Alveolar Concentration Research Articles

Effect of buprenorphine delivered by target-controlled infusion on the minimum alveolar concentration of isoflurane in cats

ObjectiveTo characterize the effect of buprenorphine on the minimum alveolar concentration of isoflurane (MACiso) in cats. Study designRandomized, crossover experimental study. AnimalsA group of six healthy 2 to 8 years old male neutered cats, body mass 5.0 ± 0.3 kg. MethodsThe MACiso had been determined in each cat in a previous study. Cats were anesthetized with isoflurane in oxygen. Catheters were placed in a medial saphenous vein for drug and fluid administration and in a jugular vein for blood sampling. Buprenorphine was given intravenously using a target-controlled infusion system to reach and maintain plasma concentrations of 0.5, 1, 2, 4, 8, 16, 32 and 64 ng mL-1 and MACiso was determined in duplicate at each concentration using the tail clamp technique. Four target plasma buprenorphine concentrations were administered on each study day, with at least 2 weeks between experiments. Blood was sampled after the second MAC determination at each target for determination of plasma buprenorphine concentration. ResultsA significant effect of buprenorphine on MAC was found; however, pairwise comparisons to MACiso without buprenorphine did not reach statistical significance. Maximum reduction in MACiso in individual cats ranged from 2 to 34% at plasma buprenorphine concentrations ranging from 0.25 to 8.15 ng mL-1. Conclusions and clinical relevanceAlthough buprenorphine significantly affected MACiso in cats, the magnitude of the effect and the plasma concentration at which the largest effect occurred was highly variable among cats, limiting the clinical usefulness of buprenorphine as an agent to reduce MAC in cats.

Advancing Breathomics through Accurate Discrimination of Endogenous from Exogenous Volatiles in Breath.

Breathomics, a growing field in exposure monitoring and clinical diagnostics, has faced accuracy challenges due to unclear contributing factors. This study aims to enhance the potential of breathomics in various frontiers by categorizing exhaled volatile organic compounds (VOCs) as endogenous or exogenous. Analyzing ambient air and breath samples from 271 volunteers via TD-GC × GC-TOF MS/FID, we identify and quantify 50 common VOCs in exhaled breath. Advanced quantitative structure-property relationships and compartment models are employed to obtain VOCs kinetic parameters. This in-depth approach allows us to accurately determine the alveolar concentration of VOCs and further discern their origins, facilitating personalized application of breathomics in exposure assessment and disease diagnosis. Our findings demonstrate that prolonged external exposure turns humans into secondary pollutant sources. Analysis of endogenous VOCs reveals that internal exposure poses more significant health risks than external. Moreover, by correcting environmental backgrounds, we improve the accuracy of gastrointestinal disease diagnostic models by 15-25%. This advancement in identifying VOC origins via compartmental models promises to elevate the clinical relevance of breathomics, marking a leap forward in exposure assessment and precision medicine.

The activity of suprahyoid muscles during sevoflurane-induced gasping in mice

Sevoflurane-induced gasping in mice involves an enormous increase in inspiratory effort, mandibular movement, and a marked decrease in respiratory frequency (fR). We examined differences in breathing patterns and electromyogram activity (EMGSH) of the suprahyoid muscles (SHMs) during eupnea under 3.2 % (1 MAC: minimum alveolar concentration) sevoflurane inhalation and sevoflurane-induced gasping under 6.5 % (2 MAC) sevoflurane inhalation in eight spontaneously breathing, tracheally intubated, adult mice. We found that the phasic EMGSH is obtained only during inspiration in eupnea and gasping and that integrated EMGSH increases more, as a percent of baseline (% baseline) than tidal volume (VT) during gasping (median [interquartile range]; integrated EMGSH: 720 [425–1965] vs. VT: 300 [238–373], P < 0.05). We also found that the onset of EMGSH precedes the start of airflow while maintaining a bell-shaped EMGSH contour, which characterizes the EMG of upper airway dilator (UAD) muscles during eupnea and gasping. Vigorous respiratory-related mandibular movements were never observed during eupnea but were observed in seven of 8 mice during sevoflurane-induced gasping. Our observations indicate that SHMs act as a preferentially activating UAD muscle, contributing to the development of mandibular respiratory movements.

Different ethanol exposure durations affect cytochrome P450 2E1-mediated sevoflurane metabolism in rat liver

BackgroundChronic alcohol users often exhibit an increased minimum alveolar concentration (MAC) of sevoflurane, yet the specific mechanism remains unclear. It has been reported that ethanol exposure can upregulate the protein expression and enzyme activity of cytochrome P450 2E1 (CYP2E1). CYP2E1 is a key enzyme that converts 2–5% of sevoflurane into equimolar amounts of hexafluoroisopropanol (HFIP) and F−. This study aims to explore whether ethanol exposure could alter sevoflurane metabolism through CYP2E1 modulation, potentially explaining the increased MAC observed in alcohol users.MethodsEighty adult male Sprague-Dawley (SD) rats were randomly divided into two groups and received either 50% ethanol (dose: 3 g/kg) or 0.9% saline twice daily by gavage. After 1, 2, 3, and 4 weeks of gavage, ten rats were randomly selected from each group to undergo 1-hour anesthesia with 2.3% sevoflurane. Blood samples were collected after anesthesia to measure the concentration of free HFIP using gas chromatography. Additionally, the left lobe tissue of the liver was collected for the analysis of CYP2E1 protein expression by Western blot and CYP2E1 enzyme activity by colorimetric assay. Correlations between these parameters were analyzed using Pearson’s correlation.ResultsIn the ethanol group, CYP2E1 expression, activity, and the concentration of free HFIP were significantly higher at all time points compared to the control group (P < 0.05), except for protein expression in the first week (P > 0.05). Within-group comparisons indicated no significant changes in any of the parameters for the control group (P > 0.05). In the ethanol group, there was no difference in free HFIP concentration between the first and second weeks (P > 0.05), but a significant increase was observed in the third and fourth weeks (P < 0.01); protein expression and enzyme activity significantly varied over time, especially showing a notable increase from the first to the third and fourth weeks (P < 0.05). Correlation analysis revealed strong positive correlations between free HFIP concentration and CYP2E1 activity (r = 0.7898), free HFIP concentration and CYP2E1 expression (r = 0.8418), and CYP2E1 activity and expression (r = 0.8740), all with P < 0.001.ConclusionsEthanol exposure increased both the expression and enzymatic activity of CYP2E1, consequently enhancing the metabolism of sevoflurane.

Effect of Sevoflurane Anesthesia on Diastolic Function: A Prospective Observational Study.

The effect of sevoflurane on left ventricular diastolic function is not well understood. We hypothesized that parameters of diastolic function may improve under sevoflurane anesthesia in patients with preexisting diastolic dysfunction compared to patients with normal diastolic function. This observational study included 60 patients undergoing breast surgery or laparoscopic cholecystectomy. Patients were assigned to diastolic dysfunction (n = 34) or normal (n = 26) groups of septal e' < 8 or ≥ 8.0 cm/s on the first thoracic echocardiography (TTE) performed before anesthesia. During anesthesia, sevoflurane was maintained at 1 to 2 minimum alveolar concentration (MAC) to maintain the bispectral index at 40 to 50. At the end of surgery, the second TTE was performed under 0.8 to 1 MAC of sevoflurane with the patient breathing spontaneously without ventilator support. Primary end point was the percentage change (Δ) of e' on 2 TTEs (Δe'). Secondary end points were ΔE/e', Δleft atrial volume index (ΔLAVI), and Δtricuspid regurgitation maximum velocity (ΔTR Vmax). These percentage changes (Δ) were compared between diastolic dysfunction and normal groups. e' (Δe': 30 [6, 64] vs 0 [-18, 11]%; P < .001), mitral inflow E wave velocity (E), mitral inflow E/A ratio (E/A), and mitral E velocity deceleration time (DT) improved significantly in diastolic dysfunction group compared to normal group. LAVI decreased in diastolic dysfunction group but did not reach statistical significance between the 2 groups (ΔLAVI:-15 [-31, -3] vs -4 [-20, 10]%, P = .091). ΔE/e' was not different between the 2 groups (11 [-16, 26] vs 12 [-9, 22]%, P = .853) (all: median [interquartile range, IQR]). TR was minimal in both groups. In this study, echocardiographic parameters of diastolic function, including septal e', E, E/A, and DT, improved with sevoflurane anesthesia in patients with preexisting diastolic dysfunction, but remained unchanged in patients with normal diastolic function.

Antinociceptive and anesthetic-sparing effects of levomethadone/fenpipramide cannot be enhanced by coadministration of metamizole in awake and anesthetized Beagles.

To determine the effect of levomethadone/fenpipramide and metamizole alone and in combination on acute nociception. 8 healthy, adult Beagles were used in 2 separate randomized, complete crossover, experimental trials (threshold testing and determination of minimal alveolar concentration [MAC]) with masked observers. In both trials, treatments were 0.2 mg·kg-1 levomethadone/fenpipramide (L), 75 mg·kg-1 metamizole (M), or their combination (LM). In conscious dogs, mechanical thresholds were determined using constantly rising force. Thermal thresholds were measured via ramped contact heat. The MAC of sevoflurane was determined using the bracketing method with electrical stimulus (50 V, 50 Hz, 10 ms) before and 1 and 4 hours after treatment. Mechanical thresholds in L and LM were significantly increased above baseline (BL) for 165 minutes and above M for 135 minutes. Percent thermal threshold excursion significantly increased above BL in L for 75 minutes and in LM for 135 minutes. In L and LM, the percent thermal threshold excursion was significantly higher than in M from 15 to 75 or 135 minutes, respectively. In L and LM, the MAC of sevoflurane was significantly reduced at 1 hour compared to BL and M. Duration but not the magnitude of thermal antinociception of levomethadone/fenpipramide was increased by metamizole. Mechanical antinociception in awake dogs and anesthetic-sparing effects of levomethadone/fenpipramide were not altered. Coadministration of levomethadone/fenpipramide and metamizole to increase antinociception is not justified.

Impact of low-dose sevoflurane with propofol-based anaesthesia on motor-evoked potentials in infants: protocol for a single-centre randomised controlled study

IntroductionMotor-evoked potentials (MEP) are widely used to mitigate the risk of nerve injury resulting from surgical manipulation. Infants are more susceptible to anaesthetics that suppress MEP because of the immaturity...

End-Tidal Control Versus Manual Control of Inhalational Anesthesia Delivery: A Randomized Controlled Noninferiority Trial.

Precise anesthesia delivery helps ensure amnesia, analgesia, and immobility. Conventionally, the end-tidal anesthetic concentration is maintained through manual adjustment of the fresh gas flow and anesthetic vaporizer output. Some anesthesia delivery systems can deliver and maintain clinician-selected end-tidal anesthetic agent (EtAA) concentration using a modified closed-loop system. We evaluated the performance of an End-tidal Control (EtC) system on the Aisys CS 2 anesthesia machine (GE HealthCare). We hypothesized EtC anesthetic delivery would be noninferior to manually controlled anesthetic delivery. The Multi-site Anesthesia randomized controlled STudy of End-tidal control compared to conventional Results (MASTER) Trial evaluated anesthetic delivery in 210 adult patients receiving inhaled anesthesia. Patients were randomized to either EtC or manual control (MC) anesthetic delivery. The primary objective was to determine whether, compared to conventional anesthesia practice, EtC achieves and maintains clinician-specified EtAA and end-tidal oxygen (Et o2 ) concentrations within defined noninferiority limits. Noninferiority was concluded if the lower limit of the 95% confidence interval (CI) of the difference between the percent duration within the acceptable range (5% of steady state or a margin of ~10% of each agent's minimum alveolar concentration) for EtC and MC was ≥ -5% for both EtAA and Et o2 . Secondary objectives included performance measures: response time: time required to attain 90% of the first desired EtAA, overshoot: amount the controller (or vaporizer delivery) exceeded the desired EtAA, and accuracy: average deviation from the desired EtAA. EtC achieved and sustained targeted EtAA and Et o2 concentrations within the noninferiority threshold. The EtAA was within 5% of the desired value 98% ± 2.05% of the time with EtC compared to 45.7% ± 31.7% of the time with MC (difference 52.3% [95% CI, 45.9%-58.6%], P < .0001). For Et o2 , EtC was within the noninferiority limit 86.3% ± 22.8% of the time compared with MC at 41% ± 33.3% ( P < .0001, difference 45.3% [95% CI, 36.1%-54.5%]). The median response time for achieving 90% of the initial EtAA desired value was 75 seconds with EtC and 158 seconds with MC ( P = .0013). EtC exhibited a median overshoot of 6.64% of the selected EtAA concentration, whereas MC often failed to reach the clinician's desired value. The difference in median percent deviation from desired EtAA value was 15.7% ([95% CI, 13.5%-19.0%], P < 0001). EtC achieves and maintains the EtAA and Et o2 concentration in a manner that is noninferior to manually controlled anesthesia delivery.

Pulmonary herpes simplex virus and cytomegalovirus in patients with acute respiratory distress syndrome related to COVID-19

PurposeHuman herpesviruses, particularly cytomegalovirus (CMV) and herpes simplex virus (HSV), frequently reactivate in critically ill patients, including those with acute respiratory distress syndrome (ARDS) related to coronavirus disease 2019 (COVID-19). The clinical interpretation of pulmonary herpesvirus reactivation is challenging and there is ongoing debate about its association with mortality and benefit of antiviral medication. We aimed to quantify the incidence and pathogenicity of pulmonary CMV and HSV reactivations in critically ill COVID-19 patients.MethodsMechanically ventilated COVID-19 patients seropositive for CMV or HSV were included in this observational cohort study. Diagnostic bronchoscopy with bronchoalveolar lavage was performed routinely and analyzed for alveolar viral loads and inflammatory biomarkers. Utilizing joint modeling, we explored the dynamic association between viral load trajectories over time and mortality. We explored alveolar inflammatory biomarker dynamics between reactivated and non-reactivated patients.ResultsPulmonary reactivation (> 104 copies/ml) of CMV occurred in 6% of CMV-seropositive patients (9/156), and pulmonary reactivation of HSV in 37% of HSV-seropositive patients (63/172). HSV viral load dynamics prior to or without antiviral treatment were associated with increased 90-day mortality (hazard ratio [HR] 1.24, 95% confidence interval [CI] 1.04–1.47). The alveolar concentration of several inflammatory biomarkers increased with HSV reactivation, including interleukin (IL)-6, IL-1β, granulocyte colony stimulating factor (G-CSF), and tumor necrosis factor (TNF).ConclusionIn mechanically ventilated COVID-19 patients, HSV reactivations are common, while CMV reactivations were rare. HSV viral load dynamics prior to or without antiviral treatment are associated with mortality. Alveolar inflammation is elevated after HSV reactivation.

Heart rate variability as a predictor of intraoperative autonomic nervous system homeostasis.

The aim of the proof-of-concept study is to investigate the level of concordance between the heart rate variability (HRV), the EEG-based Narcotrend Index as a surrogate marker for the depth of hypnosis, and the minimal alveolar concentration (MAC) of the inhalation anesthetic sevoflurane across the entire course of a surgical procedure. This non-blinded cross-sectional study recorded intraoperative HRV, Narcotrend Index, and MAC in 31 male patients during radical prostatectomy using the Da-Vinci robotic-assisted surgical system at Mannheim University Medical Center. The degree of concordance was calculated using repeated measures correlation with the R package (rmcorr) and presented using the rmcorr coefficient (rrm). The Narcotrend Index correlates significantly across all measures with the time-dependent parameter of HRV, the standard deviation of the means of RR intervals (SDNN) (rrm = 0.2; p < 0.001), the frequency-dependent parameters low frequency (LF) (rrm = 0.09; p = 0.04) and the low frequency/high frequency ratio (LF/HF ratio) (rrm = 0.11; p = 0.002). MAC correlated significantly negatively with the time-dependent parameter of heart rate variability, SDNN (rrm = -0.28; p < 0.001), the frequency-dependent parameter LF (rrm = -0.06; p < 0.001) and the LF/HF ratio (rrm = -0.18; p < 0.001) and the Narcotrend Index (rrm = -0.49; p < 0.001) across all measures. HRV mirrors the trend of the Narcotrend Index used to monitor depth of hypnosis and the inhibitory influence of the anesthetic sevoflurane on the autonomic nervous system. Therefore, HRV can provide essential information about the homeostasis of the autonomic nervous system during general anesthesia. DRKS00024696, March 9th, 2021.

The Ventilatory Changes of Pediatric Peroral Endoscopic Myotomy Patients.

Peroral endoscopic myotomy (POEM) has proven to be a successful treatment method for achalasia in both adult and pediatric patients. Yet, there is a lack of evidence for anaesthetic management of pediatric patients who underwent POEM procedure. In this study, we aim to present perioperative and postoperative management strategies for pediatric patients with achalasia from in anaesthesia aspect. Medical records were reviewed for 16 pediatric patients at a single center who underwent POEM procedure for achalasia between 2017 and 2020. Patients' data regarding demographics, preoperative diet, body mass index, perioperative monitoring and vitals, airway management, anaesthesia maintenance, mechanical ventilation settings duration of recovery, length of stay, pain management and adverse events were evaluated. The study cohort included 7 female and 9 male patients with a mean age of 5.5 years. Anaesthesia maintenance was provided with 0.8-1.2 minimum alveolar concentration sevoflurane in a 40-60% O2-air mixture, Remifentanil infusion and bolus doses of Rocuronium. The median age was 3 years for patients ventilated in pressure controlled ventilation mode and 10 years in volume controlled ventilation mode. Respiration rate and minute ventilation were adjusted to maintain end tidal carbon dioxide (ETCO2) below 45 mmHg. Needle decompression was applied for 14 patients (87.5%) for treatment of capnoperitoneum. The mean procedure duration and recovery room duration were 66 (±22.9) minutes and 62 (±21) minutes, respectively. Postoperative pain management is provided with paracetamol and tramadol in total 8 patients (50%). There was no adverse event during postoperative period and all patients discharged in a mean time of 3 days. POEM has demonstrated encouraging outcomes in terms of safety and effectiveness in pediatric patients. Due to challenging nature of the pediatric patients, it is important to acknowledge that the procedure requires specialized anaesthesia management. Management of perioperative complications of increased ETCO2 requires understanding the physiologic results of pneumo-mediastinum and pneumo-peritoneum. Beside the known anaesthetic management strategies, a tailored approach should be adopted for each patient. Further investigations should be conducted to develop standardized management.

Cannabis Use and Inhalational Anesthesia Administration in Older Adults: A Propensity-matched Retrospective Cohort Study.

Cannabis use is associated with higher intravenous anesthetic administration. Similar data regarding inhalational anesthetics are limited. With rising cannabis use prevalence, understanding any potential relationship with inhalational anesthetic dosing is crucial. Average intraoperative isoflurane or sevoflurane minimum alveolar concentration equivalents between older adults with and without cannabis use were compared. The electronic health records of 22,476 surgical patients 65 yr or older at the University of Florida Health System between 2018 and 2020 were reviewed. The primary exposure was cannabis use within 60 days of surgery, determined via (1) a previously published natural language processing algorithm applied to unstructured notes and (2) structured data, including International Classification of Diseases codes for cannabis use disorders and poisoning by cannabis, laboratory cannabinoids screening results, and RxNorm codes. The primary outcome was the intraoperative time-weighted average of isoflurane or sevoflurane minimum alveolar concentration equivalents at 1-min resolution. No a priori minimally clinically important difference was established. Patients demonstrating cannabis use were matched 4:1 to non-cannabis use controls using a propensity score. Among 5,118 meeting inclusion criteria, 1,340 patients (268 cannabis users and 1,072 nonusers) remained after propensity score matching. The median and interquartile range age was 69 (67 to 73) yr; 872 (65.0%) were male, and 1,143 (85.3%) were non-Hispanic White. The median (interquartile range) anesthesia duration was 175 (118 to 268) min. After matching, all baseline characteristics were well-balanced by exposure. Cannabis users had statistically significantly higher average minimum alveolar concentrations than nonusers (mean ± SD, 0.58 ± 0.23 vs. 0.54 ± 0.22, respectively; mean difference, 0.04; 95% confidence limits, 0.01 to 0.06; P = 0.020). Cannabis use was associated with administering statistically significantly higher inhalational anesthetic minimum alveolar concentration equivalents in older adults, but the clinical significance of this difference is unclear. These data do not support the hypothesis that cannabis users require clinically meaningfully higher inhalational anesthetics doses.

The Effects of Sevoflurane and Aβ Interaction on CA1 Dendritic Spine Dynamics and MEGF10-Related Astrocytic Synapse Engulfment.

General anesthetics may accelerate the neuropathological changes related to Alzheimer's disease (AD), of which amyloid beta (Aβ)-induced toxicity is one of the main causes. However, the interaction of general anesthetics with different Aβ-isoforms remains unclear. In this study, we investigated the effects of sevoflurane (0.4 and 1.2 maximal alveolar concentration (MAC)) on four Aβ species-induced changes on dendritic spine density (DSD) in hippocampal brain slices of Thy1-eGFP mice and multiple epidermal growth factor-like domains 10 (MEGF10)-related astrocyte-mediated synaptic engulfment in hippocampal brain slices of C57BL/6 mice. We found that both sevoflurane and Aβ downregulated CA1-dendritic spines. Moreover, compared with either sevoflurane or Aβ alone, pre-treatment with Aβ isoforms followed by sevoflurane application in general further enhanced spine loss. This enhancement was related to MEGF10-related astrocyte-dependent synaptic engulfment, only in AβpE3 + 1.2 MAC sevoflurane and 3NTyrAβ + 1.2 MAC sevoflurane condition. In addition, removal of sevoflurane alleviated spine loss in Aβ + sevoflurane. In summary, these results suggest that both synapses and astrocytes are sensitive targets for sevoflurane; in the presence of 3NTyrAβ, 1.2 MAC sevoflurane alleviated astrocyte-mediated synaptic engulfment and exerted a lasting effect on dendritic spine remodeling.

Effect of Atracurium and Rocuronium on the State and Response Entropy during Isoflurane Anesthesia: Randomized Prospective Study

Abstract Background Several researches have inspected the impact of inhalation anesthetics, intravenous anesthetics, and muscle relaxants on spectral entropy, but many didn’t evaluate the extent of neuromuscular block. Besides, they didn’t inspect the impact of distinct degrees of neuromuscular blockade on spectral entropy under dissimilar saturations of isoflurane inhalation. Hence, this study evaluated variant degrees of minimum alveolar concentration (MAC) to estimate the isoflurane concentration, along with various level of neuromuscular blockade. Aim of this study is to evaluate the effect of muscle relaxants (atracurium and rocuronium) on entropy readings (state, response entropy and response- state difference) during isoflurane anesthesia. This is a prospective randomized study where forty patients were included and divided into two study groups; patients in Group A received atracurium, while patients in Group R received rocuronium. State and response entropy were observed under MAC 0.8% and 1% under 50% and 100% neuromuscular blockage. Results There was a positive correlation between state (SE) and response entropy (RE) at baseline, different MAC, and different train of four (TOF) for both atracurium and rocuronium. State and response entropy decreased with increasing MAC of isoflurane (p &amp;lt; 0.001), while atracurium and rocuronium at TOF 50% and 100% showed no effect on SE or RE or RE-SE (P &amp;gt; 0.05). Conclusions State and response entropy can be used effectively to evaluate depth of anesthesia at different isoflurane MAC and atracurium or rocuronium doses. Registration number: ClinicalTrials.gov Identifier: NCT 05097508, Registered 5 October 2021 - prospectively registered, http://www.ClinicalTrial.gov

Practice of Low Flow Anaesthesia and Volatile Agents Choices among Anaesthesia Providers at Muhimbili National Hospital and Muhimbili Orthopaedic Institute

With the availability of modern workstations and heightened awareness of the Health services cost and environmental effects of waste anaesthesia gases, anaesthesia providers worldwide are practicing low flow anaesthesia. In most developing countries Low Flow Anaesthesia is still underutilized due to lack of monitoring equipments and sufficient knowledge. Tanzania appears to have a paucity of studies on the prevailing practice pattern of fresh gas flow. Objective; The study aimed at assessing the practice of low flow anaesthesia and volatile agents choices among anaesthesia providers at Muhimbili national hospital and Muhimbili orthopaedic institute. Methods: A descriptive cross-sectional study was carried out for a period of 8 months involving 158 anaesthesia providers. A Structured questionnaire was used to collect data which included demographic, practice setting of Low Flow Anaesthesia, Workstations, scavenging, monitoring equipments, Volatile agents routinely used and preferred Agent. Data were analysed using the IBM Statistical package for social science’s version 23.0. Result: Prevalence of Low flow anaesthesia was 27.2%, however, only 6% used the fresh gas flow of 1l/min – 500mls/min. All anaesthesia providers had workstations and only 2.3% displayed Minimum Alveolar concentration (MAC), 79.1% worked in theatre with functioning scavenging systems, 55.8% used capnography, 6.9% monitored inspiratory Oxygen and none of anaesthesia providers used Bispectral and Agent Analyzers. Isoflurane was the most routinely used inhalational agents (100%) followed by Sevoflurane (69%), then Halothane (32%). Desflurane still not available in these hospitals. Conclusion: Low flow anaesthesia is seldom practiced in our locality despite having strong evidence of attractive advantages in medical practice and ergonomics.

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

Prolonged times to tracheal extubation are intervals from the end ofsurgery 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. The retrospective cohort study used 11.7 years of data from one hospital. All p‑values were adjusted for multiple comparisons. There was a greater odds ofprolonged 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 atthe 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 ofMAC fractions at the end of surgery among cases ofthe same anesthesia practitioner, with the mean (standard deviation) among practitioners of each practitioner's standard deviation being 0.35 (0.05) and the coefficient ofvariation being 71% (13%). More prolonged extubations were associated with greater MAC fractions at the end ofsurgery. The cause of the large MAC fractions was the substantial variability of MAC fractions among cases of each practitioner at the end ofsurgery. 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 ofsurgical 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.

Testosterone and Erythrocyte Lifespan.

Endogenous and exogenous androgens increase circulating erythrocytes and hemoglobin but their effects on erythrocyte lifespan is not known. To investigate androgen effects on immature and mature erythrocyte lifespan in humans and mice using novel non-radioactive minimally invasive methods. Human erythrocyte lifespan was estimated using alveolar carbon monoxide concentration and blood hemoglobin in Levitt's formula in hypogonadal or transgender men before and up to 18 weeks after commencing testosterone (T) treatment. Erythrocyte lifespan was estimated in androgen receptor (AR) knockout and wild-type mice after T or dihydrotestosterone (DHT) treatment of intact females or orchidectomized males using in vivo biotin labelling of erythrocyte surface epitopes for reticulocytes (Ter119+CD71+) and two markers of erythrocytes (CD45-, Ter119+CD71-) monitoring their blood disappearance rate by flow cytometry. Before treatment, hypogonadal and transgender men had marked reduction in erythrocyte lifespan compared with controls. T treatment increased erythrocyte lifespan at 6 weeks but returned to pre-treatment levels at 18 weeks while serum T and blood hemoglobin were increased by T treatment remaining elevated at 18-weeks. In mice T and DHT treatment had higher erythrocyte (but not reticulocyte) lifespan but neither orchidectomy nor AR inactivation significantly influenced erythrocyte or reticulocyte lifespan. We conclude that hypogonadal men have reduced erythrocyte lifespan and acute androgen-induced increase in circulating erythrocyte lifespan may contribute to the well-known erythropoietic effects of androgens, but longer-term effects require further investigation to determine how much they contribute to androgen-induced increases in circulating hemoglobin.

Electroencephalography-Guided Anesthesia and Delirium in Older Adults After Cardiac Surgery

Intraoperative electroencephalogram (EEG) waveform suppression, suggesting excessive general anesthesia, has been associated with postoperative delirium. To assess whether EEG-guided anesthesia decreases the incidence of delirium after cardiac surgery. Randomized, parallel-group clinical trial of 1140 adults 60 years or older undergoing cardiac surgery at 4 Canadian hospitals. Recruitment was from December 2016 to February 2022, with follow-up until February 2023. Patients were randomized in a 1:1 ratio (stratified by hospital) to receive EEG-guided anesthesia (n = 567) or usual care (n = 573). Patients and those assessing outcomes were blinded to group assignment. The primary outcome was delirium during postoperative days 1 through 5. Intraoperative measures included anesthetic concentration and EEG suppression time. Secondary outcomes included intensive care and hospital length of stay. Serious adverse events included intraoperative awareness, medical complications, and 30-day mortality. Of 1140 randomized patients (median [IQR] age, 70 [65-75] years; 282 [24.7%] women), 1131 (99.2%) were assessed for the primary outcome. Delirium during postoperative days 1 to 5 occurred in 102 of 562 patients (18.15%) in the EEG-guided group and 103 of 569 patients (18.10%) in the usual care group (difference, 0.05% [95% CI, -4.57% to 4.67%]). In the EEG-guided group compared with the usual care group, the median volatile anesthetic minimum alveolar concentration was 0.14 (95% CI, 0.15 to 0.13) lower (0.66 vs 0.80) and there was a 7.7-minute (95% CI, 10.6 to 4.7) decrease in the median total time spent with EEG suppression (4.0 vs 11.7 min). There were no significant differences between groups in median length of intensive care unit (difference, 0 days [95% CI, -0.31 to 0.31]) or hospital stay (difference, 0 days [95% CI, -0.94 to 0.94]). No patients reported intraoperative awareness. Medical complications occurred in 64 of 567 patients (11.3%) in the EEG-guided group and 73 of 573 (12.7%) in the usual care group. Thirty-day mortality occurred in 8 of 567 patients (1.4%) in the EEG-guided group and 13 of 573 (2.3%) in the usual care group. Among older adults undergoing cardiac surgery, EEG-guided anesthetic administration to minimize EEG suppression, compared with usual care, did not decrease the incidence of postoperative delirium. This finding does not support EEG-guided anesthesia for this indication. ClinicalTrials.gov Identifier: NCT02692300.

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.

Precision in practice: An audit study on low-flow anesthesia techniques with desflurane and sevoflurane for cost-effective and sustainable care.

In the backdrop of escalating healthcare costs and an increasing focus on resource optimization, this audit study delves into the realm of anesthesia management, specifically exploring the application of low-flow anesthesia (LFA). The primary objective was to assess adherence to hospital standards and evaluate the economic implications of LFA (<1 L/min). This retrospective audit focused on 700 adult patients undergoing elective surgeries with general anesthesia. Data sources included anesthesia records, electronic recording systems, and audits by a dedicated team. Fresh gas flow rates (FGFRs), minimum alveolar concentration (MAC), and volatile anesthetic consumption were analyzed. Cost comparisons between low-flow and high-flow anesthesia were conducted, employing specific cost per milliliter metrics. The average FGFR during the maintenance phase was found to be 0.45 ± 0.88 L/min. Adherence to hospital standards was notably high, with 94.29% of patients being maintained on low-flow gas rates. The differences in anesthetic consumption between low-flow and high-flow FGFR were statistically significant for both desflurane (12.17 ± 10.84 ml/MAC hour versus 43.12 ± 27.25 ml/MAC hour) and sevoflurane (3.48 ± 7.22 ml/MAC hour versus 5.20 ± 5.20 ml/MAC hour, P < 0.001). The calculated savings per patient with low-flow desflurane and sevoflurane anesthesia compared to high flow were found to be 109.25 AED and 6.74 AED, respectively. This audit advocates for the widespread adoption of LFA as a standard practice. Beyond aligning with hospital standards, the study highlights the multi-faceted benefits of LFA, encompassing economic savings, environmental safety, and enhanced patient care.