Bispectral index guided titration of sevoflurane in on-pump cardiac surgery reduces plasma sevoflurane concentration and vasopressor requirements: a prospective, controlled, sequential two-arm clinical study

Hypotension Prediction Index guided Goal Directed therapy and the amount of Hypotension during Major Gynaecologic Oncologic Surgery: a Randomized Controlled clinical Trial

Intraoperative hypotension (IOH) is associated with increased morbidity and mortality. Hypotension Prediction Index (HPI) is a machine learning derived algorithm that predicts IOH shortly before it occurs. We tested the hypothesis that the application of the HPI in combination with a pre-defined Goal Directed Therapy (GDT) hemodynamic protocol reduces IOH during major gynaecologic oncologic surgery. We enrolled women scheduled for major gynaecologic oncologic surgery under general anesthesia with invasive arterial pressure monitoring. Patients were randomized to a GDT protocol aimed at optimizing stroke volume index (SVI) or hemodynamic management based on HPI guidance in addition to GDT. The primary outcome was the amount of IOH, defined as the timeweighted average (TWA) mean arterial pressure (MAP) < 65 mmHg. Secondary outcome was the TWA-MAP < 65 mmHg during the first 20 min after induction of GA. After exclusion of 10 patients the final analysis included 60 patients (30 in each group). The median (25-75th IQR) TWA-MAP < 65 mmHg was 0.14 (0.04-0.66) mmHg in HPI group versus 0.77 (0.36-1.30) mmHg in Control group, P < 0.001. During the first 20 min after induction of GA, the median TWA-MAP < 65 mmHg was 0.53 (0.06-1.8) mmHg in the HPI group and 2.15 (0.65-4.2) mmHg in the Control group, P = 0.001. Compared to a GDT protocol aimed to SVI optimization, a machine learning-derived algorithm for prediction of IOH combined with a GDT hemodynamic protocol, reduced IOH and hypotension after induction of general anesthesia in patients undergoing major gynaecologic oncologic surgery.Trial registration number: NCT04547491. Date of registration: 10/09/2020.

Inhaled Sedation with Volatile Anesthetics for Mechanically Ventilated Patients in Intensive Care Units: A Narrative Review

Inhaled sedation was recently approved in Europe as an alternative to intravenous sedative drugs for intensive care unit (ICU) sedation. The aim of this narrative review was to summarize the available data from the literature published between 2005 and 2023 in terms of the efficacy, safety, and potential clinical benefits of inhaled sedation for ICU mechanically ventilated patients. The results indicated that inhaled sedation reduces the time to extubation and weaning from mechanical ventilation and reduces opioid and muscle relaxant consumption, thereby possibly enhancing recovery. Several researchers have reported its potential cardio-protective, anti-inflammatory or bronchodilator properties, alongside its minimal metabolism by the liver and kidney. The reflection devices used with inhaled sedation may increase the instrumental dead space volume and could lead to hypercapnia if the ventilator settings are not optimal and the end tidal carbon dioxide is not monitored. The risk of air pollution can be prevented by the adequate scavenging of the expired gases. Minimizing atmospheric pollution can be achieved through the judicious use of the inhalation sedation for selected groups of ICU patients, where the benefits are maximized compared to intravenous sedation. Very rarely, inhaled sedation can induce malignant hyperthermia, which prompts urgent diagnosis and treatment by the ICU staff. Overall, there is growing evidence to support the benefits of inhaled sedation as an alternative for intravenous sedation in ICU mechanically ventilated patients. The indication and management of any side effects should be clearly set and protocolized by each ICU. More randomized controlled trials (RCTs) are still required to investigate whether inhaled sedation should be prioritized over the current practice of intravenous sedation.

Sevoflurane administration from extracorporeal membrane oxygenation via the AnaConDa device for a patient with COVID-19: a breakthrough solution for the shortage of intravenous anesthetics

One of the major issues encountered during the coronavirus disease 2019 (COVID-19) pandemic has been the shortage of intravenous anesthetics. Moreover, patients undergoing extracorporeal membrane oxygenation (ECMO) need large quantities of intravenous anesthetics for sedation. We report the case of a 52-year-old man who was admitted to our hospital due to acute respiratory distress syndrome by COVID-19 and treated with ECMO. As controlling sedation with intravenous anesthetics was challenging, we attempted to administer inhaled anesthetics via the gas flow of ECMO. We decreased the quantity of intravenous anesthetics and opioids. This method might help overcome the shortage of intravenous anesthetics.

Impact of Processed Electroencephalography in Cardiac Surgery: A Retrospective Analysis

OBJECTIVE

The use of brain function monitoring with processed electroencephalography (pEEG) during cardiac surgery is gaining interest for the optimization of hypnotic agent delivery during the maintenance of anesthesia. The authors sought to determine whether the routine use of pEEG-guided anesthesia is associated with a reduction of hemodynamic instability during cardiopulmonary bypass (CPB) separation and subsequently reduces vasoactive and inotropic requirements in the intensive care unit.

DESIGN

This is a retrospective cohort study based on an existing database.

SETTING

A single cardiac surgical center.

PARTICIPANTS

Three hundred patients undergoing cardiac surgery, under CPB, between December 2013 and March 2020.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One hundred and fifty patients had pEEG-guided anesthesia, and 150 patients did not have a pEEG-guided anesthesia. Multiple logistic regression demonstrated that pEEG-guided anesthesia was not associated with a successful CPB separation (p = 0.12). However, the use of pEEG-guided anesthesia reduced by 57% the odds of being in a higher category for vasoactive inotropic score compared to patients without pEEG (odds ratio = 0.43; 95% confidence interval: 0.26-0.73; p = 0.002). Duration of mechanical ventilation, fluid balance, and blood losses were also reduced in the pEEG anesthesia-guided group (p < 0.003), but there were no differences in organ dysfunction duration and mortality.

CONCLUSION

During cardiac surgery, pEEG-guided anesthesia allowed a reduction in the use of inotropic or vasoactive agents at arrival in the intensive care unit. However, it did not facilitate weaning from CPB compared to a group where pEEG was unavailable. A pEEG-guided anesthetic management could promote early vasopressor weaning after cardiac surgery.

Association between high dose catecholamine support and liver dysfunction following cardiac surgery

BACKGROUND

Cardiac surgery using cardiopulmonary bypass is a well-established procedure. However, up to 20% to 30% of patients require high dose vasopressor or inotropic support following surgery, enhancing the risk of organ dysfunction and impacting mortality. Nonalcoholic fatty liver disease (NAFLD) is a frequent finding in these patients and may be involved in the pathophysiology of vasoplegia and cardiac failure.

METHODS

Retrospective analysis of 463 patients undergoing elective cardiac surgery in 2014 at our institution. NAFLD was defined using the NAFLD fibrosis score and the vasoactive-inotropy score was used to determine postoperative vasopressor and inotropic dependency.

RESULTS

Patients with NAFLD more often presented with high vasopressor or inotropic support compared to patients without NAFLD, resulting in significant differences after 6 hours (n = 20 [27.0%] of 74 patients), 12 hours (n = 20 [27.0%] of 74 patients), and on the first postoperative day (n = 12 [16.4%] of 73 patients) of intensive care unit (ICU) treatment. Multivariate analysis revealed time of catecholamine application (P = .001), preoperative left ventricular ejection fraction (P = .001), type of surgery (P = .001), model of endstage liver disease on hospital admission (P = .002), pre-existing pulmonary hypertension (P = .004) and NAFLD-time interaction (P = .05) as independent predictors of high vasopressor and inotropic support. Patients with NAFLD had higher degrees of extrahepatic organ dysfunction, were more dependent on hemodialysis, spent more days in the ICU and within the hospital. Patients with NAFLD and high catecholamine support had the highest mortality rates among the study population.

CONCLUSIONS

NAFLD is a common finding in elective cardiac surgery patients. Anesthesiologists and intensivists should be sensitive for the specific risk profile of this population.

Depth of anesthesia by Narcotrend® and postoperative characteristics in children undergoing cardiac surgery under extracorporeal circulation: a retrospective comparison of two anesthetic regimens

BACKGROUND

Depth of anesthesia may be insufficient in pediatric cardiac anesthesia if a total intravenous anesthetic regimen with opioids and midazolam is used during cardiopulmonary bypass. The advantages of sevoflurane-based balanced anesthesia may be (1) a more graduated regulation of the depth of anesthesia during cardiopulmonary bypass and (2) a reduction in postoperative ventilation time for children in comparison with total intravenous anesthesia.

AIM

To evaluate a possibly positive effect of sevoflurane-based balanced anesthesia in children undergoing cardiac surgery we analyzed whether this anesthetic regimen had a significant effect related to (1) depth of anesthesia, (2) the need for opioids during cardiopulmonary bypass as well as on postoperative characteristics such as (3) time of postoperative ventilation, and (4) duration of stay in the intensive care unit in comparison with total intravenous anesthesia.

METHODS

In a retrospective analysis, data from heart-lung machine protocols from 2013 to 2016 were compared according to anesthetic regimen (sevoflurane-balanced anesthesia, n = 70 vs. total intravenous anesthesia, n = 65). Children (age: 8 weeks to 14 years) undergoing cardiac surgery with cardiopulmonary bypass were included. As a primary outcome measure, we compared Narcotrend^® system-extracted data to detect insufficient phases of anesthetic depth during extracorporeal circulation under moderate hypothermia. Postoperatively, we measured the postoperative ventilation time and the number of days in the intensive care unit. Furthermore, we analyzed patients' specific characteristics such as opioid consumption during cardiopulmonary bypass. Regression analysis relating primary objectives was done using the following variables: anesthetic regimen, age, severity of illness/surgery, and cumulative dosage of opiates during cardiopulmonary bypass.

RESULTS

No significant differences were observed in descriptive patient characteristics (age, body weight, height, and body temperature) between the two groups. Further, no significant differences were found in depth of anesthesia by analyzing phases of superficial B1-C2-electroencephalography Narcotrend^® data. No marked difference between the groups was observed for the duration of postoperative intensive care unit stay. However, the postoperative ventilation time (median (95% CI, hours)) was significantly lower in the sevoflurane-based balanced anesthesia group (6.0 (2.0-15.0)) than in the total intravenous anesthesia group (13.5 (7.0-25)). A higher dosage of opioids and midazolam was required in the total intravenous anesthesia group to maintain adequate anesthesia during cardiopulmonary bypass. Regression analysis showed an additional, significant impact of the following factors: severity of illness and severity grade of cardiac surgery (according to Aristotle) on the primary endpoint.

CONCLUSION

In children undergoing cardiac surgery in our department, the use of sevoflurane-balanced anesthesia during cardiopulmonary bypass showed no superiority of inhalational agents over total intravenous anesthesia with opioids and benzodiazepines preventing phases of superficial anesthesia, but a marked advantage for the postoperative ventilation time compared with total intravenous anesthesia.

Bispectral index for improving intraoperative awareness and early postoperative recovery in adults

BACKGROUND

The use of clinical signs, or end-tidal anaesthetic gas (ETAG), may not be reliable in measuring the hypnotic component of anaesthesia and may lead to either overdosage or underdosage resulting in adverse effects because of too deep or too light anaesthesia. Intraoperative awareness, whilst uncommon, may lead to serious psychological disturbance, and alternative methods to monitor the depth of anaesthesia may reduce the incidence of serious events. Bispectral index (BIS) is a numerical scale based on electrical activity in the brain. Using a BIS monitor to guide the dose of anaesthetic may have advantages over clinical signs or ETAG. This is an update of a review last published in 2014.

OBJECTIVES

To assess the effectiveness of BIS to reduce the risk of intraoperative awareness and early recovery times from general anaesthesia in adults undergoing surgery.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, and Web of Science on 26 March 2019. We searched clinical trial registers and grey literature, and handsearched reference lists of included studies and related reviews.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and quasi-RCTs in which BIS was used to guide anaesthesia compared with standard practice which was either clinical signs or end-tidal anaesthetic gas (ETAG) to guide the anaesthetic dose. We included adult participants undergoing any type of surgery under general anaesthesia regardless of whether included participants had a high risk of intraoperative awareness. We included only studies in which investigators aimed to evaluate the effectiveness of BIS for its role in monitoring intraoperative depth of anaesthesia or potential improvements in early recovery times from anaesthesia.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion, extracted data, and assessed risk of bias. We assessed the certainty of evidence with GRADE.

MAIN RESULTS

We included 52 studies with 41,331 participants; two studies were quasi-randomized and the remaining studies were RCTs. All studies included participants undergoing surgery under general anaesthesia. Three studies recruited only participants who were at high risk of intraoperative awareness, whilst two studies specifically recruited an unselected participant group. We analysed the data according to two comparison groups: BIS versus clinical signs; and BIS versus ETAG. Forty-eight studies used clinical signs as a comparison method, which included titration of anaesthesia according to criteria such as blood pressure or heart rate and, six studies used ETAG to guide anaesthesia. Whilst BIS target values differed between studies, all were within a range of values between 40 to 60.BIS versus clinical signsWe found low-certainty evidence that BIS-guided anaesthesia may reduce the risk of intraoperative awareness in a surgical population that were unselected or at high risk of awareness (Peto odds ratio (OR) 0.36, 95% CI 0.21 to 0.60; I2 = 61%; 27 studies; 9765 participants). However, events were rare with only five of 27 studies with reported incidences; we found that incidences of intraoperative awareness when BIS was used were three per 1000 (95% CI 2 to 6 per 1000) compared to nine per 1000 when anaesthesia was guided by clinical signs. Of the five studies with event data, one included participants at high risk of awareness and one included unselected participants, four used a structured questionnaire for assessment, and two used an adjudication process to identify confirmed or definite awareness.Early recovery times were also improved when BIS was used. We found low-certainty evidence that BIS may reduce the time to eye opening by mean difference (MD) 1.78 minutes (95% CI -2.53 to -1.03 minutes; 22 studies; 1494 participants), the time to orientation by MD 3.18 minutes (95% CI -4.03 to -2.33 minutes; 6 studies; 273 participants), and the time to discharge from the postanaesthesia care unit (PACU) by MD 6.86 minutes (95% CI -11.72 to -2 minutes; 13 studies; 930 participants).BIS versus ETAGAgain, events of intraoperative awareness were extremely rare, and we found no evidence of a difference in incidences of intraoperative awareness according to whether anaesthesia was guided by BIS or by ETAG in a surgical population at unselected or at high risk of awareness (Peto OR 1.13, 95% CI 0.56 to 2.26; I2 = 37%; 5 studies; 26,572 participants; low-certainty evidence). Incidences of intraoperative awareness were one per 1000 in both groups. Only three of five studies reported events, two included participants at high risk of awareness and one included unselected participants, all used a structured questionnaire for assessment and an adjudication process to identify confirmed or definite awareness.One large study (9376 participants) reported a reduced time to discharge from the PACU by a median of three minutes less, and we judged the certainty of this evidence to be low. No studies measured or reported the time to eye opening and the time to orientation.Certainty of the evidenceWe used GRADE to downgrade the evidence for all outcomes to low certainty. The incidence of intraoperative awareness is so infrequent such that, despite the inclusion of some large multi-centre studies in analyses, we believed that the effect estimates were imprecise. In addition, analyses included studies that we judged to have limitations owing to some assessments of high or unclear bias and in all studies, it was not possible to blind anaesthetists to the different methods of monitoring depth of anaesthesia.Studies often did not report a clear definition of intraoperative awareness. Time points of measurement differed, and methods used to identify intraoperative awareness also differed and we expected that some assessment tools were more comprehensive than others.

AUTHORS' CONCLUSIONS

Intraoperative awareness is infrequent and, despite identifying a large number of eligible studies, evidence for the effectiveness of using BIS to guide anaesthetic depth is imprecise. We found that BIS-guided anaesthesia compared to clinical signs may reduce the risk of intraoperative awareness and improve early recovery times in people undergoing surgery under general anaesthesia but we found no evidence of a difference between BIS-guided anaesthesia and ETAG-guided anaesthesia. We found six studies awaiting classification and two ongoing studies; inclusion of these studies in future updates may increase the certainty of the evidence.

Intraoperative reduction of vasopressors using processed electroencephalographic monitoring in patients undergoing elective cardiac surgery: a randomized clinical trial

Intraoperative vasopressor and fluid application are common strategies against hypotension. Use of processed electroencephalographic monitoring (pEEG) may reduce vasopressor application, a known risk factor for organ dysfunction, in elective cardiac surgery patients. Randomized single-centre clinical trial at Jena University Hospital. Adult patients operated on cardiopulmonary bypass or off-pump coronary artery bypass grafting were randomised to receive anesthesia with visible or blinded pEEG using Narcotrend™. In blinded-Narcotrend (NT) depth of anesthesia was extrapolated from clinical signs, hemodynamic response and anesthetic concentration, supplemented by target indices between 37 and 64 in the visible-NT group. Intraoperative norepinephrine requirement (primary endpoint), fluid balance, extubation time, delirium occurrence and adverse events were evaluated. Patients of the intent-to-treat population (visible-NT: n = 123, blinded-NT: n = 122) had similar patient and procedural characteristics. Adjusted for type of surgery intraoperative Norepinephrine application was significantly reduced in visible-NT (n = 120, robust mean of cumulative dose 4.71 µg/kg bodyweight) compared to blinded-NT patients (n = 119, 6.14 µg/kg bodyweight) (adjusted robust mean difference 1.71 (95% CI 0.33-3.10) µg/kg bodyweight). Although reduction in patients operated on cardiopulmonary bypass was higher the interaction was not significant in post-hoc subgroup analysis. Intraoperative fluid balance was similar among both groups and strata. Extubation time was non-significantly lower in visible than in blinded-NT group. Overall postoperative delirium risk was 16.4% without differences among the groups. Adverse events-sudden movement/coughing, perspiration or hypertension-occurred more often with visible-NT, while one blinded-NT patient experienced intraoperative awareness. Titration of depth of anesthesia in elective cardiac surgery patients using pEEG allows to reduce application of norepinephrine.

An Exploratory Study of Sevoflurane as an Alternative for Difficult Sedation in Critically Ill Children

OBJECTIVES

To analyze the effectiveness of inhaled sevoflurane in critically ill children with challenging sedation.

DESIGN

Prospective case series.

SETTING

Two PICUs of university hospitals in Spain.

INTERVENTIONS

Prospective observational study and exploratory investigation conducted in two PICUs in Madrid, Spain, over a 6-year period. Children treated with inhaled sevoflurane due to difficult sedation were included. Sevoflurane was administered via the anesthetic conserving device (AnaConDa) connected to a Servo-I ventilator (Maquet, Solna, Sweden). A morphine infusion was added to sevoflurane for analgesia. Demographic and clinical data, oral and IV sedatives, Sedation and Analgesic Clinical scores, and Bispectral Index Score monitoring were registered.

MEASUREMENTS AND MAIN RESULTS

Twenty-three patients with a median age of 6 months old were included. Fifty percentage of the patients had critical heart diseases. Sedative and analgesic drugs used before starting sevoflurane were mainly midazolam (63%) and fentanyl (53%). Six patients (32%) also received muscle relaxants. Sevoflurane was administered for a median of 5 days (interquartile range, 5.5-8.5 d). Median end-tidal sevoflurane concentration was 0.8% (interquartile range, 0.7-0.85%), achieved with an infusion rate of 7.5 mL/hr (5.7-8.6 mL/hr). After 48 hours of treatment, some sedative drugs could be removed in 18 patients (78%). Median Bispectral Index Score value prior to sevoflurane administration was 61 (interquartile range, 49-62), falling to 42 (interquartile range, 41-47; p < 0.05) after 6 hours of treatment. Six patients (26%) presented withdrawal syndrome after sevoflurane suspension, and all of them had received sevoflurane at least for 6 days. The main side effect was moderate hypotension in seven patients (30%).

CONCLUSIONS

Inhaled sevoflurane appeared to be an effective sedative agent in critically ill children and can be useful in those patients on mechanical ventilation difficult to sedate with conventional drugs. It can be administered easily in the PICU with conventional ventilators using the AnaConDa system. Withdrawal syndrome may occur with prolonged treatment.

The prediction probabilities for emergence from sevoflurane anesthesia in children: A comparison of the perfusion index and the bispectral index

BACKGROUND

Predicting recovery of consciousness is one of the most essential functions of anesthesia depth monitors in anesthesia practice. Perfusion index and bispectral index are 2 indicators of the anesthesia depth monitoring with different working principles. The progression of the anesthesia emergence stages reflected by those monitors has not been well understood, especially in pediatric patients. The goals of this study were to compare the prediction probabilities of perfusion index and bispectral index in predicting awakening and in differentiating the different levels of arousal during emergence after sevoflurane anesthesia in children undergoing open inguinal hernia repairs.

METHODS

Forty-five patients, aged 1 to 5 years, ASA Status I or II and scheduled for elective open inguinal hernia repairs under general anesthesia were enrolled. The perfusion index and bispectral index were monitored simultaneously during anesthesia recovery. The University of Michigan Sedation Scale was applied to evaluate the clinical arousal levels during emergence. The prediction probability was used to assess the performance of perfusion index and bispectral index in predicting awakening and distinguishing different levels of arousal corresponding to the University of Michigan Sedation Scale during recovery.

RESULTS

The prediction probability of perfusion index (Pk_PI-Awakening  = .81, 95% CI 0.73-0.89) in differentiating full consciousness from unconsciousness during recovery was comparable to that of bispectral index (Pk_{BIS- Awakening}  = .86, 95% CI 0.79-0.92) (P = .47). The prediction probability for perfusion index (Pk_PI-UMSS  = .61, 95% CI 0.55-0.73) and bispectral index (Pk_BIS-UMSS  = .64, 95% CI 0.53-0.69) had similar performance in distinguishing different University of Michigan Sedation Scale levels.

CONCLUSION

Both the perfusion index and bispectral index performed comparably well in predicting awakening and different arousal levels when emerging from sevoflurane anesthesia in children.

Isoflurane's Effect on Intraoperative Systolic Left Ventricular Performance in Cardiac Valve Surgery Patients

BACKGROUND

Isoflurane, a common anesthetic for cardiac surgery, reduced myocardial contractility in many experimental studies, few studies have determined isoflurane's direct impact on the left ventricular (LV) contractile function during cardiac surgery. We determined whether isoflurane dose-dependently reduces the peak systolic velocity of the lateral mitral annulus in tissue Doppler imaging (S') in patients undergoing cardiac surgery.

METHODS

During isoflurane-supplemented remifentanil-based anesthesia for patients undergoing cardiac surgery with preoperative LV ejection fraction greater than 50% (n = 20), we analyzed the changes of S' at each isoflurane dose increment (1.0, 1.5, and 2.0 minimum alveolar concentration [MAC]: T1, T2, and T3, respectively) with a fixed remifentanil dosage (1.0 μg/min/kg) by using transesophageal echocardiography.

RESULTS

Mean S' values (95% confidence interval [CI]) at T1, T2, and T3 were 10.5 (8.8-12.2), 9.5 (8.3-10.8), and 8.4 (7.3-9.5) cm/s, respectively (P < 0.001 in multivariate analysis of variance test). Their mean differences at T1 vs. T2, T2 vs. T3, and T1 vs. T3 were -1.0 (-1.6, -0.3), -1.1 (-1.7, -0.6), and -2.1 (-3.1, -1.1) cm/s, respectively. Phenylephrine infusion rates were significantly increased (0.26, 0.22, and 0.47 μg/kg/min at T1, T2, and T3, respectively, P < 0.001).

CONCLUSION

Isoflurane increments (1.0-2.0 MAC) dose-dependently reduced LV systolic long-axis performance during cardiac surgeries with a preserved preoperative systolic function.

Impact of temperature on the Narcotrend Index during hypothermic cardiopulmonary bypass in children with sevoflurane anesthesia

Background:

During cardiopulmonary bypass (CPB) in children, anesthesia maintained by sevoflurane administered via the oxygenator is increasingly common. Anesthetic uptake and requirement may be influenced by the non-physiological conditions during hypothermic CPB. Narcotrend-processed EEG monitoring may, therefore, be useful to guide the administration of sevoflurane during this phase.

Objective:

The objective of this prospective, clinical, observational study was to assess the correlation between body temperature, Narcotrend Index (NI) and administered sevoflurane in children during CPB.

Methods:

Forty-four children aged 0 to 10 years undergoing hypothermic cardiac surgery were studied. On bypass, anesthesia was maintained with sevoflurane administered via the oxygenator of the heart-lung machine. Nasopharyngeal temperature, NI and minimum alveolar concentration (MAC) of sevoflurane were recorded in intervals of 10 minutes. Expiratory gas was sampled from the oxygenator’s sole expiratory port via a separate connecting line and the MAC was measured by the agent analyzer of the anesthesia machine.

Results:

Raw (r = 0.74) and corrected (r = 0.73) r-values show that narcosis depth (as indicated by NI) can primarily be explained by the interaction of MAC and temperature. The analysis of variance (without the interaction term) confirms the significant and independent association of both factors, MAC (p<0.004, 95%CI: 0.19 to 0.46) and temperature (p<0.0001, 95%CI: 0.68 to 0.78), with the NI. During hypothermia, sevoflurane had been reduced significantly (r = 0.41, p<0.0001, 95%CI: 0.33 to 0.48).

Conclusion:

Perfusionists and anesthetists should be aware of the results of processed electroencephalograph (EEG) monitoring during CPB. Sevoflurane requirements differ inter-individually; they may decrease during cooling and increase during rewarming. Therefore, it seems reasonable to include the results of processed EEG monitoring when administering sevoflurane during CPB in children, but further studies are necessary to confirm this thesis.

Relationship between Sevoflurane Plasma Concentration, Clinical Variables and Bispectral Index Values during Cardiopulmonary Bypass

Background

Anesthetic administration is increasingly guided by electroencephalography (EEG)-based monitoring, such as the bispectral index (BIS). However, during cardiopulmonary bypass (CPB), factors other than the administered hypnotic agents may influence EEG signals, and their effects on BIS values are unknown.

Methods

This report is a secondary analysis of data from a prospective, controlled interventional study comparing the effect of sevoflurane administration guided by BIS monitoring (group Sevo_BIS) and constant administration of sevoflurane (group Sevo_1.8Vol%) during CPB. Sevoflurane plasma concentration (SPC) was measured using gas chromatography. The relationships of BIS to SPC, CPB pump flow, arterial pressure, hematocrit, temperature, time on CPB, and patient characteristics were analysed.

Results

No association was observed between BIS values and SPC in group Sevo_BIS. In group Sevo_1.8Vol%, a 40 μg ml^-1 increase in SPC, which encompassed the entire range of observed values of the SPC in this analysis, was associated with a decrease of 3.6 (95% confidence interval (CI): 1.1–6.1) in BIS values (p = 0.005). Each increase in CPB time of 10 minutes was associated with an increase in BIS values of 0.25 (95%CI: 0.11–0.39, p<0.001). Path analysis revealed that the BIS values of Sevo_BIS patients were 5.3 (95%CI: 3.2–7.5) units higher than those of Sevo_1.8Vol% patients (p<0.001), which was the strongest effect on BIS values. Path analysis revealed a slope of 0.5 (95%CI: 0.3–0.7) BIS units per 1°C body temperature (p<0.001).

Conclusion

BIS monitoring is insensitive to clinically relevant changes in SPC in individual patients during CPB.

Bispectral index for improving anaesthetic delivery and postoperative recovery

BACKGROUND

The use of clinical signs may not be reliable in measuring the hypnotic component of anaesthesia. The use of bispectral index (BIS) to guide the dose of anaesthetic may have certain advantages over clinical signs. This is the second update of a review originally published in 2007.

OBJECTIVES

The primary objective of this review focused on whether the incorporation of BIS into the standard practice for management of anaesthesia can reduce the risk of intraoperative awareness, consumption of anaesthetic agents, recovery time and total cost of anaesthesia in surgical patients undergoing general anaesthesia.

SEARCH METHODS

In this updated version, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 1), MEDLINE (1990 to 31 January 2013), EMBASE (1990 to 31 January 2013) and reference lists of articles. Previously, we searched to May 2009.

SELECTION CRITERIA

We included randomized controlled trials comparing BIS with standard practice criteria for titration of anaesthetic agents.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality, extracted data and analysed the data. We contacted study authors for further details.

MAIN RESULTS

We included 36 trials. In studies using clinical signs as standard practice, the results demonstrated a significant effect of the BIS-guided anaesthesia in reducing the risk of intraoperative awareness among surgical patients at high risk for awareness (7761 participants; odds ratio (OR) 0.24, 95% confidence interval (CI) 0.12 to 0.48). This effect was not demonstrated in studies using end tidal anaesthetic gas (ETAG) monitoring as standard practice (26,530 participants; OR 1.13, 95% CI 0.56 to 2.26). BIS-guided anaesthesia reduced the requirement for propofol by 1.32 mg/kg/hr (672 participants; 95% CI -1.91 to -0.73) and for volatile anaesthetics (desflurane, sevoflurane, isoflurane) by 0.65 minimal alveolar concentration equivalents (MAC) (95% CI -1.01 to -0.28) in 985 participants. Irrespective of the anaesthetics used, BIS reduced the following recovery times: time for eye opening (2557 participants; by 1.93 min, 95% CI -2.70 to -1.16), response to verbal command (777 participants; by 2.73 min, 95% CI -3.92 to -1.54), time to extubation (1501 participants; by 2.62 min, 95% CI -3.46 to -1.78), and time to orientation (373 participants; by 3.06 min, 95% CI -3.63 to -2.50). BIS shortened the duration of postanaesthesia care unit stay by 6.75 min (1953 participants; 95% CI -11.20 to -2.31) but did not significantly reduce the time to home readiness (329 participants; -7.01 min, 95% CI -30.11 to 16.09).

AUTHORS' CONCLUSIONS

BIS-guided anaesthesia can reduce the risk of intraoperative awareness in surgical patients at high risk for awareness in comparison to using clinical signs as a guide for anaesthetic depth. BIS-guided anaesthesia and ETAG-guided anaesthesia may be equivalent in protection against intraoperative awareness but the evidence for this is inconclusive. In addition, anaesthesia guided by BIS kept within the recommended range improves anaesthetic delivery and postoperative recovery from relatively deep anaesthesia.