A-line ARX Index Research Articles

Population pharmacokinetic-pharmacodynamic model of propofol in adolescents undergoing scoliosis surgery with intraoperative wake-up test: a study using Bispectral index and composite auditory evoked potentials as pharmacodynamic endpoints

BackgroundIn adolescents limited data are available on the pharmacokinetics (PK) and pharmacodynamics (PD) of propofol. In this study we derived a PK-PD model for propofol in adolescents undergoing idiopathic scoliosis surgery with an intraoperative wake-up test with reinduction of anesthesia using both Bispectral Index (BIS) and composite A-line ARX index (cAAI) as endpoints.MethodsFourteen adolescents (9.8–20.1 years) were evaluated during standardized propofol-remifentanil anesthesia for idiopathic scoliosis surgery with an intraoperative wake-up test with reinduction of anesthesia. BIS and cAAI were continuously measured and blood samples collected. A propofol PKPD model was developed using NONMEM.ResultsThe time courses of propofol concentrations, BIS and cAAI values during anesthesia, intra-operative wakeup and reduction of anesthesia were best described by a two-compartment PK model linked to an inhibitory sigmoidal Emax PD model. For the sigmoidal Emax model, the propofol concentration at half maximum effect (EC50) was 3.51 and 2.14 mg/L and Hill coefficient 1.43 and 6.85 for BIS and cAAI, respectively. The delay in PD effect in relation to plasma concentration was best described by a two compartment effect-site model with a keo of 0.102 min− 1, ke12 of 0.121 min− 1 and ke21 of 0.172 min− 1.ConclusionsA population PKPD model for propofol in adolescents was developed that successfully described the time course of propofol concentration, BIS and cAAI in individuals upon undergoing scoliosis surgery with intraoperative wake-up test and reinduction of anesthesia. Large differences were demonstrated between both monitors. This may imply that BIS and cAAI measure fundamentally different endpoints in the brain.

How Bispectral Index Compares to Spectral Entropy of the EEG and A-line ARX Index in the Same Patient.

BackgroundBispectral index (BIS) monitoring of depth of anesthesia has pioneered the field for more recent monitoring devices like the A-line ARX Index (AAI) or the state (SE) and response entropy (RE) monitoring devices. Following an observational design the present study aimed to simultaneously compare in the same patient recorded BIS, AAI and entropy values.MethodsData from patients (n = 32) undergoing minor gynecological operations were analyzed. For all patients, standardized anesthesia was used. Before induction of anesthesia AEP electrodes, BIS and entropy sensors were simultaneously placed on the forehead and recordings were started at 3 minutes before induction and continued until patient transfer to the postanesthesia care unit. Markers were set at defined landmarks.ResultsAnesthesia reduced mean BIS, AAI and entropy values. During uneventful, and even more pronounced, during eventful anesthesia BIS/ entropy and BIS/ AAI values showed better correlation than did AAI and entropy values. The prediction probability (Pk) of AAI (0.824 ± 0.036) and RE (0.786 ± 0.040) or SE (0.781 ± 0.040) for preanesthesia awake, postanesthesia awake or anesthesia was comparable and significantly greater than that of BIS (0.705 ± 0.047). However, only 20% of BIS, AAI and entropy values simultaneously categorized the state of the patient as awake, inadequate anesthesia, optimal anesthesia or deep anesthesia.ConclusionThe prediction probability (Pk) of entropy and AAI was comparable and better than that of BIS. However, agreement between BIS, AAI and entropy measurements on patient state was poor.

The effect of monitoringanesthetic depth on the intraoperative anesthetic dose and postoperative recovery of gerontal patients after general anesthesia

Objective To explore the effect of anesthetic depth regulated by A-line ARX-index (AAI) and BIS on the intraoperative anesthetic dose and postoperative recovery of gerontal patients suffering total knee replacement surgery under general anesthesia. Methods Sixty old patients undergoing total knee replacement surgery, aged 65-75 y, weighing 45-85 kg, ASA physical statusⅠor Ⅱwere divided into group AAI, group BIS and group contract (group CON)(n=20) using the random digits table method. At 1 d before and 1, 3, 5, 7 d after operation, cognitive function was assessed by mini-mental state examination(MMSE) and the scores were recorded. The total drug dosage during general anesthesia, the recovery time extubation time, the observer assessment of sedation(OAA/S) scale and VAS were also recorded. Results Compared with group CON[propofol(810±17) mg, remifentanil(1.26±0.07) mg], both the propofol dosage[group AAI(450±19), group BIS(500±18) mg] and the remifentanil dosage[group AAI(0.78±0.07) mg, group BIS(0.80±0.08) mg] were less(P 0.05). There was no significant differences among three groups in the MMSE scores at 1 d before and 1, 3, 5, 7 d after operation(P>0.05). Conclusions Application of anesthetic depth monitoring can reduce the dosage of anesthetic, shorten the awakening time and extubation time, while has no significant effect on the MMSE. Key words: A-line ARX-index; Bispectral index; Anesthetic depth; Gerontisml; Total knee replacement; Postoperative cognitive dysfunction

Median effective concentration of remifentanil for the inhibition of laryngoscope-induced cardiovascular responses.

The aim of this study was to calculate the median effective concentration (EC50) of remifentanil (Rem) for the inhibition of laryngoscope-induced cardiovascular responses, and to observe its effects on the cardiovascular system and stress system. The study included 20 patients, who underwent time-scheduled vocal cord polyp resection with monitoring of heart rate (HR), mean blood pressure (MBP) and auditory evoked potential (AEP)-based A-line ARX Index (AAI). The Rem concentration was initially 5 ng/ml in the first patient, and the concentration selected for each subsequent patient was calculated from the previous case on the basis of whether or not cardiovascular reactions occurred. The HR, MBP and AAI at baseline, after the induction of anesthesia, and before and after the insertion of a self-retaining laryngoscope were recorded, with a change >15% recorded as a positive cardiovascular response. The EC50 sequential method was used to calculate the EC50 of Rem for the inhibition of laryngoscope-induced responses. Cortisol, interleukin-6 and blood glucose levels before and after laryngoscope insertion were also measured. The target-controlled concentrations for the 20 patients were as follows: 2 cases at 5 ng/ml, 6 cases at 4.2 ng/ml, 6 cases at 3.5 ng/ml, 4 cases at 2.9 ng/ml and 2 cases at 2.4 ng/ml. The EC50 of Rem for the inhibition of laryngoscope-induced responses was 3.5 ng/ml with a 95% confidence interval (CI) of 3.47-3.60 ng/ml. A reasonable dose for inhibiting laryngoscope-induced responses was within the range 2.9-4.2 ng/ml. In conclusion, Rem exhibited an EC50 of 3.5 ng/ml for the inhibition of laryngoscope-induced cardiovascular responses, with a 95% CI of 3.47-3.60 ng/ml, and a reasonable dose for the inhibition of such responses was 2.9-4.2 ng/ml.

Assessment of aversion and unconsciousness during exposure to carbon dioxide at high concentration in lambs

AbstractThe most widely used stunning method in sheep is electrical. However, in lambs, this method leads to rupture of the blood vessels, provoking ecchymoses. In pigs (Sus scrofa), the use of CO2-stunning systems has increased in popularity due to positive effects on meat quality and animal welfare (movement of animals in groups). The aim here was to assess the effectiveness of a progressive exposure to 90% carbon dioxide (CO2) in inducing unconsciousness in lambs (Ovis aries) through changes in the middle latency auditory-evoked potentials (MLAEP) of the central nervous system (CNS), blood parameters (pH, carbon dioxide partial pressure (pCO2), oxygen partial pressure (pO2), oxygen saturation (SatO2) and bicarbonate (HCO3J, behaviour (head-shaking, sneezing, gasping and gagging) and physiological reflexes (corneal reflex, breathing and sensitivity to pain). Fourteen male lambs of the Ripollesa breed, weighing between 19 and 25 kg were progressively exposed to an atmosphere of 90% CO2 over 66 s. All blood parameters changed between 23 and 43 s after the onset of the immersion. The MLAEP did not decrease significantly until after 48 s exposure to CO2, suggesting an absence of auditory-evoked brain activity. Before that, lambs exhibited head-shaking and sneezing starting at 10.6 (± 0.77) s, and gasping starting at 20.6 (± 1.36) s. After exposure, all animals showed absence of breathing and sensibility to pain, and 36% of them absence of corneal reflex. The pH and pCO2 recovered basal values at 90 and 120 s, respectively, after the end of the exposure. The burst suppression index (BS%) and the A-Line ARX index (AAI) recovered basal levels at 116 and 159 s, respectively. Exposure to CO2 at high concentration induces effective stunning in sheep for a period of 124 s. However, during exposure, the animals exhibited signs of aversion and breathlessness.

Application of different concentrations of sevoflurane during the induction of combined anesthesia in the elderly

Objective To investigate the reasonable application of different concentrations of sevoflurane inhalation during the induction of combined anesthesia in the elderly and the effect of that on the depth of anesthesia.Methods Sixty ASA Ⅰ or Ⅱ elderly patients who undergoing elective abdominal surgery under endotracheal anesthesia were randomly divided into four groups (n=15).In group Ⅰ,anesthesia was induced with inhalation of 4％ sevoflurane (group S1).In group Ⅱ,anesthesia was induced with inhalation of 6％ sevoflurane (group S2).In group Ⅲ,anesthesia was induced with inhalation of 8％ sevoflurane (group S3).In group Ⅳ,anesthesia was induced with target plasma concentration of 3 mg/L propofol (group P).Remifentanil and rocuronium were administered iv after alertness/sedation scale(OAA/S)=1 in all 4 groups,tracheal intubation was performed 2 min later.Duration from the start of induction to loss of consciousness and eyelash reflex,duration from the start of induction to OAMS =1,electroencephalogram bispectral index (BIS) and A-line ARX index (AAI) at corresponding points were recorded.Mean arterial pressure (MAP),heart rate (HR),BIS,AAI value at time of before induction,before administration of remifentanil,before intubation,tracheal intubation,1,2,3 min after intubation were recorded.Results Time to loss of consciousness,loss of eyelash reflex,OAA/S=1 in group S3 [(84±5),(92±5),(178±9) s] were significantly shorter than that in group S1 [(109±5),(117±4),(197±9) s] and S2[(95±5),(102±5),(188±8) s](P＜0.01),time in group S2 at corresponding points were significandy shorter than that in group S1 (P＜0.01),time in group P[(131±4),(139±4),(222±8) s] at corresponding points were significantly longer than that in groups S1,S2 and S3(P＜0.01).MAP in all groups reduced to the lowest value after induction,MAP in group P(68.9±2.3) mm Hg (1 mm Hg=0.133 kPa) was more lower than that in groups S1,S2 and S3 [(76.8±6.6),(75±3),(75±3) mm Hg](P＜0.01).MAP in all groups after tracheal intubation were higher than that before wacheal intubation,and MAP in group S1 [(99.3±4.6),(95.7±4.3) mm Hg]were higher than that in group S2[(96±5),(92±4) mm Hg],group S3[(96±3),92±3)mm Hg],group P[(96.1±3.3),(92.4±3.4) mmn Hg]at 1,2 min after tracheal intubation (P＜0.05).Conclusions Induction with 6％ or 8％ sevoflurane combined anesthesia in the elderly can provide rapid onset time,hemodynamic stability and can be used safely without increasing the incidence of adverse events. Key words: Elderly; Sevoflurane ; Remifentanil; Induction ; Depth of anesthesia

Prevention of Intraoperative Awareness with Explicit Recall

Prevention of Intraoperative Awareness with Explicit Recall: Making Sense of the Evidence Michael Avidan;George Mashour; Anesthesiology

Effects of auditory evoked potential monitoring directed anesthetic depth control on the stress response and hemodynamic

Objective To compare the effect of stress response and intraoperative hemodynamic changes by using auditory evoked potential Index (A-line ARX Index,AAI) for judge the depth of anesthesia,versus using the traditional methods such as heart rate and blood pressure. Methods 40 ASA Ⅰ -Ⅱ female patients undergoing laparoscopic surgery were randomly assigned to group A (using AAI method)and group B (control group,using heart rate and blood pressure) by coin flip method.The AAI values of Group A was controlled to maintain the depth of anesthesia in (20±5) AAI.In Group B which using heart rate and blood pressure to adjust the depth of anesthesia and the mean arterial pressure,the heart rate was maintained in the basic value±20％.Five fixed time points were selected to determine the cortisol levels and blood glucose:before induction of anesthesia (T0,baseline),laryngoscopy and endotracheal intubation (T1),5 min after CO2 gasless laparoscopic (T2),30 min after began operating (T3) and extubation (T4).AAI,hear rate,blood pressure and any clinical signs of inadequate depth of anesthesia such as coughing and lacrimation were recorded at 12 fixed time points during surgery and anesthesia. Results There were no significant differences between the two groups in the general information and general drugs.Open eyes time of the patient in group A (6±5) min were shorter than that in group B (8±6) min (P＜0.05).There were two patients in group B coughing during operation while none in group A.One patient reported intraoperative awareness in group B while none in group A.The serum cortisol of two groups had a certain degree of reduction after the start of the anesthesia.Significant difference was found in cortisol level in the patients of group A at time points T3 (146±31) μg/L and T4 (147±33) μg/L compared with that at time point To (171±31) μg/L (P=0.022,P=0.017).There were also significant differences at time points T3 and T4 between the two groups (P=0.003,P=0.049).There was downward trend of the blood glucose from induction of anesthesia in group A.There were significant differences in the blood glucose level among the time points T1(4.8±0.7) mmol/L,T2 (4.8±0.7) mmol/L and To (5.5±0.8) mmol/L in group A (P=0.014,P=0.020),while in group B there were no significant differences.The AAI value of the patients in group A began to decrease significantly after induction,dramatically increased when the CO2 was stopped and seaming the skin.There were significant differences of MAP in the time points P3,P4,P7 between two groups(P＜0.05),and there were also significant differences of HR in the time points P2,P3,P4,P10,P11,P12between two groups (P＜0.05).Conclusions Using AAI monitoring in general anesthetic depth control can restrain the stress response caused by CO2 gasless laparoscopic surgery,maintain blood dynamics to stable,and avoid intraoperative awareness. Key words: Evoked potentials, auditory; Laparoscopy; Cortisol; Blood glucose

Comparison of efficacy of sevoflurane or propofol combined with remifentanil in the maintenance of general anesthesia

Objective To explore the efficacy of sevoflurane or propofol combined with remifentanil during the maintenance of general anesthesia in thyroid gland surgery.Methods Sixty patients underwent thyroid gland surgery were randomly divided into tow groups.Once the larynx mask was intubated, anesthesia was maintained with propofol(the effect site concentration was 2.5 ～3.5mg/L) and remifentanil(the effect site concentration was 4.5 ～5.5μg/L) by TCI technique in group P,but with sevoflurane(2％～4％) and remfentanil(the effect site concentration was 2.5 ～4.0g/L)in group S.The depth of anesthesia was measured by the A-line TM AEP Monitor which expressed as A-Line ARX Index TM(AAI).All patients' SBP,DBP and HR were recorded at eight time points: before induction time(T0) ,after induction but before larynx mask intubation time(T1) ,intubate larynx mask time(T2) ,cut skin time (T3), separate thyroid gland time (T4), cut thyroid gland time (T5), remove larynx mask time (T6) ,leave the operation room time(T7).The emergency time,the conscious of the patients after anesthesia and the side effects were also recorded.Results There were no significant differences between the groups with respect to age,gender,weight,the duration of operation,the emergency time and the conscious of the patients after anesthesia.SBP,DBP,HR of the patients in both groups showed no significant difference at T0,T1 ,T2, T3 (all P ＞ 0.05), but had significant difference at T4,T5,T6, T7 (all P ＜ 0.05).Compare with group P,the incidentce of restlessness, dizziness, drowsiness, rigor and pain was significantly lower in group S(all P ＜0.05).The incidentce of nausea,vomit and aspiration did not appear in both groups.Conclusion Both groups showed good anesthesia effects and the patients also emerged from anesthesia quickly.But the anesthesia maintained with sevoflurane and remifentanil could bring more stable hemodynamics and lower incidence rate of the side effects. Key words: Sevoflurane; Propofol; Remifentanil; General anesthesia; Thyroid gland surgery

Effect of Clonidine, by infiltration and by intravenous route, on scalp block for supratentorial craniotomy

Background: The aim of this research was to study and compare the haemodynamic and analgesic effects of (A) scalp block with bupivacaine 0.25%; (B) scalp block with bupivacaine 0.25% plus clonidine 2 μg/kg; and (C) scalp block with bupivacaine 0.25%, plus intravenous (IV) clonidine 2 μg/kg in supratentorial craniotomies. Method: Sixty patients divided into three equal groups (A, B and C) were administered one of the above combinations. All the patients received propofol-based general anaesthesia. Propofol infusion was started at 25 μg /kg/minute, adjusted with an increment or decrement of 5 μg/kg/minute to obtain an A-line ARX index (AAI) of between 20 and 30 throughout the surgery, and stopped after dural closure. Fentanyl 0.5 μg/kg IV was given if a 20% increase in either heart rate (HR) and/or blood pressure (BP) was observed. HR and BP were monitored throughout the surgery and recorded on pin application, incision (planned 15 minutes after pins), at 15-minute intervals thereafter until dural closure, and every five minutes after dural closure. Propofol and fentanyl requirements were recorded for the duration of the surgery. Results: There was a significant fall in HR, SBP (systolic blood pressure), MAP (mean arterial blood pressure) and RPP (rate-pressure product) after pin application in group B (HR p = 0.018, SBP p = 0.003, MAP p = 0.0042, RPP p = 0.000) and group C (HR p = 0.412, SBP p = 0.01, MAP p = 0.0084, RPP p = 0.001) when compared to group A. Propofol and fentanyl requirements were significantly lower in group B (propofol 67.9% and fentanyl 34.85% less) and group C (propofol 59.21% and fentanyl 36.36% less) when compared to group A. Conclusions: The addition of clonidine, either to the scalp block or intravenously, offers better haemodynamic stability intraoperatively, and reduces analgesic and anaesthetic requirements. Keywords: scalp block, supratentorial craniotomy

Effect of clonidine on propofol and remifentanil TCI titrated as a function of PRST score, BIS, and the A-line ARX index (AAI) in morbidly obese patients during laparoscopic gastric by-pass

Effect of clonidine on propofol and remifentanil TCI titrated as a function of PRST score, BIS, and the A-line ARX index (AAI) in morbidly obese patients during laparoscopic gastric by-pass

Effects of A-Line Autoregression Index (AAI) Monitoring on Recovery After Sevoflurane Anesthesia for Bariatric Surgery

Monitoring depth of anesthesia may improve anesthetic dosing and postanesthetic recovery in obese patients. Sixty morbidly obese patients undergoing laparoscopic adjustable gastric bandage (LAGB) were randomly assigned to receive anesthesia with sevoflurane titrated by either standard clinical parameters (SCP) (target = baseline hemodynamic parameters ± 20%) or by A-line ARX index (AAI) (target = 20 ± 5). Heart rate, arterial blood pressure, inspiratory and expiratory gas concentrations, and AAI were recorded in all patients at 5-min intervals, but AAI was made available only to the anesthesiologist assigned to AAI-monitored patients. Emergence times in surgery room and recovery times in postanesthesia care unit (PACU) were recorded at 1- and 30-min intervals. Mean intraoperative values of AAI were higher in AAI-monitored than in SCP-monitored patients (22.5 vs 15.0, p = 0.001). Compared to SCP monitoring, AAI monitoring reduced consumption of sevoflurane by 20% (p = 0.014), times to eye opening by 2.4 min (p = 0.001) and to extubation by 2.5 min (p = 0.009) and to achieve SpO(2) 92% in room air by 17 min (p = 0.001). Aldrete scores were higher in AAI- than in SCP-monitored patients at arrival in PACU (p = 0.035), but Aldrete scores ≥ 9 were attained in similar times. AAI monitoring can improve titration of and recovery from sevoflurane for LAGB.

Prospective evaluation of the time to peak effect of propofol to target the effect site in children

The plasma-effect site equilibration rate constant (k(e0)) of propofol has been determined in children with the use of the time to maximum effect (t(peak)), however, it has not been validated. The objective was to measure the t(peak;) of propofol with two depths of anesthesia monitors in children and to evaluate these measurements with a target-controlled infusion (TCI) system. Unpremedicated, ASA I children from 3 to 11 years were studied. In Part 1, children were monitored simultaneously with the bispectral index (BIS) and the A-Line ARX-index (AAI) from the Alaris A-Line auditory-evoked potential monitor/2. The t(peak) after a bolus dose of propofol was measured. In Part 2, the t(peak) measured was used to target the effect site with a TCI system. The median (MD) and the absolute median (MDA) difference between the predicted time of peak concentration at the effect site (Ce) and the measured time of peak effect in the index of depth of anesthesia (t(error)) was used to evaluate the performance of the system. The BIS recordings were of a better quality than the AAI. The mean +/- standard deviation t(peak) was 65 +/- 14 s with the BIS (n=25) and 201 +/- 74 s with the AAI (n=10)(P<0.001). Validation was only performed with the BIS monitor in 40 children, yielding an MD t(error) of -9.5 s and an MDA t(error) of 10.0 s. The small delay between the evolution of Ce of propofol and the observed effect suggests that this can be a useful model to target the effect site in children.

Influence and clinical significance of anesthetic effect on the BI$ and AAI

In clinical anesthesia, maintaining a suitable anesthesia depth is the premise of guaranteeing the patient's safety and reducing anesthesia complications. Bispeetral index and A-line ARX Index are better means to monitor the consciousness level developed in recent years. The mechanism is different from each other and the influence of anesthetic also does not exert consistently, which deserves our attention. Key words: Anesthesia; Depth; Bispeetral index; Auditory evoked potentials

Assessment of unconsciousness during carbon dioxide stunning in pigs

AbstractThe aim of this study was to assess unconsciousness in pigs during exposure to CO2through changes in the middle latency auditory evoke potentials (MLAEP) of the central nervous system (CNS), blood parameters (pH, carbon dioxide partial pressure [pCO2], oxygen partial pressure [pO2], oxygen saturation [SatO2] and bicarbonate [HCO−3]), behaviour and the corneal reflex. The MLEAP did not decrease significantly until after 60 s exposure to CO2. The blood parameters (decreased pH, pO2and SatO2and increased pCO2and HCO3) changed 53 s after the onset of immersion. The burst suppression index (BS%) and the A-line ARX index (AAI) from the MLEAP recovered basal levels at 136 and 249 s, respectively. The first blood parameter to return to basal levels was HCO−3at 76 s of exposure, followed by SatO2at 180 s, pH and pO2at 210 s and pCO2at 240 s. During exposure to the gas, pigs exhibited lateral head movements and sneezing (10.3 s), gasping (23.5 s) and vocalisation (26.1 s). Furthermore, all pigs demonstrated muscular excitation after between 19 and 39 s exposure, when the AAI and BS% values were not significantly different from basal values. It was suggested, therefore, that these excitatory movements represent conscious movement, indicative of aversion to the gas. According to our results, loss of consciousness began, on average, after 60 s inhalation of 90% CO2. During exposure to the gas, decreased brain activity was seen, immediately following the changes in blood parameters. Following exposure, the restoration of blood parameters to basal levels allows a return to normal brain activity.

A Comparison in Adolescents of Composite Auditory Evoked Potential Index and Bispectral Index During Propofol-Remifentanil Anesthesia for Scoliosis Surgery with Intraoperative Wake-Up Test

The electroencephalogram-derived Bispectral Index (BIS), and the composite A-line ARX index (cAAI), derived from the electroencephalogram and auditory evoked potentials, have been promoted as anesthesia depth monitors. Using an intraoperative wake-up test, we compared the performance of both indices in distinguishing different hypnotic states, as evaluated by the University of Michigan Sedation Scale, in children and adolescents during propofol-remifentanil anesthesia for scoliosis surgery. Postoperative explicit recall was also evaluated. Twenty patients (aged 10-20 yr) were enrolled. Prediction probabilities were calculated for induction, wake-up test, and emergence. BIS and cAAI were compared at the start of the wake-up test, at purposeful movement to command, and after the patient was reanesthetized. During the wake-up test, patients were instructed to remember a color, and were then interviewed for explicit recall. Prediction probabilities of BIS and cAAI for induction were 0.82 and 0.63 (P < 0.001), for the wake-up test, 0.78 and 0.79 (P < 0.001), and 0.74 and 0.78 for emergence (P < 0.001). During the wake-up test, a significant increase in mean BIS and cAAI (P < 0.05) was demonstrated at purposeful movement, followed by a significant decline after reintroduction of anesthesia. During induction, BIS performed better than cAAI. Although cAAI was statistically a better discriminator for the level of consciousness during the wake-up test and emergence, these differences do not appear to be clinically meaningful. Both indices increased during the wake-up test, indicating a higher level of consciousness. No explicit recall was demonstrated.

Dose response curve of intravenous lidocaine on the depth of propofol anaesthesia assessed by the bispectral index (BIS) and the A-line ARX index (AAI)

Dose response curve of intravenous lidocaine on the depth of propofol anaesthesia assessed by the bispectral index (BIS) and the A-line ARX index (AAI)

Utilidad del BIS® y AEP Monitor/2® para el mantenimiento de la anestesia combinada sevoflurano-regional, comparada con la práctica estándar en población pediátrica

To compare the indices computed by a bispectral (BIS) monitor and an auditory evoked potential (AEP) monitor during maintenance of anesthesia in pediatric patients. A secondary objective was to compare anesthetic consumption and recovery times. Patients aged 6 months to 12 years under inhaled anesthesia with sevoflurane were administered a penile or caudal nerve block. BIS and AEP monitoring was then started. The patients were randomized to 3 groups in which the sevoflurane dosage was guided by the BIS index, the A-line ARX index (AAI), or standard procedures (control group). The BIS index, the AAI, the fraction of expired sevoflurane, hemodynamic parameters, and recovery time were the variables recorded for all patients. Thirty-five patients were enrolled. Significant differences between the 2 monitor groups were observed. The mean (SD) AAI was lower in patients whose dosage was controlled by the BIS index (19 [2]) than in those whose dosage was based on the AEP monitor's reading (22 [4]) (P=.04). According to a Bland and Altman plot, there was good agreement between the BIS index and the AAI except for the highest and, in particular, the lowest values. The volumes of sevoflurane used and the recovery times were similar between groups. There was a positive correlation between the 2 indices (Pearson correlation coefficient, 0.207; P<.001). BIS monitoring provided a more stable index than did AEP monitoring and BIS-index guidance achieved a deeper level of hypnosis. There was good correlation between the 2 indices during maintenance of anesthesia. Neither monitor offered advantages over standard procedures with regard to movement, volume of anesthetic consumed, or recovery time.

Monitoring the anaesthetic depth in children – an update

There are several commercially available electroencephalogram-derived devices for monitoring anaesthesia depth. This article reviews all published studies describing their use in children; first assessing studies of performance in measuring anaesthesia depth in observational, physiological studies and then describing relevant outcome studies. There is also a brief discussion of why they might be useful, what physiological problems may arise and what the reader should be wary of in the methodology of these studies. The subject is approached from a clinical perspective. There are several physiological studies suggesting that for older children the bispectral index, entropy, Narcotrend index, cerebral state index and A-line ARX index all change with induction of anaesthesia, and have reasonable correlations with doses of anaesthetic agent. There is consistent evidence that the performances are substantially poorer in infants. Some of these devices have been demonstrated to reduce anaesthesia drug consumption and hasten recovery in older children. The bispectral index is the most widely studied, but at this stage there is no evidence to suggest any one device is substantially superior to any other. There may be a role emerging for their use in older children, but their use in infants cannot be supported.

Correlation of the A-Line™ ARX index with acoustically evoked potential amplitude

Automated indices derived from mid-latency auditory evoked potentials (MLAEP) have been proposed for monitoring the state of anaesthesia. The A-Line ARX index (AAI) has been implemented in the A-Line monitor (Danmeter, V1.4). Several studies have reported variable and, in awake patients, sometimes surprisingly low AAI values. The purpose of this study was to reproduce these findings under steady-state conditions and to investigate their causes. Ten awake unmedicated volunteers were studied under steady-state conditions. For each subject, the raw EEG and the AAI were recorded with an A-Line monitor (V1.4) during three separate sessions of 45.0 (1.6) min duration each. MATLAB (Mathworks) routines were used to derive MLAEP responses from EEG data and to calculate maximal MLAEP amplitudes. The AAI values ranged from 15 to 99, while 11.4% fell below levels which, according to the manufacturer, indicate an anaesthetic depth suitable for surgery. Inter-individual and intra-individual variation was observed despite stable recording conditions. The amplitudes of the MLAEP varied from 0.8 to 42.0 microV. The MLAEP amplitude exceeded 2 microV in 75.3% of readings. The Spearman's rank correlation coefficient between the MLAEP amplitude and the AAI value was r=0.89 (P<0.0001). The version of the A-Line monitor used in this study does not exclude contaminated MLAEP signals. Previous publications involving this version of the A-Line monitor (as opposed to the newer A-Line/2 monitor series) should be reassessed in the light of these findings. Before exclusively MLAEP-based monitors can be evaluated as suitable monitors of depth of anaesthesia, it is essential to ensure that inbuilt validity tests eliminate contaminated MLAEP signals.