Clinical Study On The Relationship Between Cerebral Function Monitoring And The Assessment Of Anesthesia Depth

Part I Effect and potential mechanism of landiolol on anesthetic action of propofolObjective To investigate whether landiolol, a short-acting β₁-blocker, affects anesthetic action of propofol and hemodynamic response induced by tracheal intubation. Methods Twenty-eight ASA I-II female patients were equally allocated to receive either landiolol (group L) 0.15 ml/kg followed by 0.04 mg·kg^-1·min^-1 or equal volume saline (group C). Landiolol or saline was started 6 min after a target-controlled infusion (TCI) of propofol (target plasma propofol concentration 3.5μg/ml). After loss of consciousness, isolated-forearm technique(IFT) was applied to isolate an arm before vecuronium 0.1mg/kg iv. When TCI reached the target set, tracheal intubation was performed, and gross movement of the arm within the 1st minute after intubation was noted. Bispectral index (BIS), auditory evoked potential index (AAI) and hemodynamic parameters including systolic arterial pressure (SBP), diastolic arterial pressure (DBP) and heart rate (HR) were measured invasively pre-induction, pre-treatment (landiolol or saline iv), at 2min and 1min before laryngoscopy, just before laryngoscopy and at 1, 2, 4 min after orotracheal intubation. Radial arterial blood (6ml) was drawn before induction, just before laryngoscopy and at 1 min after intubation respectively for detecting plasma concentrations of epinephrine, norepinephrine, and propofol. Results Neither BIS nor AAI showed significant difference between the two groups at each observing time point (P>0.05). Eight of 14 patients in group L and 9 of 14 patients in group C moved in response to laryngoscopy and orotracheal intubation. Plasma epinephrine, norepinephrine and propofol were similar between the two groups at each observing point both before and after intubation (P>0.05). HR remained lower in group L than in group C at each observing point after treatment(P<0.01), but SBP and DBP were comparable between the two groups at all time points except 1min after intubation. Conclusion Landiolol attenuates hemodynamic, especially HR reaction to laryngoscopy and intubation. However, it can not prevent movement in response to laryngoscopy and intubation. It also had no significant effect on BIS, AAI and plasma concentrations of epinephrine, norepinephrine, or propofol. The presentstudy suggests that landiolol produce no clinically important effect on somatic and arousal reactions induced by laryngoscopy and tracheal intubation in patients anesthetized with propofol.Part II Effect of electromyogram variation on BIS accuracy during general anesthesiaObjective To investigate the effect of electromyogram (EMG) variation on BIS accuracy during the maintenance stage of propofol/fentanyl anesthesia. Methods Fourteen ASA I-II female patients, aged 31-64 yr, scheduled for elective gynecologic surgical procedures under general anesthesia were enrolled in this study. Anesthesia was induced with propofol (3.5μg/ml), fentanyl (3μg/kg), Vecuronium (0.1mg/kg), and maintained with propofol and fentanyl. For each patient, a specific TCI was selected to maintain the BIS at 40-60, and the set TCI variable kept unchanged throughout the study. As EMG rose, the BIS became unstable, When the parameters met the study requirements( BIS >70, last more than 30s; EMG >40), the values of BIS, EMG, Signal quality index (SQI), mean arterial pressure (MAP), and heart rate(HR) were recorded every minute for 5min, then additional vecuronium(0.05mg/kg)was administered and the values of the parameters mentioned above were noted for the next 10min. Results BIS value decreased significantly 3 min after the administration of the additional vecuronium (P<0.001); meanwhile, the EMG lowered (P<0.05) and SQI rose (P<0.05) markedly; the hemodynamic variables remained stable throughout the study (P>0.05). Conclusion A misleading BIS value may caused by the decline of neuromuscular block level during the maintenance stage of propofol/fentanyl anesthesia, which considerably influence the accuracy of BIS monitoring.Part III Impacts of fentanyl on cerebral function monitoring and hemodynamic response induced by tracheal intubationObjective: To investigate the effects of fentanyl on A-line ARX Index(AAI); bispectral index (BIS) and hemodynamic response induced by orotracheal intubation, using the AAI as sedation "baseline". Methods: Thirty four ASA I-II female patients were equally randomized to receive either propofol infusion (30mg·kg^-1·h^-1) 2min preceded by 4μg/kg fentanyl(group PF) or preceded by comparable volume of normal saline (group P). After loss of consciousness, and before administration of vecuronium 0.1mg/kg, a tourniquet was applied to one arm and inflated to 150 mmHg above systolic pressure. The trachea was intubated 5min after maintenance of AAI within 15±5. Gross movement within the 1st minute after orotracheal intubation was recorded; BIS, AAI and hemodynamic parameters including systolic arterial pressure (SBP), diastolic arterial pressure (DBP) and heart rate (HR) were measured invasively pre-induction, before laryngoscopy, and 1, 2, 5 min after tracheal intubation. Results: Neither within nor intergroup differences were found in BIS before or after intubation (P>0.05) . AAI in group P increased significantly only at 1min after tracheal intubation(P<0.05, vs pre-larngoscopy or group PF), and decreased to pre-laryngoscopy level rapidly. The tracheal intubation caused a greater hemodynamic increase and higher incidence of movement in group P than in group PF(P<0.01). Conclusion: At the sedation level of AAI 15±5, fentanyl 4μg/kg attenuates hemodynamic reactions and prevents body movement induced by laryngoscopy and intubation. It also inhibits transient AAI increase after intubation. However, it has no significant effect on BIS.Part IV Significance of cerebral function monitoring and hemodynamic responses in detecting "inadequate anesthesia" during propofol inductionObjective To evaluate the significance of A-line ARX Index(AAI), bispectral index (BIS), and hemodynamic responses in detecting "inadequate anesthesia"during propofol induction. Methods Thirty five ASA I-II female patients were induced with propofol. After loss of consciousness(LOC), and before administration of vecuronium 0.1mg/kg, a tourniquet was applied to one arm and inflated to 150 mmHg above systolic pressure. When TCI reached the blood concentration set (3.5μg/ml), the trachea was intubated and all patients were assigned to either group Move or group Non-move according to presence or absence of gross movement within the 1st minute after orotracheal intubation. The values of BIS, AAI and hemodynamic parameters including systolic arterial pressure, diastolic arterial pressure and heart rate pre-induction, before laryngoscopy were recorded invasively, and the maximal values of the above indices within 2 min after intubation were also measured. Results AAI in group Move only increased significantly after tracheal intubation (P<0.01, vs pre-larngoscopy). Neither within nor intergroup difference was found in BIS before or after intubation. Tracheal intubation caused greater blood pressure increase in group Move than in group Non-move (P<0.01), but heart rate of both groups were similar after intubation. Conclusion BIS is just an index that reflects sleep level, but AAI and blood pressure are the useful monitorings to detect "inadequate anesthesia" during propofol anesthesia. Part V Probability of cerebral function monitoring in predicting body movement during propofol anesthesiaObjective To evaluate the possibility of using A-line ARX Index(AAI) and bispectral index (BIS) to predict body movement during the maintenance stage of propofol anesthesia. Methods Twenty-eight ASA I-II female patients aged 24-62ys, weighing 46-71kg undergoing elective gynecologic surgical procedures under general anesthesia were enrolled in this study. The patients were premedicated with oral midazolam 10mg. Radial artery was cannulated for direct BP monitoring. ECG, S_P0₂, P_ETCO₂, AAI (AAI Danmeter Co, Denmark) and BIS (A-2000 Aspect Co, USA) were monitored. Anesthesia was induced with TCI of propofol (target plasma propofol concentration was set at 3.5μg/ml), fentanyl (2μg/kg) and vecuronium (0.1mg/kg). After tracheal intubation, target plasmapropofol concentration was adjusted to maintain BIS at 40-60. During operation under propofol anesthesia when body movement occurred, the maximal values of AAI (AAImax) and BIS (BISmax) during interval between 2min before and after movement were recorded. The relationship between BIS >75 and AAI > 40 and body movement was also examined. Results Body movement occurred in 12 of 28 patients during the maintenance stage. The mean BISmax was 63.5±15.7 and the mean AAImax 48.2±10.6. There were 14 episodes of BIS>75 and only 4 episodes were accompanied with body movement (28.5%); while there were 28 episodes of AAI>40, of which 12 episodes were accompanied with body movement (42.8%). BIS response was 84.2±18.8 seconds later while AAI response was 13.0±2.7 seconds later than body movement. Conclusion The relationship between BIS/AAI and body movement is poor and both AAI and BIS respond later than body movement, so can not be used to predict body movement during the maintenance stage of propofol anesthesia.