Anesthetic Titration Research Articles

Availability of Anesthetic Effect Monitoring: Utilization, Intraoperative Management and Time to Extubation in Liver Transplantation

Titration of volatile anesthetics to anesthetic effect monitoring using the bispectral index (BIS) has been shown to decrease anesthetic requirements and facilitate recovery from anesthesia unrelated to liver transplantation (OLT). To determine whether availability of such monitoring influences its utilization pattern and affect anesthetic care and outcomes in OLT, we conducted a retrospective analysis in recipients with and without such monitoring. We evaluated annual BIS utilization over a period of 7 years, and compared 41 BIS-monitored patients to 42 controls. All received an isoflurane/air/oxygen and opioid-based anesthetic with planned postoperative ventilation. Data collection included age, body mass index (BMI), gender, Model for End-stage Liver Disease (MELD) score, and time to extubation (TtE). Mean preanhepatic, anhepatic, and postanhepatic end-tidal isoflurane concentrations were compared, as well as BIS values for each phase of OLT using the Kruskal-Wallis and Wilcoxon signed-rank tests, respectively. The use of anesthetic effect monitoring when available increased steadily from 15% of cases in the first year to almost 93% by year 7. There was no significant difference in age, gender, BMI, MELD, or TtE between groups. The BIS group received less inhalational anesthetic during each phase of OLT compared to the control group. However, this difference was statistically significant only during the anhepatic phase ( P = .026), and was clinically not impressive. Within the BIS group, the mean BIS value was 38.74 ± 5.25 (mean ± standard deviation), and there was no difference for the BIS value between different transplant phases. Availability of anesthetic effect monitoring as an optional monitoring tool during OLT results in its increasing utilization by anesthesia care teams over time. However, unless integrated into an intraoperative algorithm and an early extubation protocol for fast tracking of OLT recipients, this utilization does not appear to provide a clinical benefit but instead drives cost.

Total Intravenous Anaesthesia for War Surgery

Total Intravenous Anaesthesia (TIVA) and Target-Controlled Infusion (TCI) of anaesthesia are techniques that have benefited from recent advances in microprocessor technology and drug design. Though dependant on technology, they offer...

Spectral entropy monitoring allowed lower sevoflurane concentration and faster recovery in children

Anesthetic titration using spectral entropy monitoring reduces anesthetic requirements and shortens recovery in adult surgical patients. This study was performed to evaluate the effect of entropy monitoring on end-tidal sevoflurane concentration and recovery characteristics in pediatric patients undergoing sevoflurane anesthesia. Seventy-eight children (aged 3-12 years) scheduled for a tonsillectomy and/or an adenoidectomy were randomly divided into one of two groups: standard practice (Standard) or entropy-guided (Entropy). In the Standard group, sevoflurane was adjusted to maintain the heart rate and systolic blood pressure (BP) within 20% of the baseline values. In the Entropy group, sevoflurane was adjusted to achieve a state entropy of 40-50. We compared the entropy values, end-tidal sevoflurane concentration and recovery times between groups. During maintenance of anesthesia, the entropy and BP values were higher in the Entropy group (P<0.05). The end-tidal sevoflurane concentration during maintenance was lower in the Entropy group (2.2 (0.3) vol%) compared with the Standard group (2.6 (0.4) vol%) (P<0.05). Recovery times were faster in the Entropy group (P<0.05). Compared with standard practice, we found that entropy-guided anesthetic administration was associated with a reduced sevoflurane concentration and a slightly faster emergence and recovery in 3-12-year-old children.

Titration of anesthesia using bispectral index monitoring does not reduce postoperative nausea and vomiting

Titration of anesthesia using bispectral index monitoring does not reduce postoperative nausea and vomiting

Anesthesia Matters: Statistical Anomaly or New Paradigm?

Anesthesia Matters: Statistical Anomaly or New Paradigm?

BIS and Entropy in the elderly

The interaction of many poorly defined, physiological, pharmacological, and pathological factors make titration of general anaesthesia in the elderly difficult. There may be a potential clinical benefit using the processed electroencephalogram (EEG) to monitor hypnotic level in this population. We prospectively studied 16 patients aged over 65 years having hip fractures repaired under general anaesthesia by experienced anaesthetists blinded to Bispectral Index (BIS(XP)) and Entropy values. Pre-induction EEG indices did not correlate with age or mini-mental state examination (MMSE). During maintenance of anaesthesia, BIS(XP) and Response Entropy (RE) values were within the recommended range of 40-60, 45% and 32% of the total time, respectively. BIS(XP) and Response Entropy (RE) values were above 60 for 11% and 13% of the total time, respectively, and below 40 for 44% and 55% of the total time, respectively. BIS(XP) correlated well with RE in 12 patients, but in the other four patients there was a difference of more than 20 points between BIS(XP) and RE.

General anaesthesia for day surgery:Preventing the problems

The ideal day case anaesthetic should provide a rapid and smooth induction with good operating conditions, rapid recovery and minimal postoperative complications. No current agent is ideal, but careful use of the available choices can still produce excellent results. No single technique has been shown to give consistently superior recovery and achieving optimal results relies on a combination of factors, including provision of effective non-opioid analgesia, use of supplemental fluids, minimising emetogenic supplements and careful titration of anaesthesia to effect. The art and skill of the individual anaesthetist are as important in this respect as their actual choice of anaesthetic drugs.

A Testable Hypothesis That May Explain the Morbidity and Mortality Caused by Surgical Stress

In Response: We thank Dr. Coleman for his interest in our article and for his thoughtful comments (1). An inflammatory response triggered by the stress of surgery and influenced by the cumulative deep hypnotic time is a possible mechanism we discussed in our report (2). As proposed by Dr. Coleman, we encourage new investigations designed to determine whether different anesthetic strategies can affect long-term outcomes after surgery. Surgical stress and anesthetic effects are inevitably linked. Studies that randomize subjects to different anesthetic techniques may result in group differences in anesthetic hypnotic depth, potentially confounding the finding of a technique effect. For this reason, it is important to separate the potential effects of the anesthetic technique from that of anesthetic hypnotic depth. This separation may be accomplished by careful adherence to an anesthetic titration protocol such as the one used by Johansen et al. (3). Ideally, such careful clinical investigation will determine whether a specific anesthetic technique or strategy can provide a measurable outcome benefit in addition to reducing surgical stress. Terri G. Monk, MD, MS B. C. Weldon, MD Department of Anesthesiology Duke University Medical Center Durham, North California [email protected] Vikas Saini, MD The Cardiovascular Specialists LLC Hyannis, Massachusetts Jeffrey C. Sigl, PhD Aspect Medical Systems Newton, Massachusetts

A‐line autoregression index monitoring to titrate inhalational anaesthesia: effects on sevoflurane consumption, emergence time and memory

A-line autoregression index (AAI) is a parameter derived from auditory evoked potentials proposed as depth of anaesthesia monitor. We evaluated the effects of AAI guidance on sevoflurane consumption, emergence time, explicit and implicit memory. One hundred patients submitted to major abdominal surgery were randomized into two groups. In group A (n = 50), sevoflurane was titrated according to AAI (target = 20 +/- 5), in group B (n = 50) according to clinical signs. Anaesthesia was induced with fentanyl, propofol, atracurium and maintained with sevoflurane. The mean value of sevoflurane consumption (g/min) and emergence time has been assessed in both groups. After emergence, A test of explicit memory was administered. We assessed implicit memory using a category generation test. In group A, mean sevoflurane consumption was significantly (P = 0.0001) reduced by 20.4% and mean emergence time was significantly (P = 0.00012) shorter by 2 min with respect to group B. No patients experienced explicit memory while the difference between the two groups in implicit memory results was not significant (P = 0107). AAI titration of anaesthesia allows a significant reduction in sevoflurane consumption and emergence time without significant effects on the incidence of explicit and implicit memory. Nevertheless the relationship between AAI and memory requires studies in larger groups of patients.

The relationship between bispectral index and targeted propofol concentration is biphasic in patients with major burns

Many pathophysiologic alterations in major burns can cause changes in the distribution of, and perhaps response to, drugs commonly used in anesthesia practice. This study was conducted to assess changes in bispectral index (BIS) caused by increasing the target propofol effect-site concentration during a target-controlled infusion (TCI) in major burns. Eighteen patients, ASA physical status 2 or 3, aged from 20 to 55 years old, weighing 50-70 kg, with major burns, scheduled for elective early escharectomy less than a week after injury were recruited. A further 18 ASA physical status class 1 or 2, non-burns, age, sex- and weight-matched adult patients scheduled for elective surgery under general anesthesia were recruited as controls. During anesthesia induction, target propofol effect-site concentrations were increased by increments of 0.5 microg ml(-1) up to 4.5 microg ml(-1). The BIS responses to each target concentration using TCI were compared in both groups. In the burns group, significantly greater BIS values relating to increasing propofol TCI were noted at deeper anesthesia when compared with controls; at > or =3.5 microg ml(-1); mean BIS remained at a plateau of about 50. Patients with burns had higher cardiac indices, and lower hemoglobin and albumin concentrations than the controls. They consumed more vecuronium to maintain the same degree of neuromuscular blockade than the controls. In major burns, the final biphasic BIS responses appeared to be determined by numerous other variables such as BIS algorithm, TCI performance, and altered propofol pharmacokinetics and pharmacodynamics. According to our results the importance of an individually tailored approach, including careful anesthetic titration, based upon the patient's clinical condition and responses can not be overemphasized.

No Evidence of Memory Function during Anesthesia with Propofol or Isoflurane with Close Control of Hypnotic State

The authors previously demonstrated memory function during apparently adequate general anesthesia in trauma patients. Hypnotic state fluctuations, stress, and variable amnesic qualities of commonly used anesthetics could account for this effect. The authors replicated the trauma investigation in 90 elective surgical patients to enable anesthetic titration to a bispectral index value of 50-55 during auditory presentation of word stimuli. Patients were randomly assigned to maintenance with propofol (n = 48) or isoflurane (n = 42). Before surgery, state anxiety and trait anxiety were assessed using self-report measures. Postoperative memory assessment relied on the process dissociation procedure using a word stem completion task. There were no differences between groups for relevant demographic, preoperative, or supplemental drug variables. Ninety-eight percent of words were presented within a bispectral index range of 40-60, with values averaging 48.8 (SD = 5.7) during word presentation. Neither the process dissociation procedure nor standard measures of conscious recall and recognition memory showed evidence of explicit or implicit memory. Preoperative stress levels did not correlate with postoperative memory test scores in either study group. In contrast to the results of their previous study, the authors found no evidence of memory function with close control of hypnotic state. This suggests that hypnotic state fluctuations are important to memory activation under anesthesia. Other variables may contribute to preserved memory function as well. Propofol and isoflurane block memory equally well during adequate anesthesia.

Continuous spinal anesthesia and postoperative analgesia for elective cesarean section in a parturient with Eisenmenger?s syndrome

We describe the use of continuous spinal anesthesia (CSA) for an elective cesarean section in a 29-year-old parturient with Eisenmenger's syndrome at 30 weeks of gestation. It is essential in patients with Eisenmenger's syndrome to prevent significant increases in right-to-left shunt following the reduction in systemic vascular resistance. In this case, the patient hoped to be awake during the operation because of her fear of death. We therefore applied CSA to this patient because single-shot spinal anesthesia and epidural anesthesia might cause sudden cardiovascular depression. In fact, sudden cardiovascular changes were avoided by the titration of local anesthetics and the operation was uneventful, although prompt treatment of hypotension was essential and adjustment of the anesthetic levels was difficult. Postoperative patient-controlled spinal analgesia provided satisfactory pain relief with hemodynamic stability and no significant side effects. However, thorough experience with the requisite techniques is critical in CSA because of the technical difficulty of the procedure, and anesthesiologists must gain such experience in less-demanding cases before attempting to administer it in patients presenting extreme challenges as described in this case report.

Effects of Bispectral Index monitoring on ambulatory anesthesia: a meta-analysis of randomized controlled trials and a cost analysis.

Ambulatory surgery is growing in popularity worldwide. For example, 50-70% of surgical procedures in North America are performed on an ambulatory basis. Use of Bispectral Index (BIS) monitoring for titration of general anesthesia may allow use of less anesthetics, reduction in side effects, and faster patient recovery. MEDLINE and other databases were searched for randomized controlled trials examining the use of BIS monitoring versus standard practice in ambulatory surgery patients. Outcomes were extracted from these articles, and a meta-analysis was performed. One thousand three hundred eighty subjects from 11 trials were included in the meta-analysis. The use of BIS monitoring significantly reduced anesthetic consumption by 19%, reduced the incidence of nausea/vomiting (32% vs. 38%; odds ratio, 0.77), and reduced time in the recovery room by 4 min. However, these benefits did not result in significant reduction in time until patient discharge from the ambulatory surgery unit. Cost analysis using pooled costs to reflect North America, Europe, and Asia indicated that use of BIS monitoring increased the cost per patient by 5.55 US dollars because of the cost of BIS electrodes. The use of BIS monitoring modestly reduced anesthetic consumption, risk of nausea and vomiting, and recovery room time. These benefits did not reduce time spent in the ambulatory surgery unit, and cost of the BIS electrode exceeded any cost savings.

Electroencephalographic Monitoring Should Not Provide Risks of Intraoperative Memory Because of Aspired Faster Emergence and Reduction of Drug Consumptions: In Reply

We thank Dr. Bischoff et al. for their interest in our study on Narcotrend (MonitorTechnik, Bad Bramstedt, Germany) and Bispectral Index® (BIS®; Aspect Medical Systems Inc., Newton, MA) monitoring used for guidance of propofol titration during propofol–remifen tanil anesthesia. 1The results of our study indicate that compared with standard practice, patients with Narcotrend or BIS monitoring needed significantly less propofol, opened their eyes earlier, and were extubated sooner.Bischoff et al. now discuss the possibility of an increased risk of memory function resulting in potential awareness if electroencephalographic monitoring is used to optimize recovery times and drug consumption. They do so especially in view of our study design, which included a lightening of anesthesia during the last 15 min before the end of surgery to a target value of C1for Narcotrend or 60 for BIS®.Now, three questions must be discussed: First, should electroencephalographic monitoring in principle be used to fast track anesthesia; second, does monitoring of the depth of anesthesia result in an increased risk of awareness; and third, is it adequate to lighten anesthesia at the end of surgery?First, electroencephalographic monitoring is a valuable tool to fast-track anesthesia. Several studies, including ours, 1–3have shown that monitoring the depth of anesthesia clearly reduces the guesswork regarding how much of the anesthetic is necessary for the individual patient. Thus, this monitoring allows for individual titration of anesthesia, resulting in a reduction of drug consumption and recovery times.Second, Myles et al. 4have now brought some light to the discussion about the impact of electroencephalographic monitoring on the risk of awareness. In their investigation, 1,227 patients were randomly assigned to a BIS-guided anesthetic protocol with BIS target values of 40–60, and 1,238 patients received “routine care,” with no electroencephalographic monitoring information available. With this study design, Myles et al. observed 2 cases of awareness in the BIS® group and 11 in the standard practice group (P &lt; 0.022). Therefore, BIS-guided anesthesia reduced the risk of awareness by 82% and was also associated with a decreased time to eye opening.Third, lightening of anesthesia at the end of surgery has been standard of care for many years without electroencephalographic monitoring. In particular, in our study, we used target values of 60 for BIS® (being within the study range of Myles et al. ) and C1for the Narcotrend. In a previous investigation, BIS values of 60 were matched to Narcotrend stages of C1, 5and therefore, these results were used as target values for the guidance of propofol titration in our investigation.In conclusion, we are convinced that it is possible to optimize recovery times, reduce drug consumption, and have a lower risk of awareness by using electroencephalographic monitoring during general anesthesia.

Comparison of a New Bispectral Index (BIS) Algorithm to Modified Observer's Assessment of Alertness/Sedation (MOAA/S) Scale in Moderate Sedation (MS)

Background: Assessment of sedation levels in endoscopy is crucial for patient safety. Sedation assessment is currently guided by indirect measures: vital signs, direct observation, and subjective sedation assessment like the MOAA/S scale. BIS monitoring is a mathematical evaluation of frontal cortex EEG activity used to improve general anesthetic titration and patient recovery. Current BIS algorithms do not differentiate various levels of MS. Aim: To compare the new BIS monitoring algorithm (BIS Revision 4.1) to MOAA/S scale for MS during elective endoscopy. Methods: 80 pts (43M/37F, mean age 61 yrs) were studied using a balanced cohort of procedures (20-EGD; 20-Colon; 20-ERCP; 20-EUS). IV MS (meperidine/midazolam) was administered. BIS levels and MOAA/S scores were recorded q 3 min. BIS level (0-100; 0=flatline EEG to 100=fully awake) and MOAA/S score (1-5; 1=unresponsive to shaking to 5=coherent). The mean BIS level and MOAA/S score were compared. Results: Levels of sedation achieved: 54 pts (67.5%) deep sedation and 26 pts (32.5%) mild to moderate sedation. The correlation coefficient between BIS level and MOAA/S score was 0.66 (p < 0.01; Graph). The new BIS algorithm had excellent correlation to mild/moderate sedation levels (MOAA/S 2-5; p < 0.001) but failed to discriminate between moderate/deep sedation levels (MOAA/S 1-2; p = 0.75). Conclusions: (1)Deep sedation occurs frequently during elective endoscopy. (2)The new BIS algorithm is successful in discriminating levels of mild/moderate sedation, but is no more effective than direct observation (MOAA/S score) at distinguishing between moderate/deep levels of sedation. Clinical implication: Since a large percentage of patients experience deep sedation during elective endoscopy, the new BIS algorithm needs to be refined to differentiate deeper levels of sedation.

Treatment Efficacy and Safety Related to the Use of Propofol vs. Conventional Sedation in the Performance of Colonoscopy: A Meta-Analysis of Published Randomized Controlled Trials

Background: Assessment of sedation levels in endoscopy is crucial for patient safety. Sedation assessment is currently guided by indirect measures: vital signs, direct observation, and subjective sedation assessment like the MOAA/S scale. BIS monitoring is a mathematical evaluation of frontal cortex EEG activity used to improve general anesthetic titration andpatient recovery. Current BIS algorithms do not differentiate various levels of MS. Aim: To compare the new BIS monitoring algorithm (BIS Revision 4.1) to MOAA/S scale for MS during elective endoscopy. Methods: 80 pts (43M/37F,mean age 61 yrs)were studied using a balanced cohort of procedures (20-EGD; 20-Colon; 20-ERCP; 20-EUS). IV MS (meperidine/midazolam) was administered. BIS levels and MOAA/S scores were recorded q 3 min. BIS level (0-100; 0=flatline EEG to 100=fully awake) and MOAA/S score (1-5; 1=unresponsive to shaking to5=coherent). ThemeanBIS level andMOAA/S score were compared. Results: Levels of sedation achieved: 54 pts (67.5%) deep sedation and 26 pts (32.5%) mild to moderate sedation. The correlation coefficient between BIS level and MOAA/S score was 0.66 (p < 0.01; Graph). The new BIS algorithm had excellent correlation tomild/moderate sedation levels (MOAA/S 2-5; p<0.001) but failed to discriminate betweenmoderate/deep sedation levels (MOAA/S 1-2; p= 0.75). Conclusions: (1)Deep sedation occurs frequently during elective endoscopy. (2)The new BIS algorithm is successful in discriminating levels of mild/moderate sedation, but is no more effective than direct observation (MOAA/S score) at distinguishing between moderate/deep levels of sedation. Clinical implication: Since a largepercentageofpatients experiencedeep sedationduringelective endoscopy, the new BIS algorithm needs to be refined to differentiate deeper levels of sedation. Treatment Efficacy and Safety Related to the Use of Propofol vs. Conventional Sedation in the Performance of Colonoscopy: A Meta-Analysis of Published Randomized Controlled Trials Neena S. Abraham, Maitreyi Raman, Kara Thompson Background and Aim: There is increasing interest in the use of propofol during the performance of colonoscopy. Our aim was to quantitatively evaluate the efficacy and safety of propofol as compared to conventional sedation in theperformance of routine colonoscopy. Methods: All randomized controlled trials evaluating propofol in colonoscopy, publishedas fullmanuscripts,were identifiedusing a standardized search and data abstraction policy. Comparisons between propofol and conventional sedationweremade in the areas of efficacy (pain control, patient satisfaction, recovery time) and risks (hypoxia, hypotension). A single combined estimate of treatment efficacy (ORwith 95%CI) was generated using a fixed effect model or random effects model if appropriate. When estimates could not be aggregated mathematically, a narrative systematic review was performed. Results: Eight studies were identified, however, twowere excluded for lack of control comparator. Aggregation of outcomes was impossible in all six studies due to lack of comparable outcome, failure to report a measure of variability or inability to dichotomize results. Recovery time post colonoscopy was substantially reduced using propofol when compared with conventional sedation (OR 18.25; 95% CI: 12.37 to 24.13). Hypoxic events occurred less frequently in the propofol arm, although this was not statistically significant (OR= 0.72; 95%CI: 0.72 to 2.37). Hypotension occurred less frequently using propofol, however, the heterogeneity in examination of this variablewas toogreat, rendering the result inconclusive. Pain and satisfaction were qualitatively reviewed due to heterogeneity in outcomes assessment andwere found equivalent or superior using propofol. Conclusions: There are a limited number of randomised controlled trials reporting on efficacy and safety of propofol during colonoscopy. Among the six published placebo controlled studies, there is a suggestion that propofol is superior to conventional sedationwith respect to recovery time, hypoxia, hypotension, pain control and patient satisfaction. The evidence for improved patient pain control and satisfaction is qualitative. Future studies require standardized assessment of these outcomes to allow quantitative aggregation of results. As more centers utilize propofol for routine colonoscopy, the cost-efficacy of reduced recovery time may become apparent.

Journal-related Activities at the 2003 American Society of Anesthesiologists Annual Meeting

Journal-related Activities at the 2003 American Society of Anesthesiologists Annual Meeting

Sevoflurane: an ideal agent for adult day-case anesthesia?

Sevoflurane has several properties which make it potentially useful as a day case anaesthetic. Following induction of anaesthesia with propofol, awakening from sevoflurane is faster compared to isoflurane, faster or similar compared to propofol and comparable (in the majority of studies) to desflurane. Subsequent recovery and discharge is generally similar following all agents. Sevoflurane may also be used to induce anaesthesia, which is generally well-received and causes less hypotension and apnoea compared to propofol. When used as a maintenance anaesthetic, the incidence of postoperative nausea and vomiting after sevoflurane is comparable to other inhaled anaesthetics, but this complication appears more common after inhaled inductions. The tolerability and low solubility of sevoflurane facilitate titration of anaesthesia and may reduce the need for opioid analgesia, which in turn may limit the occurrence of nausea and vomiting.

Falsely Increased Bispectral Index Values in a Series of Patients Undergoing Cardiac Surgery Using Forced-Air-Warming Therapy of the Head

Falsely Increased Bispectral Index Values in a Series of Patients Undergoing Cardiac Surgery Using Forced-Air-Warming Therapy of the Head

Bispectral index monitoring

The Bispectral Index (BIS) is a newly processed electroencephalogram parameter that was specifically developed to measure the hypnotic effects of anesthesia. Results from volunteer studies demonstrate that BIS correlates well with clinical assessments of sedation induced by sedative-hypnotic drugs. Clinical utility studies have shown also that BIS monitoring allows for better titration of anesthesia, resulting in lower hypnotic drug use and improved recovery. The data suggest that improved anesthetic titration with BIS provides sufficient clinical and economic benefits to justify its routine use. This article summarizes the clinical development and validation of BIS and describes how BIS monitoring can be used to improve anesthetic outcomes.