we observed that the amount of propofol administered to
patients during the transvaginal oocyte retrieval procedure was higher
when administered as an infusion with BIS monitoring, compared to the
administration as bolus doses according to the clinical conditions of
the patients.
There are studies showing that the success of the oocyte retrieval
process does not change with the applied anesthesia methods [5, 14,
15]. But there is increasing concern about the potential detrimental
effects of different types of anesthesia on the quality of the oocytes
and, consequently, on the reproductive outcome [3]. Since it has
been shown that exposure to anesthetic drugs, especially for a long
time, has negative effects on fertilization [8, 16], it is
recommended that the oocyte should be exposed to anesthetic agents at a
minimum level [16, 17]. Therefore, it is critical to administer the
appropriate agent at the appropriate dose and duration in anesthesia
[18].
Propofol is one of the most preferred drugs for anesthesia in oocyte
retrieval, due to its short onset time and rapid recovery from
anesthesia [13]. Nevertheless, there are conflicting results
regarding the effect of propofol used in oocyte retrieval on
fertilization. In their 1997 editorial, Hein and his colleagues ask the
following question: ”What we do really know about propofol’s effects on
human reproduction?” [19]. It seems very difficult to find the exact
answer to this question. The results of studies are confusing.
Alsalili et al., in their study on the effect of propofol on oocyte
maturation and fertilization, concluded that although propofol did not
affect fertilization, high propofol concentrations could impair in vitro
oocyte maturation in mice [20]. Although Ben-Shlomo et al. could not
show a relationship between the duration of anesthesia and propofol
concentrations in the follicular fluid [21], Janssenwillen et al.
conducted a study on mouse oocytes and showed that propofol accumulates
in the follicular fluid in a dose- and time-dependent manner [6].
They suggested caution in the clinical use of propofol during oocyte
retrieval [6]. Similarly to animal studies, it was determined that
propofol accumulates in the follicular fluid depending on the dose and
duration in studies conducted in humans [7, 8]. Considering the
possible adverse effects on fertility during anesthesia, it is
recommended to limit the total dose and duration of propofol
administration [7, 8].
In previous studies, it has been demonstrated that using BIS monitoring
reduces the amount of anesthetic drug used [9, 12]. It was also
stated in these studies that the recovery of patients after anesthesia
was faster [9, 12].
Gan et al. demonstrated that adding BIS monitoring to standard
anesthesia practice reduced the propofol infusion rate and the total
amount of propofol used. In our study, we could not observe similar
results in general anesthesia applied with BIS monitoring. In their
study, Gan et al. adjusted their propofol infusions to reach the target
BIS value of 45-60, but they allowed the BIS value to increase to 60-75
in the last 15 minutes of the case. Considering that our target value
for BIS value is in the range of 40-60 and the average procedure time is
16 minutes in our study, it is understood that the target BIS values are
very different from the study of Gan et al. [9]. They also showed
that BIS facilitates the titration of propofol, which improves patients’
recovery from anesthesia [9]. In the postoperative period, the time
to reach the PADSS≥9 value, which was considered suitable for discharge,
was longer in the group BIS than in the group bolus in our study. This
result is not surprising considering that the total dose of propofol
used was higher in the group BIS than in the bolus group.
Luginbühl et al. reported that BIS monitoring reduced propofol use and
accelerated recovery after propofol anesthesia. In this study, it was
stated that the drug concentration was adjusted to keep the BIS between
45-55 during the surgery in patients with BIS monitoring. However, if
the BIS increased above the target level, they preferred to apply muscle
relaxants before increasing the drug concentration [12]. It is not
surprising that the amount of propofol used with this method is low. In
our study, the highest targeted BIS value was 60 during the procedure,
and propofol infusion rate was increased instead of giving muscle
relaxants when the BIS value of the patients exceeded the target value.
In addition, in the above-mentioned study, the BIS value was allowed to
rise up to 65 in the last 15 minutes of the procedure. In this case, it
can be said that the target BIS value in our study is completely
different from this study. Therefore, it was inevitable that we would
come to a different conclusion from Luginbuhl et al. [12].
Based on the results of our study, is it realistic to say that the
amount of propofol used increased by using BIS, contrary to the results
of previous studies? Or should a more appropriate target be determined
for BIS value during anesthesia for oocyte retrieval? Circeo et al.
observed that the mean BIS ranged from 47 to 53 during oocyte retrieval,
and they recommended this range as a target. However, artificial airway
insertion was not used in any patient in this study [1]. Since we
are used to insert laryngeal masks under general anesthesia in all
patients during oocyte retrieval, we targeted the BIS value within the
recommended range of 40-60 for general anesthesia.
In the present study, the patients in the bolus group were given
propofol according to their clinical responses, without BIS monitoring.
Patients were questioned about their satisfaction before being
discharged after the procedure. Fifty-nine patients in this group said
that they were very satisfied with the anesthesia, while the other two
patients said they were satisfied. No patient was dissatisfied with the
anesthesia method applied. This finding shows that even if propofol is
given according to the clinical response of the patient without BIS
monitoring, patient satisfaction is high and sufficient depth of
anesthesia can be provided for the patient.
We did not use BIS in the group bolus, so we cannot recommend the BIS
value that should be targeted for oocyte retrieval based on the results
of our study. Considering these findings, we think that the targeted BIS
value should be reconsidered for patients undergoing oocyte retrieval
under general anesthesia.
In the present study, we could not confirm our hypothesis that we could
reduce the amount of propofol administered for general anesthesia in
patients undergoing transvaginal oocyte retrieval procedure for IVF
treatment, when BIS is targeted in the 40-60 range. This brought us to
the conclusion that further studies with more specific methodology and
larger series are needed to determine the appropriate target value in
the depth of anesthesia when BIS is used during anesthesia for oocyte
retrieval.
Intraoperatively, we were unable to use a double-blind study design. The
anesthesiologist who administered the anesthesia and recorded the
results during the procedure was not blind. This is a major limitation
of our study.