Minimum Alveolar Concentration Of Desflurane Research Articles

Effect of desflurane anesthesia on flash visual evoked potential monitoring in patients undergoing spine surgery: study protocol for a randomized controlled trial

BackgroundFlash visual evoked potentials (FVEPs) are a reliable method for protecting visual function during spine surgery in prone position. However, the popularization and application of FVEPs remain limited due to the unclear influence of various anesthetics on FVEPs. Exploring the effects of anesthetic drugs on FVEP and establishing appropriate anesthesia maintenance methods are particularly important for promoting and applying FVEP. According to the conventional concept, inhaled narcotic drugs significantly affect the success of FVEP monitoring, FVEP extraction, and interpretation. Nonetheless, our previous study demonstrated that sevoflurane-propofol balanced anesthesia was a practicable regimen for FVEPs. Desflurane is widely used in general anesthesia for its rapid recovery properties. As the effect of desflurane on FVEP remains unclear, this trial will investigate the effect of different inhaled concentrations of desflurane anesthesia on amplitude of FVEPs during spine surgery, aiming to identify more feasible anesthesia schemes for the clinical application of FVEP.Methods/ designA total of 70 patients undergoing elective spinal surgery will be enrolled in this prospective, randomized controlled, open-label, patient-assessor-blinded, superiority trial and randomly assigned to the low inhaled concentration of desflurane group (LD group) maintained with desflurane-propofolremifentanil-balanced anesthesia or high inhaled concentration of desflurane group (HD group) maintained with desflurane-remifentanil anesthesia maintenance group at a ratio of 1:1. All patients will be monitored for intraoperative FVEPs, and the baseline will be measured half an hour after induction under total intravenous anesthesia (TIVA). After that, patients will receive 0.5 minimum alveolar concentration (MAC) of desflurane combined with propofol and remifentanil for anesthesia maintenance in the LD group, while 0.7–1.0 MAC of desflurane and remifentanil will be maintained in the HD group. The primary outcome is the N75-P100 amplitude 1 h after the induction of anesthesia. We intend to use the dual measure evaluation, dual data entry, and statistical analysis by double trained assessors to ensure the reliability and accuracy of the results.DiscussionThis randomized controlled trial aims to explore the superiority effect of low inhaled concentration of desflurane combined with propofolremifentanil-balanced anesthesia versus high inhaled concentration of desflurane combined with remifentanil anesthesia on amplitude of FVEPs. The study is meant to be published in a peer-reviewed journal and might guide the anesthetic regimen for FVEPs. The conclusion is expected to provide high-quality evidence for the effect of desflurane on FVEPs and aim to explore more feasible anesthesia schemes for the clinical application of FVEPs and visual function protection.Trial registrationThis study was registered on clinicaltrials.gov on July 15, 2022. ClinicalTrials.gov Identifier: NCT05465330.

Anesthetic management of a patient with an electroencephalogram phenotype for a “vulnerable brain”: a case report

BackgroundLow frontal alpha power is an electroencephalogram phenotype suggesting vulnerability to anesthetics. This phenotype for a “vulnerable brain” carries risks for burst suppression at lower-than-expected anesthetic concentrations and therefore for postoperative delirium.Case presentationA 73-year-old man underwent a laparoscopic Miles’ operation. He was monitored with a bispectral index monitor. Before the skin incision, the fraction of age-adjusted minimum alveolar concentration of desflurane was 0.48, and a spectrogram showed slow-delta oscillation despite a bispectral index value of 38–48. Although the fraction of age-adjusted minimum alveolar concentration of desflurane decreased to 0.33, the EEG signature remained unchanged, along with a similar bispectral index value. No burst suppression patterns were observed throughout the whole procedure, and he did not experience postoperative delirium.ConclusionsThis case suggests that monitoring of electroencephalogram signatures is helpful for detecting patients with a “vulnerable brain” and for providing optimal anesthetic depth in such patients.

Comparison of the Effect of Anesthetic Agents on Blood Levels of Parathyroid Hormone and Ionized Calcium: A Prospective Randomized Controlled Trial.

The aim of this randomized control trial is to compare the effect of anesthetic agents on blood levels of parathyroid hormone and ionized calcium. 77 American Society of Anesthesiologists I-II patients who would undergo laparoscopic cholecystectomy were enrolled into this prospective study and randomized into 3 groups with sealed envelope technique as Group S: sevoflurane, Group D: desflurane, and Group TIVA: total intravenous anesthesia. The first blood sample was used to check the baseline blood levels of parathyroid hormone and ionized calcium. In Group S or D, maintenance of anesthesia was being performed with 1 MAC (minimum alveolar concentration) sevoflurane or desflurane, respectively, while in Group TIVA, it was performed with 150 mcg/kg/min propofol and 1 mcg/kg/min remifentanil IV infusions. At the 30th minute of anesthesia and at the 1st hour of end of anesthesia, 2nd and 3rd blood samples, respectively, were used to check the blood levels of PTH and Ca. During perioperative period, hemodynamic parameters were also noted. Blood levels of parathyroid hormone at the 30th min after anesthesia were found to be significantly different between groups (P=0,01). The PTH level at the 30th min after anesthesia was found significantly higher in Group S than that of Groups D and TIVA (P=0.005 and P=0.001, respectively). Blood levels of ionized calcium at 30th min after anesthesia were found significantly different between groups (P=0,048). It was found significantly higher in Group TIVA than that in Group S (P=0.024). Desflurane seems to be the best agent for parathyroidectomy procedures. Future research studies are needed to be conducted to reach out more correct and valuable outcomes.

Spontaneous breathing for managing analgesia during balanced anesthesia with remifentanil and desflurane: a prospective, single center randomized controlled trial.

The main goal of anesthesiology is to achieve the best level of analgesia and a fast recovery of consciousness following anesthesia. The preservation of spontaneous breathing during general anesthesia with anesthetic gases is practiced by many anesthetists. However, very few studies have dealt with these positive properties of volatile anesthetics such as sevoflurane or desflurane. Remifentanil is a very short half-life opiate that combines sufficient intra-operative analgesia with a fast post-operative recovery time. We tested the hypothesis that spontaneous breathing can reduce overdosing with remifentanil during desflurane anesthesia. In this prospective, single center, multiple anesthetist study, 30 patients were randomized into two groups (volume-controlled ventilation mode and spontaneous breathing). The spontaneous breathing group showed a significantly lower post-operative pain level than the volume-controlled ventilation mode group. Furthermore, less remifentanil as well as less piritramide was needed in the spontaneous breathing group compared with volume-controlled ventilation mode. It was possible to achieve spontaneous breathing in all patients with 0.6 minimum alveolar concentration desflurane, in order to control the remifentanil rate and prevent an overdose. All spontaneous breathing patients had low intra- and post-operative pain levels and the need for analgesics was equal to or lower than that in the volume-controlled ventilation mode group. By reducing the intra-operative amount of opiates, both the post-operative pain and the amount of post-operative analgesia required can be reduced. A balanced anesthesia with spontaneous intra-operative breathing is needed to determine the required amount of opiates. This study was approved by the Ethic Committee of the Ruhr-University of Bochum (approval No. 2435) in September, 2004.

Effect of intravenous lignocaine infusion on the quality of emergence in patients undergoing transsphenoidal resection of pituitary tumors - A prospective, randomized controlled trial.

Background: Emergence from anesthesia is a critical step in patients undergoing transsphenoidal pituitary surgery (TSS). The cough suppressant and anesthetic sparing properties of lignocaine makes it a favorable option for smooth extubation and maintaining stable hemodynamics intraoperatively. We aimed to evaluate the effect of lignocaine infusion on the quality of emergence (QOE) and intraoperative hemodynamics in patients undergoing transsphenoidal resection of pituitary tumors.Methods: Fifty patients scheduled to undergo TSS were randomly divided into ligocaine group (n = 25), receiving 1.5 mg/kg bolus dose of lignocaine followed by continuous infusion of 1.5 mg/kg/h and saline group (n = 25). Patients assigned to the control group received equal volume of saline receiving equal volume of saline. The four emergence parameters (mean arterial pressure [MAP], heart rate (HR), cough, and agitation) were abbreviated into an aggregated score for QOE. Time to emergence and intraoperative hemodynamics were also recorded.Results: The QOE was not found to be different between the two groups (P = 0.294). Lignocaine did not increase the time to emergence (P = 0.166). The intraoperative HR and MAP were comparable between the two groups. A lower minimum alveolar concentration of desflurane was required in lignocaine group during insertion of nasal speculum (P = 0.018) and at the time of seller ridge dissection (P = 0.043) compared to the saline group.Conclusion: Intraoperative lignocaine infusion of 1.5 mg/kg/h did not significantly improve the QOE with respect to hemodynamics, cough, and emergence agitation in patients undergoing transsphenoidal resection of pituitary tumors.

Evaluating NeuroSENSE for assessing depth of hypnosis during desflurane anesthesia: an adaptive, randomized-controlled trial.

Processed electroencephalography (EEG) monitors support depth-of-hypnosis assessment during anesthesia. This randomized-controlled trial investigated the performance of the NeuroSENSE electroencephalography (EEG) monitor to determine whether its wavelet anesthetic value for central nervous system (WAVCNS) index distinguishes consciousness from unconsciousness during induction of anesthesia (as assessed by the anesthesiologist) and emergence from anesthesia (indicated by patient responsiveness), and whether it correlates with changes in desflurane minimum alveolar concentration (MAC) during maintenance of anesthesia. EEG was collected using a fronto-temporal bilateral montage. The WAVCNS was continuously recorded by the NeuroSENSE monitor, to which the anesthesiologist was blinded. Anesthesia was induced with propofol/remifentanil and maintained with desflurane, with randomized changes of -0.4, 0, or +0.4 MAC every 7.5 min within the 0.8-1.6 MAC range, if clinically acceptable to the anesthesiologist. During emergence from anesthesia, desflurane was stepped down by 0.2 MAC every five minutes. Data from 75 patients with a median [interquartile range] age of 41[35-52] yr were obtained. The WAVCNS distinguished consciousness from unconsciousness as assessed by the anesthesiologist, with area under the receiver operating characteristic curve of 99.5% (95% confidence interval [CI], 98.5 to 100.0) at loss of consciousness and 99.4% (95% CI, 98.5 to 100.0) at return of consciousness. Bilateral WAVCNS changes correlated with desflurane concentrations, with -8.0 and -8.6 WAVCNS units, respectively, per 1 MAC change in the 0.8-1.6 MAC range during maintenance of anesthesia and -10.0 and -10.5 WAVCNS units, respectively, in the 0.4-1.6 MAC range including emergence from anesthesia. The NeuroSENSE monitor can reliably discriminate between consciousness and unconsciousness, as assessed by the anesthesiologist, during induction of anesthesia and with a lower level of reliability during emergence from anesthesia. The WAVCNS correlates with desflurane concentration but plateaus at higher concentrations, similar to other EEG monitors, which suggests limited utility to titrate higher concentrations of anesthetic vapour. clinicaltrials.gov, NCT02088671; registered 17 March, 2014.

Desflurane impairs hippocampal learning on day 1 of exposure: a prospective laboratory study in rats

BackgroundQuick and complete recovery of cognitive function after general anesthesia is desirable, particularly for working-age patients. Desflurane is less likely to have long-term effects than older-generation inhalational anesthetics, however, its short-term effects have not been fully investigated. Our objective was to elucidate the short-term effects of desflurane exposure on learning and memory in young adult rats.MethodsSeven-week old male Sprague–Dawley rats were exposed to air (control), or desflurane at 0.7 or 1.2 minimum alveolar concentration (MAC) for 2 h (day 0). The inhibitory avoidance (IA) test was performed on day 1 to delineate the effects on contextual learning. Separate groups of control and 1.2 MAC desflurane animals underwent the IA test on days 3 and 7 to examine the time-dependent changes. Because the IA test is known to be dependent on the long-term potentiation (LTP) of the hippocampus and the trafficking of the GluR1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor into the synapses, the effects of 1.2 MAC desflurane on these phenomena were evaluated on day 1.ResultsDesflurane at 1.2 MAC, but not 0.7 MAC, significantly decreased the IA latencies on day 1 compared with the control (one-way ANOVA, F [2,48] = 5.974, P = 0.005, post hoc Tukey’s, mean difference [95% confidence interval], control vs. 1.2 MAC, 168 [49.9 to 287], P = 0.004; control vs. 0.7 MAC, 67.5 [− 51.2 to 186], P = 0.362). The latencies were not affected on days 3 and 7 (day 3, control vs. desflurane, P = 0.861; day 7, control vs. desflurane, P > 0.999). Consistently, hippocampal LTP on day 1 was significantly suppressed in the desflurane group compared with the control group (P = 0.006). Moreover, immunoblotting analysis of synaptic GluR1 expression revealed that desflurane exposure significantly suppressed GluR1 delivery to the synapses after IA training.ConclusionExposure to a relatively high concentration of desflurane caused reversible learning and memory impairment in young adult rats associated with suppression of GluR1 delivery to the synapses in the hippocampus.

Determination of minimum alveolar concentration and cardiovascular effects of desflurane in positive-pressure ventilated sheep.

OBJECTIVE To determine the minimum alveolar concentration of desflurane (MACDES) and effects on cardiovascular variables in positive-pressure ventilated sheep. ANIMALS 13 adult female sheep. PROCEDURES Anesthesia was induced with desflurane. After a 30-minute equilibration at an end-tidal concentration of desflurane (etDES) of 10.5%, an electrical stimulus (5 Hz/ms and 50 mA) was applied for 1 minute or until gross purposeful movement occurred. The etDES was then changed by 0.5% (modified up-down method), depending on whether a positive motor response had been elicited, and stimulation was repeated. The MACDES was the etDES midway between a positive and negative response. After MACDES was determined, etDES was increased to 1.3 and 1.6 MACDES. Animals were allowed to equilibrate for 15 minutes, and cardiovascular, blood gas, acid-base, and hematologic variables were measured. Times to induction of anesthesia, extubation, attainment of sternal position, and standing and duration of anesthesia were recorded. RESULTS Mean ± SD MACDES was 9.81 ± 0.79%. Times to intubation, extubation, and standing were 4.81 ± 2.21 minutes, 14.09 ± 4.05 minutes, and 32.4 ± 12.5 minutes, respectively. Duration of anesthesia was 226 ± 22 minutes. Heart rate increased significantly at induction of anesthesia but otherwise remained at preanesthetic rates. Arterial blood pressures progressively decreased with increasing etDES; pressures increased slightly only in response to noxious stimulation. CONCLUSIONS AND CLINICAL RELEVANCE The MACDES determined here compared favorably with that determined for other sheep populations and indicated similar anesthetic potency as in other species. Desflurane caused dose-dependent arterial hypotension, which indicated the need for careful blood pressure monitoring.

Minimum Alveolar Concentration of Desflurane for Maintaining BIS Below 50 in Children and Effect of Caudal Analgesia on it.

Context:Neuraxial techniques have sedative properties secondary to decreased inputs from sensory and motor afferents. We hypothesized that caudal analgesia decreases the requirement of desflurane as measured by bispectral index (BIS).Aims:This study aims to determine the minimum alveolar concentration (MAC) of desflurane for maintaining BIS below 50 (MACBIS50) in children undergoing infraumbilical surgeries with laryngeal mask airway (LMA) and study the effect of caudal analgesia on the same.Settings and Design:This is prospective and observational study.Subjects and Methods:Thirty-nine American Society of Anesthesiologists physical status Classes I and II children in between 1 and 8 years of age undergoing elective infraumbilical surgery under general anesthesia were allocated randomly into two groups (Group C and Group D) after induction with sevoflurane and LMA insertion. In Group C, caudal block was performed with 0.75 mL/kg of 0.25% bupivacaine and BIS values were recorded after 10 min for 1 min at 10 s intervals. In Group D, BIS was recorded for desflurane for 1 min at 10 s intervals followed by a caudal block with the same dose.Statistical Analysis Used:Dixon up-down method with a step size of 0.5%, and probit analysis were used for analysis.Results:A total of 39 patients were enrolled. MAC of desflurane for maintaining MACBIS50 was 5.57 (95% confidence interval [CI] 5.22–5.95) in Group D and 4.31 (95% CI 3.12–5.08) in Group C. The use of caudal anesthesia lowered the MAC of desflurane for maintaining MACBIS50 in children by 22.36% (P < 0.001).Conclusions:The use of caudal analgesia significantly reduced MAC of desflurane for maintaining MACBIS50 in children undergoing infraumbilical surgeries using LMA.

Electrophysiological effects of desflurane in children with Wolff-Parkinson-White syndrome: a randomized crossover study.

We hypothesized that, compared with propofol, desflurane prolongs the antegrade accessory pathway effective refractory period (APERP) in children undergoing radiofrequency catheter ablation for Wolff-Parkinson-White (WPW) syndrome. In this randomized crossover study, children aged 4.1-16.1years undergoing radiofrequency catheter ablation for WPW syndrome were randomly divided into four groups according to the concentration of desflurane and anesthetics used in the first and the second electrophysiological studies (EPS). After induction of general anesthesia with propofol and tracheal intubation, they received one of the following regimens: 0.5 minimum alveolar concentration (MAC) desflurane (first EPS) and propofol (second EPS) (Des0.5-Prop group, n=8); propofol (first EPS) and 0.5 MAC desflurane (second EPS) (Prop-Des0.5 group, n=9); 1 MAC desflurane (first EPS) and propofol (second EPS) (Des1.0-Prop group, n=10); propofol (first EPS) and 1 MAC desflurane (second EPS) (Prop-Des1.0 group, n=9). Radiofrequency catheter ablation was performed upon completion of EPS. Sample size was determined to detect a difference in the APERP. Desflurane at 1.0 MAC significantly prolonged the APERP compared with propofol, but did not affect the sinoatrial conduction time, atrio-His interval or atrioventricular node effective refractory period. Supraventricular tachycardia was induced in all children receiving propofol, but not induced in 1 and 4 children receiving 0.5 MAC and 1.0 MAC desflurane, respectively. Desflurane enhances the refractoriness and may block the electrical conduction of the atrioventricular accessory pathway, and is therefore not suitable for use in children undergoing radiofrequency catheter ablation for WPW syndrome.

Time- and Dose-Dependent Effects of Desflurane in Sensitized Airways

Although the bronchodilatory actions of volatile anesthetics, such as halothane, isoflurane, and sevoflurane, have been well documented in previous studies, the properties of desflurane remain controversial. The aim of this study was to investigate the effects of desflurane at different concentrations and durations in an ovalbumin-sensitized guinea pig model of airway hyper-responsiveness. Ovalbumin-sensitized animals (n = 176) were randomly assigned to 5 groups according to the minimum alveolar concentration (MAC) of desflurane they received: 0.0, 0.5, 1.0, 1.5, and 2.0 MAC. Total lung resistance in vivo, airway smooth muscle tension in vitro, and intracellular cyclic adenosine monophosphate (AMP) levels were measured to evaluate the effects of desflurane. In 5 sensitized groups, total lung resistance increased from baseline to peak at approximately 8 minutes and then decreased slowly until about 17 minutes with extended administration of desflurane. Desflurane dose-dependently increased total lung resistance with or without incremental doses of acetylcholine and reduced muscle tension with increasing concentrations of carbacholine. Cyclic AMP levels were increased by desflurane: at the 60-minute time point, cyclic AMP concentrations (means ± SD) with 0.5 MAC (1.96 ± 0.40) and 1.0 MAC (2.11 ± 0.50) desflurane were higher than those at the 8-minute time point (1.11 ± 0.23 and 1.32 ± 0.32). Desflurane exerted time- and dose-dependent effects and could be used at 0.5 and 1.0 MAC concentrations without significant bronchoconstriction in ovalbumin-sensitized guinea pigs. Cyclic AMP-mediated airway smooth muscle relaxation might be one mechanism by which desflurane induces bronchodilation.

Effect of Intravenous Magnesium Sulfate on the Minimum Alveolar Concentrations of Desflurane Using Bispectral Index Monitoring: A Prospective Randomized Double-blind Controlled Study.

Background:Magnesium sulfate has been implicated to influence the minimum alveolar concentration (MAC) of various volatile anesthetics, but its effect on desflurane remains unanswered so far.Aim:To study the effect of perioperative intravenous magnesium sulfate on MAC of desflurane using bispectral index (BIS) monitoring.Settings:Operating room of a tertiary care hospital.Design:A prospective, randomized, controlled, double-blind clinical trial.Methods:Sixty American Society of Anesthesiologists Physical Status I/II patients aged 18–65 years and scheduled for breast conservative surgeries were randomized into three groups of 20 each. Control group (Group 1) was administered 100 ml normal saline (NS) as bolus followed by NS infusion. Magnesium (Mg) was administered as bolus of 40 mg/kg in 100 ml NS followed by NS infusion in Group 2 and as bolus of 40 mg/kg followed by infusion of 10 mg/kg/h of Mg in NS in Group 3. Anesthesia was induced with propofol, fentanyl, and atracurium. Dial setting of desflurane was adjusted to target a BIS of 45–55. Time from cessation of desflurane to beginning of spontaneous movement, time taken to respond to verbal commands, time of extubation, and time taken to reach BIS value of 70 were recorded.Statistical Analysis:Statistics was done using SPSS program using ANOVA and the Chi-square test for variables and a P < 0.05 was taken to indicate a significant difference.Results:No significant difference was present in MAC, end-tidal desflurane, and cumulative consumption of morphine. Recovery was similar in Group 2 and Group 3, but time to eye opening (P = 0.011), time to respond to verbal commands (P < 0.001), and time to extubate (P < 0.001) were significantly delayed when compared with patients in Group 1. Hemodynamic changes were comparable among three groups.Conclusions:From this study, we conclude that MACs of desflurane using BIS as a guide remains unaffected by perioperative infusion of magnesium sulfate.

Comparison of emergence after deep extubation using desflurane or desflurane with remifentanil in patients undergoing general anesthesia: a randomized trial

Study objectiveTo compare recovery times and respiratory complications during emergence after deep extubation using either desflurane alone or a lower concentration of desflurane with remifentanil. DesignProspective randomized double-blind clinical trial. SettingIntraoperative. PatientsA total of 62 patients between the ages of 20 and 60 years with American Society of Anesthesiologists class I or II and who underwent low- to intermediate-risk surgery of 2- to 4-hour duration were enrolled. InterventionsRandomly assigned either 1.5 minimum alveolar concentration desflurane (group D; n = 31) or 1.0 minimum alveolar concentration of desflurane and 1.0 ng/mL effect-site concentration of remifentanil (group DR; n = 31). MeasurementsRecovery times, from the time of extubation to the time when the patients could breathe without assistance, were awake enough to maintain the airway independently, and exited the recovery room, as well as respiratory complications were compared between the groups. Main ResultsRecovery times were significantly reduced in the group DR (P < .001). The incidence of respiratory complications was also lower in group DR than in group D (48% vs 3.8%; P < .001). ConclusionsThe combined use of remifentanil while lowering the concentration of desflurane improves recovery profiles during emergence after deep extubation.

Age-dependent decrease in desflurane concentration for maintaining bispectral index below 50.

We examined the hypothesis that the minimum alveolar concentration of desflurane for maintaining bispectral index (BIS) below 50 (MACBIS 50 ) decreases with advance of age. Sixty young (20-30 year), middle-aged (31-65 year) and elderly (66-80 year) patients were included (n = 20, each group). Five minutes following the start of continuous intravenous administration of remifentanil at 0.25 μg/kg/min, general anaesthesia was induced with propofol 2 mg/kg and rocuronium 0.8 mg/kg to facilitate tracheal intubation. Infusion of remifentanil was stopped immediately after tracheal intubation. When BIS began to increase > 60, maintenance of anaesthesia was started with an end-tidal desflurane concentration of 4.0% and maintained for 10 min followed by 1-min assessment of BIS taken at 10-s intervals. MACBIS 50 of each age group was estimated by up-down methodology. MACBIS 50 of desflurane in young, middle-aged and elderly patients was 4.25% end-tidal (95% confidence intervals 4.04-4.46), 3.58% (3.38-3.79) and 2.75% (2.50-3.00) respectively. MACBIS 50 was higher (P = 0.011) in young patients and lower (P = 0.012) in elderly patients than those in middle-aged patients. Advance in age significantly decreased the concentrations of desflurane required to maintain BIS below 50. BIS reflected age-associated decrease in end-tidal concentrations of desflurane required for maintaining adequate depth of anaesthesia during resting state.

Effects of oxymorphone hydrochloride or hydromorphone hydrochloride on minimal alveolar concentration of desflurane in sheep.

To establish the minimum alveolar concentration (MAC) of desflurane and evaluate the effects of 2 opioids on MAC in sheep. 8 adult nulliparous mixed-breed sheep. A randomized crossover design was used. Each sheep was evaluated individually on 2 occasions (to allow assessment of the effects of each of 2 opioids), separated by a minimum of 10 days. On each occasion, sheep were anesthetized with desflurane in 100% oxygen, MAC of desflurane was determined, oxymorphone (0.05 mg/kg) or hydromorphone (0.10 mg/kg) was administered IV, and MAC was redetermined. Physiologic variables and arterial blood gas and electrolyte concentrations were measured at baseline (before MAC determination, with end-tidal desflurane concentration maintained at 10%) and each time MAC was determined. Timing of various stages of anesthesia was recorded for both occasions. Mean ± SEM MAC of desflurane was 8.6 ± 0.2%. Oxymorphone or hydromorphone administration resulted in significantly lower MAC (7.6 ± 0.4% and 7.9 ± 0.2%, respectively). Cardiac output at MAC determination for desflurane alone and for desflurane with opioid administration was higher than that at baseline. No difference was identified among hematologic values at any point. Effects of oxymorphone and hydromorphone on durations of various stages of anesthesia did not differ significantly. MAC of desflurane in nulliparous adult sheep was established. Intravenous administration of oxymorphone or hydromorphone led to a decrease in MAC; however, the clinical importance of that decrease was minor relative to the effect in other species.

Direct Comparison of the Effect of Desflurane and Sevoflurane on Intraoperative Motor-evoked Potentials Monitoring

During spinal surgery, intraoperative monitoring of motor-evoked potentials (MEPs) is a useful means of assessing the intraoperative integrity of corticospinal pathways. However, MEPs are known to be particularly sensitive to the suppressive effects of inhalational halogenated anesthetic agents. To investigate the effects of increasing end-tidal concentrations of desflurane and sevoflurane anesthesia in a background of propofol and remifentanil with multipulse cortical stimulation on intraoperative monitoring of MEPs. In this randomized crossover trial, 14 consecutive patients (7 in each arm) undergoing major spine surgery, under a background anesthetic of propofol (75 to 125 mcg/kg/min) and remifentanil (0.1 to 0.2 mcg/kg/min), were randomly assigned to receive the sequence of inhalational agents studied: either DES-SEVO (desflurane followed by sevoflurane); or SEVO-DES (sevoflurane followed by desflurane). Multiples (0.3, 0.5, and 0.7) of minimum alveolar concentration (MAC) of desflurane and sevoflurane were administered. After a washout period of 15 minutes using high fresh oxygen/air flows, each of the patients then received the other gas as the second agent. Cortical stimulation was achieved with a train of 5 equivalent square pulses, each 0.05 ms in duration, delivered at 2 ms intervals. MEP recordings were made in the upper limb (UL) from first dorsal interosseus and lower limb (LL) from tibialis anterior with subdermal needle electrodes. At 0.3 MAC desflurane, there was no statistical significant difference in transcranial-evoked MEP amplitudes from the baseline in both UL and LL stimulation. However, this was not the case for sevoflurane for which even a low concentration at 0.3 MAC significantly depressed MEP amplitudes of LL (but not UL) from baseline value. Desflurane at 0.5 and 0.7 MAC depresses LL MEP to 58.4% and 59.9% of baseline, respectively (P<0.05), whereas sevoflurane at 0.3, 0.5, and 0.7 MAC depresses LL MEP to 66.2%, 41.3%, and 25.3% of baseline, respectively (P<0.05). There was no difference in latency of the responses at any MAC. Inhalational anesthetic agents (sevoflurane >desflurane) suppress MEP amplitudes in a dose-dependent manner. The use of 0.3 MAC of desflurane (but not sevoflurane) provided good MEP recordings acceptable for clinical interpretation for both upper and LLs. The LL appears to be more sensitive to anesthetic-induced depression compared with the UL. All patients studied had normal neurological examination hence, these results may not be applicable to those with preexisting deficits.

Efficacy of different doses of dezocine for decreasing minimum alveolar concentration of desflurane

Objective To evaluate the efficacy of different doses of dezocine for decreasing the minimum alveolar concentration (MAC) of desflurane.Methods ASA physical status Ⅰ or Ⅱ patients of both sexes,aged 50-70 yr,undergoing elective lower abdominal surgery performed under general anesthesia,were divided into 4 groups:control group (group C)and different doses of dezocine groups (D1,D2 and D3 groups).Before induction of anesthesia,in D1,D2 and D3 groups,dezocine 0.050,0.075 and 0.100 mg/kg were intravenously infused,respectively,while in group C,the equal volume of normal saline was given instead of dezocine.The adverse reactions were observed.Propofol 3 mg/kg was given for induction of anesthesia 15 min later until patient' s consciousness and spontaneous respiration disappeared.Laryngeal mask airway was inserted and the patients were mechanically ventilated.Up-and-down sequential allocation was used to determine the MAC of desflurane during maintenance of anesthesia.The end-tidal concentration of desflurane was set at 8.0％ and maintained at this level for at least 5 min before skin incision in the first patient.Each time the concentration of desflurane increased/decreased in the next patient depending on whether or not the body movement developed.The ratio between the two successive concentrations was 0.9.The point between the positive response and negative response served as a cross-over point.After at least 7 independent cross-over points were observed in each group,the experiment was stopped.The MAC and 95 ％ confidence interval of desflurane were calculated.Results No adverse reactions developed in each group.The MAC of desflurane was significantly lower in D1-3 groups than in group C,in groups D2.3 than in group D1,and in group D3 than in group D2.Conclusion Dezocine 0.100 mg/kg injected intravenously at 15 min before induction of anesthesia provides a better efficacy for decreasing the MAC of desflurane in the patients. Key words: Analgesics,opioid; Anesthetics, inhalation; Dose-response relationship, drug

Minimum alveolar concentration of desflurane with caudal analgesia for laryngeal mask airway removal in anesthetized children

Regional blocks have been shown to decrease the requirement of anesthetic agents. This study was conducted to determine the optimal endtidal concentrations of desflurane for removal of Laryngeal mask airway in children in presence of caudal block. Twenty-two children of ASA status I between the age group of 2-10 year undergoing infraumbilical surgery were enrolled in the study. General anesthesia was induced with sevoflurane and oxygen given via mask and laryngeal mask airway inserted. Caudal injection of bupivacaine 0.25%, 1 ml·kg(-1) was administered according to Armitage regimen. Desflurane was used for maintenance of anesthesia. Predecided endtidal concentration of desflurane was maintained for 10 min at the end of surgery and laryngeal mask airway removed. Target concentration in the next patient was thereafter determined by the Dixon up-down method (with 0.5% as a step size). 5% endtidal concentration was kept as the starting concentration. If removal of laryngeal mask airway was not associated with any coughing, teeth clenching, gross purposeful movement, breath holding or laryngospasm, during or within 1 min after removal, it was considered as successful. In the presence of caudal analgesia, endtidal concentration of desflurane required for successful laryngeal mask airway removal in 50% (ED50) children was 3.39 ± 0.38% by Dixon's method. Laryngeal mask airway can be successfully removed in 50% of anesthetized children without coughing, moving, or any other airway complications at an endtidal desflurane concentration of 3.4% in the presence of caudal analgesia.

Desflurane‐induced and ischaemic postconditioning against myocardial infarction are mediated by Pim‐1 kinase

Anaesthetic-induced (APOST) and ischaemic postconditioning (IPOST) against myocardial infarction are mediated via phosphatidylinositol-3-kinase/Akt. Pim-1 kinase is acting downstream of Akt and has recently been demonstrated to enhance cardiomyocyte survival. We tested the hypothesis that both APOST and IPOST are mediated by Pim-1 kinase. Pentobarbital-anaesthetized male C57BL/6 mice were subjected to 45-min coronary artery occlusion (CAO) and 3-h reperfusion. Animals received either no intervention, the Pim-1 kinase inhibitor II (10 μg/g intraperitoneally) or its vehicle dimethy sulfoxide (10 μl/g intraperitoneally). Three minutes prior to the end of CAO, 1.0 minimum alveolar concentration desflurane was administered for 18 min alone or in combination with Pim-1 kinase inhibitor II. IPOST was induced by three cycles of each 10-s ischaemia/reperfusion, and animals received either IPOST alone or in combination with Pim-1 kinase inhibitor II. Infarct size was determined with triphenyltetrazolium chloride and area at risk with Evans blue. Protein expression of Pim-1 kinase, Bad, phospho-Bad(Ser112) and B-cell lymphoma 2 was determined using Western immunoblotting analysis. Infarct size in control animals (CON) was 46 ± 3%. Dimethylsulfoxide (47 ± 3%) and Pim-1 kinase inhibitor II (44 ± 5%) did not significantly reduce infarct size. Desflurane (16 ± 2%*; *P < 0.05 vs. CON) and IPOST (21 ± 2%*) significantly reduced infarct size compared with CON. Inhibition of Pim-1 kinase abolished desflurane-induced postconditioning (46 ± 4%) and IPOST (44 ± 5%). Western blot analysis revealed that only desflurane enhances phosphorylation of Bad at serine 112 that was abrogated by Pim-1 kinase inhibitor II. These data suggest that Pim-1 kinase mediates both desflurane-induced postconditioning and IPOST in mice.

The median effective effect-site concentration of remifentanil for minimizing the cardiovascular changes to endotracheal intubation during desflurane anesthesia in pediatric patients

BackgroundDesflurane has the most rapid onset and offset of action among the volatile anesthetic agents used for general anesthesia, but it can cause airway reactivity, tachycardia, and hypertension during induction, especially in pediatric patients. This study was designed to determine a median effective effect-site concentration (EC50) of remifentanil to prevent the cardiovascular changes due to tracheal intubation during the 1 minimum alveolar concentration (MAC) desflurane inhalation, which was required to prevent movement in response to a noxious stimulus in 50% of subjects, in pediatric patients.MethodsTwenty-four pediatric patients between the ages 5-15 years were enrolled in this study. We injected thiopental intravenously, at the same time remifentanil was infused by Target Controlled Infusion (TCI) device. When the target effect-site concentration (Ce) of remifentanil reached a preset level, desflurane was administrated through the facial mask. Then, we assessed the signs of desflurane related airway reactivity and cardiovascular changes for 2 min. The up-and-down criteria was a 20% change in systolic blood pressure (SBP) and a heart rate (HR) between just prior to intubation and 1 min after intubation. The EC50 of remifentanil was calculated from 8 independent pairs using Dixon's up-and-down method.ResultsWe studied 24 pediatric patients in range of 1-5 ng/ml of the Ce of remifentanil. No patient showed airway reactivity during the study. The EC50 of remifentanil to suppress the hemodynamic changes after tracheal intubation during desflurane anesthesia was calculated as 3.4 ± 0.9 ng/ml.ConclusionsIn pediatric anesthesia, the EC50 of remifentanil to minimize the cardiovascular changes due to tracheal intubation during 1 MAC desflurane anesthesia was 3.4 ± 0.9 ng/ml.