Low Sevoflurane Concentration Research Articles

Anesthetic Effects of Sevoflurane on the Mouse Somatosensory Cortex: A Flavoprotein Fluorescence Imaging Study

Objective: Sevoflurane, a volatile inhaled anesthetic, is used clinically for general anesthesia in humans. However, the mechanism of action of sevoflurane is not fully understood. We used transcranial flavoprotein fluorescence imaging to visualize somatic sensory cortex responses to noxious stimuli in mice without and with sevoflurane inhalation anesthesia at different concentrations to investigate sevoflurane effects in mice. Methods: A bipolar stimulating electrode was inserted into the left buccal region of the mouse, and changes in flavoprotein fluorescence intensity in the right somatic sensory cortex were recorded before and after electrical stimulation. Measurements were taken while the mouse was awake, at four levels of sevoflurane concentration (0.5%, 1.0%, 1.5%, and 2.0%; 5 min each), and at 10, 20, and 30 min after the end of sevoflurane inhalation. Results: During the awake period, flavoprotein fluorescence intensities in the right sensory cortex decreased after the onset of electrical stimulation, but after 0.9 s, the fluorescence intensity began to increase, reaching a peak value at 2.1 s. This biphasic response significantly decreased at 0.5% sevoflurane and completely disappeared at sevoflurane concentrations above 1.5%, and restored 10 min after cessation of the sevoflurane inhalation. Furthermore, low concentrations of sevoflurane had little effect on the reduction of receptive fields or the conduction of excitation. Conclusion: We conclude that low concentrations of sevoflurane have little effect on the reduction of receptive fields or the conduction of excitation, and that sevoflurane concentrations above 1.5% completely abolish the sensory cortex response elicited by noxious stimulation.

Influence of Different Sevoflurane Concentrations on Postoperative Cognitive Function in Aged Rats.

Postoperative cognitive dysfunction may be associated with neuroinflammation, and sevoflurane suppresses surgery-induced inflammation. We hypothesized that low concentrations of sevoflurane would result in more impaired postoperative cognitive function compared to high concentrations. Aged male Sprague-Dawley rats (n = 21, 17-22 months) were randomly assigned to 1 of 3 groups: control (C), sevoflurane 2% (S2), and sevoflurane 4% (S4). Rats in the S2 and S4 groups underwent open femoral fracture and intramedullary fixation of the left hind limb under 2 hours of sevoflurane anesthesia. Neurological outcomes were evaluated using the Morris water maze (MWM) test, and histopathological outcomes were assessed 28 days after surgery. The S2 group showed prolonged swimming latency compared to S4 on day 7 (difference of means, 34.4; 95% confidence interval [CI], 2.57-66.3; P = .031) and compared to the C group on day 9 (difference of means, -33.4; 95% CI, -65.3 to -1.55; P = .037). The intact CA1 cells in the S2 group were significantly less than those in the C and S4 groups (H statistic, 10.87; P = .006 versus C; P = .033 versus S4). We found that low concentrations of sevoflurane prolonged the swimming latency of the MWM compared to high concentrations and reduced intact CA1 hippocampal neurons in aged rats. These results suggest that low-concentration sevoflurane anesthesia may be more detrimental than high concentration for spatial cognitive function and postoperative impairment of hippocampal CA1 cells in aged rats.

Use of dexmedetomidine and opioids as the primary anesthetic in infants and young children: A retrospective cohort study.

Anesthetic regimens using dexmedetomidine and short-acting opioids have been suggested as potential alternatives to sevoflurane-based anesthesia in children. The primary aim of this study is to compare demographics, intraoperative characteristics, and complications of general anesthetics in which dexmedetomidine and opioids were used without sevoflurane, or in combination with a low sevoflurane concentration, in children 36months old and younger. The secondary aim is to evaluate intraoperative bispectral index (BIS) values when available in these patients. General anesthetics performed between January 1, 2017, and May 1, 2018, in children 2years and younger who received dexmedetomidine and remifentanil, with or without sevoflurane, were identified. Additional anesthetics performed during this time in children 36months and younger who received dexmedetomidine and opioids and had BIS monitoring were also identified. Charts were reviewed for demographic and intraoperative variables, including drug administration and hemodynamic data. A total of 244 patients were identified. All but 22 patients received remifentanil. Ninety-two patients received sevoflurane with a mean end-tidal concentration of 0.84% (SD 0.43). Compared to the sevoflurane group, the nonsevoflurane group received more remifentanil (median dose 0.4μg/kg/min vs 0.2μg/kg/min, difference of 0.1μg/kg/min, 95% CI 0.1-0.3, P<.001) and more dexmedetomidine (median dose 0.9μg/kg/h vs 0.3μg/kg/h, difference of 0.6μg/kg/h, 95% CI 0.4-0.8, P<.001), and had a higher mean arterial pressure (median 53mmHg vs 42mmHg, difference of 11mmHg, 95% CI 8.1-14.8, P<.001). Complications between the two groups were comparable. The median percent intraoperative time with BIS reading <60 was 71.6% (95% CI: 63.3%-79.8%). Dexmedetomidine and opioids can effectively be used in young children as an alternative total intravenous anesthesia technique with or without <1 minimum alveolar concentration of sevoflurane. Bispectral index monitoring reveals a likely sufficient depth of hypnosis.

Supreme\u2122 laryngeal mask airway insertion requires a lower concentration of sevoflurane than ProSeal\u2122 laryngeal mask airway insertion during target-controlled remifentanil infusion: a prospective randomised controlled study

BackgroundProSeal (PLMA) and Supreme (SLMA) laryngeal mask airways are effective ventilator devices with distinctive designs that may require different anaesthetics for insertion. Sevoflurane induction provides acceptable conditions for laryngeal mask insertion, and remifentanil significantly decreases the minimum alveolar concentration of sevoflurane required for that insertion. The study aimed to evaluate the optimal end-tidal (ET) sevoflurane concentration for successful insertion of PLMA versus SLMA in patients receiving a remifentanil infusion without a neuromuscular blocking agent.MethodsAltogether, 45 patients ASA (American Society Anaesthesiologists) physical status I–II, aged 18–60 years were scheduled for elective ambulatory surgery. Exclusion criteria were a difficult airway, recent respiratory infection, reactive airway, obstructive sleep apnoea syndrome, gastric aspiration’s risk factors, pregnancy, and lactation. Patients were randomly allocated to receive the SLMA or the PLMA. Sevoflurane induction with co-administration of remifentanil was performed at an effect-site concentration of 4 ng mL− 1. ET50 was calculated with a modified Dixon’s up-and-down method (starting at 2.5% in steps of 0.5%). Predetermined sevoflurane concentration was kept constant during the 10 min before LMA insertion. Patient’s response to LMA insertion was classified as “movement” or “no movement”. Sevoflurane ET50 was determined as the midpoint concentration of all the independent pairs that manifested crossover from “movement” to “no movement”.ResultsThe ET50 sevoflurane concentration co-administered with remifentanil required for PLMA insertion was 1.20 ± 0.41% (95% confidence interval 0.76 to 1.63%). For SLMA insertion, it was 0.55 ± 0.38% (95% confidence interval 0.14 to 0.95%) (p = 0.019).ConclusionsThe end-tidal sevoflurane concentration with co-administered remifentanil required to allow insertion of the SLMA was 54% lower than that needed for inserting the PLMA.Trial registrationClinicaltrials.gov identifier: NCT03003377. Retrospectively registered. Date of registration: December 28, 2016.

Incidence of postoperative nausea and vomiting is not increased by combination of low concentration sevoflurane and propofol compared with propofol alone in patients undergoing laparoscopic gynecological surgery

BackgroundThe incidence of postoperative nausea and vomiting (PONV) is higher in patients receiving volatile anesthetics than those receiving total intravenous anesthesia (TIVA) with propofol. However, it is unclear whether its incidence is increased when a low concentration of sevoflurane is used in combination with propofol.MethodsThis prospective, randomized, controlled trial enrolled women undergoing laparoscopic gynecological surgery. Patients were randomly assigned to receive general anesthesia either with propofol alone (group P) or with 0.8% sevoflurane and propofol (group SP, n = 36, each group) for maintenance of anesthesia. The incidence of PONV and the number of patients who required antiemetics were compared.ResultsThere were no differences in the incidence of PONV and the number of patients who required antiemetics between the P and SP groups.ConclusionsA combination of 0.8% sevoflurane and propofol to maintain anesthesia does not increase the incidence of PONV compared with TIVA with propofol.Trial registrationUMIN-CTR UMIN000023647, registered 14 August 2016.

Neonatal Exposure to Low-Dose (1.2%) Sevoflurane Increases Rats' Hippocampal Neurogenesis and Synaptic Plasticity in Later Life.

The increasing usage of general anesthetics on young children and infants has drawn extensive attention to the effects of these drugs on cognitive function later in life. Recent animal studies have revealed improvement in hippocampus-dependent performance after lower concentrations of sevoflurane exposure. However, the long-term effects of low-dose sevoflurane on the developing brain remain elusive. On postnatal day (P) 7, rats were treated with 1.2% sevoflurane (1.2% sevo group), 2.4% sevoflurane (2.4% sevo group), and air control (C group) for 6h. On P35-40, rats' hippocampus-dependent learning and memory was tested using the Morris water maze. Cognition-related and synapse-related proteins in the hippocampus were measured using Western blotting on P35. On the same day, neurogenesis and synapse ultrastructure were evaluated using immunofluorescence and transmission electron microscopy (TEM). On P35, the rats neonatally exposed to 1.2% sevoflurane showed better behavioral results than control rats, but not in the 2.4% sevo group. Exposure to 1.2% sevoflurane increased the number of 5'-bromo-2-deoxyuridine (BrdU)-positive cells in the dentate gyrus and improved both synaptic number and ultrastructure in the hippocampus. The expression levels of BDNF, TrkB, postsynaptic density (PSD)-95, and synaptophysin in the hippocampus were also increased in the 1.2% sevo group. In contrast, no significant changes in neurogenesis or synaptic plasticity were observed between the C group and the 2.4% sevo group on P35. These results showed that exposure of the developing brain to a low concentration of sevoflurane for 6h could promote spatial learning and memory function, along with increased hippocampal neurogenesis and synaptic plasticity, in later life.

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.

High initial concentration versus low initial concentration sevoflurane for inhalational induction of anaesthesia.

Sevoflurane induction for general anaesthesia has been reported to be safe, reliable and well accepted by patients. Sevoflurane induction uses either low or high initial concentrations. The low initial concentration technique involves initially administering a low concentration of sevoflurane and gradually increasing the concentration of the dose until the patient is anaesthetized. The high initial concentration technique involves administering high concentrations from the beginning, then continuing with those high doses until the patient is anaesthetized. This review was originally published in 2013 and has been updated in 2016. We aimed to compare induction times and complication rates between high and low initial concentration sevoflurane anaesthetic induction techniques in adults and children who received inhalational induction for general anaesthesia. We defined 'high' as greater than or equal to and 'low' as less than a 4% initial concentration. For the updated review, we searched the following databases: Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 2), MEDLINE (1950 to February 2016), EMBASE (1980 to February 2016), Latin American Caribbean Health Sciences Literature (LILACS) (1982 to February 2016) and the Institute for Scientific Information (ISI) Web of Science (1946 to February 2016). We also searched the reference lists of relevant articles and conference proceedings and contacted the authors of included trials. The original search was run in September 2011. We sought all published and unpublished, randomized controlled trials comparing high versus low initial sevoflurane concentration inhalational induction. Our primary outcomes included two measures of anaesthesia (time to loss of the eyelash reflex (LOER) and time until a weighted object held in the patient's hand was dropped), time to successful insertion of a laryngeal mask airway (LMA) and time to endotracheal intubation. Other outcomes were complications of the technique. We used standardized methods for conducting a systematic review as described in the Cochrane Handbook for Systematic Reviews of Interventions. Two review authors independently extracted details of trial methods and outcome data from reports of all trials considered eligible for inclusion. We conducted all analyses on an intention-to-treat basis, when possible. We estimated overall treatment effects by using a fixed-effect model when we found no substantial heterogeneity, whereas we applied the random-effects model in the presence of considerable heterogeneity. We reran the searches and included one new study (100 participants) in this updated review. In total, we included 11 studies with 829 participants, although most analyses were based on data from fewer participants and evidence of low quality. We noted substantial heterogeneity in the included trials. Thus, our results should be read with caution. It was not possible to combine trials for the primary outcome (LOER), but individual trials reported faster induction times (typically 24 to 82 seconds faster, 41 seconds (31.37 to 50.62)) with high initial concentration sevoflurane (six studies, 443 participants, low-quality evidence). Apnoea appeared to be more common in the high initial concentration sevoflurane group (risk ratio (RR) 3.14, 95% confidence interval (CI) 1.72 to 5.7, two studies, 160 participants, low-quality evidence). We found no evidence of differences between the two groups in the incidence of cough (odds ratio (OR) 1.23, 95% CI 0.53 to 2.81, eight studies, 589 participants, low-quality evidence), laryngospasm (OR 1.59, 95% CI 0.16 to 15.9, seven studies, 588 participants, low-quality evidence), breath holding (OR 1.16, 95% CI 0.47 to 2.83, five studies, 389 participants, low-quality evidence), patient movement (RR 1.14, 95% CI 0.69 to 1.89, five studies, 445 participants, low-quality evidence) or bradycardia (OR 0.8, 95% CI 0.22 to 2.88, three studies, 199 participants, low-quality evidence), and the overall incidence of complications was low. A high initial concentration sevoflurane technique probably offers more rapid induction of anaesthesia and a similar rate of complications, except for apnoea, which may be more common with a high initial concentration. However, this conclusion is not definitive because the included studies provided evidence of low quality.

Rats with Chronic, Stable Pulmonary Hypertension Tolerate Low Dose Sevoflurane Inhalation as Well as Normal Rats Do.

BackgroundThe effects of low concentration of sevoflurane on right ventricular (RV) function and intracellular calcium in the setting of pulmonary arterial hypertension (PAH) have not been investigated clearly. We aim to study these effects and associated signaling pathways in rats with PAH.MethodsHemodynamics were assessed with or without sevoflurane inhalation in established PAH rats. We analysis the classic RV function parameters and RV-PA coupling efficiency using steady-state PV loop recordings. The protein levels of SERCA2, PLB and p-PLB expression was analyzed by western blot to assess their relevance in PAH.ResultsRats with PAH presented with RV hypertrophy and increased pulmonary arterial pressure. The values of Ea, R/L ratio, ESP, SW, PRSW, +dP/dtmax and the slope of the dP/dtmax-EDV relationship increased significantly in PAH rats (P<0.05). Sevoflurane induced a concentration-dependent decrease of systemic and pulmonary blood pressure, HR, RV contractility, and increased the R/L ratio in both groups. Sevoflurane reduced the expression of SERCA2 and increased the expression of PLB in both groups. Interestingly, sevoflurane only reduced the p-PLB/PLB ratio in PAH rats, not in normal rats.ConclusionsRats with chronic, stable pulmonary hypertension tolerate low concentrations of sevoflurane inhalation as well as normal rats do. It may be related to the modulation of the SERCA2-PLB signaling pathway.

Effects of sevoflurane on electroencephalography in immature rat brain

Objective To investigate the effects of sevoflurane on neonatal rats electrocephalography(EEG)and the mechanism. Methods Thirty neonatal rats, aged 14 days, weighing 35- 45 g, were randomly divided into 3 groups: without sevoflurane group(group C,n= 10), low sevoflurane concentration group(group S1,n= 10), high sevoflurane concentration group(group S2). Electroencephalogram recording started immediately after completion of the implant surgery. Anesthesia was induced with 6.0% sevoflurane over 3 min and maintained with 2.1% over 60 min in group S1. In group S2 anesthesia was induced with 8.0% sevoflurane and maintained with 3.5%. Acquisition of the EEG was performed using the Sirenia software. Sirenia Score programs were used for the EEG data analysis. Results As compared with group D and group S1, spike's frequency and amplitude were significantly increased in group S2 during anesthesia induction. Spike's frequency was higher in group S2 than group D during anesthesia maintenaed. The concentration of corticosterone among three groups were:26.8±3.8, 106.5±15.1 and 155.9±13.6, respectively. Compared with group D, the level of corticosterone were significantly increased in group S1 and group S2. Conclusion Sevoflurane anesthesia can induce spike EEG in 14- days rats, which may be induced by high level of corticosterone. Key words: Sevoflurane; Immature rat; Electrocephgraphy; Spike

Multi-capillary column-ion mobility spectrometry (MCC-IMS) as a new method for the quantification of occupational exposure to sevoflurane in anaesthesia workplaces: an observational feasibility study.

BackgroundOccupational exposure to sevoflurane has the potential to cause health damage in hospital personnel. Workplace contamination with the substance mostly is assessed by using photoacoustic infrared spectrometry with detection limits of 10 ppbv. Multi-capillary column-ion mobility spectrometry (MCC-IMS) could be an alternative technology for the quantification of sevoflurane in the room air and could be even more accurate because of potentially lower detection limits. The aim of this study was to test the hypothesis that MCC-IMS is able to detect and monitor very low concentrations of sevoflurane (<10 ppbv) and to evaluate the exposure of hospital personnel to sevoflurane during paediatric anaesthesia and in the post anaesthesia care unit (PACU).MethodsA MCC-IMS device was calibrated to several concentrations of sevoflurane and limits of detection (LOD) and quantification (LOQ) were calculated. Sevoflurane exposure of hospital personnel was measured at two anaesthesia workplaces and time-weighted average (TWA) values were calculated.ResultsThe LOD was 0.0068 ppbv and the LOQ was 0.0189 ppbv. During paediatric anaesthesia the mean sevoflurane concentration was 46.9 ppbv (8.0 - 314.7 ppbv) with TWA values between 5.8 and 45.7 ppbv. In the PACU the mean sevoflurane concentration was 27.9 ppbv (8.0 – 170.2 ppbv) and TWA values reached from 8.3 to 45.1 ppbv.ConclusionsMCC-IMS shows a significantly lower LOD and LOQ than comparable methods. It is a reliable technology for monitoring sevoflurane concentrations at anaesthesia workplaces and has a particular strength in quantifying low-level contaminations of sevoflurane. The exposure of the personnel working in these areas did not exceed recommended limits and therefore adverse health effects are unlikely.

Anesthetic management of pediatric with congenital heart disease with pulmonary hypertension.

Sir, The presence of congenital heart disease (CHD) increases the morbidity and mortality of children undergoing noncardiac surgery. Certain patients have been identified as high risk group of patients among them one is CHD with pulmonary hypertension. A 5-year-old child with 8 kg weight had atrial septal defect (ASD), ventricular septal defect (VSD), left to right shunt with severe pulmonary hypertension (PHT) and was posted for open ureterolithotomy. During preanesthetic checkup, he was having cough and tachypnea. Pulse rate was 108/min, noninvasive blood pressure (NIBP) 100/60 mm of Hg and SPO2 100% on air. His routine blood investigations were within normal limits. X-ray chest showed severe cardiomegaly. electrocardiogram (ECG) showed sinus tachycardia, biventricular hypertrophy with left axis deviation. His 2D echo showed small ostium secundum ASD with left to right shunt, large inlet VSD with bidirectional shunt (11-12 mm) and severe pulmonary arterial hypertension (PAH). Pediatric cardiologist advised surgery with very high risk. On the day of surgery, patient was premedicated with oral midazolam 0.5 mg/kg with SPO2 monitoring before 45 min. After taking him in the operation theater, ECG, pulse oxymetry, and NIBP applied. Patient was induced with injection-glycopyrrolate 0.04 mg, injection- fentanyl 2 μg/kg and injection- propofol 20 mg. Patient's airway was secured with laryngeal mask airway no. 1.5 and anesthesia was maintained with oxygen, sevoflurane with spontaneous respiration. At the end of surgery patient was extubated uneventfully and shifted to high dependency unit with standard monitoring. Postoperatively analgesic injection diclofenac sodium was given 8 hourly. Congenital heart disease is the most common birth defect, occurring in approximately one in 125 live births. Due to advances in modern medicine, mean 90% of these children now survive to adulthood; they pose a challenge for anesthesia because perioperative morbidity and mortality is greater compared with other children.[1] Left to right shunts is the most common lesions representing over 50% of children with CHD. Most children do not manifest heart failure unless their shunt produces a pulmonary to systemic fraction of 3-1.[2] Four major complications of CHD are arrhythmias, cardiac failure, PHT and cyanosis. The anesthetic goals in managing such a patient are to prevent an increase in pulmonary vascular resistance and depression of myocardial function. PHT crisis intervention measures such as 100% oxygen, inhaled nitric oxide, phosphodiesterase inhibitors, prostacyclin analogues, inotropes and other measures to maintain cardiac output and pulmonary blood flow must be prepared and administered accordingly as the need arises.[3] Retrospective analysis of children with PAH who had undergone noncardiac surgery or cardiac catheterization demonstrated incidences of major complications (cardiac arrest or pulmonary hypertensive crisis) and death that are many times greater than those reported in all children undergoing surgical procedures.[4] A complete history and physical examination, focusing on cardiac signs and symptoms previous surgical and catheterization procedures are essential. Echocardiography is noninvasive and the mainstay of diagnostic testing. Midazolam, fentanyl, a small dose of propofol or a low concentration of sevoflurane may be used for induction of anesthesia. When paralysis is required, neuromuscular blocking agents with minimal hemodynamic effects are preferable. (e.g. rocuronium and vecuronium)[3,4] Good intraoperative and postoperative analgesia is associated with improved surgical outcome.[5] Hence, these types of children require knowing about the disease, to make an efficient management plan and always to be prepared to treat complications.

Modeling of recovery profiles in mentally disabled and intact patients after sevoflurane anesthesia; a pharmacodynamic analysis.

PurposeMentally disabled patients show different recovery profiles compared to normal patients after general anesthesia. However, the relationship of dose-recovery profiles of mentally disabled patients has never been compared to that of normal patients.Materials and MethodsTwenty patients (10 mentally disabled patients and 10 mentally intact patients) scheduled to dental surgery under general anesthesia was recruited. Sevoflurane was administered to maintain anesthesia during dental treatment. At the end of the surgery, sevoflurane was discontinued. End-tidal sevoflurane and recovery of consciousness (ROC) were recorded after sevoflurane discontinuation. The pharmacodynamic relation between the probability of ROC and end-tidal sevoflurane concentration was analyzed using NONMEM software (version VII).ResultsEnd-tidal sevoflurane concentration associated with 50% probability of ROC (C50) and γ value were lower in the mentally disabled patients (C50=0.37 vol %, γ=16.5 in mentally intact patients, C50=0.19 vol %, γ=4.58 in mentally disabled patients). Mentality was a significant covariate of C50 for ROC and γ value to pharmacodynamic model.ConclusionA sigmoid Emanx model explains the pharmacodynamic relationship between end-tidal sevoflurane concentration and ROC. Mentally disabled patients may recover slower from anesthesia at lower sevoflurane concentration at ROC an compared to normal patients.

Risk factors for early postoperative cognitive dysfunction after non-coronary bypass surgery in Chinese population

BackgroundThe present study was performed to investigate the incidence of early postoperative cognitive dysfunction (POCD) after non-coronary bypass surgery and the potential risk factors in Chinese population.MethodsWe performed a prospective study in a teaching tertiary hospital from May 2012 to August 2012. One hundred and seventy-six adult patients undergoing non-coronary bypass surgery were recruited. Mini-Mental State Examination (MMSE) score was evaluated before and 3 to 5 days after surgery. Patients with a MMSE score reduction of 2 was diagnosed with POCD.ResultsThe general incidence of POCD was 33.0%, with no significant difference between the types of surgeries. In the univariate analysis, POCD associated factors included age, duration of surgery, anesthesia, cardiopulmonary bypass (CPB), cross-clamp and rewarming, and sevoflurane concentration. However, only age, cross-clamp duration and sevoflurane concentration were demonstrated to be independent risk factors for POCD.ConclusionIncidence of early POCD after non-coronary bypass surgery was relatively high in Chinese population. Advanced age, longer aortic cross-clamp duration and lower sevoflurane concentration was associated with a higher incidence of POCD.

Target-controlled induction with 2.5% sevoflurane does not avoid the risk of electroencephalographic abnormalities

BackgroundEpileptiform discharges (ED) can occur during sevoflurane induction, especially in young female patients and when high alveolar concentrations are used. The aim of this study was to evaluate whether low sevoflurane concentration reduces the occurrence of ED in female patients. MethodsThirty-four female patients scheduled for minor gynecological surgery were prospectively included and randomized in two groups. In group A, anesthesia was induced with sevoflurane inspired 8% manually set via the circuit of the Zeus® (Dräger Medical, Lübeck, Germany) anesthesia workstation (fresh gas flow 8L.min−1) for 2min and then 2.5%. In group B, induction was performed by target-controlled inhalation with a target end-tidal concentration of sevoflurane set at 2.5% (fresh gas flow in auto-control mode). Electroencephalogram (EEG) was recorded in the operating room throughout induction till two min after intubation and analyzed off-line by a neurophysiologist blinded to the randomization. ResultsED occurred in five patients (15%): one in group A and four in group B (P>0.05). ED occurred with a median delay of 303 s [25–75 interquartiles: 135–418] and the median duration of ED episode was 13 s [3–78]. Fifteen patients had abnormal movements without simultaneous EEG abnormality. ConclusionInduction of anesthesia with low target concentration of sevoflurane (2.5%) fails to totally prevent the occurrence of ED in young female patients and should be used carefully in this population.

Effect of pre-exposure to sevoflurane on the bispectral index in women undergoing Caesarean delivery under general anaesthesia

Patients undergoing Caesarean delivery under inhalation anaesthesia are at a high risk of awareness, especially in the period before delivery. We assessed the effects of pre-exposure to sevoflurane on the bispectral index (BIS) in the interval before delivery. Sixty-four patients undergoing elective Caesarean delivery were randomly assigned to receive 1.0-1.1 vol% (control 1) or 1.2-1.3 vol% (control 2) end-tidal sevoflurane, or the same concentrations of end-tidal sevoflurane combined with pre-exposure to 1 vol% sevoflurane for the last 1 min of the preoxygenation period (the preSevo 1 and preSevo 2 groups, respectively). We assessed BIS values, arterial pressure, and heart rate at the time of induction; before intubation; and upon skin incision, uterine incision, and delivery. We also determined the maternal incidence of intraoperative awareness and the neonatal Apgar scores, and conducted umbilical blood gas analysis. At skin incision, BIS values were significantly lower in the preSevo 1 group than in the control 1 group [50 (13) vs 72 (8), P<0.001] and in the preSevo 2 group than in the control 2 group [44 (11) vs 67 (10), P<0.001]. The mean BIS values in the preSevo 1 and 2 groups were maintained below 60 in the period before delivery. No other parameter differed among groups, and no patient exhibited intraoperative awareness. Pre-exposure to low concentrations of sevoflurane reduced BIS values in the interval before delivery, suggesting that this approach may reduce the risk of maternal awareness. Clinical Research Information Service (code KCT0000069, http://cris.cdc.go.kr).

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

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

The clinical effective dose of rocuronium for lightwand tracheal intubation after induction with alfentanil, propofol, and low concentrations of sevoflurane

BackgroundThe aim of this study was to determine the clinical effective dose of rocuronium for tracheal intubation using a lightwand after induction with propofol, alfentanil, and a low concentration of sevoflurane.MethodsTwenty-eight adults scheduled to undergo elective surgery lasting less than one hour were enrolled in this study. All patients received alfentanil (10 µg/kg) and propofol (1.5 mg/kg) for the induction of anesthesia. Tracheal intubation using a lightwand was attempted 3 minutes after administering rocuronium and mask ventilation with 2 vol% of sevoflurane. The initial rocuronium dose was 0.5 mg/kg. The rocuronium dose for consecutive patients, determined by Dixon's up-and-down method, was increased or decreased by 0.05 mg/kg according to the result of the previous patient. The mean arterial pressure and heart rate were recorded before induction, 1 min before intubation, 1 and 2 min after intubation.ResultsThe 50% clinical effective dose (cED50) of rocuronium for tracheal intubation using a lightwand was 0.20 ± 0.05 mg/kg according to Dixon's up and down method. Isotonic regression revealed the cED50 and cED95 (95% confidence intervals) to be 0.20 mg/kg (0.10-0.3 mg/kg) and 0.35 mg/kg (0.16-0.49 mg/kg), respectively.ConclusionsThe cED50 and cED95 of rocuronium for tracheal intubation using the lightwand were 0.20 mg/kg and 0.35 mg/kg, respectively, after induction with alfentanil, propofol, and a low concentration of sevoflurane.

Effects of sevoflurane on carrageenan- and fentanyl-induced pain hypersensitivity in Sprague-Dawley rats

Opioids are widely used for anesthesia but paradoxically induce postoperative pain hypersensitivity via N-methyl-D: -aspartate (NMDA) receptor modulation. Sevoflurane effects on opioid-induced hyperalgesia have not been yet evaluated in vivo. Nevertheless, some experimental in vitro studies reported anti-NMDA receptor properties for sevoflurane. The aim of this study was to evaluate sevoflurane effects on fentanyl-induced hyperalgesia in opioid-naive rats and in rats with inflammatory pain. Sevoflurane effects on hyperalgesia were evaluated in Sprague-Dawley rats: opioid-naive rats, rats treated with fentanyl (4 x 60 microg kg(-1)) and rats with inflammatory pain (carrageenan) treated with fentanyl (4 x 60 microg kg(-1)). On day zero, subcutaneous fentanyl injections were administered and inflammatory pain was induced with one carrageenan injection in one hind paw. Rats were exposed to low concentrations of sevoflurane (1.0 or 1.5%) on day zero prior to fentanyl injections and inflammatory pain induction, and for the duration of the fentanyl analgesic effect. The nociceptive threshold (Randall-Selitto test) was evaluated daily for 7 days. On day seven, naloxone was injected and the nociceptive threshold was assessed 5 min later. In rats without inflammatory pain but treated with fentanyl on day zero, sevoflurane 1.0% reversed the early (day zero) and long-lasting (day zero to day three) hyperalgesia classically described after high-doses of fentanyl (P < 0.05). This sevoflurane concentration antagonized the hyperalgesia induced by naloxone on day seven (P = 0.33). In a second experiment in rats with inflammatory pain, exposure to low concentrations of sevoflurane (1.0 and 1.5%) did not reduce fentanyl-induced hyperalgesia (P > 0.05), but nevertheless antagonized the naloxone induced hyperalgesia on day seven (P = 0.061). Relatively low sevoflurane concentrations (1.0%) reverse fentanyl-induced hyperalgesia in rats without inflammatory pain. Nevertheless, the lack of effect of sevoflurane concentrations of 1.0% and 1.5% to oppose hyperalgesia following high-dose fentanyl and inflammatory pain suggests that sevoflurane anti-hyperalgesic properties are weak.

Increased formation of sister chromatid exchanges, but not of micronuclei, in anaesthetists exposed to low levels of sevoflurane

We have assessed, for the first time, genotoxicity (i.e. sister chromatid exchanges and micronuclei) in anaesthetists exposed to a single volatile anaesthetic (sevoflurane) without nitrous oxide. The anaesthetists were exposed to an 8-h time-weighted average of 0.2 parts per million sevoflurane. Internists served as non-exposed controls. Mean (SD) sister chromatid exchanges per cell were significantly higher in anaesthetists compared to internists (6.6 (0.9) vs 5.1 (0.8); p < 0.001) whereas median (IQR [range]) micronuclei per 1000 binucleated cells did not differ (9.5 (6.3-10.8 [2.0-15.5]) vs 8.5 (6.0-10.5 [3.0-25.5]), respectively). Although the anaesthetists were exposed to rather low concentrations of sevoflurane, this 30% increase of sister chromatid exchanges is in agreement with a recently reported 300% increase with a high level exposure to sevoflurane and nitrous oxide. Omitting nitrous oxide does not normalise increased rates of sister chromatid exchanges.