End-tidal Sevoflurane Concentration Research Articles

End-tidal concentration of sevoflurane for optimal surgical conditions in pregnant sheep: a pragmatic approach to a retrospective observational study.

The aim of this pragmatic approach to retrospective observational study was to identify the end-tidal concentration of sevoflurane which was associated with optimal surgical conditions (i.e., absence of any movement, coughing and straining) in 127 pregnant sheep. Optimal surgical conditions were observed in 90% of the ewes with an end-tidal concentration of sevoflurane of 2.4 Vol-% [95% CI: 2.2; 2.8] during minimal-mild nociceptive stimuli (placement of arterial catheter, bladder catheter, shaving), with 4.4 Vol-% [95% CI: 4.0; 5.2] during maternal laparotomy and hysterotomy and with 4.4 Vol-% [95% CI: 3.9; 5.8] during subsequent manipulation of the uterus and fetal surgery.

The sevoflurane concentration for light sedation in critically ill patients: A protocol for experimental study

Background: Deep-inhaled sedation is increasingly used in Thai ICUs. However, there is a lack of information regarding the level of end-tidal sevoflurane concentration during light sedation. Objectives: The study aims to determine the effective dose (ED50 and ED95) of sevoflurane concentration for light sedation (RASS score -1 to 0) in mechanically ventilated critically ill patients. Methods: This is a prospective experimental single-center study. Mechanically ventilated patients with RASS ≥ 1 who required sedation in the medical and surgical intensive care unit were enrolled. Using an up-and-down sequential allocation technique, the inhaled sevoflurane level of each patient was allocated based on the previous patient’s response. RASS score and hemodynamic parameters were monitored. The primary outcome was the ED50 and ED 95 of end-tidal sevoflurane concentration. The secondary outcomes included the length of intensive care unit stay, duration of ventilator day, the incidence of delirium, hemodynamic status, and respiratory variables changed during the study period. Hypothesis: There exist specific end-tidal sevoflurane concentrations (ED50 and ED95) that will reliably induce a target RASS score of -1 to 0 in critically ill patients who are mechanically ventilated. Conclusion: This study will provide an effective dose of inhaled sevoflurane sedation for achieving targeted light sedation levels in critically ill patients, which may have minimal effects on hemodynamics. Ethics and dissemination: This study has been approved by the Office of Human Research Ethics Committee, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Thailand, on 22nd May 2023 (COA.MURA2023/390). Trial registration: TCTR20230825001

Anesthesia Practitioners' Goals for Sevoflurane Minimum Alveolar Concentration at the End of Surgery and the Incidence of Prolonged Extubations: A Prospective and Observational Study.

Prolonged times to tracheal extubation (≥15 minutes from dressing on the patient) are consequential based on their clinical and economic effect. We evaluated the variability among anesthesia practitioners in their goals for the age-adjusted end-tidal minimum alveolar concentration ofsevoflurane (MAC) at surgery end and achievement of their goals. We prospectively studied a cohort of 56 adult patients undergoing general anesthesia with sevoflurane as the sole anesthetic agent, scheduled operating room time of at least 3 hours, and non-prone positioning. At the start of surgical closure, an observer asked the anesthesia practitioner their goal for MAC when the surgical drapes are lowered (i.e., the functional end of surgery for the studied procedures). When the drapes were lowered, the MAC achieved was recorded, and the values were compared. The standard deviation of the practitioners' MAC goal was large, 0.199 (N = 56 cases, 95% confidence interval 0.17-0.24), not significantly different from the standard deviation of the MAC achieved of0.253, P= 0.071. The MAC goal and MAC achieved were correlated pairwise, Pearson r=0.65, P< 0.0001. There was no incremental effect of operating room conversation(s) related tocase progress on the association (partial correlation ‑0.01, P= 0.96). Differences among practitioners in the MAC achieved at surgery end were consequential. Specifically, for the N = 12cases with prolonged extubation, the mean MAC was 0.60 (standard deviation 0.10) versus 0.48 (0.21) among the N = 44 cases without prolonged extubation (P = 0.0070). The standard deviation ofthe MAC goal among practitioners was sufficiently large to contribute significantly tothe variability in the MAC achieved at the end of surgery. We confirmed prospectively that the age-adjusted end-tidal MAC at the end of surgery matters clinically and economically because differences of0.60 versus 0.48 were associated with more prolonged extubations. Our novel finding isthat the MAC achieved ≥0.60 werecaused in part by the anesthesia practitioners' stated MAC goals when surgical closures started.

Relationship between intraoperative requirement for anesthetics and postoperative analgesic consumption in laparoscopic colectomy: a randomized controlled double-blinded study.

This study investigated the relationship between intraoperative requirement for an inhalational anesthetic (sevoflurane) or an opioid (remifentanil) and postoperative analgesic consumption. The study included 200 adult patients undergoing elective laparoscopic colectomy. In the sevoflurane group, the effect-site concentration of remifentanil was fixed at 1.0 ng/ml, while the inspiratory sevoflurane concentration was adjusted to maintain an appropriate anesthetic depth. In the remifentanil group, the end-expiratory sevoflurane concentration was fixed at 1.0 vol.%, and the remifentanil concentration was adjusted. Pain scores and cumulative postoperative analgesic consumptions were evaluated at 2, 6, 24, and 48 h after surgery. Average end-tidal concentration of sevoflurane and effect-site concentration of remifentanil were 2.0 ± 0.4 vol.% and 3.9 ± 1.4 ng/ml in the sevoflurane and remifentanil groups, respectively. Cumulative postoperative analgesic consumption at 48 h postoperatively was 55 ± 26 ml in the sevoflurane group and 57 ± 33 ml in the remifentanil group. In the remifentanil group, the postoperative cumulative analgesic consumptions at 2 and 6 h were positively correlated with intraoperative remifentanil requirements (2 h: r = 0.36, P < 0.001; 6 h: r = 0.38, P < 0.001). However, there was no significant correlation in the sevoflurane group (r = 0.04, P = 0.691). The amount of intraoperative requirement of short acting opioid, remifentanil, is correlated with postoperative analgesic consumption within postoperative 6 h. It may be contributed by the development of acute opioid tolerance. However, intraoperative sevoflurane requirement had no effect on postoperative analgesic consumption.

Effective concentration (EC50) of sevoflurane for intraocular pressure measurement in anaesthetised children with glaucoma: A dose-finding study.

Sevoflurane, a preferred anaesthetic for children, exhibits a dose-dependent reduction in intraocular pressure (IOP). However, consensus is lacking regarding optimal end-tidal sevoflurane concentration for safe IOP measurement. This study aimed to identify the concentration at which IOP measurement could be attempted without inducing movements in paediatric patients after inhalational induction. Two paediatric groups (1-12 months and 12-36 months) with glaucoma undergoing examination under anaesthesia were recruited. After induction with 8% sevoflurane and 100% oxygen, the first child had an end-tidal sevoflurane concentration maintained at 2% for 4 min, followed by IOP measurement. Success was defined as 'no movement', and subsequent concentrations (adjusted in 0.2% steps) were determined using the Dixon and Massey method based on the previous patient's responses. The study included 75 children. The effective concentration of sevoflurane causing 'no movement' during IOP measurement in 50% of the study population for successful IOP measurement was 1.98% (95% confidence interval [CI] 1.63, 2.17, P = 0.017) for 1-12 months group and 0.55% (95% CI 0.39, 0.66, P = 0.002) for 12-36 months group. Probit regression analysis yielded effective concentration of sevoflurane causing 'no movement' during IOP measurement in 95% of the study population values of 2.47% (95% CI 2.24, 4.58, P = 0.017) for 1-12 months group and 0.94% (95% CI 0.78, 1.57, P = 0.002) for 12-36 months group. In paediatric patients, a higher end-tidal sevoflurane concentration of 2% is needed for IOP measurement in 1-12 months age group compared to 0.5% required in 12-36 months age group, achieving success in 50% of the study population.

Effect of Inhaled Sevoflurane on Pediatric Cerebrospinal Fluid Pressure During Lumbar Puncture; Implications for Intracranial Hypertension.

Objective: To determine influence of sevoflurane on changes in cerebrospinal fluid pressure in children presenting for lumbar puncture. Methods: Cerebrospinal fluid pressure, end tidal carbon dioxide, and end tidal sevoflurane concentration measurements were obtained at 2-minute intervals for a total of 10 minutes (T0 to T5). Because of concerns regarding patient safety and comfort, the study measurements were completed at the end of the lumbar procedure, starting with the closing pressure and when sevoflurane was stopped. Results: As end tidal sevoflurane concentration decreased, cerebrospinal fluid pressure initially increased up to T2 before decreasing back to around the initial point. There was no significant correlation between sevoflurane level and cerebrospinal fluid pressure. Both weight status and presence or absence of optic edema did not have a significant impact on pressure over time. However, there was a statistically significant difference in the cerebrospinal fluid pressure over time between those with spontaneous respirations compared to those without. Conclusions: There was no significant correlation between the end tidal sevoflurane concentration and cerebrospinal fluid pressure. Assisted ventilation did produce a statistically significant increase in cerebrospinal fluid pressure and suggests that the most accurate measurements are in those with spontaneous respirations.

Application of Machine Learning Strategies to Model the Effects of Sevoflurane on Somatosensory-Evoked Potentials during Spine Surgery

In this study, a small sample of patients’ neuromonitoring data was analyzed using machine learning (ML) tools to provide proof of concept for quantifying complex signals. Intraoperative neurophysiological monitoring (IONM) is a valuable asset for monitoring the neurological status of a patient during spine surgery. Notably, this technology, when operated by neurophysiologists and surgeons familiar with proper alarm criteria, is capable of detecting neurological deficits. However, non-surgical factors, such as volatile anesthetics like sevoflurane, can negatively influence robust IONM signal generation. While sevoflurane has been shown to affect the latency and amplitude of somatosensory evoked potential (SSEP), a more complex and nuanced analysis of the SSEP waveform has not been performed. In this study, signal processing and machine learning techniques were used to more intricately characterize and predict SSEP waveform changes as a function of varying end-tidal sevoflurane concentration. With data from ten patients who underwent spinal procedures, features describing the SSEP waveforms were generated using principal component analysis (PCA), phase space curves (PSC), and time-frequency analysis (TFA). A minimum redundancy maximum relevance (MRMR) feature selection technique was then used to identify the most important SSEP features associated with changing sevoflurane concentrations. Once the features carrying the maximum amount of information about the majority of signal waveform variability were identified, ML models were used to predict future changes in SSEP waveforms. Linear regression, regression trees, support vector machines, and neural network ML models were then selected for testing. Using SSEP data from eight patients, the models were trained using a range of features selected during MRMR calculations. During the training phase of model development, the highest performing models were identified as support vector machines and regression trees. After identifying the highest performing models for each nerve group, we tested these models using the remaining two patients’ data. We compared the models’ performance metrics using the root mean square error values (RMSEs). The feasibility of the methodology described provides a general framework for the applications of machine learning strategies to further delineate the effects of surgical and non-surgical factors affecting IONM signals.

Variability of predicted propofol concentrations and measured sevoflurane concentrations during general anaesthesia: a single-centre retrospective cohort study

BackgroundVariability is high in predicted propofol concentrations during clinical anaesthesia titrated by target-controlled infusion (TCI) to maintain a processed EEG parameter (bispectral index [BIS]) within a specified range. We have shown that the potential for improving the pharmacokinetic model is minimal. The drug titration paradox revealed that titration challenges the classical relationship between drug dose and effect in both individuals and the population. We hypothesised that dynamic factors during surgery beyond the static genetic, epigenetic, and other factors such as age, height, and weight affect the necessary dose. We compared the variability of measured end-tidal sevoflurane concentrations with predicted effect-site propofol concentrations when titrated to a BIS range of 40–60, with the hypothesis that the variability in measured sevoflurane concentrations would not be less than the variability in estimated propofol concentrations. MethodsClinical data from 2280 surgical procedures >1 h in duration were included in the analysis. Anaesthesia with sevoflurane or propofol was based on an institutional protocol. The titration performance for both drugs was assessed by comparing BIS values 30 min after skin incision. The variability of the required concentrations at the same time point was calculated and compared. ResultsThe achieved 30-min post-incision BIS ranges were not significantly different for sevoflurane or propofol TCI (30 [99% CI: 28–33] and 31 [99% CI: 27–36], respectively). The variability of sevoflurane concentrations was not significantly different from measured predicted propofol concentrations during BIS-guided anaesthesia (normalized concentration range of 0.89 [99% CI: 0.78–0.99] and 0.93 [99% CI 0.87–1.02). ConclusionsImprovements in prediction accuracy of pharmacokinetic models beyond that of those already in clinical use are unlikely to reduce variability in target anaesthetic concentrations across patients in clinical practice.

Effects of automatic gas control on sevoflurane gas monitor and recovery during pancreatico-duodenectomy operation: prospective randomized study

ABSTRACT Background The aim of the study was to evaluate the effect of automatic gas control (AGC) on sevoflurane gas monitoring, safety, and recovery of patients during pancreatico-duodenectomy operation. Methods Forty patients scheduled for the pancreatico-duodenectomy operation were allocated into group I manual gas control group (MGC, n = 20) and group II AGC (n = 20) group. In (the MGC group): The vaporizer set ranged from 3 to 5% Sevoflurane until reaching 1 MAC, fresh gas flow (FGF) 1–2 L/min, and FiO2 of 0.4 was set. In (the AGC group): Set target FiO2 of 0.4, end-tidal anesthetic agent (EtSev was set to 1.5–2%) with safely ventilate the patient with an FGF down to 0.3 liters per minute. Hemodynamics, anesthesia gas analysis (FiSev, EtSev, FiO2, and EtO2), total gas consumption, extubation time, incidence of perioperative hypercapnia, hypoxia, and accidental awareness were recorded. Results The volume of sevoflurane administered in the MGC group was in a mean ± standard deviation of 81.20 ± 16.47 ml which was statistically significantly greater than that administered in the AGC group (58.80 ± 10.54), P ≤ 0.001. ETSevo, FISevo, and the EtO2 were significantly larger in the MGC group than in the AGC group. The extubation time was statistically prolonged in the MGC group than in the AGC group (14.10 ± 4.75 versus 7.70 ± 1.59 min, P < 0.001). No patient developed hypoxia, hypercapnia, or awareness in both groups. Conclusion AGC maintained the targeted end-tidal sevoflurane concentration with the least sevoflurane consumption. It reduced the manual adjustment of delivered sevoflurane and oxygen. General anesthesia with manual and AGC is safe and maintains hemodynamic stability.

Laryngeal mask airway facilitates a safe and smooth emergence from anesthesia in patients undergoing craniotomy: a prospective randomized controlled study

BackgroundEndotracheal extubation under deep anesthesia (deep extubation) has been proved to present stable hemodynamics and steady intracranial pressure during emergence from anesthesia in patients undergoing craniotomy. This study aims to examine, in comparison with deep extubation, if a laryngeal mask airway (LMA) could provide a safer and smoother emergence from anesthesia in patients undergoing craniotomy.MethodsThis prospective randomized controlled study was conducted on patients undergoing elective craniotomy for brain tumors. After the complement of the surgical procedure, the patients had anesthesia maintained with end-tidal sevoflurane concentration 2.5% and also fully regained muscle power (Time Zero), they were randomly assigned to ETT Group (n = 29) for deep extubation or to LMA Group (n = 29), where the endotracheal tube was replaced by a laryngeal mask airway. The primary outcomes were respiratory complications, airway interventions and hemodynamic changes through emergence from anesthesia till 30 min following Time Zero. The secondary outcomes were re-operation incidence in 24 h, stay time in the intensive care unit and postoperative hospital days.ResultsAt 5 min before Time Zero either oxygen partial pressures (PaO2) or carbon dioxide partial pressures (PaCO2) between the two groups were comparable. No significant PaCO2 change was noted in both groups in 5 min after Time Zero, yet there was a remarkably lower PaO2 in ETT Group at that time point, 188.9 (± 71.1) in ETT Group vs 264.4 (± 85.4) in LMA Group. In ETT Group, coughs and snores were considerably more frequent, and thus more interventions were needed to maintain adequate respiration. From Time Zero on, blood pressures (systolic, diastolic and mean) and heart rates in ETT Group were generally higher than those in LMA Group, but the differences were insignificant at all time points except heart rate at 10 min after Time Zero. The secondary outcomes between the two groups were similar.ConclusionsCompared with deep extubation, a LMA, as a temporary airway replacement, facilitates a safer and smoother emergence from anesthesia for patients undergoing craniotomy, in terms of better oxygen saturation, fewer respiratory complications and fewer airway interventions.Trial registrationThe study was conducted after receiving approval from Institutional Review Board of Chang Gung Memorial Hospital, Linkou Branch, Taiwan (registration number 202102115A3; January 27, 2022), and the clinicaltrials.gov (NCT05253404) on 23 February 2022.

LMA Protector ve Baska Maskın Retrograd Üreteroskopik Cerrahide Karşılaştırılması: Prospektif Randomize Klinik Çalışma

Objective: The Baska and the Protector Laryngeal masks are single-use second-generation supraglottic airway devices with a dual gastric channel. Material and Methods: 64 American Society of Anesthesiologists physical status 1-2 patients between the ages of 18-70 undergoing retrograde ureteroscopic surgery enrolled in this prospective randomized study. Results: Demographic airway variables and airway characteristics were similar between the groups. Insertion time was shorter in the Baska mask group [14 (11-20) versus 20 (13-27) seconds, p=0.035]. The need for optimization maneuvers during insertion was higher for the Baska mask group (p=0.009). The laryngeal mask airway (LMA) insertion was easier in the LMA Protector group (p=0.023). The first insertion success rate was 75% for the LMA Protector and 84% in the Baska mask. The total success rate of both devices was 91%. Nasogastric tube insertion was faster in the Baska mask group [14 (12-15) versus 17 (13-25) seconds; p=0.003]. Fiberoptic views were similar between the groups. Minute volume after insertion of the device was higher in the LMA Protector group [8 (6.5-10) L/min versus 6 (5-7) L/min; p<0.001]. Expiratory tidal volume was higher in the LMA Protector group after insertion of the device, 15 minutes, 30 minutes, and 45 minutes after insertion (p<0.001, p=0.032, p=0.001, p=0.027 respectively). The end-tidal sevoflurane concentration (ETsevo) 30 minutes after device insertion was higher in the Baska mask group (1.49±0.38 vs 1.75±0.36; p=0.014). Conclusion: The LMA Protector is superior to the Baska mask in providing higher tidal volumes and decreased need for optimization maneuvers in retrograde ureteroscopic surgery.

An integrated information theory index using multichannel EEG for evaluating various states of consciousness under anesthesia

Background:The integrated information theory (IIT) of consciousness introduces a measure Φ to quantify consciousness in a physical system. Directly related to this, general anesthesia aims to induce reversible and safe loss of consciousness (LOC). We sought to propose an electroencephalogram (EEG)-based IIT index ΦEEG to evaluate various states of consciousness under general anesthesia. Methods:Based on the definition of mutual information, we estimated the ΦEEG by maximizing the integrated information under various time lags. We used the binning method to cut the nonGaussian EEG data for estimating mutual information. We tested two EEG databases collected from propofol- (n=20) and sevoflurane-induced (n=15) anesthesia, and especially, we compared the ΦEEG of drowsy (n=7) and responsive participants (n=13) under propofol anesthesia. We compared the effectiveness of ΦEEG with the estimated bispectral index (eBIS). Results:In all EEG frequency bands, we observed a negative correlation between ΦEEG and end-tidal sevoflurane concentration under sevoflurane-induced anesthesia (p<0.001,BF10>6000). Under propofol-induced anesthesia, drowsy participants in moderate sedation (6.96±0.26(mean±SD)) showed decreased alpha-band ΦEEG compared with baseline (7.40±0.53,p=0.016,BF10=3.58), no significant difference was observed for responsive participants. Oppositely, the responsive participants in moderate sedation (−5.32±0.38) showed decreased eBIS compared with baseline (−4.94±0.40,p=0.03,BF10=2.41). Conclusions:These findings may enable monitors of the anesthetic state that can distinguish consciousness and unconsciousness rather than the changes of anesthetic concentrations. The alpha-band ΦEEG is promising for deriving the gold standard for depth of anesthesia monitoring.

The effect of remifentanil infusion on sevoflurane minimum alveolar concentration–no movement (MACNM) and bispectral index in dogs

ObjectiveTo determine the effect of remifentanil infusion on the minimum alveolar concentration of sevoflurane preventing movement (SEVOMACNM) and bispectral index (BIS) in dogs. Study designProspective, unmasked study. AnimalsA total of 10 adult Beagle dogs weighing 9.0 ± 1.1 kg. MethodsDogs were anesthetized with sevoflurane and baseline SEVOMACNM was determined. Remifentanil was infused at 5, 10 and 20 μg kg–1 hour–1, in sequence, with 20 minutes washout between infusions. Variables monitored throughout anesthesia included heart rate (HR), oscillometric blood pressure, end-tidal partial pressure of carbon dioxide, end-tidal sevoflurane concentration (Fe′Sevo) and BIS. SEVOMACNM after remifentanil infusion (SEVOMACNM-REMI) determination started 20 minutes after the start of each infusion. Venous blood samples were collected for plasma remifentanil concentration determination at baseline, SEVOMACNM-REMI determination time points, and 20 minutes after each infusion was stopped. A mixed model analysis was used to determine the effect of remifentanil infusion on response variables. The relationships between BIS and Fe′Sevo, plasma remifentanil concentrations and the percentage decrease in baseline SEVOMACNM were evaluated (p < 0.05). ResultsThe overall SEVOMACNM at baseline was 2.47 ± 0.11%. Addition of remifentanil at all infusion rates significantly decreased SEVOMACNM, but the medium and high doses resulted in significantly greater decreases in SEVOMACNM than the lower dose. There was no difference in SEVOMACNM percentage change between infusions 10 and 20 μg kg–1 hour–1. Plasma remifentanil concentrations were significantly different in all infusion rates. Baseline BIS value was 70 ± 1 and was lower than the BIS values recorded during all remifentanil infusions. BIS values were not significantly different among infusion rates. HR was lower and mean arterial pressure was higher during remifentanil infusions than at baseline. Conclusions and clinical relevanceAll remifentanil infusions decreased SEVOMACNM in dogs. Remifentanil infusion at any rate studied did not reduce BIS values.

50% effective concentration of sevoflurane for immobility in cerebral palsy children undergoing botulinum toxin injection.

Background:This prospective study aimed to determine the optimum end-tidal sevoflurane concentration required for immobility during botulinum toxin injection in spontaneously breathing children with cerebral palsy (CP).Methods:Twenty-three children with spastic CP, aged 3 to 12 years, with American Society of Anesthesiologists (ASA) physical status I and II, scheduled to receive botulinum toxin type A injection were enrolled in the study. After induction of deep sedation using pre-filled 8% sevoflurane in oxygen and maintenance of the predetermined end-tidal sevoflurane concentration, the botulinum toxin was injected in spontaneously breathing children. The response to the botulinum toxin injection was classified as “movement” or “no movement” by an independent investigator who was blinded to the predetermined end-tidal sevoflurane concentration and bispectral index (BIS) value. The end-tidal sevoflurane concentration was predetermined, initiating at 2.0% with 0.2% as a step size in the next patient depending on the previous patient’s response using the modified Dixon’s up-and-down method.Results:Of 21 children, 12 (57.1%) showed “no movement” in response to the botulinum toxin injection. By Dixon’s up-and-down method, the 50% effective end-tidal concentration (EC50) of sevoflurane for successful botulinum toxin injection was 1.76 ± 0.15% (95% CI 1.62–1.90). Based on the dose‐response curve using probit analysis, the predicted EC50 and 95% effective end-tidal concentrations (EC95) of sevoflurane without movement were 1.77% (95% CI 1.59–2.35) and 2.09% (95% CI 1.89–5.80), respectively.Conclusion:Botulinum toxin injection can be successfully accomplished at an end-tidal sevoflurane concentration of 1.76 ± 0.15% in 50% of spontaneously breathing children with CP aged 3–12 years.

The depth of anesthesia under sevoflurane can be monitored based on calling names language paradigm and Ag/AgCl electrooculogram electrode

In the depth of anesthesia monitoring, electrooculogram is usually treated as an artifact of EEG. However, the amplitude of the electrooculogram is much greater than that of electroencephalography. Its requirements for electrode materials and detection circuits are also far lower than electroencephalography. In this prospective cohort study, we use a new language paradigm that elicited rhythmic ocular muscle activity to explore whether the electrooculogram can be used for monitoring the depth of anesthesia. Thirty-three patients inhaled sevoflurane via a laryngeal mask for induction of anesthesia. According to the end-tidal sevoflurane concentration, patients were studied under three depth of sedation. Throughout all periods, the rhythmic calling of the patient’s own name script was sporadically played at a frequency of 0.5 Hz. We found that the electrooculogram was synchronized to the language paradigm during induction with sevoflurane, and the Ag/AgCl electrode has a significantly higher signal-to-noise ratio and 0.5 hz spectral peak value than other electrode. With the increase in the sevoflurane concentration, the synchronizing ability gradually weakened and eventually disappeared. Based on this evidence, we proposed a new method that can improve the performance of the anesthesia prediction monitoring model.

Effects of vatinoxan in dogs premedicated with medetomidine and butorphanol followed by sevoflurane anaesthesia: a randomized clinical study

ObjectiveTo investigate effects of vatinoxan in dogs, when administered as intravenous (IV) premedication with medetomidine and butorphanol before anaesthesia for surgical castration. Study designA randomized, controlled, blinded, clinical trial. AnimalsA total of 28 client-owned dogs. MethodsDogs were premedicated with medetomidine (0.125 mg m−2) and butorphanol (0.2 mg kg−1) (group MB; n = 14), or medetomidine (0.25 mg m−2), butorphanol (0.2 mg kg−1) and vatinoxan (5 mg m−2) (group MB-VATI; n = 14). Anaesthesia was induced 15 minutes later with propofol and maintained with sevoflurane in oxygen (targeting 1.3%). Before surgical incision, lidocaine (2 mg kg−1) was injected intratesticularly. At the end of the procedure, meloxicam (0.2 mg kg−1) was administered IV. The level of sedation, the qualities of induction, intubation and recovery, and Glasgow Composite Pain Scale short form (GCPS-SF) were assessed. Heart rate (HR), respiratory rate (fR), mean arterial pressure (MAP), end-tidal concentration of sevoflurane (Fe′Sevo) and carbon dioxide (Pe′CO2) were recorded. Blood samples were collected at 10 and 30 minutes after premedication for plasma medetomidine and butorphanol concentrations. ResultsAt the beginning of surgery, HR was 61 ± 16 and 93 ± 23 beats minute−1 (p = 0.001), and MAP was 78 ± 7 and 56 ± 7 mmHg (p = 0.001) in MB and MB-VATI groups, respectively. No differences were detected in fR, Pe′CO2, Fe′Sevo, the level of sedation, the qualities of induction, intubation and recovery, or in GCPS-SF. Plasma medetomidine concentrations were higher in group MB-VATI than in MB at 10 minutes (p = 0.002) and 30 minutes (p = 0.0001). Plasma butorphanol concentrations were not different between groups. Conclusions and clinical relevanceIn group MB, HR was significantly lower than in group MB-VATI. Hypotension detected in group MB-VATI during sevoflurane anaesthesia was clinically the most significant difference between groups.

EEG-Parameter-Guided Anesthesia for Prevention of Emergence Delirium in Children.

Background: Emergence delirium (ED) usually occurs in children after surgery with an incidence of 10−80%. Though ED is mostly self-limited, its potential injuries cannot be ignored. Whether electroencephalography (EEG)-parameter-guided anesthesia could reduce the incidence of ED in pediatric surgery has not been fully discussed to date. Methods: Fifty-four boys aged 2–12 years undergoing elective hypospadias surgery under sevoflurane anesthesia were selected. In the EEG-parameter-guided group (E group), sevoflurane was used for anesthesia induction and was maintained by titrating the spectral edge frequency (SEF) to 10–15 and combining the monitoring of density spectral array (DSA) power spectra and raw EEG. While in the control group (C group), anesthesiologists were blinded to the SedLine screen (including SEF, DSA, and raw EEG) and adjusted the intraoperative drug usage according to their experience. Patients with a Pediatric Anesthesia Emergence Delirium (PAED) score > 10 were diagnosed with ED, while patients with a PAED score > 2 were diagnosed with emergence agitation (EA). Results: Finally, a total of 37 patients were included in this trial. The incidence of ED in the E group was lower than in the C group (5.6% vs. 36.8%; p = 0.04), while the incidence of EA was similar in the two groups (61% vs. 78.9%; p = 0.48). Intraoperative parameters including remifentanil dosage and the decrease in mean arterial pressure (MAP) were not different between the two groups (p > 0.05), but the mean end-tidal sevoflurane concentration (EtSevo) was lower in the E group than in the C group (p > 0.05). Moreover, during PACU stay, the extubation time and discharge time of the groups were similar, while the PAED scores within 5 min from extubation and the Face, Legs, Activity, Cry, and Consolability (FLACC) scores within 30 min from extubation were lower in the E group than in the C group. Conclusion: EEG-parameter-guided anesthesia management reduced the incidence of ED in children. Studies with larger sample sizes are needed to obtain more convincing results.

Minimal alveolar concentration of sevoflurane in combination with dexmedetomidine in patients with hysteroscopy: An up-down sequential allocation study.

Dexmedetomidine is commonly used in hysteroscopy surgery due to its analgesia and sedation without respiratory depression. Many studies have shown that dexmedetomidine can reduce the consumption of sevoflurane. However, the optimal end-tidal concentration of sevoflurane when it is co-administered with dexmedetomidine has not been established. The primary purpose of this study was to investigate the minimal alveolar concentration (MAC) of sevoflurane for cervical dilatation combined with different doses of dexmedetomidine in patients with hysteroscopy surgery. One-hundred patients undergoing hysteroscopy surgery were enrolled in this clinical trial. All the patients were randomly assigned into four groups (C, D1 , D2 , D3 ) and received a loading dose of dexmedetomidine (0, 0.6, 0.8 and 1.0μg/kg) over 10min before anaesthesia induction, respectively. Anaesthesia was induced in each patient with 5% sevoflurane in 100% oxygen via a facemask. A laryngeal mask (LMA) was inserted when the patient had lost consciousness and the BIS value decreased below 40. The response to cervical dilatation stimulus (movement vs non-movement) by the insert of hysteroscope was recorded. The MAC of sevoflurane was measured by up and down sequential method of Dixon and Mood and centred isotonic regression analysis. The calculated MAC of sevoflurane using up-and-down method of Dixon and Mood in patients with hysteroscopy surgery was (1.90 ± 0.13)%, (1.23 ± 0.16)%, (1.03 ± 0.10)% and (0.93 ± 0.08)% in groups C, D1 , D2 and D3 , respectively. The administration of dexmedetomidine can significantly decrease the MAC of sevoflurane for hysteroscopy surgery. However, a ceiling effect of the reduction was observed when the dose of dexmedetomidine was higher than 0.8μg/kg.

Sevoflurane requirements during electroencephalogram (EEG)-guided vs standard anesthesia Care in Children: A randomized controlled trial

Study ObjectivesIntra-operative electroencephalographic (EEG) monitoring utilizing the spectrogram allows visualization of children's brain response during anesthesia and may complement routine cardiorespiratory monitoring to facilitate titration of anesthetic doses. We aimed to determine if EEG-guided anesthesia will result in lower sevoflurane requirements, lower incidence of burst suppression and improved emergence characteristics in children undergoing routine general anesthesia, compared to standard care. DesignRandomized controlled trial. SettingTertiary pediatric hospital. Patients200 children aged 1 to 6 years, ASA 1 or 2, undergoing routine sevoflurane anesthesia for minor surgery lasting 30 to 240 min. InterventionsChildren were randomized to either EEG-guided anesthesia (EEG-G) or standard care (SC). EEG-G group had sevoflurane titrated to maintain continuous slow/delta oscillations on the raw EEG and spectrogram, aiming to avoid burst suppression and, as far as possible, maintain a patient state index (PSI) between 25 and50. SC group received standard anesthesia care and the anesthesia teams were blinded to EEG waveforms. MeasurementsThe primary outcomes were the average end-tidal sevoflurane concentration during induction and maintenance of anesthesia. Secondary outcomes include incidence and duration of intra-operative burst suppression and Pediatric Anesthesia Emergence Delirium (PAED) scores. ResultsThe EEG-G group received lower end-tidal sevoflurane concentrations during induction [4.80% vs 5.67%, −0.88% (−1.45, −0.31) p = 0.003] and maintenance of anesthesia [2.23% vs 2.38%, −0.15% (−0.25, −0.05) p = 0.005], and had a lower incidence of burst suppression [3.1% vs 10.9%, p = 0.044] compared to the SC group. PAED scores were similar between groups. Children <2 years old required higher average end-tidal sevoflurane concentrations, regardless of group. ConclusionsEEG-guided anesthesia care reduces sevoflurane requirements in children undergoing general anesthesia, possibly lowering the incidence of burst suppression, without altering emergence characteristics. EEG monitoring allows direct visualization of brain responses in real time and allows clearer appreciation of varying sevoflurane requirements in children of different ages.

Laparoscopic versus Open Ovariectomy in Bitches: Changes in Cardiorespiratory Values, Blood Parameters, and Sevoflurane Requirements Associated with the Surgical Technique.

Simple SummaryLaparoscopic neutering techniques are widely used in veterinary medicine due to their numerous advantages compared to open ones. However, laparoscopy requires the creation of pneumoperitoneum to establish a working space, and it has been related to the occurrence of pathophysiological alterations. The objective of this study was to evaluate the potential global systemic changes associated to the establishment of the pneumoperitoneum in laparoscopic ovariectomy and to compare them with those determined in conventional open surgery in dogs. Additionally, we evaluated the gas anesthetic requirements based on the surgical technique. The results of our study suggested that the cardiorespiratory alterations related to pneumoperitoneum seemed to be well-tolerated and reversible after CO2 deflation. Regarding the anesthetic gas evaluation, we determined higher requirements during ovarian resection in the open ovariectomy group. In conclusion, laparoscopic neutering procedures should be currently recommended by veterinarians due to their lower invasiveness and resulting complications. Nevertheless, a thorough understanding of the changes associated with pneumoperitoneum is essential to plan and obtain an adequate perioperative management.The aim of this study was to examine the cardiorespiratory and blood changes associated with pneumoperitoneum (PNP) in laparoscopic ovariectomy (LAP Ove), as well as sevoflurane requirements, comparing them to those determined in open surgery (LPT Ove). The study was performed in 16 bitches submitted to LAP or LPT Ove. The cardiorespiratory and end-tidal sevoflurane concentration values were recorded as follows: at the beginning of surgery (T1), after the right ovary resection (T2), after the left ovary resection (T3), and after surgical closure (T4). Blood samples were taken before and after PNP. Among the cardiorespiratory parameters, no differences were observed in the values of end-tidal CO2, minute volume, and heart rate. In the LAP Ove group, a significant increase in inspiratory pressures and a decreased compliance were identified at T2 and T3. Significant higher arterial pressure values were observed in both groups at T2 and T3, with this increase especially marked at T2 in the LPT Ove group. Sevoflurane requirements were significantly higher in the LPT group during ovarian resection. Finally, in terms of the hematochemical parameters, statistical differences were recorded between pre- and post-operative assessments, but not between both surgical groups. The pathophysiological effects associated with PNP seemed to be transient and well-tolerated by healthy dogs.