Age-related iso-MAC charts for isoflurane, sevoflurane and desflurane in man

Effect of volatile anaesthetic agents on intracranial pressure, cerebrovascular flow and autoregulation: a protocol for a systematic review and meta-analysis

INTRODUCTION

The use of volatile anaesthetic agents for the sedation of patients requiring critical care treatment offers several theoretical advantages over intravenous sedation, which may be of benefit in neurocritical care. However, there are concerns that they may increase intracranial pressure. The objective of this systematic review is to assess whether, and if so, to what extent volatile anaesthetic agents affect intracranial pressure, cerebral blood flow (CBF), cerebral oximetry and cerebrovascular autoregulation. If sufficient data exist, subgroup analyses will be conducted in traumatic brain injury and decompressive craniectomy patients.

METHODS AND ANALYSIS

A database search of PubMed, Medline (including Medline plus), CINAHL (including CINAHL Plus), Embase databases and the Cochrane Central Controlled Trials Register without time limits will be conducted. The search results will be screened by title and abstract by two independent researchers on a rule-in basis against predetermined criteria-controlled studies in humans of contemporary fluorinated volatile anaesthetic agents against a control, which measures intracranial pressure, CBF, cerebral oximetry or cerebrovascular autoregulation. Articles responsive to screening will then be reviewed in full text by two independent researchers, requiring consensus or a tie-break by a third independent researcher. Reference lists and a non-generative AI tool will be examined for missed articles, with all identified articles being reviewed in full text by two independent researchers. The included articles will be assessed for risk of bias and will have data extracted by two independent researchers. If sufficient data exist, a meta-analysis will be performed; otherwise, a narrative description of outcomes will be performed.

ETHICS AND DISSEMINATION

No ethics approval will be sought for this systematic review. This study has no explicit funding. The results of this study will be disseminated in a peer-reviewed journal, in a conference presentation and on PROSPERO.

TRIAL REGISTRATION NUMBER

PROSPERO number CRD42023474587.

Fetal bradycardia in open versus fetoscopic prenatal repair of spina bifida

OBJECTIVE

To compare the occurrence of fetal bradycardia in open versus fetoscopic fetal spina bifida surgery.

METHODS

This is a single-institution retrospective cohort study of patients undergoing open (n = 25) or fetoscopic (n = 26) spina bifida repair between 2017 and 2022. From October 2017 to June 2020, spina bifida repairs were performed via an open classical hysterotomy, and from November 2020 to June 2022 fetoscopic repairs were performed following transition to this technique. Fetal heart rate (FHR) in beats per minute (bpm) was recorded via echocardiography every 15 min during the procedure. Cohort characteristics, fetal bradycardia and maternal physiologic parameters were compared between the groups.

RESULTS

Fetuses undergoing an open repair more frequently developed bradycardia defined as <110 bpm (32% vs. 3.8%, p = 0.008), and a trend was observed for FHR decreases more than 25 bpm from baseline (20% vs. 3.8%, p = 0.073). Profound bradycardia less than 80 bpm was rare, occurring in only three operations (two in open, one in fetoscopic repair) with two fetuses (one in each group) requiring emergency cesarean delivery.

CONCLUSION

When compared to open fetal surgery, fetal bradycardia occurred less frequently in fetoscopic surgery despite a significantly greater anesthetic exposure and the use of the intraamniotic carbon dioxide insufflation.

Inhalational Agent Dosing Behaviors of Anesthesia Practitioners Cause Variability in End-Tidal Concentrations at the End of Surgery and Prolonged Times to Tracheal Extubation

INTRODUCTION

Prolonged times to tracheal extubation are intervals from the end of surgery to extubation ≥15 minutes. We examined why there are associations with the end-tidal inhalational agent concentration as a proportion of the age‑adjusted minimum alveolar concentration (MAC fraction) at the end of surgery.

METHODS

The retrospective cohort study used 11.7 years of data from one hospital. All p‑values were adjusted for multiple comparisons.

RESULTS

There was a greater odds of prolonged time to extubation if the anesthesia practitioner was a trainee (odds ratio 1.68) or had finished fewer than five cases with the surgeon during the preceding three years (odds ratio 1.12) (both P<0.0001). There was a greater risk of prolonged time to extubation if the MAC fraction was >0.4 at the end of surgery (odds ratio 2.66, P<0.0001). Anesthesia practitioners who were trainees and all practitioners who had finished fewer than five cases with the surgeon had greater mean MAC fractions at the end of surgery and had greater relative risks of the MAC fraction >0.4 at the end of surgery (all P<0.0001). The source for greater MAC fractions at the end of surgery was not greater MAC fractions throughout the anesthetic because the means during the case did not differ among groups. Rather, there was substantial variability of MAC fractions at the end of surgery among cases of the same anesthesia practitioner, with the mean (standard deviation) among practitioners of each practitioner's standard deviation being 0.35 (0.05) and the coefficient of variation being 71% (13%).

CONCLUSION

More prolonged extubations were associated with greater MAC fractions at the end of surgery. The cause of the large MAC fractions was the substantial variability of MAC fractions among cases of each practitioner at the end of surgery. That variability matches what was expected from earlier studies, both from variability among practitioners in their goals for the MAC fraction given at the start of surgical closure and from inadequate dynamic forecasting of the timing of when surgery would end. Future studies should examine how best to reduce prolonged extubations by using anesthesia machines' display of MAC fraction and feedback control of end-tidal agent concentration.

Age-dependent coupling characteristics of bilateral frontal EEG during desflurane anesthesia

Objectives.The purpose of this study is to investigate the age dependence of bilateral frontal electroencephalogram (EEG) coupling characteristics, and find potential age-independent depth of anesthesia monitoring indicators for the elderlies.Approach.We recorded bilateral forehead EEG data from 41 patients (ranged in 19-82 years old), and separated into three age groups: 18-40 years (n= 12); 40-65 years (n= 14), >65 years (n= 15). All these patients underwent desflurane maintained general anesthesia (GA). We analyzed the age-related EEG spectra, phase amplitude coupling (PAC), coherence and phase lag index (PLI) of EEG data in the states of awake, GA, and recovery.Main results.The frontal alpha power shows age dependence in the state of GA maintained by desflurane. Modulation index in slow oscillation-alpha and delta-alpha bands showed age dependence and state dependence in varying degrees, the PAC pattern also became less pronounced with increasing age. In the awake state, the coherence in delta, theta and alpha frequency bands were all significantly higher in the >65 years age group than in the 18-40 years age group (p< 0.05 for three frequency bands). The coherence in alpha-band was significantly enhanced in all age groups in GA (p< 0.01) and then decreased in recovery state. Notably, the PLI in the alpha band was able to significantly distinguish the three states of awake, GA and recovery (p< 0.01) and the results of PLI in delta and theta frequency bands had similar changes to those of coherence.Significance.We found the EEG coupling and synchronization between bilateral forehead are age-dependent. The PAC, coherence and PLI portray this age-dependence. The PLI and coherence based on bilateral frontal EEG functional connectivity measures and PAC based on frontal single-channel are closely associated with anesthesia-induced unconsciousness.

T2-weighted Imaging Hyperintensity and Transcranial Motor-evoked Potentials During Cervical Spine Surgery: Effects of Sevoflurane in 150 Consecutive Cases

BACKGROUND

There is debate on the impact of inhalational esthetic agents on transcranial motor evoked potentials (TcMEPs) during intraoperative neuromonitoring. Current guidelines advise their avoidance, which contrasts with common clinical practice.

METHODS

This retrospective cohort study of 150 consecutive cervical spine surgeries at a single institution compared stimulation voltages and TcMEP amplitudes in patients who did and did not receive sevoflurane as part of a balanced anesthetic technique. Patients were divided into 3 groups stratified by the presence or absence of increased signal intensity within the cervical spinal cord on T2-weighted magnetic resonance imaging (indicative or myelopathy/spinal cord injury [SCI]) and sevoflurane use.

RESULTS

Patients with no magnetic resonance imaging evidence of myelopathy/SCI that received sevoflurane (n=80) had the lowest stimulation voltages and largest TcMEP amplitude responses in the lower extremities compared with those with no magnetic resonance imaging evidence of myelopathy/SCI (n=30). In patients with evidence of myelopathy/SCI who did not receive sevoflurane (n=19), lower extremity TcMEP amplitudes were similar to patients with a myelopathy/SCI that received sevoflurane. Six of these 19 patients had initial low-dose sevoflurane discontinued because of concerns of low/absent baseline TcMEP amplitudes.

CONCLUSIONS

Balanced anesthesia with 0.5 MAC sevoflurane in patients with and without radiological evidence of myelopathy/SCI allows reliable TcMEP monitoring. However, in communication with surgical and neuromonitoring teams, it may be advisable in a subset of patients to avoid or discontinue sevoflurane in favor of a propofol/opioid-based anesthetic to ensure adequate and reproducible TcMEPs.

Genotype- and sex-specific changes in vital parameters during isoflurane anesthesia in a mouse model of Alzheimer's disease

Background

The prevalence of neurodegenerative diseases is increasing as is life expectancy with Alzheimer's disease accounting for two-thirds of dementia cases globally. Whether general anesthesia and surgery worsen cognitive decline is still a matter of debate and most likely depending on the interplay of various influencing factors. In order to account for this complexity, Alzheimer's disease animal models have been developed. The Tg2576 model of Alzheimer's disease is a well-established mouse model exhibiting amyloidopathy and age-dependent sex-specific differences in Alzheimer's disease symptomology. Yet, data on anesthesia in this mouse model is scarce and a systematic comparison of vital parameters during anesthesia with wild-type animals is missing. In order to investigate the safety of general anesthesia and changes in vital parameters during general anesthesia in Tg2576 mice, we did a secondary analysis of vital parameters collected during general anesthesia in aged Tg2576 mice.

Methods

After governmental approval (General Administration of the Free State of Bavaria, file number: 55.2-1-54-2532-149-11) 60 mice at 10-12 months of age were exposed to isoflurane (1.6 Vol%) for 120 min, data of 58 mice was analyzed. During general anesthesia, heart rate, respiratory rate, temperature, isoflurane concentration and fraction of inspired oxygen were monitored and collected. Data were analyzed using univariate and multivariate linear mixed regression models.

Results

During general anesthesia, heart rate decreased in a sex-specific manner. Respiratory rate decreased and body temperature increased dependent on genotype. However, the changes were limited and all vital parameters stayed within physiological limits.

Conclusion

Isoflurane anesthesia in the Tg2576 mouse model is safe and does not seem to influence experimental results by interacting with vital parameters. The present study provides information on appropriate anesthesia in order to advance research on anesthesia and AD and could contribute to improving laboratory animal welfare.

Preventing Prolonged Times to Awakening While Mitigating the Risk of Patient Awareness: Gas Man Computer Simulations of Sevoflurane Consumption From Brief, High Fresh Gas Flow Before the End of Surgery

Prolonged times to tracheal extubation are associated with adverse patient and economic outcomes. We simulated awakening patients from sevoflurane after long-duration surgery at 2% end-tidal concentration, 1.0 minimum alveolar concentration (MAC) in a 40-year-old. Our end-of-surgery target was 0.5 MAC, the Michigan Awareness Control Study's threshold for intraoperative alerts. Consider an anesthetist who uses a 1 liter/minute gas flow until surgery ends. During surgical closure, the inspired sevoflurane concentration is reduced from 2.05% to 0.62% (i.e., MAC-awake). The estimated time to reach 0.5 MAC is 28 minutes. From a previous study, 28 minutes exceeded ≥95% of surgical closure times for all 244 distinct surgical procedures (N=23,343 cases). Alternatively, the anesthetist uses 8 liters/minute gas flow with the vaporizer at MAC-awake for 1.8 minutes, which reduces the end-tidal concentration to 0.5 MAC. The anesthetist then increases the vaporizer to keep end-tidal 0.5 MAC until the surgery ends. An additional simulation shows that, compared with simulated end-tidal agent feedback control, this approach consumed 0.45 mL extra agent. Simulation results are the same for an 80-year-old patient. The extra 0.45 mL has a global warming potential comparable to driving 26 seconds at 40 kilometers (25 miles) per hour, comparable to route modification to avoid potential roadway hazards.

Bispectral Index Changes Following Boluses of Commonly Used Intravenous Medications During Volatile Anesthesia Identified From Retrospective Data

BACKGROUND

Although patients are commonly monitored for depth of anesthesia, it is unclear to what extent administration of intravenous anesthetic medications may affect calculated bispectral (BIS) index values under general anesthesia.

METHODS

In a retrospective analysis of electronic anesthesia records from an academic medical center, we examined BIS index changes associated with 14 different intravenous medications, as administered in routine practice, during volatile-based anesthesia using a novel screening approach. Discrete-time windows were identified in which only a single drug bolus was administered, and subsequent changes in the BIS index, concentration of volatile anesthetic, and arterial pressure were analyzed. Our primary outcome was change in BIS index, following drug administration. Adjusted 95% confidence intervals were compared to predetermined thresholds for clinical significance. Secondary sensitivity analyses examined the same outcomes, with available data separated according to differences in baseline volatile anesthetic concentrations, doses of the administered medications, and length of time window.

RESULTS

The study cohort was comprised of data from 20,170 distinct cases, 54.7% of patients were men, with a median age of 55. In the primary analysis, ketamine at a median dose of 20 mg was associated with a median (confidence limits) increase in BIS index of 3.8 (2.5-5.0). Midazolam (median dose 2 mg) was associated with a median decrease in BIS index of 3.0 (1.5-4.5). Neither of these drug administrations occurred during time periods associated with changes in volatile anesthetic concentration. Analysis for dexmedetomidine was confounded by concomitant decreases in volatile anesthetic concentration. No other medication analyzed, including propofol and common opioids, was associated with a significant change in BIS index. Secondary analyses revealed that similar BIS index changes occurred when midazolam and ketamine were administered at different volatile anesthetic concentrations and different doses, and these changes persisted 11 to 20 minutes postadministration.

CONCLUSIONS

Modest, but persistent changes in BIS index occurred following doses of ketamine (increase) and midazolam (decrease) during periods of stable volatile anesthetic administration.

Development of Postanesthesia Care Unit Delirium Is Associated with Differences in Aperiodic and Periodic Alpha Parameters of the Electroencephalogram during Emergence from General Anesthesia: Results from a Prospective Observational Cohort Study

BACKGROUND

Intraoperative alpha-band power in frontal electrodes may provide helpful information about the balance of hypnosis and analgesia and has been associated with reduced occurrence of delirium in the postanesthesia care unit. Recent studies suggest that narrow-band power computations from neural power spectra can benefit from separating periodic and aperiodic components of the electroencephalogram. This study investigates whether such techniques are more useful in separating patients with and without delirium in the postanesthesia care unit at the group level as opposed to conventional power spectra.

METHODS

Intraoperative electroencephalography recordings of 32 patients who developed perioperative neurocognitive disorders and 137 patients who did not were considered in this post hoc secondary analysis. The power spectra were calculated using conventional methods and the "fitting oscillations and one over f" algorithm was applied to separate aperiodic and periodic components to see whether the electroencephalography signature is different between groups.

RESULTS

At the group level, patients who did not develop perioperative neurocognitive disorders presented with significantly higher alpha-band power and a broadband increase in power, allowing a "fair" separation based on conventional power spectra. Within the first third of emergence, the difference in median absolute alpha-band power amounted to 8.53 decibels (area under the receiver operator characteristics curve, 0.74 [0.65; 0.82]), reaching its highest value. In relative terms, the best separation was achieved in the second third of emergence, with a difference in medians of 7.71% (area under the receiver operator characteristics curve, 0.70 [0.61; 0.79]). The area under the receiver operator characteristics curve values were generally lower toward the end of emergence with increasing arousal.

CONCLUSIONS

Increased alpha-band power during emergence in patients who did not develop perioperative neurocognitive disorders can be traced back to an increase in oscillatory alpha activity and an overall increase in aperiodic broadband power. Although the differences between patients with and without perioperative neurocognitive disorders can be detected relying on traditional methods, the separation of the signal allows a more detailed analysis. This may enable clinicians to detect patients at risk for developing perioperative neurocognitive disorders in the postanesthesia care unit early in the emergence phase.

EDITOR’S PERSPECTIVE

Effects of anesthetics on nociceptive sensory evoked potentials by intraepidermal noxious electrical stimulation of A-δ fibers

PURPOSE

Generation of nociceptive sensory evoked potentials (NEPs) by selective stimulation of nociceptive intraepidermal nerve fibers is a simple technique which could be used as intraoperative nociception monitor. We evaluated the effects of remifentanil, propofol and sevoflurane on NEPs by this technique.

METHODS

Patients undergoing general anesthesia were assigned to groups in two studies. A-δ fiber selective NEPs were recorded. Study 1: NEPs were recorded at control, under anesthetics administration: remifentanil at an effect-site concentration (Ce) of 1.0 ng/mL (n = 10), propofol at Ce of 0.5 µg/mL (n = 10), or sevoflurane at 0.2 minimum alveolar concentration (MAC) (n = 10), and recovery from the anesthetics. Study 2: NEPs were recorded at control and under administration of higher dose anesthetics: propofol at Ce of 0.5 and 1.0 µg/mL (n = 10) or sevoflurane at 0.2 and 0.5 MAC (n = 10). A P-value < 0.016 was considered statistically significant in multiple analyses.

RESULTS

Study 1: Remifentanil at Ce of 1.0 ng/mL significantly suppressed the amplitude of NEPs (mean amplitude (standard deviation) of control vs. remifentanil administration: 16.8 µV (3.8) vs. 10.1 µV (2.5), P < 0.001). Propofol and sevoflurane did not suppress the amplitude significantly. Study 2: Propofol at Ce of 0.5 and 1.0 µg/mL and sevoflurane at 0.2 and 0.5 MAC did not suppress the amplitude significantly.

CONCLUSION

The amplitude of A-δ fiber selective NEPs was suppressed by remifentanil but not propofol or sevoflurane. NEPs with intraepidermal electrical stimulation can assess the analgesic effect of anesthetics.

CLINICAL TRIAL NUMBER

UMIN000038214 REGISTRY URL: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000043328.

Prediction of blood pressure changes during surgical incision using the minimum evoked current of vascular stiffness value under sevoflurane anesthesia

Necessary and sufficient opioids should be administered for safe and stable anesthesia. However, opioid sensitivity varies among individuals. We previously reported that sympathetic responses to nociceptive stimuli under propofol anesthesia could be predicted by measuring the minimum evoked current of the vascular stiffness value (MECK). However, this result has only been proven under propofol anesthesia. We propose that MECK could be used under anesthesia with a volatile anesthetic. Thirty patients undergoing laparotomy with sevoflurane anesthesia received 0.7 minimum alveolar concentration (MAC) sevoflurane and intravenous remifentanil at a constant concentration of 2 ng/mL, followed by tetanic stimulation, to measure MECK. After tetanic stimulation, the same anesthetic conditions were maintained, and the rate of change in systolic blood pressure (ROCBP) during the skin incision was measured. The correlation coefficient between the MECK and ROCBP during skin incision under sevoflurane anesthesia was R =  - 0.735 (P < 0.01), similar to that in a previous study with propofol (R =  - 0.723). Thus, a high correlation was observed. The slope of the linear regression equation was - 0.27, similar to that obtained in the study on propofol (- 0.28). These results suggest that, as with propofol anesthesia, MECK can be used as a predictive index for ROCBP under 0.7 MAC sevoflurane anesthesia.Clinical trial registration: Registry, University hospital Medical Information Network; registration number, UMIN000047425; principal investigator's name, Noboru Saeki; date of registration, April 8, 2022.

Volatile anesthetic and outcome in acute trauma care: planned secondary analysis of the PROPPR study

Background

This retrospective analysis of prospectively collected data from the PROPPR study describes volatile anesthetic use in severely injured trauma patients undergoing anesthesia.

Methods

After exclusions, 402 subjects were reviewed of the original 680, and 292 had complete data available for analysis. Anesthesia was not protocolized, so analysis was of contemporary practice.

Results

The small group who received no volatile anesthetic (n = 25) had greater injury burden (Glasgow Coma Scale P = 0.05, Injury Severity Score P = 0.001, Revised Trauma Score P = 0.03), higher 6- and 24-hour mortality (P < 0.001), and higher incidence of systemic inflammatory response syndrome (P = 0.003) and ventilator-associated pneumonia (P = 0.02) than those receiving any volatile (n = 267). There were no differences in mortality between volatile agents at 6 hours (P = 0.51) or 24 hours (P = 0.35). The desflurane group was less severely injured than the isoflurane group. Mean minimum alveolar concentration was < 0.6 and lowest in the isoflurane group compared to the sevoflurane and desflurane groups (both P < 0.01). The incidence of systemic inflammatory response syndrome was lower in the desflurane group than in the isoflurane group (P = 0.007).

Conclusion

In this acutely injured trauma population, choice of volatile anesthetic did not appear to influence short-term mortality and morbidity. Subjects who received no volatile were more severely injured with greater mortality, representing hemodynamic compromise where volatile agent was limited until stable. As anesthetic was not protocolized, these findings that choice of specific volatile was not associated with short-term survival require prospective, randomized evaluation.

Sevoflurane but not propofol enhances ovarian cancer cell biology through regulating cellular metabolic and signaling mechanisms

Perioperative risk factors, including the choice of anesthetics, may influence ovarian cancer recurrence after surgery. Inhalational anesthetic sevoflurane and intravenous agent propofol might affect cancer cell metabolism and signaling, which, in turn, may influence the malignancy of ovarian cancer cells. The different effects between sevoflurane and propofol on ovarian cancer cell biology and underlying mechanisms were studied. Cultured ovarian cancer cells were exposed to 2.5% sevoflurane, 4 μg/mL propofol, or sham condition as the control for 2 h followed by 24-h recovery. Glucose transporter 1 (GLUT1), mitochondrial pyruvate carrier 1 (MPC1), glutamate dehydrogenase 1 (GLUD1), pigment epithelium-derived factor (PEDF), p-Erk1/2, and hypoxia-inducible factor 1-alpha (HIF-1α) expressions were determined with immunostaining and/or Western blot. Cultured media were collected for 1H-NMR spectroscopy-based metabolomics analysis. Principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA) were used to analyze metabolomics data. Sevoflurane increased the GLUT1, MPC1, GLUD1, p-Erk1/2, and HIF-1α expressions but decreased the PEDF expression relative to the controls. In contrast to sevoflurane, propofol decreased GLUT1, MPC1, GLUD1, p-Erk1/2, and HIF-1α but increased PEDF expression. Sevoflurane increased metabolite isopropanol and decreased glucose and glutamine energy substrates in the media, but the opposite changes were found after propofol treatment. Our data indicated that, unlike the pro-tumor property of sevoflurane, propofol negatively modulated PEDF/Erk/HIF-1α cellular signaling pathway and inhibited ovarian cancer metabolic efficiency and survival, and hence decreased malignancy. The translational value of this work warrants further study. • Sevoflurane promoted but propofol inhibited ovarian cancer cell biology. • Sevoflurane upregulated but propofol downregulated the GLUT1, MPC1, and GLUD1 expressions of ovarian cancer cells. • Sevoflurane enhanced but propofol inhibited ovarian cancer cellular glucose. metabolism and glutaminolysis. • Sevoflurane downregulated PEDF but upregulated the Erk pathway and HIF-1α, while propofol had the adverse effects on ovarian cancer cells.

The Effect of Anaesthesia Management with Different Fresh Gas Flows on Cognitive Functions of Geriatric Patients: A Randomized Double-blind Study

Objective

The present study aimed to compare the effects of two different fresh gas flows (FGFs) (0.5 L min^-1 and 2 L min^-1) applied during maintenance of anaesthesia on recovery from anaesthesia and early cognitive functions in geriatric patients.

Methods

In this prospective, randomised, double-blind study, sixty patients were divided into two groups according to the amount of FGF. Minimal-flow anaesthesia (0.5 L min^-1 FGF) was applied to group I and medium-flow anaesthesia (2 L min^-1 FGF) was applied to group II during maintenance of anaesthesia. Following the termination of inhalation anaesthesia, recovery times were recorded. The evaluation of cognitive functions was performed using the Addenbrooke's Cognitive Examination (ACE-R).

Results

There was no significant difference between the two groups in terms of demographic characteristics and recovery (P > 0.05). There was no significant difference between the two groups in terms of the preoperative day, the first postoperative day, and the third postoperative day; ACE-R scores (P > 0.05). In group II, on the third postoperative day ACE-R scores were found to be significantly lower than the preoperative ACE-R scores (P=0.04). In group II, third postoperative day ACE-R memory sub-scores (14.53 ± 3.34) were found to be significantly lower than preoperative ACE-R memory sub-scores (15.03 ± 3.57) (P=0.04).

Conclusion

In geriatric patients, minimal-flow anaesthesia was not superior to medium-flow anaesthesia in terms of recovery properties and cognitive functions. Keeping in mind that hypoxaemia and changes in anaesthesia levels may occur with the reduction of FGF, both minimal- and medium-flow anaesthesia can be applied with appropriate monitoring without adverse effects on recovery and cognitive functions.

Age-dependent neurovascular coupling characteristics in children and adults during general anesthesia

General anesthesia is an indispensable procedure in clinical practice. Anesthetic drugs induce dramatic changes in neuronal activity and cerebral metabolism. However, the age-related changes in neurophysiology and hemodynamics during general anesthesia remain unclear. Therefore, the objective of this study was to explore the neurovascular coupling between neurophysiology and hemodynamics in children and adults during general anesthesia. We analyzed frontal electroencephalogram (EEG) and functional near-infrared spectroscopy (fNIRS) signals recorded from children (6-12 years old, n = 17) and adults (18-60 years old, n = 25) during propofol-induced and sevoflurane-maintained general anesthesia. The neurovascular coupling was evaluated in wakefulness, maintenance of a surgical state of anesthesia (MOSSA), and recovery by using correlation, coherence and Granger-causality (GC) between the EEG indices [EEG power in different bands and permutation entropy (PE)], and hemodynamic responses the oxyhemoglobin (Δ[HbO]) and deoxy-hemoglobin (Δ[Hb]) from fNIRS in the frequency band in 0.01-0.1 Hz. The PE and Δ[Hb] performed well in distinguishing the anesthesia state (p > 0.001). The correlation between PE and Δ[Hb] was higher than those of other indices in the two age groups. The coherence significantly increased during MOSSA (p < 0.05) compared with wakefulness, and the coherences between theta, alpha and gamma, and hemodynamic activities of children are significantly stronger than that of adults' bands. The GC from neuronal activities to hemodynamic responses decreased during MOSSA, and can better distinguish anesthesia state in adults. Propofol-induced and sevoflurane-maintained combination exhibited age-dependent neuronal activities, hemodynamics, and neurovascular coupling, which suggests the need for separate rules for children's and adults' brain states monitoring during general anesthesia.

The use of processed electroencephalography (pEEG) in obstetric anaesthesia: a narrative review

Accidental awareness under general anaesthesia (AAGA) remains a major complication of anaesthesia. The incidence of AAGA during obstetric anaesthesia is high relative to other specialities. The use of processed electroencephalography (pEEG) in the form of "depth of anaesthesia" monitoring has been shown to reduce the incidence of AAGA in the non-obstetric population. The evidence for using pEEG to prevent AAGA in the obstetric population is poor and requires further exploration. Furthermore, pregnancy and disease states affecting the central nervous system, such as pre-eclampsia, may alter the interpretation of pEEG waveforms although this has not been fully characterised. National guidelines exist for pEEG monitoring with total intravenous anaesthesia and for "high-risk" cases regardless of technique, including the obstetric population. However, none of the currently available guidelines relates specifically to obstetric anaesthesia. Using pEEG monitoring for obstetric anaesthesia may also provide additional benefits beyond a reduction in risk of AAGA. These potential benefits include reduced postoperative nausea and vomiting, reduced anaesthetic agent use, a shorter post-anaesthetic recovery stay. In addition, pEEG acts as a surrogate marker of cerebral perfusion, and thus as an additional monitor for impending cardiovascular collapse, as seen in amniotic fluid embolism. The subtle physiological and pathological changes in EEG activity that may occur during pregnancy are an unexplored research area in the context of anaesthetic pEEG monitors. We believe that the direction of clinical practice is moving towards greater use of pEEG monitoring and individualisation of anaesthesia.

Effect of atropine and propofol on the minimum anaesthetic concentration of isoflurane in the freshwater turtle Trachemys scripta (yellow-bellied slider)

OBJECTIVE

To determine if the administration of atropine would reduce the measured minimum anaesthetic concentration of isoflurane (MAC_isoflurane) in freshwater turtles - the yellow-bellied slider (Trachemys scripta scripta).

STUDY DESIGN

Paired, blinded, randomized, prospective studies of 1) the effect of atropine in isoflurane anaesthetized freshwater turtles (T. scripta scripta) and 2) the effect of atropine in yellow-bellied sliders in which anaesthesia was induced with propofol and maintained with isoflurane.

ANIMALS

T. scripta scripta (n = 8), female, adult.

METHODS

Atropine (2 mg kg^-1) or an isovolumetric control injection of saline was administered intraperitoneally 15 minutes prior to induction of anaesthesia with isoflurane. Individual MAC_isoflurane was then determined by end-tidal gas analysis in a bracketing design by an experimenter blinded to the administered drug, with a 2 week washout period. The experiment was repeated, with atropine (2 mg kg^-1) or saline administered intravascularly in combination with propofol for anaesthetic induction. Linear mixed modelling was used to determine the effects of atropine and propofol on the individual MAC_isoflurane. Data are presented as mean ± standard deviation.

RESULTS

Premedication with atropine significantly reduced MAC_isoflurane (p = 0.0039). In isoflurane-induced T. scripta scripta, MAC_isoflurane decreased from 4.2 ± 0.4% to 3.3 ± 0.8% when atropine had been administered. Propofol as an induction agent had a MAC-sparing effect (p < 0.001) such that MAC_isoflurane following propofol and a control injection of saline was 2.3 ± 1.0%, which decreased further to 1.5 ± 0.8% when propofol was combined with atropine.

CONCLUSIONS AND CLINICAL RELEVANCE

Atropine, presumably by inhibiting parasympathetically mediated pulmonary artery constriction, decreases right-to-left cardiac shunting and the MAC_isoflurane in yellow-bellied sliders, and thereby may facilitate control of inhalant anaesthesia. Propofol can be used for induction of anaesthesia and reduces the required concentration of inhaled anaesthesia assessed 1.5 hours following induction.

Inhibition of mitochondrial respiration by general anesthetic drugs

General anesthetic drugs have been associated with various unwanted effects including an interference with mitochondrial function. We had previously observed increases of lactate formation in the mouse brain during anesthesia with volatile anesthetic agents. In the present work, we used mitochondria that were freshly isolated from mouse brain to test mitochondrial respiration and ATP synthesis in the presence of six common anesthetic drugs. The volatile anesthetics isoflurane, halothane, and (to a lesser extent) sevoflurane caused an inhibition of complex I of the electron transport chain in a dose-dependent manner. Significant effects were seen at concentrations that are reached under clinical conditions (< 0.5 mM). Pentobarbital and propofol also inhibited complex I but at concentrations that were two-fold higher than clinical EC50 values. Only propofol caused an inhibition of complex II. Complex IV respiration was not affected by either agent. Ketamine did not affect mitochondrial respiration. Similarly, all anesthetic agents except ketamine suppressed ATP production at high concentrations. Only halothane increased cytochrome c release indicating damage of the mitochondrial membrane. In summary, volatile general anesthetic agents as well as pentobarbital and propofol dose-dependently inhibit mitochondrial respiration. This action may contribute to depressive actions of the drugs in the brain.

The Influence of Carbon Dioxide on Cerebral Autoregulation During Sevoflurane-based Anesthesia in Patients With Type 2 Diabetes

BACKGROUND

Cerebral autoregulation (CA) continuously adjusts cerebrovascular resistance to maintain cerebral blood flow (CBF) constant despite changes in blood pressure. Also, CBF is proportional to changes in arterial carbon dioxide (CO 2 ) (cerebrovascular CO 2 reactivity). Hypercapnia elicits cerebral vasodilation that attenuates CA efficacy, while hypocapnia produces cerebral vasoconstriction that enhances CA efficacy. In this study, we quantified the influence of sevoflurane anesthesia on CO 2 reactivity and the CA-CO 2 relationship.

METHODS

We studied patients with type 2 diabetes mellitus (DM), prone to cerebrovascular disease, and compared them to control subjects. In 33 patients (19 DM, 14 control), end-tidal CO 2 , blood pressure, and CBF velocity were monitored awake and during sevoflurane-based anesthesia. CA, calculated with transfer function analysis assessing phase lead (degrees) between low-frequency oscillations in CBF velocity and mean arterial blood pressure, was quantified during hypocapnia, normocapnia, and hypercapnia.

RESULTS

In both control and DM patients, awake CO 2 reactivity was smaller (2.8%/mm Hg CO 2 ) than during sevoflurane anesthesia (3.9%/mm Hg; P <0.005). Hyperventilation increased CA efficacy more (3 deg./mm Hg CO 2 ) in controls than in DM patients (1.8 deg./mm Hg CO 2 ; P <0.001) in both awake and sevoflurane-anesthetized states.

CONCLUSIONS

The CA-CO 2 relationship is impaired in awake patients with type 2 DM. Sevoflurane-based anesthesia does not further impair this relationship. In patients with DM, hypocapnia induces cerebral vasoconstriction, but CA efficacy does not improve as observed in healthy subjects.

Quiescence during burst suppression and postictal generalized EEG suppression are distinct patterns of activity

OBJECTIVE

Periods of low-amplitude electroencephalographic (EEG) signal (quiescence) are present during both anesthetic-induced burst suppression (BS) and postictal generalized electroencephalographic suppression (PGES). PGES following generalized seizures induced by electroconvulsive therapy (ECT) has been previously linked to antidepressant response. The commonality of quiescence during both BS and PGES motivated trials to recapitulate the antidepressant effects of ECT using high doses of anesthetics. However, there have been no direct electrographic comparisons of these quiescent periods to address whether these are distinct entities.

METHODS

We compared periods of EEG quiescence recorded from two human studies: BS induced in 29 healthy adult volunteers by isoflurane general anesthesia and PGES in 11 patients undergoing right unilateral ECT for treatment-resistant depression. An automated algorithm allowed detection of EEG quiescence based on a 10-microvolt amplitude threshold. Spatial, spectral, and temporal analyses compared quiescent epochs during BS and PGES.

RESULTS

The median (interquartile range) voltage for quiescent periods during PGES was greater than during BS (1.81 (0.22) microvolts vs 1.22 (0.33) microvolts, p < 0.001). Relative power was greater for quiescence during PGES than BS for the 1-4 Hz delta band (p < 0.001), at the expense of power in the theta (4-8 Hz, p < 0.001), beta (13-30 Hz, p = 0.04) and gamma (30-70 Hz, p = 0.006) frequency bands. Topographic analyses revealed that amplitude across the scalp was consistently higher for quiescent periods during PGES than BS, whose voltage was within the noise floor.

CONCLUSIONS

Quiescent epochs during PGES and BS have distinct patterns of EEG signals across voltage, frequency, and spatial domains.

SIGNIFICANCE

Quiescent epochs during PGES and BS, important neurophysiological markers for clinical outcomes, are shown to have distinct voltage and frequency characteristics.

Efficacy of early goal-directed therapy using FloTrac/EV1000 to improve postoperative outcomes in patients undergoing off-pump coronary artery bypass surgery: a randomized controlled trial

Background

Early goal-directed therapy (EGDT) using FloTrac reduced length of stay (LOS) in intensive care (ICU) and hospital among patients undergoing coronary artery bypass graft (CABG) with a cardiopulmonary bypass. However, this platform in off-pump CABG (OPCAB) has received scant attention, so we evaluated the efficacy of EGDT using FloTrac/EV1000 as a modality for improving postoperative outcomes in patients undergoing OPCAB.

Methods

Forty patients undergoing OPCAB were randomized to the EV1000 or Control group. The Control group received fluid, inotropic, or vasoactive drugs (at the discretion of the attending anesthesiologist) to maintain a mean arterial pressure 65–90 mmHg; central venous pressure 8–12 mmHg; urine output ≥ 0.5 mL kg⁻¹ h⁻¹; SpO₂ > 95%; and hematocrit ≥ 30%. The EV1000 group achieved identical targets using information from the FloTrac/EV1000. The goals included stroke volume variation < 13%; cardiac index (CI) of 2.2–4.0 L min⁻¹ m⁻²; and systemic vascular resistance index of 1500–2500 dynes s⁻¹ cm⁻⁵ m⁻².

Results

The EV1000 group had a shorter LOS in ICU (mean difference − 1.3 d, 95% CI − 1.8 to − 0.8; P < 0.001). The ventilator time for both groups was comparable (P = 0.316), but the hospital stay for the EV1000 group was shorter (mean difference − 1.4 d, 95% CI − 2.1 to − 0.6; P < 0.001).

Conclusions

EGDT using FloTrac/EV1000 compared to conventional protocol reduces LOS in ICU and hospital among patients undergoing OPCAB.

Trial registration This study was retrospectively registered at www.ClinicalTrials.gov (NCT04292951) on 3 March 2020.

Spatial signatures of anesthesia-induced burst-suppression differ between primates and rodents

During deep anesthesia, the electroencephalographic (EEG) signal of the brain alternates between bursts of activity and periods of relative silence (suppressions). The origin of burst-suppression and its distribution across the brain remain matters of debate. In this work, we used functional magnetic resonance imaging (fMRI) to map the brain areas involved in anesthesia-induced burst-suppression across four mammalian species: humans, long-tailed macaques, common marmosets, and rats. At first, we determined the fMRI signatures of burst-suppression in human EEG-fMRI data. Applying this method to animal fMRI datasets, we found distinct burst-suppression signatures in all species. The burst-suppression maps revealed a marked inter-species difference: in rats, the entire neocortex engaged in burst-suppression, while in primates most sensory areas were excluded-predominantly the primary visual cortex. We anticipate that the identified species-specific fMRI signatures and whole-brain maps will guide future targeted studies investigating the cellular and molecular mechanisms of burst-suppression in unconscious states.

Comparison of Antinociceptive Properties Between Sevoflurane and Desflurane Using Pupillary Dilation Reflex Under Equivalent Minimum Alveolar Concentration: A Randomized Controlled Trial

BACKGROUND

The pupillary dilation reflex (PDR), the change in pupil size after a nociceptive stimulus, has been used to assess antinociception during anesthesia. The aim of this study was to compare the antinociceptive properties of sevoflurane and desflurane by measuring the PDR amplitude.

METHODS

Seventy patients between 20 and 55 years of age were randomly allocated to receive either sevoflurane or desflurane. The PDR amplitude after an electrical standardized noxious stimulation (SNT) was measured using an infrared pupillometer under 1.0 minimum alveolar concentration (MAC). The pupil diameter was measured from 5 seconds before to 5 minutes after the SNT. The mean arterial pressure (MAP), heart rate (HR), and bispectral index (BIS) were also measured immediately before and after SNT as well as 1 minute and 5 minutes after SNT. The primary outcome was the maximum percent increase from the prestimulation value of the pupil diameter, and the secondary outcomes were the maximum percent increase from the prestimulation value of the MAP, HR, and BIS after SNT.

RESULTS

The maximum percent increase of the pupil diameter after SNT was not different between the 2 groups (median [first quartile to third quartile], 45.1 [29.3-80.3] vs 43.4 [27.0-103.1]; median difference, -0.3 [95% confidence interval, -16.0 to 16.5]; P = .986). Before SNT, the MAP was higher under 1.0 MAC of sevoflurane than desflurane; however, the maximum percent increase of MAP, HR, and BIS was not different between the 2 groups.

CONCLUSIONS

The amount of change in the PDR amplitude, MAP, and HR after SNT was not different between sevoflurane and desflurane anesthesia. This result might suggest that sevoflurane and desflurane may not have different antinociceptive properties at equivalent MAC.

Cerebral hemodynamics during sustained intra-operative hypotension

Background Static cerebral autoregulation (CA) maintains cerebral blood flow (CBF) relatively constant above a mean arterial blood pressure (BP_mean) of 60-65 mmHg. Below this lower limit of CA (LLCA), CBF declines along with BP_mean. Data are lacking describing how CA reacts to sustained hypotension, since hypotension is usually avoided. In this study, we took advantage of a procedure requiring sustained hypotension. We assessed static CA for LLCA determination, and a more continuous CA, which counter short-term blood pressure variations. With these data, we analyzed CA during longstanding hypotension. Methods Continuous arterial blood pressure and middle cerebral artery blood flow velocity (MCAV_mean) were monitored in 23 patients that required deep intra-operative hypotension. The LLCA was determined for every patient, and BP_mean below this LLCA was classified as the patient specific hypotension. With the mean flow index (Mx_a) continuous CA (Mx_a-CA) was quantified. Mx_a was calculated and averaged after induction of general anesthesia (baseline), every 15 minutes during, and 15 minutes after one-hour of hypotension. Functioning CA was defined as Mx_a <0.4. Data are expressed as median (25^th-75^th percentile). Results The LLCA was located at 56 (47-74) mmHg. At baseline, Mx_a was 0.21 (0.14-0.32) and 0.61 (0.48-0.78) during hypotension (p<0.01), with no appreciable change over time, n=12. After blood pressure restoration, Mx_a improved, 0.25 (0.06-0.35, n=9). Conclusions Mx_a-CA became and remained disturbed during the one-hour of hypotension, and improved after blood pressure restoration. This completely reversible situation suggests no ischemic hyperemia occurs and renders an adaptation mechanism during sustained hypotension unlikely.

Age, minimum alveolar concentration and choice of depth of sedation monitor: examining the paradox of age when using the Narcotrend monitor: A secondary analysis of an observational study

BACKGROUND

With an ageing global population, it is important to individualise titration of anaesthetics according to age and by measuring their effect on the brain. A recent study reported that during general surgery, the given concentration of volatile anaesthetics, expressed as a fraction of the minimum alveolar concentration (MAC fraction), decreases by around only 3% per age-decade, which is less than the 6% expected from age-adjusted MAC. Paradoxically, despite the excessive dosing, Bispectral index (BIS) values also increased.

OBJECTIVE

We planned to investigate the paradox of age when using the Narcotrend depth of anaesthesia monitor.

DESIGN

Secondary analyses of a prospective observational study.

SETTING

Tertiary hospital in Switzerland, recordings took place during 2016 and 2017.

PATIENTS

One thousand and seventy-two patients undergoing cardiac surgery entered the study, and 909 with noise-free recordings and isoflurane anaesthesia were included in this analysis.

INTERVENTION

We calculated mean end-tidal MAC fraction and mean index value of the Narcotrend depth of sedation monitor used in the study during the prebypass period. Statistical associations were modelled using linear regression, local weighted regression (LOESS) and a generalised additive model (GAM).

MAIN OUTCOME MEASURES

Primary endpoints in this study were the change in end-tidal MAC fraction and mean Narcotrend index values, both measured per age-decade.

RESULTS

We observed a linear decrease in end-tidal MAC fraction of 3.2% per age-decade [95% confidence interval (CI) -3.97% to -2.38%, P < 0.001], consistent with previous findings. In contrast to the BIS, mean Narcotrend index values decreased with age at 3.0 index points per age-decade (95% CI, -3.55 points to -2.36 points, P < 0.001), a direction of change commensurate with the increasing age-adjusted MAC fraction with patient age. These relationships were consistent regardless of whether age-adjusted MAC was displayed on the anaesthetic machine.

CONCLUSIONS

We caution that the 'paradox of age' may in part depend on the choice of depth of sedation monitor.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02976584.

Perioperative Anesthesia and Acute Smell Alterations in Spine Surgery: A "Sniffing Impairment" Influencing Refeeding?

Medications for general anesthesia can cause smell alterations after surgery, with inhalation anesthetics being the most acknowledged drugs. However, spine patients have been poorly studied in past investigations and whether these alterations could influence the refeeding remains unclear. This research aims to observe detectable dysosmias after spine surgery, to explore any amplified affection of halogenates (DESflurane and SEVoflurane) against total intravenous anesthesia (TIVA), and to spot potential repercussions on the refeeding. Fifty patients between 50 and 85 years old were recruited before elective spine procedure and tested for odor acuity and discrimination using the Sniffin' Sticks test. The odor abilities were re-assessed within the first 15 h after surgery together with the monitoring of food intakes. The threshold reduced from 4.92 ± 1.61 to 4.81 ± 1.64 (p = 0.237) and the discrimination ability reduced from 10.50 ± 1.83 to 9.52 ± 1.98 (p = 0.0005). Anesthetic-specific analysis showed a significant reduction of both threshold (p = 0.004) and discrimination (p = 0.004) in the SEV group, and a significant reduction of discrimination abilities (p = 0.016) in the DES group. No dysosmias were observed in TIVA patients after surgery. Food intakes were lower in the TIVA group compared to both DES (p = 0.026) and SEV (p = 0.017). The food consumed was not associated with the sniffing impairment but appeared to be inversely associated with the surgical time. These results confirmed the evidence on inhalation anesthetics to cause smell alterations in spine patients. Furthermore, the poor early oral intake after complex procedures suggests that spinal deformity surgery could be a practical challenge to early oral nutrition.

The Requirement of Isoflurane and Remifentanil During Liver Transplantation Using Bispectral Index and Surgical Pleth Index: An Observational Study

BACKGROUND

During liver transplantation (LT), patients and surgical factors potentially influence the pharmacokinetics of the anesthetic agents. The aim of this study was to investigate the requirement of isoflurane and remifentanil according to severity of liver disease during LT under balanced anesthesia.

METHODS

We enrolled 44 patients undergoing LT. Anesthetic depth was maintained within the bispectral index score of 40 to 60 and Surgical Pleth Index of 20 to 60. Patients were divided into 2 groups according to their median Model for End-Stage Liver Disease (MELD) score: low MELD group and high MELD group. We compared end-tidal inhaled anesthetics and remifentanil consumption.

RESULTS

Patients were divided into 2 groups according to median value of MELD score: MELD score <16 (low MELD group; n = 20) or MELD ≥16 (high MELD group; n = 20). There was no significant difference between the 2 groups in end-tidal concentration of isoflurane during 3 phases. However, the remifentanil requirement was lower in the high MELD group during the dissection and anhepatic phases (mean (SD), 0.105 (0.067) vs 0.064 (0.055) µg/kg/min; P = .037, and 0.167 (0.096) vs 0.108 (0.079) µg/kg/min; P = .039, respectively; low MELD group vs high MELD group) with no significant difference during the neohepatic phase.

CONCLUSIONS

The severity of liver dysfunction based on MELD score affected the intraoperative remifentanil requirement during LT. Patients with cirrhosis are required to use analgesics appropriate to their individual patient characteristics in clinical practice.

Sevoflurane-based enhancement of phase-amplitude coupling and localization of the epileptogenic zone

OBJECTIVE

Phase-amplitude coupling between high-frequency (≥150 Hz) and delta (3-4 Hz) oscillations - modulation index (MI) - is a promising, objective biomarker of epileptogenicity. We determined whether sevoflurane anesthesia preferentially enhances this metric within the epileptogenic zone.

METHODS

This is an observational study of intraoperative electrocorticography data from 621 electrodes chronically implanted into eight patients with drug-resistant, focal epilepsy. All patients were anesthetized with sevoflurane during resective surgery, which subsequently resulted in seizure control. We classified 'removed' and 'retained' brain sites as epileptogenic and non-epileptogenic, respectively. Mixed model analysis determined which anesthetic stage optimized MI-based classification of epileptogenic sites.

RESULTS

MI increased as a function of anesthetic stage, ranging from baseline (i.e., oxygen alone) to 2.0 minimum alveolar concentration (MAC) of sevoflurane, preferentially at sites showing higher initial MI values. This phenomenon was accentuated just prior to sevoflurane reaching 2.0 MAC, at which time, the odds of a site being classified as epileptogenic were enhanced by 86.6 times for every increase of 1.0 MI.

CONCLUSIONS

Intraoperative MI best localized the epileptogenic zone immediately before sevoflurane reaching 2.0 MAC in this small cohort of patients.

SIGNIFICANCE

Prospective, large cohort studies are warranted to determine whether sevoflurane anesthesia can reduce the need for extraoperative, invasive evaluation.

Inhalational Anesthetics Do Not Deteriorate Amyloid-β-Derived Pathophysiology in Alzheimer's Disease: Investigations on the Molecular, Neuronal, and Behavioral Level

BACKGROUND

Studies suggest that general anesthetics like isoflurane and sevoflurane may aggravate Alzheimer's disease (AD) neuropathogenesis, e.g., increased amyloid-β (Aβ) protein aggregation resulting in synaptotoxicity and cognitive dysfunction. Other studies showed neuroprotective effects, e.g., with xenon.

OBJECTIVE

In the present study, we want to detail the interactions of inhalational anesthetics with Aβ-derived pathology. We hypothesize xenon-mediated beneficial mechanisms regarding Aβ oligomerization and Aβ-mediated neurotoxicity on processes related to cognition.

METHODS

Oligomerization of Aβ 1-42 in the presence of anesthetics has been analyzed by means of TR-FRET and silver staining. For monitoring changes in neuronal plasticity due to anesthetics and Aβ 1-42, Aβ 1-40, pyroglutamate-modified amyloid-(AβpE3), and nitrated Aβ (3NTyrAβ), we quantified long-term potentiation (LTP) and spine density. We analyzed network activity in the hippocampus via voltage-sensitive dye imaging (VSDI) and cognitive performance and Aβ plaque burden in transgenic AD mice (ArcAβ) after anesthesia.

RESULTS

Whereas isoflurane and sevoflurane did not affect Aβ 1-42 aggregation, xenon alleviated the propensity for aggregation and partially reversed AβpE3 induced synaptotoxic effects on LTP. Xenon and sevoflurane reversed Aβ 1-42-induced spine density attenuation. In the presence of Aβ 1-40 and AβpE3, anesthetic-induced depression of VSDI-monitored signaling recovered after xenon, but not isoflurane and sevoflurane removal. In slices pretreated with Aβ 1-42 or 3NTyrAβ, activity did not recover after washout. Cognitive performance and plaque burden were unaffected after anesthetizing WT and ArcAβ mice.

CONCLUSION

None of the anesthetics aggravated Aβ-derived AD pathology in vivo. However, Aβ and anesthetics affected neuronal activity in vitro, whereby xenon showed beneficial effects on Aβ 1-42 aggregation, LTP, and spine density.

Is Prevention of Postoperative Vomiting Surgery Dependent? A Retrospective Cohort Study of Total Knee Arthroplasty

The study of postoperative nausea and vomiting (PONV) has been ongoing since the early days of general anesthesia. The search for risk factors of PONV and the development of new agents to treat PONV are the two main strategies to combat the adverse side effects of general anesthesia. Female sex, non-smoking status, a history of PONV/motion sickness, and postoperative opioid use are the four independent risk factors for PONV derived after a series of prospective studies, evidence-based systematic reviews, and meta-analyses. The two frequently asked questions that arise ask whether risk factors apply to different clinical settings and whether prevention measures of PONV can be surgery dependent. We conducted a comprehensive review of 665 patients who underwent primary total knee arthroplasty (TKA) between January and December 2019. As nausea is subjective and its measurement is not standardized, postoperative vomiting (POV) was used as a study endpoint. The exclusion criteria were desflurane anesthesia, spinal anesthesia, anesthesia without bispectral index monitoring, and day surgery. Three well-recognized risk factors, consisting of body weight, sevoflurane consumption, and postoperative opioid consumption, were not considered as independent risk factors of POV, while female sex, preoperative adductor canal block (ACB), and dexamethasone were identified as being so in this study. The risk of POV in the female sex was 2.49 times that in the male sex; however, when dexamethasone was used, this risk was reduced by >40% compared with no antiemetic use, and by >50% when patients received preoperative ACB compared with those without the block. The clinical characteristics of our TKA patients—female dominance, old age, and their fairly constant body weights that were distinct from those of other surgical patients—suggested that age may play a crucial role in determining the relative contributions of the different risk factors of POV. We concluded that risk factors of POV are dependent on clinical settings. Based on these results, it is reasonable to speculate that a surgery-dependent plan for the prevention of POV is feasible for patients in similar clinical settings.

Sevoflurane and Desflurane Exposures Following Aneurysmal Subarachnoid Hemorrhage Confer Multifaceted Protection against Delayed Cerebral Ischemia

Numerous studies have demonstrated the ability of isoflurane conditioning to provide multifaceted protection against aneurysmal subarachnoid hemorrhage (SAH)-associated delayed cerebral ischemia (DCI); however, preclinical studies have not yet examined whether other commonly used inhalational anesthetics in neurological patients such as sevoflurane or desflurane are also protective against SAH-induced neurovascular deficits. We therefore sought to identify the potential for sevoflurane and desflurane conditioning to protect against DCI in an endovascular perforation mouse model of SAH. Neurological function was assessed daily via neuroscore. Large artery vasospasm and microvessel thrombosis were assessed three days after SAH or sham surgery. Four groups were examined: Sham, SAH + room air, SAH + 2% Sevoflurane, and SAH + 6% Desflurane. For the SAH groups, one hour after surgery, mice received 2% sevoflurane, 6% desflurane, or room air for one hour. We found that conditioning with sevoflurane or desflurane attenuated large artery vasospasm, reduced microvessel thrombosis, and improved neurologic function. Given their frequent clinical use and strong safety profile in patients (including those with SAH), these data strongly support further studies to validate these findings in preclinical and clinical studies and to elucidate the mechanisms by which these agents might be acting.

Age-dependent cross frequency coupling features from children to adults during general anesthesia

BACKGROUND

The frequency coupling characteristics in electroencephalogram (EEG) induced by anesthetics have been well studied in adults, but the investigation of the age-dependent cross frequency coupling features from children to adults is still lacking.

METHODS

We analyzed EEG signals recorded from pediatric to adult patients (n = 131), separated into six age groups: <1 year (n = 15), 1-3 years (n = 23), 3-6 years (n = 19), 6-12 years (n = 18), 12-18 years (n = 16), and 18-45 years (n = 40). Age related EEG power and cross frequency coupling analysis (phase amplitude coupling (PAC) and quadratic phase coupling) of data from maintenance of a surgical state of anesthesia (MOSSA) was conducted. Also, for patients of ages less than 6 years, we analyzed the performance of cross frequency coupling derived indices in distinguishing the states of wakefulness, MOSSA, and recovery of consciousness (ROC).

RESULTS

(1) During MOSSA, EEG power substantially increased with age from infancy to 3-6 years then decreased with age in the theta-gamma frequency bands. The infant group (<1 year) had the highest slow oscillation (SO) power among all age groups. (2) The distinct PAC pattern is absent in patients less than 1 year of age both in SO-alpha and delta-alpha frequency band coupling during propofol induced unconsciousness. The modulation index between delta and alpha oscillations in MOSSA increased with age. (3) Wavelet bicoherence derived indices reach their peaks in the 3-6 years group and then decrease with age growth. (4) The Diag_En index (normalized entropy of the diagonal bicoherence entries of the bicoherence matrix) performed the best at distinguishing different states for ages less than 6 years (p<0.05).

CONCLUSIONS

The combination of propofol induction and sevoflurane maintenance exhibited age-dependent EEG power spectra, PAC, and bicoherence, likely related to brain development. These observations suggest new rules for infant and child brain state monitoring during general anesthesia are needed.

Cannabis Exposure Decreases Need for Blood Pressure Support During General Anesthesia in Orthopedic Trauma Surgery

Introduction:

As cannabis use continues to increase in popularity, it is important to investigate how it impacts public health in all sectors of the population, including patients undergoing anesthetic management. This retrospective study focuses on the orthopedic trauma population presenting through an emergency department (ED) and receiving a urine drug screen (UDS) with subsequent urgent surgical intervention. We aimed to evaluate differences in response to general anesthesia in patients with exposure to THC, a major cannabinoid, compared to controls that screened negative for THC.

Materials and Methods:

All ED visits at UC Irvine, a level 1 trauma center between November 4, 2017 and January 7, 2020, were evaluated in this study. Only adult patients who received a UDS and underwent urgent orthopedic trauma surgery within 48 h of ED visit were included in this study. Additional inclusion criteria required an anesthesia time greater than 1 h as well as anesthesia induction and intubation while in the operating room. Overall, we analyzed a total of 221 adult patients.

Discussion:

When adjusting for demographic variability, there were statistically significant differences in response to general anesthesia between these two groups. The THC-positive (THC(+)) group was less likely to receive intraoperative vasopressors, had higher mean arterial blood pressure and mean diastolic blood pressure, needed less total fluid input and had a lower overall fluid balance. Chronic exposure to THC has been shown to downregulate cannabinoid 1 receptors and cause alterations in endocannabinoid tone. These are two potential mechanisms by which the THC(+) group in our study may have become more resistant to the typically observed hypotensive effects of general anesthesia.

Conclusion:

The present study suggests that prior use of cannabis, objectively assessed by urinalysis, results in a decreased need for blood pressure support during general anesthesia. The physiological basis for this phenomenon is unclear, but possible causes might include the downregulation of vascular cannabinoid receptor 1 and/or altered endocannabinoid levels after exposure to cannabis.

Efficacy of Intraoperative Hemodynamic Optimization Using FloTrac/EV1000 Platform for Early Goal-Directed Therapy to Improve Postoperative Outcomes in Patients Undergoing Coronary Artery Bypass Graft with Cardiopulmonary Bypass: A Randomized Controlled Trial

Purpose

Early goal-directed therapy (EGDT) using the FloTrac system reportedly improved postoperative outcomes among high-risk patients undergoing non-cardiac surgery. This study's objective was to evaluate the FloTrac/EV1000 platform's efficacy for improving postoperative outcomes in cardiac surgery.

Patients and Methods

Eighty-six adults undergoing coronary artery bypass graft (CABG) with cardiopulmonary bypass (CPB) in 2 tertiary referral centers were randomized to the EGDT or Control group. The Control group was managed with standard care to achieve the following goals: mean arterial pressure 65-90 mmHg; central venous pressure 8-12 mmHg; urine output ≥0.5 mL·kg^-1·h^-1; oxygen saturation >95%; and hematocrit 26-30%. The EGDT group was managed to reach similar goals using information from the FloTrac/EV1000 monitor. The targets were stroke volume variation <13%; stroke volume index 33-65 mL·beat^-1·m^-2; cardiac index 2.2-4.0 L·min^-1·m^-2; and systemic vascular resistance index 1600-2500 dynes·s·cm^-5·m^-2.

Results

The intensive care unit (ICU) stay of the EGDT group was significantly shorter (mean difference -29.5 h; 95% CI -17.2 to -41.8, P < 0.001). The mechanical ventilation time was also shorter in the EGDT group (mean difference -11.3 h; 95% CI -2.7 to -19.9, P = 0.011). The hospital LOS was shorter in the EGDT group (mean difference -1.1 d; 95% CI -0.1 to -2.1, P = 0.038).

Conclusion

EGDT using FloTrac/EV1000 can be applied in CABG with CPB to improve postoperative outcomes.

Comparison of isoflurane and propofol sedation in critically ill COVID-19 patients-a retrospective chart review

Purpose

In this retrospective study, we compared inhaled sedation with isoflurane to intravenous propofol in invasively ventilated COVID-19 patients with ARDS (Acute Respiratory Distress Syndrome).

Methods

Charts of all 20 patients with COVID-19 ARDS admitted to the ICU of a German University Hospital during the first wave of the pandemic between 22/03/2020 and 21/04/2020 were reviewed. Among screened 333 days, isoflurane was used in 97 days, while in 187 days, propofol was used for 12 h or more. The effect and dose of these two sedatives were compared. Mixed sedation days were excluded.

Results

Patients’ age (median [interquartile range]) was 64 (60–68) years. They were invasively ventilated for 36 [21–50] days. End-tidal isoflurane concentrations were high (0.96 ± 0.41 Vol %); multiple linear regression yielded the ratio (isoflurane infusion rate)/(minute ventilation) as the single best predictor. Infusion rates were decreased under ECMO (3.5 ± 1.4 versus 7.1 ± 3.2 ml∙h⁻¹; p < 0.001). In five patients, the maximum recommended dose of propofol of 4 mg∙hour⁻¹∙kg⁻¹ABW was exceeded on several days. On isoflurane compared to propofol days, neuro-muscular blocking agents (NMBAs) were used less frequently (11% versus 21%; p < 0.05), as were co-sedatives (7% versus 31%, p < 0.001); daily opioid doses were lower (720 [720–960] versus 1080 [720–1620] mg morphine equivalents, p < 0.001); and RASS scores indicated deeper levels of sedation (− 4.0 [− 4.0 to − 3.0] versus − 3.0 [− 3.6 to − 2.5]; p < 0.01).

Conclusion

Isoflurane provided sufficient sedation with less NMBAs, less polypharmacy and lower opioid doses compared to propofol. High doses of both drugs were needed in severely ill COVID-19 patients.

Predicting cost of inhalational anesthesia at low fresh gas flows: impact of a new generation carbon dioxide absorbent

It is well known that low fresh gas flows result in lower cost of inhalational agents. A new generation of carbon dioxide absorbents allows low flow anesthesia with all anesthetics but these new compounds are more expensive. This study examines the cost of inhalational anesthesia at different fresh gas flows combined with the cost of absorbent. The cost of sevoflurane and desflurane is lower at low fresh gas flows. Paradoxically the cost of isoflurane is cheaper at 2 L/min than at lower fresh gas flows due to increased cost of carbon dioxide absorbent. Therefore low fresh gas flows should be used when feasible with sevoflurane and desflurane, but higher fresh gas flows up to 2 L/min may be more economical with isoflurane during maintenance phase of anesthesia.

Correlation between pain rating index and end-tidal sevoflurane concentration during sevoflurane anesthesia

Objective

To investigate the correlation between the pain rating index (PRi), which is an index derived from processed electroencephalography signals, and the end-tidal sevoflurane concentration (ETsevo).

Methods

This study involved 50 adults with a body mass index of 18 to 25 kg/m² who were undergoing elective surgery under general anesthesia. Thyrocricocentesis was performed with 2.5 mL of 2% tetracaine for endotracheal surface anesthesia, and intravenous injections of midazolam, etomidate, and rocuronium were then administered. The patients’ tracheas were intubated and their ventilatory rate was adjusted to maintain the partial pressure of end-tidal carbon dioxide at 30 to 35 mmHg. Anesthesia was maintained with sevoflurane. The ETsevo was adjusted to maintain anesthesia at 0.6, 0.8, 1.0, and 1.2 minimum alveolar concentration for 15 minutes each, and the PRi, mean arterial pressure (MAP), and heart rate were recorded at each concentration.

Results

A negative correlation was found between the PRi and ETsevo (−0.882) and between the MAP and ETsevo (−0.571). A low positive correlation was found between the PRi and MAP (0.484).

Conclusions

The PRi showed a high negative correlation with the ETsevo. Therefore, the PRi can be used to guide the depth regulation of sevoflurane anesthesia.

Clinical trial registration number: ChiCTR-IPR-17012092

Recovery of consciousness and cognition after general anesthesia in humans

Understanding how the brain recovers from unconsciousness can inform neurobiological theories of consciousness and guide clinical investigation. To address this question, we conducted a multicenter study of 60 healthy humans, half of whom received general anesthesia for 3 hr and half of whom served as awake controls. We administered a battery of neurocognitive tests and recorded electroencephalography to assess cortical dynamics. We hypothesized that recovery of consciousness and cognition is an extended process, with differential recovery of cognitive functions that would commence with return of responsiveness and end with return of executive function, mediated by prefrontal cortex. We found that, just prior to the recovery of consciousness, frontal-parietal dynamics returned to baseline. Consistent with our hypothesis, cognitive reconstitution after anesthesia evolved over time. Contrary to our hypothesis, executive function returned first. Early engagement of prefrontal cortex in recovery of consciousness and cognition is consistent with global neuronal workspace theory.

Longer time to extubation after general anesthesia with desflurane in patients with obstructive respiratory dysfunction: a retrospective study

Background

The prospect of patients with obstructive respiratory dysfunction undergoing surgery has increased with the growth in the elderly population; however, there have been few investigations about the recovery profile from volatile anesthesia. This study aimed to investigate the impact of obstructive respiratory dysfunction on recovery from desflurane anesthesia.

Methods

A retrospective cohort study included patients who underwent orthopedic lower limb surgery between September 2018 and March 2020. Patients were divided into two groups: those whose preoperative forced expiratory volume in 1 s/forced vital capacity ratio was <70% (obstructive respiratory dysfunction group, n = 180) or ≥70% (control group, n = 45). Time from discontinuation of desflurane to extubation (extubation time) was compared between the two groups. Univariate and multivariable Cox regression models were used to compare odds ratios for prolonged extubation (≥10 min).

Results

A total of 45 patients with obstructive respiratory dysfunction and 180 control patients were eligible for analysis. Extubation time was significantly longer in patients in the obstructive respiratory dysfunction group than those in the control group. In the multivariable Cox model, male sex (HR = 2.00, 95% CI 1.12–3.57; P = 0.020) and obstructive respiratory dysfunction (HR = 2.07, 95% CI 1.05–4.08; P = 0.036) were associated with prolonged extubation.

Conclusions

This retrospective study indicated that extubation time was longer in patients with obstructive respiratory function than in patients without obstructive respiratory function. Male sex and obstructive respiratory function were factors that contributed to extubation time.

Intraoperative impaired cerebrovascular autoregulation and delayed neurocognitive recovery after major oncologic surgery: a secondary analysis of pooled data

Cerebral blood flow is tightly regulated by cerebrovascular autoregulation (CVA), and intraoperative impairment of CVA has been linked with perioperative neurocognitive disorders. We aim to assess whether impairment of CVA during major oncologic surgery is associated with delayed neurocognitive recovery (DNCR) postoperatively. We performed a secondary analysis of prospectively collected data. Patients were included if they had undergone complete pre- and postoperative neuropsychological assessments, continuous intraoperative measurement of CVA, and major oncologic surgery for visceral, urological, or gynecological cancer. Intraoperative CVA was measured using the time-correlation method based on near-infrared-spectroscopy, and DNCR was assessed with a neuropsychological test battery. A decline in cognitive function before hospital discharge compared with a preoperative baseline assessment was defined as DNCR. One hundred ninety-five patients were included in the analysis. The median age of the study population was 65 years (IQR: 60–68); 11 patients (5.6%) were female. Forty-one patients (21.0%) fulfilled the criteria for DNCR in the early postoperative period. We found a significant association between impaired intraoperative CVA and DNCR before hospital discharge (OR = 1.042 [95% CI: 1.005; 1.080], p = 0.028). The type of surgery (radical prostatectomy vs. other major oncologic surgery; OR = 0.269 [95% CI: 0.099; 0.728], p = 0.010) and premedication with midazolam (OR = 3.360 [95% CI: 1.039; 10.870], p = 0.043) were significantly associated with the occurrence of DNCR in the early postoperative period. Intraoperative impairment of CVA is associated with postoperative neurocognitive function early after oncologic surgery. Therefore, intraoperative monitoring of CVA may be a target for neuroprotective interventions. The initial studies were retrospectively registered with primary clinical trial registries recognized by the World Health Organization (ClinicalTrials.gov Identifiers: DRKS00010014, 21.03.2016 and NCT04101006, 24.07.2019).

Reflection Versus Rebreathing for Administration of Sevoflurane During Minor Gynecological Surgery

BACKGROUND

Contemporary anesthetic circle systems, when used at low fresh gas flows (FGF) to allow rebreathing of anesthetic, lack the ability for rapid dose titration. The small-scale anesthetic reflection device Anaesthetic Conserving Device (50mL Version; AnaConDa-S) permits administration of volatile anesthetics with high-flow ventilators. We compared washin, washout, and sevoflurane consumption using AnaConDa-S versus a circle system with low and minimal FGF.

METHODS

Forty patients undergoing breast surgery were randomized to receive 0.5 minimal alveolar concentration (MAC) sevoflurane with AnaConDa-S (21 patients, reflection group) or with a circle system (low flow: FGF = 0.2 minute ventilation [V'E], 9 patients; or minimal flow: 0.1 V'E, 10 patients). In the reflection group, syringe pump boluses were given for priming and washin; to simulate an open system, the FGF of the anesthesia ventilator was set to 18 L·min-1 with the soda lime removed. In the other groups, the FGF was increased for washin (1 V'E for 8 minutes) and washout (3 V'E). For all patients, tidal volume was 7 mL·kg-1 and the respiratory rate adjusted to ensure normoventilation. Analgesia was attained with remifentanil 0.3 µg·kg-1·min-1. Sevoflurane consumption was compared between the reflection group and the low- and minimal-flow groups, respectively, using a post hoc test (Fisher Least Significant Difference). To compare washin and washout (half-life), the low- and minimal-flow groups were combined.

RESULTS

Sevoflurane consumption was reduced in the reflection group (9.4 ± 2.0 vs 15.0 ± 3.5 [low flow, P < .001] vs 11.6 ± 2.3 mL·MAC h-1 [minimal flow, P = .02]); washin (33 ± 15 vs 49 ± 12 seconds, P = .001) and washout (28 ± 15 vs 55 ± 19 seconds, P < .001) times were also significantly shorter.

CONCLUSIONS

In this clinical setting with short procedures, low anesthetic requirements, and low tidal volumes, AnaConDa-S decreased anesthetic consumption, washin, and washout times compared to a circle system.

Effects of Volatile Anesthetics on Postoperative Ischemic Stroke Incidence

Background

Preclinical studies suggest that volatile anesthetics decrease infarct volume and improve the outcome of ischemic stroke. This study aims to determine their effect during noncardiac surgery on postoperative ischemic stroke incidence.

Methods and Results

This was a retrospective cohort study of surgical patients undergoing general anesthesia at 2 tertiary care centers in Boston, MA, between October 2005 and September 2017. Exclusion criteria comprised brain death, age <18 years, cardiac surgery, and missing covariate data. The exposure was defined as median age‐adjusted minimum alveolar concentration of all intraoperative measurements of desflurane, sevoflurane, and isoflurane. The primary outcome was postoperative ischemic stroke within 30 days. Among 314 932 patients, 1957 (0.6%) experienced the primary outcome. Higher doses of volatile anesthetics had a protective effect on postoperative ischemic stroke incidence (adjusted odds ratio per 1 minimum alveolar concentration increase 0.49, 95% CI, 0.40–0.59, P<0.001). In Cox proportional hazards regression, the effect was observed for 17 postoperative days (postoperative day 1: hazard ratio (HR), 0.56; 95% CI, 0.48–0.65; versus day 17: HR, 0.85; 95% CI, 0.74–0.99). Volatile anesthetics were also associated with lower stroke severity: Every 1‐unit increase in minimum alveolar concentration was associated with a 0.006‐unit decrease in the National Institutes of Health Stroke Scale (95% CI, −0.01 to −0.002, P=0.002). The effects were robust throughout various sensitivity analyses including adjustment for anesthesia providers as random effect.

Conclusions

Among patients undergoing noncardiac surgery, volatile anesthetics showed a dose‐dependent protective effect on the incidence and severity of early postoperative ischemic stroke.

Brain network motifs are markers of loss and recovery of consciousness

Motifs are patterns of inter-connections between nodes of a network, and have been investigated as building blocks of directed networks. This study explored the re-organization of 3-node motifs during loss and recovery of consciousness. Nine healthy subjects underwent a 3-h anesthetic protocol while 128-channel electroencephalography (EEG) was recorded. In the alpha (8-13 Hz) band, 5-min epochs of EEG were extracted for: Baseline; Induction; Unconscious; 30-, 10- and 5-min pre-recovery of responsiveness; 30- and 180-min post-recovery of responsiveness. We constructed a functional brain network using the weighted and directed phase lag index, on which we calculated the frequency and topology of 3-node motifs. Three motifs (motifs 1, 2 and 5) were significantly present across participants and epochs, when compared to random networks (p < 0.05). The topology of motifs 1 and 5 changed significantly between responsive and unresponsive epochs (p-values < 0.01; Kendall's W = 0.664 (motif 1) and 0.529 (motif 5)). Motif 1 was constituted of long-range chain-like connections, while motif 5 was constituted of short-range, loop-like connections. Our results suggest that anesthetic-induced unconsciousness is associated with a topological re-organization of network motifs. As motif topological re-organization may precede (motif 5) or accompany (motif 1) the return of responsiveness, motifs could contribute to the understanding of the neural correlates of consciousness.

Comparative study of analgesia nociception index (ANI) vs. standard pharmacokinetic pattern for guiding intraoperative fentanyl administration among mastectomy patients

Background

The Analgesia Nociception Index (ANI) has been suggested as a non-invasive guide for analgesia. Our objective was to compare the efficacy of ANI vs. standard pharmacokinetic pattern for guiding intraoperative fentanyl administration.

Methods

This was a prospective, randomized, controlled study of adult female patients undergoing elective mastectomy under general anesthesia. The patients were randomized to the ANI-guided group receiving a loading dose of 75 μg of fentanyl followed by 25 μg when the ANI score was under 50. The Control group received the same loading dose followed by 25 μg every 30 min with additional doses when there were signs of inadequate analgesia (viz., tachycardia or hypertension).

Results

Sixty patients—30 in each group—were recruited. Although the actual mean ANI score was higher in the ANI-guided than in the Control group (mean difference 2.2; 95% CI: 0.3 to 4.0, P = 0.022), there was no difference in the primary outcome—i.e., intraoperative fentanyl consumption (mean difference − 4.2 μg; 95% CI: − 24.7 to 16.4, P = 0.686 and − 0.14 μg·kg^− 1·h^− 1; 95% CI: − 0.31 to 0.03, P = 0.105). No difference between groups was shown for either intraoperative blood pressure and heart rate, or for postoperative outcomes (i.e., pain scores, morphine consumption, or sedation scores) in the postanesthesia care unit.

Conclusions

Intraoperative fentanyl administration guided by ANI was equivalent to that guided by a modified pharmacologic pattern. In a surgical model of mastectomy, the ANI-guided intraoperative administration of fentanyl had no impact on clinical outcomes.

Trial registration

The study was registered with ClinicalTrials.gov (NCT03716453) on 21/10/2018.

Prediction of expiratory desflurane and sevoflurane concentrations in lung-healthy patients utilizing cardiac output and alveolar ventilation matched pharmacokinetic models: A comparative observational study

The Gas Man simulation software provides an opportunity to teach, understand and examine the pharmacokinetics of volatile anesthetics. The primary aim of this study was to investigate the accuracy of a cardiac output and alveolar ventilation matched Gas Man model and to compare its predictive performance with the standard pharmacokinetic model using patient data.Therefore, patient data from volatile anesthesia were successively compared to simulated administration of desflurane and sevoflurane for the standard and a parameter-matched simulation model with modified alveolar ventilation and cardiac output. We calculated the root-mean-square deviation (RMSD) between measured and calculated induction, maintenance and elimination and the expiratory decrement times during emergence and recovery for the standard and the parameter-matched model.During induction, RMSDs for the standard Gas Man simulation model were higher than for the parameter-matched Gas Man simulation model [induction (desflurane), standard: 1.8 (0.4) % Atm, parameter-matched: 0.9 (0.5) % Atm., P = .001; induction (sevoflurane), standard: 1.2 (0.9) % Atm, parameter-matched: 0.4 (0.4) % Atm, P = .029]. During elimination, RMSDs for the standard Gas Man simulation model were higher than for the parameter-matched Gas Man simulation model [elimination (desflurane), standard: 0.7 (0.6) % Atm, parameter-matched: 0.2 (0.2) % Atm, P = .001; elimination (sevoflurane), standard: 0.7 (0.5) % Atm, parameter-matched: 0.2 (0.2) % Atm, P = .008]. The RMSDs during the maintenance of anesthesia and the expiratory decrement times during emergence and recovery showed no significant differences between the patient and simulated data for both simulation models.Gas Man simulation software predicts expiratory concentrations of desflurane and sevoflurane in humans with good accuracy, especially when compared to models for intravenous anesthetics. Enhancing the standard model by ventilation and hemodynamic input variables increases the predictive performance of the simulation model. In most patients and clinical scenarios, the predictive performance of the standard Gas Man simulation model will be high enough to estimate pharmacokinetics of desflurane and sevoflurane with appropriate accuracy.

Measurement of anesthetic pollution in veterinary operating rooms for small animals: Isoflurane pollution in a university veterinary hospital

Introduction

Inhaled anesthetics are used worldwide for anesthesia maintenance both in human and veterinary operating rooms. High concentrations of waste anesthetic gases can lead to health risks for the professionals exposed. Considering that anesthetic pollution in a veterinary surgical center in developing countries is unknown, this study aimed, for the first time, to measure the residual concentration of isoflurane in the air of operating rooms for small animals in a Brazilian university hospital.

Method

Residual isoflurane concentrations were measured by an infrared analyzer at the following sites: corner opposite to anesthesia machine; breathing zones of the surgeon, anesthesiologist, and patient (animal); and in front of the anesthesia machine at three time points, that is, 5, 30 and 120 minutes after anesthesia induction.

Results

Mean residual isoflurane concentrations gradually increased in the corner opposite to anesthesia machine and in the breathing zones of the surgeon and the anesthesiologist (p <  0.05). There was an increase at 30 minutes and 120 minutes when compared to the initial time points in the animal's breathing zone, and in the front of the anesthesia machine (p <  0.05). There was no significant difference at measurement sites regardless of the moment of assessment.

Conclusion

This study reported high residual isoflurane concentrations in veterinary operating rooms without an exhaust system, which exceeds the limit recommended by an international agency. Based on our findings, there is urgent need to implement exhaust systems to reduce anesthetic pollution and decrease occupational exposure.

Differences in midazolam premedication effects on recovery after short-duration ambulatory anesthesia with propofol or sevoflurane for gynecologic surgery in young patients: A randomized controlled trial

BACKGROUND

Anxiolytic premedication requires careful consideration owing to potential side effects including delayed recovery after ambulatory anesthesia. We aimed to compare the effect of midazolam on recovery profiles postoperatively, depending on whether propofol or sevoflurane was the primary anesthetic.

METHODS

We enrolled 226 patients (age, 18-50 years) undergoing ambulatory gynecologic laparoscopic surgery. Patients were categorized into propofol without midazolam (P), propofol with midazolam (MP), sevoflurane without midazolam (S), and sevoflurane with midazolam (MS) groups. As premedication, placebo or 0.02 mg/kg intravenous midazolam was used. The primary outcome was the difference in the time from anesthetic discontinuation to eye opening in response to verbal command. Secondary outcomes included postoperative nausea and pain occurrence and time to reach the discharge score.

RESULTS

The time from anesthetic discontinuation to eye opening was longer in the MP group (n = 49) than in the P group (n = 50; P < .001) but was not significantly different between the MS (n = 50) and S groups (n = 49; P = .1). Midazolam premedication did not significantly affect postoperative nausea in the MP group compared with that in the P group (P = .3) but had a nausea prevention effect in the MS group compared with that in the S group (P < .001). The time to reach the discharge score was similar in all patients regardless of midazolam administration.

CONCLUSION

In the recovery from short-duration ambulatory gynecologic surgery in young patients, intravenous midazolam premedication showed positive effects on postoperative nausea without affecting the time from anesthetic discontinuation to eye opening with sevoflurane-based anesthesia but prolonged the time from anesthetic discontinuation to eye opening with propofol-based anesthesia. Because this difference between the propofol groups is not clinically significant, the results support midazolam premedication in young women. Further studies assessing larger populations are needed.