Bispectral Index During Maintenance of Total Intravenous Anesthesia: Frequency of Out of Recommended Range and Impact of Patients' Characteristics: A Brief Report

Little is known about respecting the recommended range of bispectral index (BIS) in practice. This exploratory retrospective analysis of 138 robotic surgical patients having received total intravenous anesthesia shows that BIS was between 40 and 60 during 61.3% ± 25.2% (mean ± standard deviation [SD]) of maintenance, >60 during 3.1% ± 5.5%, and <40 during 35.7% ± 26.9%. Burst suppression was present during 17.8% ± 22.2%. Female sex is associated with increased periods of BIS <40 (P = .002) as is body mass index (BMI) <26 (P = .012). Increased age is associated with increase in burst suppression (P = .005). A larger study is required to confirm the role of patients' factors on the number of periods of low BIS.

A prospective randomized controlled study of combined spinal-general anesthesia vs. general anesthesia for laparoscopic gynecological surgery: Opioid sparing properties

STUDY OBJECTIVE

We aimed to determine the magnitude of peri-operative opioid sparing effect when general anesthesia is combined with spinal analgesia for laparoscopic gynecological surgery.

DESIGN

A prospective randomized controlled study; a three-group trial with two comparisons (each intervention group to control).

SETTING

Operating room and postoperative recovery area.

PATIENTS

Patients aged between 18 and 65 years with American Society of Anesthesiologists physical status 1 or 2 who were scheduled for inpatient elective laparoscopic gynecological surgery with expected pneumoperitoneum duration of at least 20 min. Of 102 randomized patients, 99 completed the study.

INTERVENTIONS

Patients were randomized to general anesthesia alone (control group) or combined with very-low-dose (levobupivacaine 3.75 mg; sufentanil 2.5 μg) or low-dose (levobupivacaine 7.5 mg; sufentanil 2.5 μg) spinal analgesia.

MEASUREMENTS

Primary endpoints were perioperative opioid consumption and pain scores (11-point numeric rating scale) at 30 min, 1 h, 2 h, 4 h and 24 h post-surgery. Secondary endpoints were patient satisfaction with anesthetic care and participation in research, sevoflurane consumption and adverse effects.

MAIN RESULTS

Intra-operative sufentanil (median [95% CI]) consumption was 16.1 (10.5-22.6) μg/h in the control group versus 4.7 (3.2-9.2) μg/h in the very-low-dose and versus 2.9 (0.0-4.0) μg/h in the low-dose spinal analgesia groups (p < 0.001, for both comparisons). Median (95% CI) piritramide consumption at 24 h post-surgery was 7.5 (3-8) mg in the control group versus 5 (0-7.5) mg in the very-low dose spinal analgesia group (p = 0.182) and versus 2 (0-2.5) mg in the low-dose spinal analgesia group (p = 0.001). Postoperative pain scores were consistently <3 only in the low dose spinal analgesia group. Patient satisfaction with anesthetic care and participation in research was very high in all groups.

CONCLUSIONS

Low-dose spinal analgesia in combination with general anesthesia reduces peri-operative opioid consumption in laparoscopic gynecological surgery in immediate postoperative period.

Pilot study of closed-loop anaesthesia for liver transplantation

BACKGROUND

Automated titration of propofol and remifentanil guided by the bispectral index (BIS) has been used for numerous surgical procedures. Orthotopic liver transplantation (OLT) uniquely combines major changes in circulating volume, an anhepatic phase, and ischaemia-reperfusion syndrome. We assessed the behaviour of this automated controller during OLT.

METHODS

Adult patients undergoing OLT were included in this pilot study. Consumption of propofol and remifentanil was calculated for each surgery period (dissection, anhepatic, and liver reperfusion phases). Arterial blood samples were collected at several time points to allow comparison of actual with calculated propofol and remifentanil concentrations. Data are presented as median [25th and 75th percentiles] or percentage (95% confidence interval).

RESULTS

Thirteen patients were studied. System performance, defined as the percentage of time with BIS in the range 40-60, was 88% (86-94) of the total duration of anaesthesia. Propofol requirement was decreased during the anhepatic phase compared with the dissection phase (2.9 [1.9-5.0] mg kg(-1) h(-1) and 4.6 [3.5-8.1] mg kg(-1) h(-1); P<0.03) while remifentanil consumption was unchanged (0.11 [0.09-0.19] µg kg- (1) min(-1)). Bland-Altman analysis showed a weak concordance for propofol (bias of 0.7 µg ml(-1) and limits of agreement of -2.2 to +3.7 µg ml(-1)) and remifentanil (bias of 1.3 ng ml(-1) and limits of agreement -4.3 to +6.8 ng ml(-1)). No adverse events were reported during anaesthesia.

CONCLUSIONS

This pilot study indicates that automated titration of propofol and remifentanil guided by the BIS is feasible during OLT.

Male requires a higher median target effect-site concentration of propofol for I-gel placement when combined with dexmedetomidine

OBJECTIVE

The supraglottic airway device (SAD) can be used for airway management of spontaneous breathing patients, and propofol is commonly applied for the SAD placement. This study was designed to assess the effect of gender on median target effect-site concentration (Ce₅₀) of propofol for I-gel placement when combined with dexmedetomidine.

MATERIAL AND METHOD

19 males and 18 females, aged 18 to 59 and undergoing elective surgery, were enrolled. After intravenous infusion of dexmedetomidine 1.0μg/kg over 10min followed by continuous infusion of 0.4μg/kg/h, target-controlled infusion of propofol under Marsh model was started and the initial Ce of propofol was set at 4.79μg/mL and 4.35μg/mL in the male and female patients, respectively. The I-gel was inserted when the Ce of propofol reached the pre-set concentration and bispectral index value was less than 60. The Ce of propofol required for I-gel placement was determined by the Dixon up-and-down method.

RESULTS

The Ce₅₀ (95% confidence interval) of propofol required for I-gel placement were 4.082μg/mL (3.798-4.332μg/mL) and 3.509μg/mL (3.266-3.749μg/mL) in male and female patients, respectively, with a significantly higher Ce₅₀ in males.

CONCLUSION

When combined with dexmedetomidine, males require a higher Ce₅₀ of propofol for I-gel placement compared to females.

Model-based drug administration: current status of target-controlled infusion and closed-loop control

PURPOSE OF REVIEW

Drug administration might be optimized by incorporating pharmacokinetic-dynamic (PK/PD) principles and control engineering theories. This review gives an update of the actual status of target-controlled infusion (TCI) and closed-loop computer-controlled drug administration and the ongoing research in the field.

RECENT FINDINGS

TCI is becoming mature technology clinically used in many countries nowadays with proven safety. Nevertheless, changing populations might require adapting the established PK/PD models. As TCI requires accurate PK/PD models, new models have been developed which should now be incorporated into the pumps to allow more general use of this technology. Closed-loop administration of hypnotic drugs using an electro-encephalographic-derived-controlled variable has been well studied and has been shown to outperform manual administration. Computer administration for other drugs and fluids have been studied recently. Feasibility has been shown for systems controlling multiple components of anaesthesia, but more work is required to show clinical safety and efficiency.

SUMMARY

Evidence in the literature is increasing that TCI and closed-loop technology could assist the anaesthetists to optimize drug administration during anaesthesia.

Nitrous oxide-based vs. nitrous oxide-free general anaesthesia and accidental awareness in surgical patients: an abridged Cochrane systematic review

Accidental awareness during general anaesthesia can arise from a failure to deliver sufficient anaesthetic agent, or from a patient's resistance to an expected sufficient dose of such an agent. Awareness is 'explicit' if the patient is subsequently able to recall the event. We conducted a systematic review into the effect of nitrous oxide used as part of a general anaesthetic on the risk of accidental awareness in people over the age of five years undergoing general anaesthesia for surgery. We included 15 randomised controlled trials, 14 of which, representing a total of 3439 participants, were included in our primary analysis of the frequency of accidental awareness events. The awareness incidence rate was rare within these studies, and all were considered underpowered with respect to this outcome. The risk of bias across all studies was judged to be high, and 76% of studies failed adequately to conceal participant allocation. We considered the available evidence to be of very poor quality. There were a total of three accidental awareness events reported in two studies, one of which reported that the awareness was the result of a kink in a propofol intravenous line. There were insufficient data to conduct a meta- or sub-group analysis and there was insufficient evidence to draw outcome-related conclusions. We can, however, recommend that future studies focus on potentially high-risk groups such as obstetric or cardiac surgery patients, or those receiving neuromuscular blocking drugs or total intravenous anaesthesia.

Nociceptive stimulation during Macintosh direct laryngoscopy compared with McGrath Mac videolaryngoscopy: A randomized trial using indirect evaluation using an automated administration of propofol and remifentanil

BACKGROUND

Decrease of the nociceptive stimulation induced by laryngoscopy could be an advantage for patients without risk of difficult intubation. The present study aimed to compare the difference in nociceptive stimulation between the use of a conventional laryngoscope or of a videolaryngoscope. Amount of nociception was assessed indirectly using the peak remifentanil concentration determined by a closed-loop administration of propofol and remifentanil with bispectral index (BIS) as the input signal (target 50).

METHODS

A prospective single-center randomized study was performed including surgical patients without predictable risk of difficult mask ventilation or of difficult tracheal intubation. Forty consecutive surgery patients were randomly assigned to CL group (conventional laryngoscope) or VL group (McGrath Mac videolaryngoscope). Induction of anesthesia was performed automatically using the closed-loop system and myorelaxation with atracurium. The allocation was revealed just before tracheal intubation. The primary outcome was the peak plasma remifentanil concentration observed during the 5-minute period which followed intubation.

RESULTS

Sixteen patients in the CL group and 11 in the VL group were analyzed. Plasmatic remifentanil and propofol concentrations were similar in both groups either before tracheal intubation or during the 5 minutes following intubation. There was a nonsignificant between-group difference (P = .09) for the peak concentration of remifentanil. A comparable result was observed for other outcomes except for the heart rate which increased in the CL group.

CONCLUSION

Use of the videolaryngoscope McGrath Mac did not reduce the nociceptive stimulation induced during intubation as evaluated by the automatically administered remifentanil concentration.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02245789.

Hypnosis closed loop TCI systems in outpatient surgery

OBJECTIVE

Determine the influence of general anaesthesia with closed-loop systems in the results of outpatient varicose vein surgery.

PATIENTS AND METHODS

Retrospective observational study including data from 270 outpatients between 2014 and 2015. The patients were divided into 2 groups according to the type of general anaesthesia used. The CL Group included patients who received propofol in closed-loop guided by BIS and remifentanil using TCI, and the C Group received non-closed-loop anaesthesia. Age, sex, surgical time, discharge time and failure of outpatient surgery were recorded. Quantitative data were checked for normal distribution by the method of Kolmogorov-Smirnov-Lilliefors. Differences between groups were analysed by a Student-t-test or Mann-Whitney-Wilcoxon test, depending on their distribution. Categorical data were analysed by a Chi-squared test. We used Kaplan-Meier estimator and the effect size (calculated by Cohen's d) to study the discharge time. Statistical analysis was performed using R 3.2.3 binary for Mac OS X 10.9.

RESULTS

There were no significant differences in age, sex and surgical time and failure of outpatient surgery. Discharge time was different in both groups: 200 (100) vs. 180 (82.5) minutes, C Group and CL Group, respectively (data are median and interquartile rank); P=.005.

CONCLUSION

The use of closed-loop devices for the hypnotic component of anaesthesia hastens discharge time. However, for this effect to be clinically significant, some improvements still need to be made in our outpatient surgery units.

Nitrous oxide-based versus nitrous oxide-free general anaesthesia and accidental awareness during general anaesthesia in surgical patients

BACKGROUND

Accidental awareness during general anaesthesia (AAGA) is when a patient unintentionally becomes conscious during a procedure performed with general anaesthesia and subsequently has explicit recall of this event. Incidence estimates for AAGA vary, with the most common estimate being one to two cases per 1000 general anaesthetics. Evidence linking nitrous oxide use and an increased risk of AAGA has come from observational studies data but the literature is contradictory, with some studies finding a protective effect of nitrous oxide.

OBJECTIVES

To assess the effect of general anaesthesia including nitrous oxide on the risk of AAGA in patients aged five years and over.

SEARCH METHODS

We searched the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and trial registers ((www.clinicaltrials.gov), the WHO International Clinical Trials Registry Platform (www.who.int/ictrp/network/en/) and Current Controlled Trials (www.isrctn.com/)) for eligible studies on December 9 2015. In addition, we conducted forward and backward citation searching using key identified papers.

SELECTION CRITERIA

We considered all randomized controlled trials (RCTs), including quasi-randomized studies and cluster-randomized studies, of participants aged five years or older receiving general anaesthesia for any type of surgery.We included trials in which participants receiving general anaesthesia that included nitrous oxide for maintenance at a concentration of at least 30% were compared with participants receiving no nitrous oxide during general anaesthesia. The intervention group must have received nitrous oxide in conjunction with an additional anaesthetic. We excluded studies where the depth of anaesthesia differed between the study arms. For inclusion in the review, studies needed to state in their methods that they planned to assess AAGA. We defined this as when a patient becomes conscious during a procedure performed with general anaesthesia and subsequently has explicit recall of this event.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane to identify studies. We extracted data and conducted 'Risk of bias' assessment using the Covidence database.

MAIN RESULTS

We included 15 studies. The total number of participants included in the analyses was 3520. Most studies were small with fewer than 120 participants, although two larger studies with 2012 and 671 participants were included. There was considerable variation in many of the study characteristics, including the anaesthetics used. The concentrations of nitrous oxide varied between 50% and 70%, and half of the studies used clinical signs and haemodynamic changes to monitor depth of anaesthesia.As it was not possible to blind the anaesthetist to the anaesthetic used, we rated all studies at high risk of performance bias and we therefore downgraded the quality of evidence by one level for risk of bias using the GRADE approach. Other types of bias were generally low, or were rated unclear due to missing information.No studies were designed to measure AAGA as the primary outcome, and were therefore statistically underpowered to answer this review question. Despite the inclusion of 3520 participants, only three awareness events were reported by two studies. In one study the event was due to technical failure. Due to the rarity of the events, we did not consider it appropriate to pool the data, and we therefore downgraded the quality of evidence by a further level for imprecision using GRADE.

AUTHORS' CONCLUSIONS

It is not possible to draw any conclusions from this review. The included studies were mainly small (fewer than 120 participants) and there were limited estimates of effect, with only two studies reporting any events. We cannot therefore determine whether the use of nitrous oxide in general anaesthesia increases, decreases or has no effect on the risk of accidental awareness.

Feasibility of Closed-loop Titration of Propofol and Remifentanil Guided by the Bispectral Monitor in Pediatric and Adolescent Patients

Background:

This study was designed to assess the feasibility of dual closed-loop titration of propofol and remifentanil guided solely by the Bispectral Index (BIS) monitor in pediatric and adolescent patients during anesthesia.

Methods:

Children undergoing elective surgery in this single-blind randomized study were allocated into the closed-loop (auto) or manual (manual) group. Primary outcome was the percentage of time with the BIS in the range 40 to 60 (BIS40–60). Secondary outcomes were the percentage of deep (BIS&lt;40) anesthesia and drug consumption. Data are presented as median (interquartile range) or number (%).

Results:

Twenty-three patients (12 [10 to 14] yr) were assigned to the auto group and 19 (14 [7 to 14] yr) to the manual group. The closed-loop controller was able to provide induction and maintenance for all patients. The percentage of time with BIS40–60 was greater in the auto group (87% [75 to 96] vs. 72% [48 to 79]; P = 0.002), with a decrease in the percentage of BIS&lt;40 (7% [2 to 17] vs. 21% [11 to 38]; P = 0.002). Propofol (2.4 [1.9 to 3.3] vs. 1.7 [1.2 to 2.8] mg/kg) and remifentanil (2.3 [2.0 to 3.0] vs. 2.5 [1.2 to 4.3] μg/kg) consumptions were similar in auto versus manual groups during induction, respectively. During maintenance, propofol consumption (8.2 [6.0 to 10.2] vs. 7.9 [7.2 to 9.1] mg kg−1 h−1; P = 0.89) was similar between the two groups, but remifentanil consumption was greater in the auto group (0.39 [0.22 to 0.60] vs. 0.22 [0.17 to 0.32] μg kg−1 min−1; P = 0.003). Perioperative adverse events and length of stay in the postanesthesia care unit were similar.

Conclusion:

Intraoperative automated control of hypnosis and analgesia guided by the BIS is clinically feasible in pediatric and adolescent patients and outperformed skilled manual control.

Principles of pharmacologic hemodynamic management and closed-loop systems

Every day, physicians in critical-care settings are challenged with the hemodynamic management of patients with severe cardiovascular derangements. There is a potential role for closed-loop (automated) systems to assist clinicians in managing these patients and growing interest in the possible applications. In this review, we discuss the basic principles of critical-care hemodynamic management and the closed-loop systems that have been developed to help in this setting.