End-tidal Anesthetic Concentration Research Articles

End-Tidal Control Versus Manual Control of Inhalational Anesthesia Delivery: A Randomized Controlled Noninferiority Trial.

Precise anesthesia delivery helps ensure amnesia, analgesia, and immobility. Conventionally, the end-tidal anesthetic concentration is maintained through manual adjustment of the fresh gas flow and anesthetic vaporizer output. Some anesthesia delivery systems can deliver and maintain clinician-selected end-tidal anesthetic agent (EtAA) concentration using a modified closed-loop system. We evaluated the performance of an End-tidal Control (EtC) system on the Aisys CS 2 anesthesia machine (GE HealthCare). We hypothesized EtC anesthetic delivery would be noninferior to manually controlled anesthetic delivery. The Multi-site Anesthesia randomized controlled STudy of End-tidal control compared to conventional Results (MASTER) Trial evaluated anesthetic delivery in 210 adult patients receiving inhaled anesthesia. Patients were randomized to either EtC or manual control (MC) anesthetic delivery. The primary objective was to determine whether, compared to conventional anesthesia practice, EtC achieves and maintains clinician-specified EtAA and end-tidal oxygen (Et o2 ) concentrations within defined noninferiority limits. Noninferiority was concluded if the lower limit of the 95% confidence interval (CI) of the difference between the percent duration within the acceptable range (5% of steady state or a margin of ~10% of each agent's minimum alveolar concentration) for EtC and MC was ≥ -5% for both EtAA and Et o2 . Secondary objectives included performance measures: response time: time required to attain 90% of the first desired EtAA, overshoot: amount the controller (or vaporizer delivery) exceeded the desired EtAA, and accuracy: average deviation from the desired EtAA. EtC achieved and sustained targeted EtAA and Et o2 concentrations within the noninferiority threshold. The EtAA was within 5% of the desired value 98% ± 2.05% of the time with EtC compared to 45.7% ± 31.7% of the time with MC (difference 52.3% [95% CI, 45.9%-58.6%], P < .0001). For Et o2 , EtC was within the noninferiority limit 86.3% ± 22.8% of the time compared with MC at 41% ± 33.3% ( P < .0001, difference 45.3% [95% CI, 36.1%-54.5%]). The median response time for achieving 90% of the initial EtAA desired value was 75 seconds with EtC and 158 seconds with MC ( P = .0013). EtC exhibited a median overshoot of 6.64% of the selected EtAA concentration, whereas MC often failed to reach the clinician's desired value. The difference in median percent deviation from desired EtAA value was 15.7% ([95% CI, 13.5%-19.0%], P < 0001). EtC achieves and maintains the EtAA and Et o2 concentration in a manner that is noninferior to manually controlled anesthesia delivery.

Prevention of accidental awareness under general anaesthesia: A regional service evaluation.

The United Kingdom's Fifth National Audit Project investigated the incidence and causes of accidental awareness during general anaesthesia. Subsequently, guidelines produced by the Association of Anaesthetists of Great Britain and Ireland provide key recommendations to minimise awareness. These include using processed electroencephalogram for patients receiving total intravenous anaesthesia while paralysed and using audible low end-tidal anaesthetic concentration alarms. The Southcoast Perioperative Audit and Research Collaboration undertook a five-day regional service evaluation, assessing the measures in place to minimise awareness and conducting a practitioner survey. Eight hospitals participated with 382 theatre attendances were analysed. Processed electroencephalograph monitoring for patients receiving total intravenous anaesthesia with neuromuscular blockade has been widely adopted into regional practice, from 23% of cases in the Fifth National Audit Project, to 85% in this snapshot. During volatile anaesthesia, age-adjusted low end-tidal anaesthetic concentration alarms were used in 34% cases. The range was 0-97% at different hospitals, suggesting heterogeneity in practice. Seventy-six per cent of anaesthetists rarely alter the default anaesthetic machine alarm settings. Therefore, instigating default low end-tidal anaesthetic concentration alarms could improve compliance with guidelines and reduce the risk of awareness for patients.

Lower alpha frequency of intraoperative frontal EEG is associated with postoperative delirium: A secondary propensity-matched analysis

BackgroundPostoperative delirium (POD) is a serious complication of surgery, especially in the elderly patient population. It has been proposed that decreasing the amount of anesthetics by titrating to an EEG index will lower POD rate, but clear evidence is missing. A strong age-dependent negative correlation has been reported between the peak oscillatory frequency of alpha waves and end-tidal anesthetic concentration, with older patients generating slower alpha frequencies. We hypothesized, that slower alpha oscillations are associated with a higher rate of POD. MethodRetrospective analysis of patients` data from a prospective observational study in cardiac surgical patients approved by the Bernese Ethics committee. Frontal EEG was recorded during Isoflurane effect-site concentrations of 0.7 to 0.8 and peak alpha frequency was measured at highest power between 6 and 17 Hz. Delirium was assessed by chart review. Demographic and clinical characteristics were compared between POD and non-POD groups. Selection bias was addressed using nearest neighbor propensity score matching (PSM) for best balance. This incorporated 18 variables, whereas patients with missing variable information or without an alpha oscillation were excluded. ResultOf the 1072 patients in the original study, 828 were included, 73 with POD, 755 without. PSM allowed 328 patients into the final analysis, 67 with, 261 without POD. Before PSM, 8 variables were significantly different between POD and non-POD groups, none thereafter. Mean peak alpha frequency was significantly lower in the POD in contrast to non-POD group before and after matching (7.9 vs 8.9 Hz, 7.9 vs 8.8 Hz respectively, SD 1.3, p < 0.001). ConclusionIntraoperative slower frontal peak alpha frequency is independently associated with POD after cardiac surgery and may be a simple intraoperative neurophysiological marker of a vulnerable brain for POD. Further studies are needed to investigate if there is a causal link between alpha frequency and POD.

Journal-related Activities and Other Special Activities at the 2022 American Society of Anesthesiologists Meeting

Journal-related Activities and Other Special Activities at the 2022 American Society of Anesthesiologists Meeting

End-tidal Anesthetic Concentration: Monitoring, Interpretation, and Clinical Application

Age-adjusted fraction of minimum alveolar concentration derived from end-tidal anesthetic partial pressure measurement remains a useful drug advisory display to help prevent awareness if interpreted with proper understanding of the quantal and probabilistic nature of minimum alveolar concentration, semantics, drug interactions, and hysteresis.

This Month in Anesthesiology

This Month in Anesthesiology

Comparison of recovery times by using bispectral index monitoring versus end-tidal agent concentration monitoring in patients undergoing inhalational general anaesthesia.

Background and Aims:End-tidal anaesthetic gas concentration (ETAG) and bispectral index (BIS) are both used to monitor depth of anaesthesia. Maintaining an accurate depth of anaesthesia helps in early post-operative recovery. This study compared the recovery times from sevoflurane–nitrous oxide anaesthesia using ETAG monitoring with BIS monitoring.Methods:Four hundred and two patients undergoing elective surgeries under sevoflurane- nitrous oxide anaesthesia were enroled in this double blinded parallel group prospective randomised trial and allocated into two groups. The depth of anaesthesia was monitored using BIS in BIS group (n = 202) and end-tidal sevoflurane concentration (EtSevo) in ETAG group (n = 200). The time to extubation and recovery were compared between the groups. Parametric, non-parametric and categorical variables were compared using Student’s ‘t’ test, Wilcoxon’s rank sum test and Chi-square test, respectively.Results:Time to extubation (min) [BIS group – 10, 5; ETAG group – 10, 5 (median, inter-quartile range, IQR), P = 0.32] and time to recovery (min) [BIS group – 14, 6; ETAG group – 13.5, 7 (median, IQR), P = 0.34] did not differ significantly between the two groups. The EtSevo concentration (vol%) was significantly higher in the BIS group at 5 min [BIS group – 1.2, 0.4; ETAG group – 1.0, 0.4 (median, IQR), P < 0.001], 30 min [BIS group – 1.1, 0.4; ETAG group – 1.0, 0.3 (median, IQR), P = 0.002] and 120 min [BIS group – 1.11 ± 0.28; ETAG group – 0.96 ± 0.27 (mean ± standard deviation), P = 0.014] after induction of anaesthesia.Conclusions:BIS and ETAG monitoring are associated with comparable recovery profiles. ETAG monitoring is associated with significantly less sevoflurane consumption.

A comparative randomized study of awareness during two anesthetic induction techniques in old aged patients using isolated forearm technique

Background &amp; Objective: Awareness under anesthesia is defined as intraoperative consciousness and/or postoperative recall of surgical events. The isolated forearm technique (IFT) is a technique that has the ability to assess consciousness of the external world through a verbal command during general anesthesia. It provides live information about the presence of consciousness.&#x0D; We compared inhalational induction technique versus intravenous induction technique regarding awareness during laryngoscopy and intubation in elderly patients.&#x0D; Design: A prospective, randomized trial&#x0D; Methodology: A total of 50 patients scheduled for elective surgery under general anesthesia; aged 60 to 80 years were recruited. Patients were randomized into either Group A (inhalational induction group) or Group B (total intravenous induction group). Awareness reaction using IFT technique was observed during laryngoscopy and intubation phase to identify awareness incidence. A patient was considered a responder if IFT score &gt; 2.&#x0D; Results: At laryngoscopy and intubation phase, 32% of cases had an awareness reaction in intravenous induction group (Group B): While in the inhalational induction group (Group A), only 8% of cases had an awareness reaction. Additionally, none of the patients, suffered from postoperative explicit recall as detected by modified Brice questionnaire (MBQ).&#x0D; Conclusions: On the basis of the results of our study, we conclude that intravenous induction of general anesthesia may subject old aged patients to a higher incidence of awareness when compared to inhalational induction technique.&#x0D; Trial Registration: NCT05019560&#x0D; Abbreviations: TIVA - Total intravenous anesthesia; IFT - Isolated forearm technique; MBQ - Modified Brice questionnaire; BISTM -Bispectral Index™; ETAC - End-tidal anesthetic concentration; MAC – Minimum alveolar concentration&#x0D; Key words: Awareness; The modified Brice questionnaire; Elderly patients; Isolated forearm technique; Sevoflurane; TIVA&#x0D; Citation: Ibrahim TH, Ayoub AH, Ibrahim IM, Ismaiel MAA, Mostafa RH. A comparative randomized study of awareness during two anesthetic induction techniques in old aged patients using isolated forearm technique. Anaesth. pain intensive care 2022;26(1):81-88.&#x0D; DOI: 10.35975/apic.v26i1.1772&#x0D; Received: November 14, 2021, Reviewed: December 18, 2021, Accepted: December 22, 2021

Phase Lag Entropy as a Surrogate Measurement of Hypnotic Depth during Sevoflurane Anesthesia.

Background and Objectives: Phase lag entropy, an electroencephalographic monitor, evaluates the variety in temporal patterns of phase relationship between frontal and prefrontal brain region. Phase lag entropy can reflect the depth of anesthesia induced by propofol, but the association between sevoflurane and phase lag entropy has not been elucidated. This study examined the effect of sevoflurane on phase lag entropy during induction of general anesthesia. We also explored the pharmacodynamic model between end-tidal anesthetic concentration and electroencephalographic monitor. Materials and Methods: A total of 20 patients were enrolled. General anesthesia was produced by escalating the sevoflurane (1 vol% up to 8 vol%). The relationship between phase lag entropy and end-tidal anesthetic concentration was analyzed. A non-linear mixed-effects model was used to get the relationship of pharmacodynamics between the end-tidal sevoflurane concentration and phase lag entropy. Mean blood pressure, heart rate, and the modified observer’s assessment of alertness/sedation scale were also recorded during sevoflurane anesthesia. Results: As level of sedation increased, phase lag entropy decreased. A significant correlation was showed between phase lag entropy and end-tidal sevoflurane concentration (r = −0.759, p < 0.001). The correlation coefficient between the modified observer’s assessment of alertness/sedation scale and phase lag entropy was 0.731 (p < 0.001). The pharmacodynamic factors assessed by the sigmoid Emax model were E0 = 84.9, Emax = 42, Ce50 = 1.81, γ = 4.78, and ke0 = 0.692. The prediction probability of phase-lag entropy for measuring the modified observer’s assessment of alertness/sedation scale and end-tidal sevoflurane concentration were 0.764 and 0.789, respectively. With the increasing concentration of sevoflurane, mean blood pressure decreased, but heart rate did not change. Conclusions: The continuing escalation in end-tidal sevoflurane concentration caused a decline in phase lag entropy. Phase lag entropy can serve as an indicator of hypnotic depth in patients receiving sevoflurane anesthesia.

Influence of Body Temperature on Bispectral Index-Guided Anesthetic Management in Off-Pump Coronary Artery Bypass Grafting

Abstract Background Perioperative hypothermia is not uncommon in surgical patients due to anesthetic-induced inhibition of thermoregulatory mechanisms and exposure of patients to cold environment in the operating rooms. Core temperature reduction up to 35°C is often seen in off-pump coronary artery bypass graft (OP-CABG) surgery. Anesthetic depth can be monitored by using bispectral (BIS) index. The present study was performed to evaluate the influence of mild hypothermia on the anesthetic depth using BIS monitoring and correlation of BIS with end-tidal anesthetic concentration at varying temperatures during OP-CABG. Materials and Methods In a prospective observational study design in a tertiary care teaching hospital, patients who underwent elective OP-CABG under endotracheal general anesthesia, were included in the study. Standard technique of anesthesia was followed. BIS, nasopharyngeal temperature, and end-tidal anesthetic concentration of inhaled isoflurane was recorded every 10 minutes. The BIS was adjusted to between 45 and 50 during surgery. Results There were 40 patients who underwent OP-CABG during the study period. The mean age was 51.2 ± 8.7 years, mean body mass index 29.8 ± 2.2, and mean left ventricular ejection fraction was 55.4 ± 4.2%. Anesthetic requirement as guided by BIS between 45 and 50 correlated linearly with core body temperature (r = 0.999; p &lt; 0.001). The mean decrease in the body temperature at the end of 300 minutes was 2.2°C with a mean decrease in end-tidal anesthetic concentration of 0.29%. The reduction in end-tidal anesthetic concentration per degree decrease in temperature was 0.13%. None of the patients reported intraoperative recall. Conclusion In this study, BIS monitoring was used to guide the delivery concentration of inhaled anesthetic using a targeted range of 45 to 50. BIS monitoring allowed the appropriate reduction of anesthetic dosing requirements in patients undergoing OP-CABG without risk of awareness. There was a significant reduction in anesthetic requirements associated with reduction of core temperature. The routine use of BIS is recommended in OP-CABG to titrate anesthetic requirement during occurrence of hypothermia and facilitate fast-track anesthesia in this patient population.

Comparison of End-Tidal Anesthetic Gas Concentration versus Bispectral Index-Guided Protocol as Directing Tool on Time to Tracheal Extubation for Sevoflurane-Based General Anesthesia.

Background:Modalities for titrating anesthetic drug-like bispectral index (BIS) and end-tidal anesthetic gas (ETAG) concentration in predicting early extubation had been studied with old anesthetic agents such as isoflurane.Aim:The aim of this study is to compare the effect of ETAG concentration versus BIS-guided protocol as directing tool on time to tracheal extubation for sevoflurane-based general anesthesia.Materials and Methods:This prospective, randomized, double-blind trial studied sixty patients with American Society of Anesthesiologists physical status classes I and II who received sevoflurane-based general anesthesia and were allocated to either BIS–guided anesthesia group (n = 30) or ETAG–guided anesthesia group (n = 30). Time to tracheal extubation was measured. BIS value was kept between 40 and 60 in BIS group, whereas minimum alveolar concentration value was kept between 0.7 and 1.3 in ETAG group. The two groups were compared using Student's t-test, and P < 0.05 was considered statistically significant. The statistical analysis was performed using the open source “R” programming language.Results:Mean time to tracheal extubation was significantly shorter in BIS group (308.77 ± 20.48 s) as compared to ETAG group (377.90 ± 25.06 s) (P < 0.001). The sevoflurane concentration used was also significantly less in group BIS than group ETAG at multiple time intervals (P = 0.001).Conclusion:Prediction of extubation was significantly early with BIS monitoring as compared to ETAG monitoring in sevoflurane-based general anesthesia.

End Tidal Anesthetic Concentration in Different Anesthesia Techniques Where Depth of Anesthesia Adjusted With Entropy

End Tidal Anesthetic Concentration in Different Anesthesia Techniques Where Depth of Anesthesia Adjusted With Entropy

Assessment of Common Criteria for Awake Extubation in Infants and Young Children.

Practice patterns surrounding awake extubation of pediatric surgical patients remain largely undocumented. This study assessed the value of commonly used predictors of fitness for extubation to determine which were most salient in predicting successful extubation following emergence from general anesthesia with a volatile anesthetic in young children. This prospective, observational study was performed in 600 children from 0 to 7 yr of age. The presence or absence of nine commonly used extubation criteria in children were recorded at the time of extubation including: facial grimace, eye opening, low end-tidal anesthetic concentration, spontaneous tidal volume greater than 5 ml/kg, conjugate gaze, purposeful movement, movement other than coughing, laryngeal stimulation test, and oxygen saturation. Extubations were graded as Successful, Intervention Required, or Major Intervention Required using a standard set of criteria. The Intervention Required and Major Intervention Required outcomes were combined as a single outcome for analysis of predictors of success. Successful extubation occurred in 92.7% (556 of 600) of cases. Facial grimace odds ratio, 1.93 (95% CI, 1.03 to 3.60; P = 0.039), purposeful movement odds ratio, 2.42 (95% CI, 1.14 to 5.12; P = 0.022), conjugate gaze odds ratio, 2.10 (95% CI, 1.14 to 4.01; P = 0.031), eye opening odds ratio, 4.44 (95% CI, 1.06 to 18.64; P= 0.042), and tidal volume greater than 5 ml/kg odds ratio, 2.66 (95% CI, 1.21 to 5.86; P = 0.015) were univariately associated with the Successful group. A stepwise increase in any one, in any order, of these five predictors being present, from one out of five and up to five out of five yielded an increasing positive predictive value for successful extubation of 88.3% (95% CI, 82.4 to 94.3), 88.4% (95% CI, 83.5 to 93.3), 96.3% (95% CI, 93.4 to 99.2), 97.4% (95% CI, 94.4 to 100), and 100% (95% CI, 90 to 100). Conjugate gaze, facial grimace, eye opening, purposeful movement, and tidal volume greater than 5 ml/kg were each individually associated with extubation success in pediatric surgical patients after volatile anesthetic. Further, the use of a multifactorial approach using these predictors, may lead to a more rational and robust approach to successful awake extubation.

Neural Correlates of Anesthesia in Newborn Mice and Humans

Monitoring the hypnotic component of anesthesia during surgeries is critical to prevent intraoperative awareness and reduce adverse side effects. For this purpose, electroencephalographic (EEG) methods complementing measures of autonomic functions and behavioral responses are in use in clinical practice. However, in human neonates and infants existing methods may be unreliable and the correlation between brain activity and anesthetic depth is still poorly understood. Here, we characterized the effects of different anesthetics on brain activity in neonatal mice and developed machine learning approaches to identify electrophysiological features predicting inspired or end-tidal anesthetic concentration as a proxy for anesthetic depth. We show that similar features from EEG recordings can be applied to predict anesthetic concentration in neonatal mice and humans. These results might support a novel strategy to monitor anesthetic depth in human newborns.

Correlation between bispectral index, end-tidal anaesthetic gas concentration and difference in inspired-end-tidal oxygen concentration as measures of anaesthetic depth in paediatric patients posted for short surgical procedures.

Background and Aims:Measurement of end-tidal anaesthetic gas concentrations (ETAG) is currently a pragmatic indicator for monitoring anaesthetic depth. We aimed to assess the performance of ETAG for sevoflurane (ETAG-sevo) with bispectral index (BIS) and difference between inspired and end-tidal oxygen concentration (Fi−Et)O2% in measuring anaesthetic depth in toddlers and preschool children. Primary outcome was to correlate BIS with ETAG-sevo. Secondary outcome was to correlate (Fi−Et)O2% with ETAG-sevo and to derive cut-off value of (Fi−Et)O2%which corresponds with light planes of anaesthesia [minimum alveolar concentration (MAC <0.6)].Methods:Thirty patients between 1 and 5 years of age undergoing short procedures were included. ETAG, MAC, BIS and (Fi−Et)O2% were measured at intubation, maintenance phase, last 15 min of surgery, end of surgery, extubation, recovery. Pearson's correlation coefficient was used to measure correlation. Receiver operating characteristic (ROC) curves were used to derive cut-off value of (Fi−Et)O2% which corresponded with MAC <0.6.Results:BIS correlated poorly with ETAG at all time intervals. Significant correlation was seen between (Fi−Et)O2% and ETAG at intubation (P = 0.042), last 15 min of surgery (P = 0.019) and end of surgery (P = 0.001). Cut-off value >7 was obtained for (Fi−Et)O2% corresponding to MAC <0.6 at extubation with area under ROC curve0.955 (95% confidence interval 0.811–0.997), with sensitivity 0.8571 and specificity 1.00.Conclusion:BIS was an unreliable measure of anaesthetic depth. (Fi−Et)O2% values >7 corresponded with light planes of anaesthesia.

Desflurane reduces intraoperative remifentanil requirements more than sevoflurane: comparison using surgical pleth index-guided analgesia

BackgroundSevoflurane and desflurane are widely used in balanced anaesthesia in combination with opioid analgesics. The opioid remifentanil is frequently chosen because of its extremely rapid pharmacokinetics. However, intraoperative high-dose remifentanil is associated with increased postoperative pain and rescue analgesic use owing to acute tolerance and opioid-induced hyperalgesia. This study aimed to compare intraoperative remifentanil requirements during equi-minimum alveolar concentration (MAC) sevoflurane and desflurane anaesthesia via surgical pleth index-guided remifentanil administration. MethodsEighty-two subjects undergoing laparoscopic cholecystectomy were randomly allocated to two groups receiving either sevoflurane (n=40) or desflurane (n=42). Anaesthesia was maintained with the assigned inhaled anaesthetics and remifentanil. End-tidal anaesthetic concentration was maintained at age-corrected 1.0 MAC, and remifentanil infusion was continuously adjusted to achieve a surgical pleth index of 20–50. Mean remifentanil infusion rate, which was the primary outcome of the study, was calculated as the total infused remifentanil dose per kg body weight per minute of total operative time. ResultsMean remifentanil infusion rate [mean (standard deviation)] was significantly higher in the sevoflurane group than in the desflurane group [0.192 (0.064) vs. 0.099 (0.033) μg kg−1 min−1; difference, 0.093 (95% confidence interval, 0.071–0.115); P<0.001]. ConclusionsDuring equi-MAC anaesthesia of 1.0 MAC, sevoflurane and desflurane did not show similar intraoperative remifentanil consumption under surgical pleth index-guided opioid administration. Further studies using other monitors with different measuring mechanisms are warranted to determine the cause of this difference. Clinical trial registrationNCT02830243 (ClinicalTrials.gov).

Intraoperative electroencephalogram suppression at lower volatile anaesthetic concentrations predicts postoperative delirium occurring in the intensive care unit

BackgroundPostoperative delirium is a common complication associated with increased morbidity and mortality. A recently-reported association between intraoperative electroencephalogram suppression and postoperative delirium might be mediated in some patients by a heightened sensitivity to volatile anaesthetics. MethodsThis retrospective cohort study included 618 elective surgery patients with planned intensive care unit admission, who also received intraoperative electroencephalogram monitoring and had delirium assessments documented in the medical record. Sensitivity to volatile anaesthetics was assessed using a mixed effects model predicting the likelihood of electroencephalogram suppression at each time point based on the current end-tidal anaesthetic concentration. Patients with a random intercept above the population median (electroencephalogram suppression at lower anaesthetic concentrations) were classified as having heightened sensitivity to volatile anaesthetics. Delirium was defined as a positive Confusion Assessment Method for the Intensive Care Unit assessment anytime in the first five postoperative days. ResultsPostoperative delirium was observed in 162 of 618 patients (26%). Patients who experienced electroencephalogram suppression at lower volatile anaesthetic concentrations had a higher incidence of postoperative delirium [109/309 (35%)] than other patients [53/309 (17%)] [unadjusted odds ratio 2.63; 95% confidence interval (CI), 1.81–3.84, P<0.001]. This association remained significant after adjusting for patient characteristics, surgical variables, and duration of electroencephalogram suppression (adjusted odds ratio 2.13; 95% CI 1.24–3.65, P=0.006). ConclusionsThese data support the hypothesis that patients with electroencephalogram suppression at lower volatile anaesthetic concentrations have an increased incidence of postoperative delirium. Such patients appear to exhibit a phenotype of anaesthetic sensitivity, which might predispose them to adverse cognitive outcomes.

Comparison of bispectral index and end-tidal anaesthetic concentration monitoring on recovery profile of desflurane in patients undergoing lumbar spine surgery

Background and Aims:Several techniques have evolved over time to monitor depth of anesthesia and ensure enhanced recovery. This randomized double-blinded trial was designed to compare bispectral index (BIS) or end-tidal anaesthetic concentration (ETAC) monitoring on the recovery characteristics of patients undergoing thoracolumbar spine surgeries.Methods:Seventy American Society of Anesthesiologist I–II patients of either sex were randomized to Group B – BIS-guided protocol, Group E – ETAC-guided protocol, or Group S – Standard protocol. After intravenous induction, anaesthesia was maintained with desflurane in O2/N2O (50:50) mixture. In BIS, ETAC and Standard groups, inspired end-tidal desflurane concentration was varied to achieve BIS of 45–55, 0.8–1.0 age-corrected minimum alveolar concentration, and haemodynamic parameters within 20% of the baseline, respectively. Time to eye opening (emergence time, the primary outcome), time to extubation, and time to name recall from the discontinuation of the anaesthetic agent were recorded. Incidence of nausea, vomiting, and total analgesic consumption was noted for 24 h.Results:Emergence time (mean ± SD) in ETAC (5.1 ± 1.53 min) and BIS (5.0 ± 2.12 min)-guided groups was significantly lower than Standard group (7.5 ± 2.90 min). Extubation time in ETAC (6.3 ± 2.22 min) and BIS-guided group (6.5 ± 1.78 min) was significantly lower than Standard group (9.0 ± 3.20 min) (P < 0.001). Time to achieve fast track score of more than 12 was significantly less in BIS-guided group (13.12 ± 2.59 min).Conclusion:ETAC-guided anaesthesia is comparable to BIS-guided anaesthesia in achieving early recovery.

Incidence of Anesthetic Awareness may be Higher in Low Flow Anesthesia

Awareness is one of the most feared complications of general anesthesia. Incidence of anesthetic awareness is rare but it can be higher in haemodynamic unstable patients, trauma patients, obese patients, those with chronic pain, children and cardiac surgery. Scarce information is available on the incidence of awareness in low flow anesthesia. Literature search of databases yielded studies that refer to awareness during general anesthesia, and always referring to high flow anesthesia, but there are no references on awareness in low flow anesthesia. However, due to small amounts of inhaled anesthetics in low flow anesthesia there is a possibility of a higher incidence of awareness in this setting. The term “depth of anesthesia” must be distinguished from anesthetic awareness and it is necessary to take into account everything that is closely related to it, such as memory, consciousness or unconsciousness. Minimal alveolar concentration (MAC) and end-tidal anesthetic gas concentration (ETAG) can measure depth of anesthesia, but they are not enough regarding awareness and memory. MAC does not represent the effect of anesthesia on the brain, since movement in response to a surgical stimulus is mediated at the level of the spinal cord. Bispectral index (BIS) and entropy as objective techniques should be used to monitor awareness although there are confusing results even with their application. More studies are needed to investigate awareness during low flow anesthesia that will shed some light on the additional restrictions of its application.

Effect of magnesium sulphate on bi-spectral index (BIS) values during general anesthesia in children.

BackgroundMagnesium was reported to reduce both the anesthetic requirements and the period needed to reach a bi-spectral index value of 60 when used intra-operatively (Br J Anaesth 83:302-20, 1999; Anesth Analg 20:1273-5, 1988; Br J Anaesth 89:594-8, 2002; Anesth Analg 87:206-10, 1998; Br J Anaesth 89:594-8, 2002; Br J Anaesth 94:438-41, 2005) and to minimize the emergence agitation (Anaesthesia 61:1058-63, 2006). Previous studies examined the influence of magnesium on the anesthetic requirements while the bi-spectral Index values were kept within a constant range. We evaluated the effect of intraoperative magnesium on the bi-spectral index values during pediatric anesthesia while we kept other anesthetic variables unchanged.MethodsEighty pediatric patients with ASA physical status I, age 2–8 years and scheduled for minor infra-umbilical elective procedures included in a prospective randomized controlled study. We randomly divided patients into two groups. Group I (40 patients); received a bolus dose 50 mg/kg of magnesium sulphate followed by an infusion at rate of 15 mg/kg/h throughout the procedure. Group II (40 patients); received the same amount in the form of ringer acetate for blinding. We compared between the groups regarding: 1) BIS values. 2) Hemodynamic parameters. 3) Arterial oxygen saturation 4) End-tidal CO2 5) Respiratory rate and 6) Tidal volume.ResultsMagnesium group (Group I) showed significantly lower BIS values and shorter time to achieve BIS values below 60. Respiratory parameters (tidal volume and respiratory rate) were significantly lower in the magnesium group. Otherwise, no significant differences between the study group and the control group were detected.DiscussionOur study has the advantage of evaluating the direct effect of magnesium sulphate on the Bi-spectral index scale with keeping other intraoperative factors almost constant (as the type of operations, induction and maintenance techniques, end-tidal anesthetic concentration, analgesia and mode of ventilation) for accurate assessment.ConclusionMagnesium produced significantly lower BIS values, less time to reach BIS values below 60, lower tidal volume and lower respiratory rate during pediatric general anesthesia.Trial registrationPan African Clinical Trial Registry, www.pactr.org, PACTR201312000666231. Registered at 6 October 2013.