4. Discussion
ANI, shock, breast cancer, cataract, amnesia, PONV
CATARACT, SHOCK, MALIGNANT HYPERTHERMIA, BREAST CANCER
The major finding in this study was that remifentanil combined with propofol proved a safe and effective anesthetic approach in breast cancer surgery under BIS and ANI monitoring. Our result was consistent with previous studies showing that the RP combination is practical during not only procedure sedation, such as for fibreoptic bronchoscopy, MRI, colonoscopy, breast biopsy surgery, shock wave lithotripsy, day-case urological surgery, radiation (photon beam) therapy, cataract surgery, endoscopic retrograde cholangiopancreatography, and third molar surgery [TCI with propofol is an ideal anesthetic technique with advantages in terms of less PONV, a rapid patient awakening profile, and helping to minimize malignant hyperthermia [Stewart et al., reported that remifentanil can be mixed with propofol at low concentrations (5 mcg.mLWe addressed safety concerns and made sure that adequate amnesia and analgesia were maintained by the RP mixture. First, the mixture is prepared routinely just before anesthesia induction to minimize losses from possible breakdown of remifentanil in the mixture. Second, the syringe is placed horizontally in the TCI pump to prevent layer formation. Third, to achieve an adequate Ce at induction, propofol needs to be administered as a bolus, but this is likely to result in an excessive dose of remifentanil [The mean anesthetic times were 67 and 68 min in the S and M groups, respectively. However, the mixed regimen infusion was stopped immediately after skin closure, and the time for emergence from anesthesia (3.9 and 2.9 min) was also included in this period. Thus, the true mixed regimen delivering period is believed to be within approximately 60 min. In addition, the BIS and ANI-guided anesthesia ensured an adequate depth of amnesia/analgesia until the end of operation. The total times of TCI adjustment in the M group were significantly lower than in the S group. The median numbers of bolus injections of propofol and remifentanil were 0 (0–1) and 0 (0–1) in the M group, respectively. This might have resulted from the ‘two-in-one’ property of the RP mixture combining both hypnotic and analgesic effects. Accordingly, when patients appear to have inadequate hypnosis or analgesia by monitoring, a single increment of Ce in the M group would achieve two goals in one step, which is as effective as adjusting individually. In addition, physicians treating the M group were inevitably confronted with a dilemma when the BIS and ANI monitors indicated opposite directions, allowing only single specific adjustment and then a ‘wait and see’ period (i.e., when BIS > 60 and ANI > 70, bolus injection of propofol for sedation and an observing period for analgesia). Thus, they were unable to alter each component separately, and the number of times of adjusting for TCI was one. However, in the same situation, the participants in the S group received increased propofol and reduced remifentanil, making two changes with respect to the Ce target.As participants in the M group were unable to receive gradual withdrawal of remifentanil separately, this might have led to a difference in the incidence of RIH between groups [There were some limitations of this study. First, there were flaws in the methodology of this work: a lack of proper PK-PD analysis for the use of the RP mixture by a TCI pump which was specifically designed following intensive PK-PD analysis made the results less desirable and reliable. However, several clinical studies (