Are intrinsic neural timescales related to sensory processing? Evidence from abnormal behavioral states

The brain exhibits a complex temporal structure which translates into a hierarchy of distinct neural timescales. An open question is how these intrinsic timescales are related to sensory or motor information processing and whether these dynamics have common patterns in different behavioral states. We address these questions by investigating the brain's intrinsic timescales in healthy controls, motor (amyotrophic lateral sclerosis, locked-in syndrome), sensory (anesthesia, unresponsive wakefulness syndrome), and progressive reduction of sensory processing (from awake states over N1, N2, N3). We employed a combination of measures from EEG resting-state data: auto-correlation window (ACW), power spectral density (PSD), and power-law exponent (PLE). Prolonged neural timescales accompanied by a shift towards slower frequencies were observed in the conditions with sensory deficits, but not in conditions with motor deficits. Our results establish that the spontaneous activity's intrinsic neural timescale is related to the neural capacity that specifically supports sensory rather than motor information processing in the healthy brain.

Frontal electroencephalogram activity during emergence from general anaesthesia in children with and without emergence delirium

BACKGROUND

Emergence delirium (ED) in children after general anaesthesia causes significant distress in patients, their family members, and clinicians; however, electroencephalogram (EEG) markers predicting ED have not been fully investigated.

METHODS

This prospective, single-centre observational study enrolled children aged 2-10 yr old under sevoflurane anaesthesia. ED was assessed according to Diagnostic and Statistical Manual of Mental Disorders (DSM) IV or 5 criteria. The relative power of low-frequency (delta and theta) and high-frequency (alpha and beta) EEG waves during the emergence period was compared between the children with and without ED. The linear relationships between the relative power and peak Paediatric Assessment of Emergence Delirium (PAED) score were investigated.

RESULTS

Among the 60 patients, 22 developed ED (ED group), whereas the other 38 did not (non-ED group). The relative power of the delta wave was higher (mean [standard deviation], 0.579 [0.083] vs 0.453 [0.090], respectively, P<0.001) in the ED group, whereas that of the alpha and beta waves was lower in the ED group, than in the non-ED group (0.155 [0.063] vs 0.218 [0.088], P=0.005 and 0.114 [0.069] vs 0.186 [0.070], P<0.001, respectively). The areas under the receiver operating characteristic curves of the relative power of the delta wave, low-to-high frequency power ratio, and delta-to-alpha ratio were 0.837 (95% confidence interval, 0.737-0.938), 0.835 (0.735-0.934), and 0.768 (0.649-0.887), respectively. The relative power of the delta wave and the two ratios had a positive linear relationship with the peak PAED scores.

CONCLUSIONS

Paediatric patients developing ED have increased low-frequency (delta) frontal EEG activity with reduced high-frequency (alpha and beta) activity during emergence from general anaesthesia.

CLINICAL TRIAL REGISTRATION

NCT03797274.

[Influence of Halogenated Hydroxyl-Alkanes Inhalation Anesthetic on the Determination of Ethanol Content in Blood]

Objective To study the influence of halogenated hydroxyl-alkanes inhalation anesthetic on the determination of ethanol content in blood. Methods Halogenated hydroxyl-alkanes were analyzed by headspace gas chromatography with double column confirmatory detection method. The influence of halogenated hydroxyl-alkanes on determination of ethanol content in blood sample by headspace gas chromatography was explored under the different detection conditions of KB-BAC1/ KB-BAC2 and J&W DB-ALC1/DB-ALC2 gas chromatographic column. Results The retention time of sevoflurane and enflurane was similar to that of ethanol and tert butanol respectively when using the J&W DB-ALC1/DB-ALC2 gas chromatographic column, and interfered with the detection of ethanol content in blood; only J&W DB-ALC1 gas chromatographic column can separate the sevoflurane and ethanol components, so as to eliminate their influence on the detection of ethanol content in blood. When using KB-BAC1/KB-BAC2 gas chromatographic column, the retention time of sevoflurane, isoflurane and ethanol is similar, especially that of sevoflurane and ethanol, and sevoflurane obviously interferes with the determination of ethanol content in blood. Conclusion Halogenated hydroxy-alkanes interfere with determination of ethanol content in blood by headspace gas chromatography. The interference can be discriminated effectively by choosing the suitable chromatographic column and double column confirmatory detection.

Opioid-free anesthesia under single injection paravertebral block combined with sevoflurane for pediatric renal surgery: a prospective observational pilot study

Even though several studies have demonstrated the effectiveness of opioid free anesthesia (OFA) strategies in pediatric patients, OFA has not been studied in pediatric renal surgery. We, therefore, conducted a prospective observational pilot study on a total of 26 children to assess the feasibility and efficacy of using a single injection ultrasound-guided paravertebral block (PVB) at T10 level with 0.4 mL/kg bupivacaine 0.25% in combination with sevoflurane as an OFA technique in elective open renal surgery. A successful PVB (defined in terms of both hemodynamic change after the skin incision and the use of rescue analgesia) was observed in 25 children (96%). The interval between PVB and skin incision was 21 min [IQR (18-25)]. End tidal sevoflurane concentration was 2.1% [IQR (1.8-2.4)]. The median time between extubation and waking was 2.5 min [IQR (1-4)]. The median Face, Legs, Activity, cry, Consolability score in post-anesthesia care unit was 1.00 [IQR (0-2)]. Blood pressure falls were not significant at different measurement times. None of the patients had complications related to PVB, and only one patient had post-operative vomiting. PVB is an attractive method that can procure an effective OFA in combination with sevoflurane in pediatric renal surgery.

Frequency dependent functional brain reorganization in anesthesia is specific to drug concentration

The differential effects of general anesthesia on brain activity in terms of drug selection, concentration and combination remain to be elucidated. Using fMRI, it has been shown that increasing doses of sevoflurane is associated with progressive breakdown in brain functional connectivity, while EEG studies have shown that higher activity in the delta band is associated with unconsciousness. Despite these promising results, the band- specific neural substrates of brain changes which occur during sevoflurane anesthesia have not yet been investigated. To this end, we employ high-density EEG-based brain connectivity estimates and graph theoretical analysis in a protocol of progressive sevoflurane administration (conditions: baseline, 1.1%, 2.1%, 2.8%, recovery), both at a global (whole-brain) and at a local (sensor-specific) level in 12 healthy subjects (7 males, mean age 25 ± 4.7 years). We show a statistically significant dependence of global strength, clustering coefficient and efficiency on sevoflurane concentration in the slow delta, beta 1 and beta 2 bands. Interestingly, high and low-frequency bands behaved in an opposite manner as a function of condition. We also found significant band*condition interactive effects in clustering coefficient, efficiency and strength both on local and global scales.

Comments on "Breakthrough analysis of continuous fixed-bed adsorption of sevoflurane using activated carbons"

This communication discusses the fixed bed modeling results of the recent paper published by Ang et al. (2020) in this journal.

May sevoflurane prevent the development of neurogenic pulmonary edema and improve the outcome? Or as a new sedation method for severe brain injury patients

Neurogenic pulmonary edema (NPE) is a life-threatening complication that develops rapidly and dramatically after injury to the central nervous system (CNS). Severe primary brain injury and subsequent secondary brain injury cascade events are thought to be involved in the development of NPE. Activation of the sympathetic nervous system and release of vasoactive substances are also essential prerequisites for NPE. We hypothesize that sevoflurane may be an effective treatment for preventing the development of NPE. Sevoflurane may play a role in protecting brain and lung tissue after acute brain injury through its sympatholytic, antioxidative, ion channel stabilizing, anti-inflammatory, anti-apoptotic, and pulmonary protection effects. It has the potential to be used as a sedative in the neurosurgical intensive care unit (NICU), which can help maintain nervous system and cardiopulmonary function in patients with acute brain injury to improve prognosis. Sevoflurane also has the advantages of fast induction of anesthesia, rapid drug metabolism, little interference to the cardiovascular system, and controllable depth of anesthesia. If our hypothesis is supported by further experiments, use of sevoflurane may open a new door for the treatment of acute brain injury and NPE.

Pressure support ventilation-pro decreases propofol consumption and improves postoperative oxygenation index compared with pressure-controlled ventilation in children undergoing ambulatory surgery: a randomized controlled trial

PURPOSE

The PSVPro mode is increasingly being used for surgeries under laryngeal mask airway owing to improved ventilator-patient synchrony and decreased work of breathing. We hypothesized that PSVPro ventilation mode would reduce consumption of anesthetic agents compared with pressure control ventilation (PCV).

METHODS

Seventy children between three and eight years of age undergoing elective lower abdominal and urological surgery were randomized into PCV group (n = 35) or PSVPro group (n = 35). General anesthesia was induced with sevoflurane and a Proseal LMA™ was inserted. Anesthesia was maintained with propofol infusion to maintain the entropy values between 40 and 60. In the PCV mode, the inspiratory pressure was adjusted to obtain an expiratory tidal volume of 8 mL·kg-1 and a respiratory rate of 12-20/min. In the PSVPRO group, the flow trigger was set at 0.4 L·min-1 and pressure support was adjusted to obtain expiratory tidal volume of 8 mL·kg-1. Consumption of anesthetic agent was recorded as the primary outcome. Emergence time and discharge time were recorded as secondary outcomes.

RESULTS

The PSVPro group showed significant reduction in propofol consumption compared with the PCV group (mean difference, 33.3 µg-1·kg-1·min-1; 95% confidence interval [CI], 24.2 to 42.2). There was decrease in the emergence time in the PSVPro group compared with the PCV group (mean difference, 3.5 min; 95% CI, 2.8 to 4.2) and in time to achieve modified Aldrete score > 9 (mean difference, 3.6 min; 95% CI, 1.9 to 5.2).

CONCLUSION

The PSVPro mode decreases propofol consumption and emergence time, and improves oxygenation index in children undergoing ambulatory surgery.

TRIAL REGISTRATION

Clinical Trial Registry of India (CTRI/2017/12/010942); registered 21 December, 2017.

Effects of fullerenol nanoparticles on kidney tissue in sevoflurane‑treated rats

AIM

The aim of this study is to demonstrate whether fullerenol C60 protects renal injury in sevoflurane‑administered rats.

METHOD

Rats (n: 24) were randomly divided into four groups: Control (Group C), Fullerenol C60 (Group F), Sevoflurane (Group S), Fullerenol C60-Sevoflurane (Group FS). Thirty minutes before the procedure, Fullerenol C60, 100 mg/kg, was administered intraperitoneally. Sevoflurane (2.3 %) was applied for 3 hours to rats in S and FS groups. Biochemical and histopathological parameters were analyzed in renal tissue samples. Kruskal-Wallis and Mann-Whitney U tests were used in statistical analyzes.

RESULTS

Malondialdehyde (MDA) level and catalase (CAT) enzyme activity in Group S were significantly higher than that in all other groups. Paraoxanase (PON) enzyme activity in Group S was significantly lower than in Groups C and FS. The histopathological examination showed that vascular vacuolization and hypertrophy (VVH) and lymphocyte infiltration (LI) were significantly higher in the Group S compared to the Group C.

CONCLUSION

Renal histopathology revealed that the administration of Fullerenol C60 prior to sevoflurane inhalation reduced oxidative stress and partially corrected the damage caused by anesthesia. We concluded that Fullerenol C60 has a renal protective effect in rats when administered before sevoflurane anesthesia (Tab. 2, Fig. 4, Ref. 40).

Development of a prototype anti-pollution filter for volatile anesthetics

INTRODUCTION

The use of volatile agents during cardiopulmonary bypass allows a "single drug anesthesia" and is associated with reduced peak postoperative troponin levels. Connecting the exhaust systems to the oxygenator's gas outlet port is mandatory and allows to prevent operating room (but not atmospheric) pollution by volatile agents. The aim of this study was to create a prototype filter for volatile agents and to test its adsorption efficacy during an ex-vivo simulated conventional cardiopulmonary bypass test.

METHODS

We carried out bench tests to conceive a prototype filter that could prevent room and environment pollution without damaging membrane oxygenators. We performed the tests at the Engineering Center for Circulatory Assistance Laboratory, Dante Pazzanese Institute of Cardiology, São Paulo, Brazil. Bench tests included simulation of integral adsorption tests, filter dimensions and design, flow versus pressure curve, sizing, and tightness.

RESULTS

Calgon AT 410 was the best kind of activated charcoal granules for adsorption of sevoflurane, isoflurane, and desflurane. Filter dimension tests showed that a chamber of 30-cm width over 10-cm diameter filled with 200 g of the Calgon AT410 granules was the minimum required to fully adsorb sevoflurane for 90 min. Adsorption tests showed that the prototype filter fully adsorbed isoflurane in 100 ± 2.3 min, sevoflurane in 95 ± 3.4 min, and desflurane in 95 ± 4.3 min.

CONCLUSION

The new version of our prototype filter adsorbed most of the volatile anesthetics agents during an ex-vivo simulated conventional cardiopulmonary bypass test.

[Protection Effect of Dexamethasone on the Memory Impairment and Neuronal Damage of Neonate Rats that Repeatedly Suffered Sevoflurane Exposure]

OBJECTIVE

To investigate the protection effect of dexamethasone (DXMS) on the memory impairment and neuronal damage of neonate rats that caused by sevoflurane (SEVO) exposure.

METHODS

5-days-old newborn SD rats were randomly divided into normal group (NC group) (10 rats), SEVO group (10 rats) and SEVO+DXMS group (10 rats). Rats of SEVO group and SEVO+DXMS group were exposed to 2.5% SEVO 2 h per day for 1 week, meanwhile the rats of SEVO+DXMS group were given 20 mg/kg DXMS treatment before exposure and the normal group was given the same amount of placebo and carrier gas as control. All rats were fed normally till infancy. Then the Morris water maze test was used to assess the learning and memory function of rats of each group. HE and Nissl staining were used to observe the histomorphology and neuronal changes in the hippocampus of rats. ELISA was performed to test the changes in nitric oxide (NO), superoxide dismutase (SOD) and malondialdehyde (MDA) level in brain tissues. The expression of silent information regulator 1 (SIRT1), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), fork head protein transcription factor 3α (FOXO3α) mRNA in brain tissue was detected by qRT-PCR. Western blot was used to explore the changes in SIRT1 and caspase-3 protein expression of hippocampus.

RESULTS

Compared with the NC group, the pathologic damage of hippocampus tissues was severely in SEVO group, and the number of neuronal cells was decreased as well. After SEVO intervention, the degree of pathologic damage was alleviated, and the number of neuronal cells was significantly increased. The Morris water maze test showed that the escape latency, number of platform crossing and target quadrant retention time between SEVO group and SEVO+DXMS group were significant different. The level of NO and MDA in brain of SEVO+DXMS group was significantly decreased than that of SEVO group, while the level of SOD was increased. qRT-PCR showed that the mRNA levels of SIRT1, PGC-1α and FOXO3α in SEVO+DXMS group were significantly higher those in SEVO group, but mRNA level of SIRT1 was still significantly lower than that of NC group. Western blot showed that the expression of SIRT1 protein in SEVO+DXMS group was significantly higher than that of SEVO group, and the expression of caspase-3 was reduced in SEVO+DXMS compared with SEVO group.

CONCLUSION

DXMS could reduce the level of oxidative stress and suppress the apoptosis of neuronal cells, reduce SEVO-induced brain damage in neonatal rats and improve learning and memory ability in infant rats.

Provider Education and Vaporizer Labeling Lead to Reduced Anesthetic Agent Purchasing With Cost Savings and Reduced Greenhouse Gas Emissions

Anesthetic agents are known greenhouse gases with hundreds to thousands of times the global warming impact compared with carbon dioxide. We sought to mitigate the negative environmental and financial impacts of our practice in the perioperative setting through multidisciplinary staff engagement and provider education on flow rate reduction and volatile agent choice. These efforts led to a 64% per case reduction in carbon dioxide equivalent emissions (163 kg in Fiscal Year 2012, compared with 58 kg in Fiscal Year 2015), as well as a cost savings estimate of $25,000 per month.

Evaluation of Sevoflurane Anesthesia in Donkeys (Equus asinus) Premedicated With Xylazine and Induced With Thiopental

Sevoflurane is a volatile anesthetic agent that has become popular in the field of large animal anesthesia. The aim of this study was to evaluate the use of sevoflurane in adult healthy donkeys. Six male, adult, healthy donkeys were premedicated with xylazine (1 mg/kg IV), induced with thiopental (5 mg/kg IV), and then maintained for 90 minutes with sevoflurane in 100% oxygen at a flow rate of 6 L/min with spontaneous breathing. Rectal temperature (RT), respiratory rate, heart rate (HR), oxygen hemoglobin saturation (OHS), and mean arterial blood pressure (MBP) were measured before and 20 minutes after the administration of xylazine, 10 minutes after the injection of thiopental, and then continuously every 10 minutes until recovery. Times for various signs of recovery, total duration of recovery, and quality of recovery were recorded. Jugular blood samples were collected from each donkey and complete blood counts and venous blood gases including concentrations of oxygen (PO₂) and carbon dioxide (PCO₂) were measured. In addition, the concentrations of sodium, potassium, calcium, lactate, bicarbonate, and glucose in venous blood were measured. Results showed that during the anesthesia maintained with sevoflurane, there was a significant decrease in HR, MBP, RT, red blood corpuscles, hematocrit, total white blood cells, neutrophils, and lymphocytes, whereas the levels of OHS and glucose significantly increased. The concentrations of PO₂, PCO₂, and lactate in venous blood significantly increased, whereas the pH significantly decreased. The levels of calcium significantly decreased immediately following the recovery. Sternal recumbency and standing occurred 15.8 ± 2.6 minutes and 28.2 ± 2.2 minutes, respectively, after turning off the vaporizer. Overall, the quality of recovery was good and relatively quick. It was concluded that sevoflurane appears to provide safe and effective anesthesia in donkeys, with relatively rapid induction and recovery.

Cost-effectiveness of Basal Flow Sevoflurane Anaesthesia Using the Komesaroff Vaporizer inside the Circle System

After ethics committee approval, 51 consenting ASA physical status 1 or 2 adult patients were given basal flow sevoflurane anaesthesia using fresh gas flows of 150 to 300 ml.min-1 oxygen. A Komesaroff vaporizer was placed on the inspiratory limb of the circle system. Basal flows were introduced immediately following intravenous induction of anaesthesia. The vaporizer was set to deliver the maximum concentration until the inspired sevoflurane concentration (FSI) reached 3%. The dial was then adjusted to maintain the FSI at 3%. After every 60 minutes, the circuit was washed out with 100% oxygen at a flow rate of 10 l.min-1 for one minute.

The FSI reached 3% after an average of 8.5 (3.8) [mean (SD)] minutes. The trends in FSI and the expired sevoflurane concentrations were significantly different (P<0.05) between the mechanically ventilated patients (n=21) and the spontaneously ventilating patients (n=30) and demonstrated a more gradual build-up in the former group. The consumption of sevoflurane was found to be 9.2 (2.8) ml.h-1. This represented a 52.5% cost saving over the clinical application of the Mapleson's ideal fresh gas flow sequence for low-flow anaesthesia.

Bispectral Index Guided Timing of Intubation without Neuromuscular Blockade during Sevoflurane Induction of Anaesthesia in Adults

The aim of this study was to assess the effectiveness of bispectral index monitoring (BIS) as a guide to the timing of intubation during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents in adults, and specifically, whether a target BIS value of 25 provides better intubating conditions than a target BIS of 40.

Forty patients were randomized into one of two groups, a target BIS 25 (n=21) or a target BIS 40 (n =19). Patients received premedication with midazolam 20 μg/kg and fentanyl 0.5 μg/kg. Sevoflurane induction of anaesthesia was initiated and titrated to reach the target BIS value and maintained within the target range for two minutes. The trachea was then intubated, with intubating conditions being assessed using a standardized scale.

The BIS 25 group had a superior median intubating score of 4 (range 3–9, [IQR 4–5]) vs the BIS 40 group with a median of 7 (5–10, [6–9], P<0.001).

The time to reach target BIS values was not statistically different (BIS 25 group 6.6 min, BIS 40 group 5.1 min, P=0.054). End-tidal sevoflurane concentration upon reaching the target BIS was higher in the BIS 25 group (5.3%±1.2%) vs the BIS 40 group (3.5% ±0.95) (P<0.001). There was no statistical difference in haemodynamic parameters between groups.

A target BIS value of 25 provides good to excellent intubating conditions and better intubating conditions than a target BIS of 40 during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents.

A Comparison of the Effects of Prolonged (>10 Hour) Low-flow Sevoflurane, High-flow Sevoflurane, and Low-flow Isoflurane Anaesthesia on Hepatorenal Function in Orthopaedic Patients

This study compared the effects of low-flow sevoflurane, high-flow sevoflurane and low-flow isoflurane on hepatorenal function during and after more than 10 hours of anaesthesia. Twenty-five patients scheduled for elective orthopaedic surgery were categorized into three groups; low-flow sevoflurane (fresh gas flow at 1 litre/min, n=9), high-flow sevoflurane (5 l/min, n=7), or low-flow isoflurane (1 l/min, n=9). Inspiratory compound A concentrations were measured. The groups had similar duration of anaesthesia and exposure to anaesthetic agents. The area under the curve of concentration (mean, SD) of compound A in the low-flow sevoflurane group (359.8, 106.1 ppm.h) was greater than that in the high-flow sevoflurane group (61.1, 29.3 ppm.h; P<0.01). All groups showed normal plasma creatinine and creatinine clearance, and transient postoperative increases in plasma alanine aminotrans-ferase and alpha glutathione-S-transferase, as well as urinary glucose and alpha glutathione-S-transferase, with no significant differences between groups. There were no significant relationships between the area under the curve of concentration of compound A and the biomarkers. These findings suggest that prolonged anaesthesia with low-flow sevoflurane has similar effects on hepatorenal function to prolonged anaesthesia with high-flow sevoflurane and low-flow isoflurane.

Effect of Newer Anaesthetics on Duration of Stay in Postanaesthesia Care Unit in Patients Undergoing Major Abdominal Surgery

Newer anaesthetic agents, such as remifentanil and sevoflurane, are more expensive than conventional anaesthetics, such as isoflurane and fentanyl. However, newer anaesthetics might outweigh their higher acquisition costs by reducing length of stay in the postanaesthesia care unit and thereby reducing personnel costs. We retrospectively investigated the influence of newer anaesthetics on time to eligibility for discharge from the postanaesthesia care unit in consecutive patients undergoing major abdominal surgery.

Using a chart review, patients undergoing major abdominal surgery with three different anaesthetic regimens (isoflurane/fentanyl (n=80), sevoflurane/fentanyl (n=40), and sevoflurane/remifentanil (n=42)) were compared regarding duration of anaesthesia, surgery, time till extubation, and time to eligibility for discharge from the post-anaesthesia care unit.

Extubation times were shorter in patients in the sevoflurane/fentanyl and the sevoflurane/remifentanil groups compared to patients in the isoflurane/fentanyl group. Time to eligibility to discharge from the postanaesthesia care unit was similar in isoflurane/fentanyl and sevoflurane/fentanyl group. In the sevoflurane/fentanyl group, time to eligibility for discharge from the unit showed a tendency to be increased (P=0.08), however these patients were significantly older compared to the other groups.

Sevoflurane and remifentanil did not appear to reduce time to eligibility to discharge from the postanaesthesia care unit in our patients undergoing major abdominal surgery compared to isoflurane and fentanyl. This study highlighted the necessity for carefully planned transition from remifentanil to other longer-acting analgesia in our patients.

Anaesthesia for Electroconvulsive Therapy: A Comparison of Sevoflurane with Propofol

This study was a prospective audit of patients receiving either intravenous induction of anaesthesia with propofol 2 mg/kg or inhalational induction using 8% sevoflurane for patients undergoing electroconvulsive therapy (ECT). All patients received inhaled 50% nitrous oxide. The anaesthetic agent was determined by psychiatrist preference. Each psychiatrist nominated only one induction technique for all his or her patients. Seventy treatments were studied in each group. Induction time was longer in the sevoflurane group. The time from commencing induction to loss of verbal contact was [mean (SD)] 64 (29.9) seconds for sevoflurane and 36 (33.6) seconds for propofol (P=0.001). Time to loss of eyelash reflex was 82 (32.6)s for sevoflurane and 44 (17.9)s for propofol (P<0.001). The duration of seizure activity was longer in sevoflurane patients, 35 (17.8)s, compared with 20 (9.8)s in the propofol group (P< 0.001). Discharge times were similar. Minor adverse effects occurred in three patients, all in the sevoflurane group (one bradycardia and two episodes of post-procedural nausea). There were no major adverse events in either group. Propofol and sevoflurane both appear to be suitable agents for induction of anaesthesia for ECT.

Sevoflurane versus Propofol for Induction of Anaesthesia for Electroconvulsive Therapy: A Randomized Crossover Trial

Propofol is often used to induce anaesthesia for electroconvulsive therapy. Some patients who receive propofol have fits of poor quality or inadequate duration despite increasing electroconvulsive therapy doses. Sevoflurane has been reported to exhibit pro-convulsant properties in some “at-risk” patients during anaesthesia for other procedures. The purpose of this study was to perform a randomized crossover trial in patients undergoing electroconvulsive therapy, comparing the effects on seizure parameters of propofol versus sevoflurane induction. Patients were randomly allocated to receive either sevoflurane or propofol for their first treatment. In the subsequent treatment the alternative agent was used.

Patients in both treatment groups exhibited equally good fits, with those in the sevoflurane group having slightly better morphology, which is the most subjective of the parameters measured. The sevoflurane administrations were associated with slightly higher pulse rates and blood pressures.

Sevoflurane provides a suitable alternative to propofol for anaesthesia in patients undergoing electroconvulsive therapy, although the slightly greater pulse rate rise and blood pressure rise should be considered in patients with ischaemic heart disease.

The Relationship between Calculated Effect-site Sevoflurane Levels and Awakening from Anaesthesia

We have previously described a system that displays real-time estimates of effect-site sevoflurane concentrations. Estimates of effect-site levels should be similar to minimum alveolar concentration (MAC) values, which are determined after allowing time for equilibrium. This study aimed to determine estimated effect-site sevoflurane concentrations at awakening from routine anaesthesia and to compare this with published estimates of MAC-awake. If these values were similar, this would validate our approach to the calculation of effect-site concentration. Sixty-five patients undergoing a variety of surgical procedures were observed. Prior to disconnection from the breathing circuit, forward estimates of effect-site sevoflurane were recorded. Patients were observed in the postanaesthesiacare unit and the time at which they responded to comm and wasrecorded. Age-adjusted effect-site sevoflurane at the time of awakeningwas determined. Correlation with patient, surgical and anaestheticfactors includingage, gender, ASA status and intraoperative opioid usage were explored. Mean age-adjusted calculated effect-site concentration at awakening was 0.59 (SD 0.27) vol%. This value is within the range of values determined for MAC-awake of sevoflurane. There was no correlation with any of the demographic or anaesthetic factors, but patients undergoing major surgery woke at a significantly lower mean sevoflurane level. These results support the use of effect-site sevoflurane concentration to guide administration of anaesthesia.

Reduction of oxidative stress a key for enhanced postoperative recovery with fewer complications in esophageal surgery patients: Randomized control trial to investigate therapeutic impact of anesthesia management and usefulness of simple blood test for prediction of high-risk patients

BACKGROUND

Oxidative stress may be an integral determinant of surgical stress severity. We examined whether the preoperative level of derivatives of reactive oxygen metabolites (d-ROMs), an oxidative stress biomarker based on total hydroperoxides in circulating blood, is predictive of increased risk of delayed recovery and complications after surgery, as well as the effects of anesthesia management on postoperative recovery in light of oxidative stress.

METHODS

Patients (American Society of Anesthesiologists physical status I-II) scheduled for a radical esophagectomy (n = 186) were randomly selected to receive inhalational sevoflurane (n = 94) or intravenous propofol (n = 92) anesthesia. Preoperative blood d-ROMs level, as well as pre-and postoperative plasma ferric-reducing ability, were analyzed to assess oxidative stress, with white blood cell (WBC) count, C-reactive protein (CRP) level, incidence of severe postoperative complications, and postoperative recovery process within 30 days after surgery also examined in a double-blind fashion.

RESULTS

Postoperative normalization of WBC and CRP was extended in patients with elevated preoperative d-ROMs [WBC versus d-ROMs: correlation coefficient (r) = 0.58 P < .001; CRP versus d-ROMs: r = 0.46 P < .001]. Receiver operating characteristics analysis of d-ROMs in relation to incidence of severe postoperative complications revealed an optimum d-ROMs threshold value of 410 UCarr and that patients with ≥410 UCarr had a greater risk of complications as compared to those with lower values (odds ratio = 4.7). Plasma ferric-reducing ability was decreased by 61 ± 185 mmol·l (P < .001) after surgery, demonstrating development of surgery-related oxidative stress, the magnitude of which was positively correlated with preoperative d-ROMs level (r = 0.16, P = .043). A comparison of the 2 anesthesia management protocols showed that patients who received propofol, an antioxidant anesthetic, had no postoperative decrease in ferric-reducing ability, lower incidence of severe postoperative complications (7 of 92 versus 18 of 94, P = .030, odds ratio = 0.35), and faster uneventful recovery time (WBC normalization days 7.1 ± 5.2 versus 13.6 ± 10.2, P < .001) as compared to those who received sevoflurane.

CONCLUSIONS

Elevated preoperative blood d-ROMs predicts greater intraoperative oxidative stress and increased postoperative complications with prolonged recovery, thus is useful for identifying high-risk patients for delayed and complicated surgical recovery. Reduction of oxidative stress is vital for enhanced recovery, with control by antioxidants such as propofol a possible solution.

Equipment failure of intravenous syringe pump detected by increase in Narcotrend stage: A case report

RATIONALE

Awareness is the recovery of consciousness during general anesthesia. It occurs when patients under general anesthesia receive inadequate anesthetic medications to maintain unconsciousness during surgery. Equipment failure is a common cause of intraoperative awareness.

PATIENT CONCERNS

A 16-year-old boy, 85 kg in weight, was admitted to our hospital for thyroglossal cystectomy under general anesthesia. Six minutes after the intubation, we noted that the Narcotrend index indicated a condition of light anesthesia and the patient was observed to be in tears.

DIAGNOSIS

Improper positioning of the syringe fixing clamp on the CP700TCI infusion pump caused equipment failure and light anesthesia.

INTERVENTIONS

Bolus of 50 mg propofol and 2 mg midazolam were administered manually by syringe, and inhalation of 2% sevoflurane was supplemented. Infusion pump was replaced.

OUTCOMES

The Narcotrend index of the patient returned to state of deep anesthesia following manual administration of the anesthetic medications. Following the surgery, the patient had an uneventful recovery, and did not present with evidence of awareness.

LESSONS

Users of the CP700TCI syringe pump should pay attention to the position of the syringe fixing clamp. Anesthesiologists should check all the equipment according to a defined checklist prior to anesthesia. Narcotrend monitor could help to detect light anesthesia and prevent potential awareness.

Sevoflurane is an effective adjuvant to propofol-based total intravenous anesthesia for attenuating cough reflex in nonintubated video-assisted thoracoscopic surgery

BACKGROUND

Nonintubated video-assisted thoracic surgery (VATS) has been widely developed during the recent years. Cough reflex is an inevitably encountered problem while approaching lung lesions, and it may induce major bleeding. Sevoflurane anesthesia may attenuate cough reflex by inhibiting the pulmonary irritant receptors. However, the incidence of postoperative nausea and vomiting (PONV) in inhalational anesthesia is higher than in the propofol-based total intravenous anesthesia (TIVA). We investigated the effect of sevoflurane combination with propofol-based TIVA on cough reflex and PONV in nonintubated VATS.

METHODS

Ninety patients undergoing nonintubated VATS with laryngeal mask airway (LMA) and spontaneous breathing were randomly assigned for TIVA or propofol/sevoflurane anesthesia. In the TIVA group (n = 45), anesthesia was induced and maintained with propofol and fentanyl; in the propofol/sevoflurane (P/S) group (n = 45), 1% sevoflurane anesthesia was added to propofol and fentanyl anesthesia. The primary outcome measurements were cough reflex. In addition, the incidence of PONV and extubation time were investigated.

RESULTS

Patients with cough reflex were significantly fewer in the P/S group than in the TIVA group (10/45 vs 34/45; P < .001). The cough severity (35/5/5/0 vs 11/17/17/0; P < .001) and limb movement (40/5/0/0 vs 28/17/0/0; P < .001) were lower in the P/S group than in the TIVA group. Besides, incremental fentanyl bolus for cough reflex was 5 (0 [0-1]) in the P/S group and 17 (0 [0-3]) in the TIVA group (P < .05). And there was no conversion to general anesthesia, postoperative hemorrhage, aspiration pneumonia, or PONV in the 2 groups. Besides, there was no significant difference in extubation time (TIVA: 5.04 ± 2.88 vs P/S: 4.44 ± 2.98 minutes; P = .33).

CONCLUSION

Sevoflurane attenuated cough reflex under propofol-based TIVA and did not increase the incidence of PONV and extubation time in nonintubated VATS.

Suppression of Long Non-Coding RNA LINC00652 Restores Sevoflurane-Induced Cardioprotection Against Myocardial Ischemia-Reperfusion Injury by Targeting GLP-1R Through the cAMP/PKA Pathway in Mice

BACKGROUND/AIMS

Long non-coding RNA (lncRNA) and glucagon-like peptide 1 receptor (GLP-1R) are crucial for heart development and for adult heart structural maintenance and function. Herein, we performed a study to explore the effect of lncRNA LINC00652 (LINC00652) on myocardial ischemia-reperfusion (I/R) injury by targeting GLP-1R through the cyclic adenosine monophosphate-protein kinase A (cAMP/PKA) pathway.

METHODS

Bioinformatics software was used to screen the long-chain non-coding RNAs associated with myocardial ischemia-reperfusion and to predict target genes. The mRNA and protein levels of LINC00652, GLP-1R and CREB were detected by RT-qPCR and western blotting. In order to identify the interaction between LINC00652 and myocardial I/R injury, the cardiac function, the hemodynamic changes, the pathological changes of the myocardial tissues, the myocardial infarct size, and the apoptosis of myocardial cells of mice were measured. Meanwhile, the levels of serum IL-1β and TNF-α were detected.

RESULTS

LINC00652 was overexpressed in the myocardial cells of mice with myocardial I/R injury. GLP-1R is the target gene of LINC00652. We also determined higher levels of LINC00652 and GLP-1R in the I/R modeled mice. Additionally, si-LINC00652 decreased cardiac pathology, infarct size, apoptosis rates of myocardial cells, and levels of IL-1β and TNF-α, and increased GLP-1R expression cardiac function, normal hemodynamic index, and the expression and phosphorylation of GLP-1R and CREB proteins.

CONCLUSION

Taken together, our key findings of the present highlight LINC00652 inhibits the activation of the cAMP/PKA pathway by targeting GLP-1R to reduce the protective effect of sevoflurane on myocardial I/R injury in mice.

Sevoflurane addiction due to workplace exposure: A case report and literature review

RATIONALE

Anesthesiologists have a well-known increased risk of substance abuse. High-concentration of inhalation anesthetics in exhaled air of operating room personnel is detected. such secondhand exposure produces neurobiological sensitization to the reinforcing effects of inhalation anesthetics.

PATIENT CONCERNS

An addictive young male anesthesiologist who was long-term abuse with sevoflurane after 4 years occupational exposure. A 28-year-old anesthesiologist on duty was found deeply sleep in the locker room and coved his nose with Gauze with high-concentration of sevoflurane. He was found addiction to sevoflurane second time. Several life-threatening incidents occurred including severe aspiration pneumonia. No other addiction was found in his history before he became severely dependent on sevoflurane.

DIAGNOSES

A visual analog scale was employed to assess the severity of craving for sevoflurane and the Benzodiazepine Withdrawal Symptom Scale (BWSQ2)-scale was used to assess sevoflurane withdrawal syndrome(WS).

INTERVENTIONS

First time an opened original sevoflurane container filled with water instead of sevoflurane was handed out for a minute in order to elicit craving and withdrawal symptom in five therapeutic single-sessions. Second time an opened original sevoflurane container filled with sevoflurane instead of water was used as his powerful cur-stimulus and also was handed out for a minute.

OUTCOMES

After professional therapy and continuous surveillance he was rehabilitation and back to work. However, after three weeks he became addiction to sevoflurane again. He showed very sensitive to sevoflurane and switched to other career.

LESSONS

This case emphasizes that secondhand exposure to inhalation anesthetics may be dangerous and increase the life-threatening professional risk to anesthesiologists, although identification of the responsible factor remains difficult. However, the safety of operating room staff should be aroused wide-spread social concern.

Intravenous versus inhalational maintenance of anaesthesia for postoperative cognitive outcomes in elderly people undergoing non-cardiac surgery

BACKGROUND

The use of anaesthetics in the elderly surgical population (more than 60 years of age) is increasing. Postoperative delirium, an acute condition characterized by reduced awareness of the environment and a disturbance in attention, typically occurs between 24 and 72 hours after surgery and can affect up to 60% of elderly surgical patients. Postoperative cognitive dysfunction (POCD) is a new-onset of cognitive impairment which may persist for weeks or months after surgery.Traditionally, surgical anaesthesia has been maintained with inhalational agents. End-tidal concentrations require adjustment to balance the risks of accidental awareness and excessive dosing in elderly people. As an alternative, propofol-based total intravenous anaesthesia (TIVA) offers a more rapid recovery and reduces postoperative nausea and vomiting. Using TIVA with a target controlled infusion (TCI) allows plasma and effect-site concentrations to be calculated using an algorithm based on age, gender, weight and height of the patient.TIVA is a viable alternative to inhalational maintenance agents for surgical anaesthesia in elderly people. However, in terms of postoperative cognitive outcomes, the optimal technique is unknown.

OBJECTIVES

To compare maintenance of general anaesthesia for elderly people undergoing non-cardiac surgery using propofol-based TIVA or inhalational anaesthesia on postoperative cognitive function, mortality, risk of hypotension, length of stay in the postanaesthesia care unit (PACU), and hospital stay.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 11), MEDLINE (1946 to November 2017), Embase (1974 to November 2017), PsycINFO (1887 to November 2017). We searched clinical trials registers for ongoing studies, and conducted backward and forward citation searching of relevant articles.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) with participants over 60 years of age scheduled for non-cardiac surgery under general anaesthesia. We planned to also include quasi-randomized trials. We compared maintenance of anaesthesia with propofol-based TIVA versus inhalational maintenance of anaesthesia.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion, extracted data, assessed risk of bias, and synthesized findings.

MAIN RESULTS

We included 28 RCTs with 4507 randomized participants undergoing different types of surgery (predominantly cardiovascular, laparoscopic, abdominal, orthopaedic and ophthalmic procedures). We found no quasi-randomized trials. Four studies are awaiting classification because we had insufficient information to assess eligibility.All studies compared maintenance with propofol-based TIVA versus inhalational maintenance of anaesthesia. Six studies were multi-arm and included additional TIVA groups, additional inhalational maintenance or both. Inhalational maintenance agents included sevoflurane (19 studies), isoflurane (eight studies), and desflurane (three studies), and was not specified in one study (reported as an abstract). Some studies also reported use of epidural analgesia/anaesthesia, fentanyl and remifentanil.We found insufficient reporting of randomization methods in many studies and all studies were at high risk of performance bias because it was not feasible to blind anaesthetists to study groups. Thirteen studies described blinding of outcome assessors. Three studies had a high of risk of attrition bias, and we noted differences in the use of analgesics between groups in six studies, and differences in baseline characteristics in five studies. Few studies reported clinical trials registration, which prevented assessment of risk of selective reporting bias.We found no evidence of a difference in incidences of postoperative delirium according to type of anaesthetic maintenance agents (odds ratio (OR) 0.59, 95% confidence interval (CI) 0.15 to 2.26; 321 participants; five studies; very low-certainty evidence); we noted during sensitivity analysis that using different time points in one study may influence direction of this result. Thirteen studies (3215 participants) reported POCD, and of these, six studies reported data that could not be pooled; we noted no difference in scores of POCD in four of these and in one study, data were at a time point incomparable to other studies. We excluded one large study from meta-analysis because study investigators had used non-standard anaesthetic management and this study was not methodologically comparable to other studies. We combined data for seven studies and found low-certainty evidence that TIVA may reduce POCD (OR 0.52, 95% CI 0.31 to 0.87; 869 participants).We found no evidence of a difference in mortality at 30 days (OR 1.21, 95% CI 0.33 to 4.45; 271 participants; three studies; very low-certainty evidence). Twelve studies reported intraoperative hypotension. We did not perform meta-analysis for 11 studies for this outcome. We noted visual inconsistencies in these data, which may be explained by possible variation in clinical management and medication used to manage hypotension in each study (downgraded to low-certainty evidence); one study reported data in a format that could not be combined and we noted little or no difference between groups in intraoperative hypotension for this study. Eight studies reported length of stay in the PACU, and we did not perform meta-analysis for seven studies. We noted visual inconsistencies in these data, which may be explained by possible differences in definition of time points for this outcome (downgraded to very low-certainty evidence); data were unclearly reported in one study. We found no evidence of a difference in length of hospital stay according to type of anaesthetic maintenance agent (mean difference (MD) 0 days, 95% CI -1.32 to 1.32; 175 participants; four studies; very low-certainty evidence).We used the GRADE approach to downgrade the certainty of the evidence for each outcome. Reasons for downgrading included: study limitations, because some included studies insufficiently reported randomization methods, had high attrition bias, or high risk of selective reporting bias; imprecision, because we found few studies; inconsistency, because we noted heterogeneity across studies.

AUTHORS' CONCLUSIONS

We are uncertain whether maintenance with propofol-based TIVA or with inhalational agents affect incidences of postoperative delirium, mortality, or length of hospital stay because certainty of the evidence was very low. We found low-certainty evidence that maintenance with propofol-based TIVA may reduce POCD. We were unable to perform meta-analysis for intraoperative hypotension or length of stay in the PACU because of heterogeneity between studies. We identified 11 ongoing studies from clinical trials register searches; inclusion of these studies in future review updates may provide more certainty for the review outcomes.

The analgesic effects of intraoperative total intravenous anesthesia (TIVA) with propofol versus sevoflurane after colorectal surgery

Clinical studies have shown that total intravenous anesthesia (TIVA) with propofol is associated with better postoperative pain control compared with inhalational anesthesia, while other studies have not shown any benefit. The analgesic effect of TIVA with propofol in colorectal surgery has not been studied. The aim of this study is to evaluate the postoperative analgesic effects of TIVA with propofol versus inhalational sevoflurane in colorectal surgery.This is a retrospective case-control study. Records of patients undergoing colorectal surgery from 2014 to 2016 (36 months) were retrieved. Ninety-five patients who received TIVA with propofol were matched against 95 patients who received inhalational sevoflurane. Acute postoperative numerical rating scale (NRS) pain scores, postoperative morphine consumption, patient satisfaction, and side effects were compared and analyzed for differences between TIVA with propofol and sevoflurane.There were no significant differences in NRS pain scores, incidence of side effects, and patient satisfaction between the 2 groups. Patients receiving TIVA with propofol had significantly reduced total morphine consumption (P < .001), and daily morphine consumption on postoperative days 1 (P = .031), 2 (P = .002), and 3 (P = .031) compared with those receiving sevoflurane.TIVA with propofol was not associated with improved postoperative analgesia, better patient satisfaction, or reduced side effects. It may reduce postoperative opioid consumption after colorectal surgery.

Effect of magnesium sulfate on anesthesia depth, awareness incidence, and postoperative pain scores in obstetric patients. A double-blind randomized controlled trial

Objectives:

To assess the effects of magnesium on the depth of anesthesia and to determine the effects of magnesium on incidence of awareness and postoperative pain after caesarean section.

Methods:

The study was designed as a double-blind, controlled, randomized study and conducted in Hacettepe University Hospital, Ankara, Turkey between January 2015 and March 2016. A total of 100 pregnant healthy women who were between 17 and 41 years old, ASA II, and scheduled for an elective cesarean section with general anesthesia were included in the study. After induction, sevoflurane was used for maintenance in Group S and desflurane in Group D (control groups). At Group S-M and Group D-M (study groups), magnesium infusion was started with sevoflurane and desflurane anesthesia respectively. Minimum alveolar concentration of sevoflurane and desflurane were kept constant. Bispectral index scores (BIS), fentanyl consumption and postoperative visual analogue scale (VAS) values were recorded. All of the patients had been followed-up for awareness until the postoperative first year.

Results:

Demographic variables of the patients were similar. BIS values were significantly higher in control groups throughout the operation (p<0.001). No significant difference was detected for intraoperative fentanyl consumption and awareness incidence. VAS values were significantly lower in study groups (p<0.05).

Conclusion:

Magnesium infusion provided significantly lower intraoperative BIS values and lower postoperative VAS scores. We believe that magnesium can be useful as an adjuvant to general anesthesia.

MicroRNA-374 Exerts Protective Effects by Inhibiting SP1 Through Activating the PI3K/Akt Pathway in Rat Models of Myocardial Ischemia-Reperfusion After Sevoflurane Preconditioning

BACKGROUND/AIMS

Ischemic heart disease is a leading cause of death in cardiovascular diseases, and microRNAs (miRs) have been reported to be potential therapeutic targets in heart disease. Herein, this study aims to investigate the effects of microRNA (miR)-374 on myocardial ischemia-reperfusion (I/R) injury in rat models pretreated with sevoflurane by targeting SP1 through the PI3K/Akt pathway.

METHODS

SD rats were grouped into sham, I/R and sevoflurane + I/R (sevoflurane preconditioning and I/R) groups. The biochemical indicators, pathological changes, positive expression of SP1 protein, and apoptosis rates were measured using biochemical detection, Evans blue-TTC staining, immunohistochemistry and TUNEL staining. RT-qPCR and Western blotting were used to investigate the expression of miR-374 mRNA and the protein expression of SP1, PI3K, HO-1, p53, iNOS, c-fos, Akt/p-Akt, and GSK-3β/p-GSK-3β. Cardiomyocytes were treated with miR-374 mimics, miR-374 inhibitors, or siRNA-SP1. Cardiomyocyte proliferation and cycle distribution and apoptosis were studied by MTT and flow cytometry.

RESULTS

Compared with the I/R group, in the sevoflurane + I/R group, serum SOD and IL-10 increased, while MDA, LDH, CK, TNF-α, IL-6 and IL-10 decreased, as did the percentage of infarct area, the positive rate of SP1 and the apoptosis index. The expression of SP1, p53, iNOS and c-fos decreased, and the miR-374 expression of PI3K, HO-1, Akt/p-Akt, GSK-3β/p-GSK-3β increased. With the upregulation of miR-374 and the downregulation of SP1, the expression of SP1, p53, iNOS and c-fos decreased, as did the proportion of cells in G1 phase and the apoptosis rate; the expression of PI3K, HO-1, Akt/p-Akt, GSK-3β/p-GSK-3β increased. The results in the miR-374 inhibitor group contrasted with the above results.

CONCLUSION

The results indicated that miR-374 could alleviate myocardial I/R damage in rat models pretreated with sevoflurane by targeting SP1 by activating the PI3K/Akt pathway.

Efficacy Of Intravenous Lignocain Vs Sevoflurane In Prevention Of Coughing And Desaturation At Extubation In Children

BACKGROUND

Inadvertent coughing and desaturation are the most commonly faced and feared respiratory complications in post-anaesthesia period. The study was done to compare the efficacy of intravenous lignocaine versus sevoflurane in prevention of coughing and desaturation at extubation in children less than 6 years of age.

METHODS

This Randomized Control Trial was carried out from May 2013 to May 2016, at Combined Military Hospital Nowshera after obtaining approval from the hospital ethics committee (IREC-0003/5/13/Aneas). Children aged three months to six years undergoing surgical procedures requiring the placement of definitive airway were randomly assigned into two groups. Patients were anaesthetized by standardized balanced anaesthesia technique. In Group A (n=355), three minutes prior to extubation lignocaine 2% was used intravenously. In Group B (n=355), isoflurane was switched off, breathing circuit changed and sevoflurane started at minimum alveolar concentration (MAC 3-4%) for 3 minutes prior to extubation. Assessment for extubation was clinical. Oxygen saturation and severity of coughing were noted for 5 consecutive minutes, after extubation.

RESULTS

In group-A, 156 patients were less than 2 years of age while in group-B, 135 patients were less than 2 years old. In group-A, 199 and in group-B, 220 children were 2-6 years of age respectively. Post stratification the p-value for weight was 0.17 (p-value >0.05) and t-statistic was 1.36. Post stratification p-value for gender was 0.12 (p-value>0.05) and chi square statistic was 2.49. Group A had more eventful extubation with 270 cases of cough (76%) as compared to group-B where it was noted in 199 cases (56%). Similarly, desaturation was observed in 85 cases in group-A (24%) as compared to 28 cases (8%) in group-B. The difference between the groups was statistically significant.

CONCLUSIONS

Sevoflurane based anaesthetic vapours mixture causes statistical significant prevention from events like coughing episodes and desaturation in post-extubation in children less than six years of age undergoing elective surgery.

Mid-gestational sevoflurane exposure inhibits fetal neural stem cell proliferation and impairs postnatal learning and memory function in a dose-dependent manner

Advancements in fetal intervention procedures have led to increases in the number of pregnant women undergoing general anesthesia during the second trimester-a period characterized by extensive proliferation of fetal neural stem cells (NSCs). However, few studies have investigated the effects of mid-gestational sevoflurane exposure on fetal NSC proliferation or postnatal learning and memory function. In the present study, pregnant rats were randomly assigned to a control group (C group), a low sevoflurane concentration group (2%; L group), a high sevoflurane concentration group (3.5%; H group), a high sevoflurane concentration plus lithium chloride group (H + Li group), and a lithium chloride group (Li group) at gestational day 14. Rats received different concentrations of sevoflurane anesthesia for 2 h. The offspring rats were weaned at 28 days for behavioral testing (i.e., Morris Water Maze [MWM]), and fetal brains or postnatal hippocampal tissues were harvested for immunofluorescence staining, real-time PCR, and Western blotting analyses in order to determine the effect of sevoflurane exposure on NSC proliferation and the Wnt/β-catenin signaling pathway. Our results indicated that maternal exposure to 3.5% sevoflurane (H group) during the mid-gestational period impaired the performance of offspring rats in the MWM test, reduced NSC proliferation, and increased protein levels of fetal glycogen synthase kinase-3 beta (GSK-3β). Such treatment also decreased levels of β-catenin protein, CD44 RNA, and Cyclin D1 RNA relative to those observed in the C group. However, these effects were transiently attenuated by treatment with lithium chloride. Conversely, maternal exposure to 2% sevoflurane (L group) did not influence NSC proliferation or the Wnt signaling pathway. Our results suggest that sevoflurane exposure during the second trimester inhibits fetal NSC proliferation via the Wnt/β-catenin pathway and impairs postnatal learning and memory function in a dose-dependent manner.

Sevoflurane posttreatment prevents oxidative and inflammatory injury in ventilator-induced lung injury

Mechanical ventilation is a life-saving clinical treatment but it can induce or aggravate lung injury. New therapeutic strategies, aimed at reducing the negative effects of mechanical ventilation such as excessive production of reactive oxygen species, release of pro-inflammatory cytokines, and transmigration as well as activation of neutrophil cells, are needed to improve the clinical outcome of ventilated patients. Though the inhaled anesthetic sevoflurane is known to exert organ-protective effects, little is known about the potential of sevoflurane therapy in ventilator-induced lung injury. This study focused on the effects of delayed sevoflurane application in mechanically ventilated C57BL/6N mice. Lung function, lung injury, oxidative stress, and inflammatory parameters were analyzed and compared between non-ventilated and ventilated groups with or without sevoflurane anesthesia. Mechanical ventilation led to a substantial induction of lung injury, reactive oxygen species production, pro-inflammatory cytokine release, and neutrophil influx. In contrast, sevoflurane posttreatment time dependently reduced histological signs of lung injury. Most interestingly, increased production of reactive oxygen species was clearly inhibited in all sevoflurane posttreatment groups. Likewise, the release of the pro-inflammatory cytokines interleukin-1β and MIP-1β and neutrophil transmigration were completely prevented by sevoflurane independent of the onset of sevoflurane administration. In conclusion, sevoflurane posttreatment time dependently limits lung injury, and oxidative and pro-inflammatory responses are clearly prevented by sevoflurane irrespective of the onset of posttreatment. These findings underline the therapeutic potential of sevoflurane treatment in ventilator-induced lung injury.

MAC-sparing effect of nitrous oxide in sevoflurane anesthetized sheep and its reversal with systemic atipamezole administration

INTRODUCTION

Nitrous oxide (N2O) is an anesthetic gas with antinociceptive properties and reduces the minimum alveolar concentration (MAC) for volatile anesthetic agents, potentially through mechanisms involving central alpha2-adrenoceptors. We hypothesized that 70% N2O in the inspired gas will significantly reduce the MAC of sevoflurane (MACSEVO) in sheep, and that this effect can be reversed by systemic atipamezole.

MATERIALS AND METHODS

Animals were initially anesthetized with SEVO in oxygen (O2) and exposed to an electrical current as supramaximal noxious stimulus in order to determine MACSEVO (in duplicates). Thereafter, 70% N2O was added to the inspired gas and the MAC re-determined in the presence of N2O (MACSN). A subgroup of sheep were anesthetized a second time with SEVO/N2O for re-determination of MACSN, after which atipamezole (0.2 mg kg-1, IV) was administered for MACSNA determinations. Sheep were anesthetized a third time, initially with only SEVO/O2 to re-determine MACSEVO, after which atipamezole (0.2 mg kg-1, IV) was administered for determination of MACSA.

RESULTS

MACSEVO was 2.7 (0.3)% [mean (standard deviation)]. Addition of N2O resulted in a 37% reduction of MACSEVO to MACSN of 1.7 (0.2)% (p <0.0001). Atipamezole reversed this effect, producing a MACSNA of 3.1 (0.7)%, which did not differ from MACSEVO (p = 0.12). MACSEVO did not differ from MACSA (p = 0.69). Cardiorespiratory variables were not different among experimental groups except a lower ETCO2 in animals exposed to SEVO/N2O.

CONCLUSIONS

N2O produces significant MACSEVO-reduction in sheep; this effect is completely reversed by IV atipamezole confirming the involvement of alpha2-adrenoreceptors in the MAC-sparing action of N2O.

Effect of sevoflurane preconditioning on light-induced retinal damage in diabetic rats

Hyperglycemia and bright light are powerful stress agents that produce an enhanced retinal damage, when simultaneously acting on retina. Previous studies have shown that preconditioning with sevoflurane anesthesia offers a certain degree of protection to retinal cells against light damage. The objective of this study was to explore the effect of sevoflurane anesthetic preconditioning on a model of light-induced retinal degeneration in diabetic rats. Wistar rats that were randomly divided into four groups: control (rats exposed to photostress), group 1 (rats exposed to photostress and sevoflurane preconditioning), group 2 (diabetic rats exposed to photostress), group 3 (diabetic rats exposed to photostress and sevoflurane preconditioning) were used for this experiment. We recorded basal electroretinogram (ERG), at 36 h and 14 days after photostress and performed histological analysis of the retina. Results showed that sevoflurane has a protective effect on light-induced neuroretinal degeneration proved by significantly less variations of the ERG before and after photostress. Diabetes appears to increase the damaging effect of photostress on retina and attenuate the protection provided by sevoflurane preconditioning.

Evaluation of Endotracheal Tube Cuff Pressure in Laparoscopic Cholecystectomy and Postoperative Sore Throat

BACKGROUND

The use of nitrous oxide and carboperitoneum in laparoscopic cholecystectomy lead to increase in endotracheal tube cuff pressure. It may impair tracheal mucosal perfusion with subsequent tracheal damage. The purpose of this study was to evaluate cuff pressure and incidence of post-operative sore throat in patients undergoing laparoscopic cholecystectomy.

METHODS

In this prospective observational study, 128 patients aged 18-65 years of American Society of Anesthesiologist physical status I and II undergoing laparoscopic cholecystectomy were enrolled and allocated alternately into two groups, Study Group (Maintenance of anesthesia with sevoflurane 1-2%, oxygen/nitrous oxide mixture; 40/60), Control Group (Maintenance of anesthesia with sevoflurane 1-2%, oxygen/air mixture; 40/60) were analysed and comapared. Each group contained 64 patients. Aneroid manometer was used to monitor cuff pressure. Volume of air used to inflate the cuff, baseline cuff pressure, comparison of intraoperative cuff pressure and incidence of post-operative sore throat were measured.

RESULTS

The study results demonstrated higher cuff pressure in study group at all times after the creation of carboperitoneum (p=0.00) with increased incidence of sore throat(p=0.004).

CONCLUSIONS

Increase in endotracheal tube cuff pressure was noted with the use of nitrous oxide in laparoscopic cholecystectomy with subsequent post-operative airway complication. Monitoring of cuff pressure is simple, noninvasive and efficient way of achieving therapeutic cuff pressure of 20-30 cm of H2O and thus recommends its use.

Effects of TLR3 and TLR9 Signaling Pathway on Brain Protection in Rats Undergoing Sevoflurane Pretreatment during Cardiopulmonary Bypass

OBJECTIVE

To investigate the effects of TLR3 and TLR9 signaling pathway on brain injury during CPB in rats pretreated with sevoflurane and its possible molecular mechanism.

METHODS

SD rats were randomly assigned to sham group, CPB group, and Sev group. Brain tissue was obtained at before CPB (T0), at CPB for 30 minutes (T1), 1 hour after CPB (T3), and 3 hours after CPB (T5). ELISA was used to measure S100-β and IL-6. Western blot was utilized to determine TLR3 and TLR9 expression. TUNEL was applied to detect neuronal apoptosis.

RESULTS

Compared with CPB group, at T1, at termination after 1 hour of CPB (T2), T3, 2 hours after CPB (T4) and T5, S100-β and IL-6 decreased in Sev group. Compared with CPB group, IFN-β were increased in Sev group, except T0. Compared with CPB group, TLR3 expression increased, and TLR9 and NF-κB decreased in Sev group. The apoptotic neurons were less in Sev group than in CPB group (P < 0.05).

CONCLUSION

Sevoflurane intervention can activate TLR3 and TLR9 signaling pathway, upregulate TLR3 expression and downstream TRIF expression, decrease TLR9 expression, and downregulate downstream NF-κB expression in CPB rat models, thereby mitigating brain injury induced by inflammatory response during CPB.

Effects of sevoflurane on apoptosis, BDNF and cognitive functions in neonatal rats

OBJECTIVE

To evaluate the early and late effects of sevoflurane on the neonatal brain.

BACKGROUND

Sevoflurane is the most used anaesthetics in neonatal subjects.

METHODS

The study included 7-day-old male Wistar-Albino rats (n = 30), which were divided into the two groups according to the anaesthetic received: sevoflurane (S) and control group (C). Half of each group was sacrificed six hours after anaesthesia (early, E) while the remaining subjects were sacrificed six weeks later (late, L). The serum brain-derived-neurotrophic factor (BDNF), brain BDNF and caspase-3 were evaluated. In addition, elevated plus arm test and Morris water test were performed in the late group.

RESULTS

BDNF levels were higher in the late groups than in the early ones (p < 0.05). BDNF levels in cerebral cortex were higher in the Group CE than in the Group CL and SL (p < 0.05). There was a significant negative correlation between serum BDNF and cortex BDNF levels (p = 0.003, r = -0.425). Cortex caspase 3 levels were significantly higher in the Groups SE and SL than in the Group CE and CL (p < 0.05). There was no significant difference between the groups in the terms of open arm index, locomotor activity and Morris water test.

CONCLUSIONS

Although sevoflurane induced apoptosis, it didn't affect BDNF levels and showed no long-term negative effects on learning and anxiety in neonatal rats (Tab. 1, Fig. 3, Ref. 26).

Comparison of hemodynamic effects of sevoflurane and ketamine as basal anesthesia by a new and direct monitoring during induction in children with ventricular septal defect: A prospective, randomized research

BACKGROUND

Sevoflurane and ketamine are commonly used to obtain sedation and facilitate intravenous anesthetic induction in children undergoing cardiac surgery who are uncooperative. We used a new and direct systemic hemodynamic monitoring technique pressure recording analytical method and compared the hemodynamic effects of sevoflurane and ketamine to facilitate intravenous anesthetic induction.

METHODS

Forty-four children with ventricular septal defect (2.2 ± 1.2 years) were enrolled and randomized to receive sevoflurane (Group S) or intramuscular ketamine (Group K) for sedation, followed by intravenous midazolam-sufentanil induction and tracheal intubation. Recorded parameters included heart rate (HR), arterial pressures, stroke volume index (SVI), cardiac index (CI), systemic vascular resistance index (SVRI), the maximal slope of systolic upstroke (dp/dtmax) after sedation obtained with sevoflurane or ketamine, 1, 2, 5 minutes after midazolam-sufentanil, 1, 2, 5, and 10 minutes after tracheal intubation. Rate-pressure product (RPP) and cardiac power output (CPO) were calculated.

RESULTS

As compared with Group S, Group K had faster decreases during intravenous anesthetic induction in arterial pressures (P < .01 for all), higher HR, arterial pressures, SVRI, dp/dtmax, RPP, lower SVI, CI, CPO (P < .05 for all) during the study period.

CONCLUSION

As compared with sevoflurane, ketamine facilitated intravenous anesthetic induction exerts unfavorable effects on systemic hemodynamic and myocardial energetic in children with ventricular septal defect.

Sevoflurane causes greater QTc interval prolongation in chronically hyperglycemic patients than in normoglycemic patients

QTc interval prolongation is a serious diabetic complication and increases mortality rate. Hyperglycemia inhibits the rapid component of delayed rectifier potassium channel currents (Ikr) and prolongs the QTc interval on electrocardiograms. Sevoflurane also inhibits the Ikr and causes QTc interval prolongation. In fact, torsade de pointes occurred in a patient with poorly controlled diabetes mellitus during sevoflurane anesthesia. We enrolled 74 patients, including 37 normoglycemic patients (glycated hemoglobin [HbA1c]: <6.5%) (NG group) and 37 chronically hyperglycemic patients (HbA1c: ≥6.5%) (HG group). Anesthesia was induced with 2 mg/kg propofol and 0.3 μg/kg/min remifentanil, and maintained with 2% sevoflurane in 40% O2 and 0.2-0.3 μg/kg/min remifentanil. The QT interval and Tp-e interval (from the peak to the end of the T wave) were measured before and at 5, 10, 30, 60, 90, and 120 min after the administration of sevoflurane and adjusted for the patient's heart rate (QTc and Tp-ec, respectively). P-values of <0.05 were considered statistically significant. The QTc and the Tp-ec intervals of the two groups did not differ significantly before the administration of sevoflurane. The QTc interval gradually increased with time in both groups and was significantly longer than the baseline value at 10 min after the administration of sevoflurane in both groups. The QTc interval of the HG group was significantly longer than that of the NG group at 90 min and 120 min after the administration of sevoflurane. The Tp-ec interval was not affected by sevoflurane in either group.We have demonstrated that sevoflurane significantly prolongs the QTc interval, and that the extent of the prolongation is significantly greater in chronically hyperglycemic patients than in normoglycemic patients. Although Tp-ec is not affected by sevoflurane, it should be noted that the simultaneous blockade of potassium channels would increase the risk of arrhythmias.

Healing of chronic venous ulcer with topical sevoflurane

The present study assesses the efficacy and safety of topical sevoflurane in chronic venous ulcers and its impact on analgesia and healing. This retrospective study included 30 patients older than 65 years with painful refractory chronic venous ulcers. Patients were treated with topical sevoflurane prior to the usual ulcer cleaning every 2 days for a period of 1 month. Treatment was initiated with a saline solution, followed by direct irrigation of 1 ml of liquid sevoflurane over the wound size, which was measured as cm2 . Sevoflurane had a fast, intense and long-lasting analgesic effect. Latency time ranged from 2 to 7 minutes (3·9 ± 1·5 minutes), and duration varied from 8 to 18 hours (12 ± 2·9). The mean ulcer size was 8·4 ± 9·7 cm2 . There was a progressive decrease in size in all patients, with a mean size of 4·2 ± 5·4 cm2 at the end of the study. There were no adverse systemic effects. Local adverse effects were mild and transient, including pruritus, erythema and heat. Topical sevoflurane is a new, efficient and safe therapeutic alternative in painful chronic venous ulcers, refractory to usual analgesic treatment. It can improve the ulcer-healing process that shortens the cicatrisation period.

Volatile sedation in the intensive care unit: A systematic review and meta-analysis

BACKGROUND

Volatile sedation in the intensive care unit (ICU) may reduce the number of adverse events and improve patient outcomes compared with intravenous (IV) sedation. We performed a systematic review and meta-analysis comparing the effects of volatile and IV sedation in adult ICU patients.

METHODS

We searched the PubMed, Embase, Cochrane Central Register, and Web of Science databases for all randomized trials comparing volatile sedation using an anesthetic-conserving device (ACD) with IV sedation in terms of awakening and extubation times, lengths of ICU and hospital stay, and pharmacologic end-organ effects.

RESULTS

Thirteen trials with a total of 1027 patients were included. Volatile sedation (sevoflurane or isoflurane) administered through an ACD shortened the awakening time [mean difference (MD), -80.0 minutes; 95% confidence intervals (95% CIs), -134.5 to -25.6; P = .004] and extubation time (MD, -196.0 minutes; 95% CIs, -305.2 to -86.8; P < .001) compared with IV sedation (midazolam or propofol). No differences in the lengths of ICU and hospital stay were noted between the 2 groups. In the analysis of cardiac effects of sedation from 5 studies, patients who received volatile sedation showed lower serum troponin levels 6 hours after ICU admission than patients who received IV sedation (P < .05). The effect size of troponin was largest between 12 and 24 hours after ICU admission (MD, -0.27 μg/L; 95% CIs, -0.44 to -0.09; P = .003).

CONCLUSION

Compared with IV sedation, volatile sedation administered through an ACD in the ICU shortened the awakening and extubation times. Considering the difference in serum troponin levels between both arms, volatile anesthetics might have a myocardial protective effect after cardiac surgery even at a subanesthetic dose. Because the included studies used small sample sizes with high heterogeneity, further large, high-quality prospective clinical trials are needed to confirm our findings.

Impact of inhalational versus intravenous anaesthesia on early delirium and long-term survival in elderly patients after cancer surgery: study protocol of a multicentre, open-label, and randomised controlled trial

INTRODUCTION

Elderly patients who have solid organ cancer often receive surgery. Some of them may develop delirium after surgery and delirium development is associated with worse outcomes. Furthermore, despite all of the advances in medical care, the long-term survival in cancer patients is far from optimal. Evidences suggest that choice of anaesthetics during surgery, that is, either inhalational or intravenous anaesthetics, may influence outcomes. However, the impact of general anaesthesia type on the occurrence of postoperative delirium is inconclusive. Although retrospective studies suggest that propofol-based intravenous anaesthesia was associated with longer survival after cancer surgery when compared with inhalational anaesthesia, prospective studies as such are still lacking. The purposes of this randomised controlled trial are to test the hypotheses that when compared with sevoflurane-based inhalational anaesthesia, propofol-based intravenous anaesthesia may reduce the incidence of early delirium and prolong long-term survival in elderly patients after major cancer surgery.

METHODS AND ANALYSIS

This is a multicentre, open-label, randomised controlled trial with two parallel arms. 1200 elderly patients (≥65 years but <90 years) who are scheduled to undergo major cancer surgery (with predicted duration ≥2 hours) are randomised to receive either sevoflurane-based inhalational anaesthesia or propofol-based intravenous anaesthesia. Other anaesthetics and supplemental drugs including sedatives, opioids and muscle relaxants are administered in both arms according to routine practice. The primary early outcome is the incidence of 7-day delirium after surgery and the primary long-term outcome is the duration of 3-year survival after surgery.

ETHICS AND DISSEMINATION

The study protocol has been approved by the Clinical Research Ethics Committees of Peking University First Hospital (2015[869]) and all participating centres. The results of early and long-term outcomes will be analysed and reported separately.

TRIAL REGISTRATION NUMBER

ChiCTR-IPR-15006209; NCT02662257; NCT02660411.

Sevoflurane Postconditioning-Induced Anti-Inflammation via Inhibition of the Toll-Like Receptor-4/Nuclear Factor Kappa B Pathway Contributes to Neuroprotection against Transient Global Cerebral Ischemia in Rats

The anti-inflammatory actions of sevoflurane postconditioning are suggested as an important mechanism of sevoflurane postconditioning-induced neuroprotection against cerebral ischemia. Here, we determined whether the anti-inflammatory effects of sevoflurane postconditioning were mediated via inhibition of the toll-like receptor (TLR)-4/nuclear factor kappa B (NF-κB) pathway after global transient cerebral ischemia in rats. Forty-five rats were randomly assigned to five groups as follows: (1) control (10 min of ischemia, n = 10); (2) sevoflurane postconditioning (two periods of sevoflurane inhalation after ischemia for 10 min with a wash period of 10 min, n = 10); (3) resatorvid (intraperitoneal injection of a selective TLR-4 antagonist (3 mg/kg) 30 min before ischemia, n = 10); (4) sevoflurane postconditioning plus resatorvid (n = 10), and sham (n = 5). The numbers of necrotic and apoptotic cells in the hippocampal CA1 region, the expression levels of TLR-4, NF-κB, cleaved caspase-3, and tumor necrosis factor alpha (TNF-α) in the anterior part of each brain, and the serum levels of TNF-α, interleukin 6 (IL-6), and interleukin 1 beta (IL-1β) were assessed 1 day after ischemia. The necrotic cell counts and expression levels of TLR-4, NF-κB, caspase-3, and TNF-α in brain tissue as well as serum levels of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) were significantly higher in the control group than in the other groups. Our findings suggest that the anti-inflammatory actions of sevoflurane postconditioning via inactivation of the TLR-4/NF-κB pathway and subsequent reduction in pro-inflammatory cytokine production, in part, contribute to sevoflurane postconditioning-induced neuroprotection after global transient cerebral ischemia in rats.

Optimum end-tidal concentration of sevoflurane to facilitate supraglottic airway device insertion with propofol at induction allowing spontaneous respiration in obese patients: A prospective observational study

Obese patients are more likely to encounter with difficult airway management, and supraglottic airway device has been adopted to facilitate tracheal intubation. The optimum anesthetic concentration for obese patients to insert a supraglottic airway device with spontaneous respiration has not been investigated. This study was designed to determine the end-tidal concentration of sevoflurane that would provide acceptable condition for supraglottic airway device insertion with propofol at induction in obese patients without using neuromuscular blockade.Thirty elective obese patients [body mass index (BMI) 30-50 kg/m] scheduled for bariatric surgery were enrolled in this study. Sevoflurane was inhaled at a concentration of 5% after infusion of 1 mg/kg propofol (within 1 minute) according to lean body weight. The target concentration of sevoflurane was initiated at 2.5% with 0.5% as a step size using a modified Dixon up-and-down method. Five minutes after target concentration achieved, the insertion of supraglottic airway device was attempted.The minimum alveolar concentration of sevoflurane for successful insertion of supraglottic airway device calculated using up-and-down method were 2.25 (0.53) % for obese patients. The values of the effective concentration of sevoflurane for successful supraglottic airway device insertion in 50% (EC50) and 95% (EC95) of the obese patients obtained by probit regression analysis were 2.09% (95% confidence interval 1.48-2.68) and 3.31% (95% confidence interval 2.70-8.12), respectively.We conclude that sevoflurane at a minimum alveolar concentration of 2.25% can provide optimal conditions for insertion of supraglottic airway device with spontaneous respiration in obese patients with 1 mg/kg propofol at induction.

Sevoflurane protects rat brain endothelial barrier structure and function after hypoxia-reoxygenation injury

Background

After cerebral injury blood-brain barrier disruption significantly impairs brain homeostasis. Volatile anesthetics have been shown to be protective in ischemia-reperfusion injury scenarios. Their impact on brain endothelial cells after hypoxia-reoxygenation (H/R) has not yet been studied in detail.

Methods

Rat brain endothelial cells (RBE4) were exposed to severe hypoxia and reoxygenated in air in the presence or absence of sevoflurane. Changes in dextran permeability and architecture of the cellular junctional proteins ZO-1 and β-catenin were measured. To determine necrosis and apoptosis rate DNA content, LDH release and caspase activity were quantified. The role of vascular endothelial growth factor (VEGF) as an inflammatory mediator increasing vascular permeability was assessed. At the same time, it was evaluated if sevoflurane effects are mediated through VEGF. Results were analyzed by unpaired t-tests or one way-analysis of variance followed by Bonferroni’s correction.

Results

H/R led to a 172% increase in permeability (p<0.001), cell swelling and qualitatively but not quantitatively modified expression of ZO-1, β-catenin and F-actin. In the presence of sevoflurane during reoxygenation, barrier function improved by 96% (p = 0.042) in parallel to a decrease of the cell size and less re-arranged junction proteins and F-actin. Sevoflurane-induced improvement of the barrier function could not be explained on the level of necrosis or apoptosis as they remained unchanged independent of the presence or absence of the volatile anesthetic. Increased expression of VEGF after H/R was attenuated by sevoflurane by 34% (p = 0.004). Barrier protection provided by sevoflurane was similar to the application of a blocking VEGF-antibody. Furthermore, the protective effect of sevoflurane was abolished in the presence of recombinant VEGF.

Conclusions

In H/R-induced rat brain endothelial cell injury sevoflurane maintains endothelial barrier function through downregulation of VEGF, which is a key player not only in mediating injury, but also with regard to the protective effect of sevoflurane.