Xenon Anesthesia Research Articles

A narrative review of gas separation and conservation technologies during xenon anesthesia.

Xenon gas has significant advantages over conventional general anesthetic agents but its use has been limited by the cost associated with its production. Xenon also has significant potential for medical use in the treatment of acquired brain injuries and for mental health disorders. As the demand for xenon gas from other industries increases, the costs associated with its medical use are only likely to increase. One solution to mitigate the significant cost of xenon use in research or medical care is the conservation of xenon gas. During delivery of xenon anesthesia, this can be achieved either by separating xenon from the other gases within the anesthetic circuit, conserving xenon and allowing other gases to be excluded from the circuit, or by selectively recapturing xenon utilized during the anesthetic episode at the conclusion of the case. Several technologies, including the pressurization and cooling of gas mixtures, the utilization of gas selective membranes and the utilization of gas selective adsorbents have been described in the literature for this purpose. These techniques are described in this narrative review along with important clinical context that informs how these technologies might be best applied. Whilst these technologies are discussed in the context of xenon general anesthesia, they could be applied in the delivery of xenon gas inhalation for other therapeutic purposes.

Effects of xenon anesthesia on postoperative neurocognitive disorders: a systematic review and meta-analysis

The latest clinical trials have reported conflicting outcomes regarding the effectiveness of xenon anesthesia in preventing postoperative neurocognitive dysfunction; thus, this study assessed the existing evidence. We searched the PubMed, Embase, Cochrane Library, and Web of Science databases from inception to April 9, 2023, for randomized controlled trials of xenon anesthesia in postoperative patients. We included English-language randomized controlled studies of adult patients undergoing surgery with xenon anesthesia that compared its effects to those of other anesthetics. Duplicate studies, pediatric studies, and ongoing clinical trials were excluded. Nine studies with 754 participants were identified. A forest plot revealed that the incidence of postoperative neurocognitive dysfunction did not differ between the xenon anesthesia and control groups (P = 0.43). Additionally, xenon anesthesia significantly shortened the emergence time for time to opening eyes (P < 0.001), time to extubation (P < 0.001), time to react on demand (P = 0.01), and time to time and spatial orientation (P = 0.04). However, the Aldrete score significantly increased with xenon anesthesia (P = 0.005). Postoperative complications did not differ between the anesthesia groups. Egger’s test for bias showed no small-study effect, and a trim-and-fill analysis showed no apparent publication bias. In conclusion, xenon anesthesia probably did not affect the occurrence of postoperative neurocognitive dysfunction. However, xenon anesthesia may effectively shorten the emergence time of certain parameters without adverse effects.

Inference-based time-resolved stability analysis of nonlinear whole-cortex modeling: application to Xenon anaesthesia.

This study characterizes the neurophysiological mechanisms underlying electromagnetic imaging signals using stability analysis. Researchers have proposed that transitions between conscious awake and anaesthetised states, and other brain states more generally, may result from system stability changes. The concept of stability in dynamical systems theory provides a mathematical framework to describe this possibility. In particular, the degree to which a system's trajectory in phase space is affected by small perturbations determines the stability. Previous studies using linear or oscillator-based whole-brain models cannot represent complex cerebrocortical dynamics, or model parameters were pre-assumed or inferred from data but did not change over time. This study proposes a nonlinear neurophysiologically plausible whole-cortex modeling framework to analyze the stability of brain dynamics for the emergence and disappearance of consciousness using time-varying parameters estimated from the data.Clinical relevance- Depth of anaesthesia is typically measured through changes in EEG statistics like the bispectral index and spectral entropy. However, these monitors have been found to fail in preventing awareness during surgery and postoperative recall. Our whole-cortex stability analysis may be useful in measuring anaesthesia levels in clinical settings, as it changes with the level of consciousness and is independent of individual differences and anaesthetic agents. The proposed method can also be used to, for example, identify critical brain regions for consciousness, locate the epileptogenic zone and investigate the dominance of extrinsic or intrinsic factors in brain functions.

Neuroprotective Effects of Inhaled Xenon for Sedation Compared With Propofol Intravenous Sedation in Severe Ischemic Stroke

ABSTRACTS Ischemic stroke occupies a leading position among the causes of mortality and disability. Long-lasting motor and cognitive impairments, a decrease in the level of consciousness over time aggravate the course of the disease, leading to immobilization syndrome and comorbidity load, which contributes to the development of life-threatening conditions in this category of patients. In this regard, the search for new neuroprotective strategies used at an early stage and capable of minimizing the severe consequences of stroke for the patient in particular and society as a whole seems extremely relevant. The paper presents the effect of inhaled xenon for sedation in patients with severe ischemic stroke on the level of consciousness and severity of neurological disorders, and also shows its effect on S100B protein, a marker for blood brain barrier damage.AIM OF STUDY To evaluate the effect of inhaled xenon for sedation in comparison with propofol intravenous sedation on the dynamics of the level of consciousness, the severity of neurological dysfunction and changes in the concentration of astroglial-derived S100B protein in severe ischemic stroke.MATERIAL AND METHODS The research was conducted on two groups of patients comparable in age, gender, comorbid background, as well as the severity of the underlying disease. In both groups, the condition of patients required the start of mechanical ventilation immediately after admission to the intensive care unit. Group I (control, n=12). After intubation and the start of ventilation, patients were sedated with propofol at a dose of 1-2 mg/ kg / hour for 24–72 hours. Group II (xenon, n=12). After intubation and the start of ventilation, patients underwent xenon inhalation at a concentration of 40 vol. % for the first 6 hours. If it was necessary to continue sedation after the end of xenon inhalation, propofol was used in doses similar to Group I. Neurological status was assessed on days 1, 3 and 8 using the Glasgow Coma Scale (GCS), the Full Outline of UnResponsivness (FOUR) score and the National Institutes of Health Stroke Scale (NIHSS). The critical analysis of the value of S100B as a marker of brain damage was carried out before the start of sedation, on the 3rd and 8th days.RESULTS Xenon inhalation (40 vol. %) in comparison with propofol intravenous sedation significantly increases the level of consciousness in patients with severe ischemic stroke (p=0,026), reduces neurological disorders assessed using NIHSS (p=0,007) on day 7, and also reduces serum S100B levels on day 3 (p&lt;0,05) after ischemic stroke.CONCLUSION Our open randomized clinical trial of xenon inhalation versus propofol intravenous sedation revealed the neuroprotective properties of xenon anesthesia in patients with severe ischemic stroke. Based on the obtained clinical and laboratory data, it can be concluded about the effective implementation of the neuroprotective effects of xenon in the administration scheme used in the research.

Assessment of Amnesic Effect and the Depth of Hypnosis During Therapeutic Inhalation of Xenon-Oxygen Mixture

The current literature lacks data on the incidence of intraoperative awakening during xenon anesthesia. This could be due to amnesia preventing memories of the intraoperative awakening.The objective: to determine the concentration of xenon in the xenon-oxygen mixture, which causes amnesia for events during inhalation in 100% of patients, and to make correlations with the depth of hypnosis as per Kugler scale.Subjects and Methods: 34 patients with chronic neurogenic pain who received 111 20-minute inhalations with concentration of xenon up to 50% were included in the study. Amnesia evaluation, EEG monitoring, and pain assessment on a visual analog scale (VAS) were performed.Results. Amnesic effect developed in 100% of patients at xenon concentration of 45%. On inhalation of xenon at concentrations of up to 50%, EEG changes did not exceed D1 grade on Kugler scale. The decrease in bispectral index (BIS) did not reach the level of deep sedation (Me 96.2%) at xenon concentration of 50%. The decrease in pain on VAS was approximately 60%.Conclusions. Xenon inhalations cause transient congradic amnesia at concentrations of 45% or more. The accuracy of the BIS monitoring readings may be reduced when using xenon in a monovariant. Inhalations of xenon-oxygen mixture in concentrations up to 50% showed good analgesic properties in the framework of combined therapy of chronic pain syndrome.

Magnetic field effects in biology from the perspective of the radical pair mechanism.

Hundreds of studies have found that weak magnetic fields can significantly influence various biological systems. However, the underlying mechanisms behind these phenomena remain elusive. Remarkably, the magnetic energies implicated in these effects are much smaller than thermal energies. Here, we review these observations, and we suggest an explanation based on the radical pair mechanism, which involves the quantum dynamics of the electron and nuclear spins of transient radical molecules. While the radical pair mechanism has been studied in detail in the context of avian magnetoreception, the studies reviewed here show that magnetosensitivity is widespread throughout biology. We review magnetic field effects on various physiological functions, discussing static, hypomagnetic and oscillating magnetic fields, as well as isotope effects. We then review the radical pair mechanism as a potential unifying model for the described magnetic field effects, and we discuss plausible candidate molecules for the radical pairs. We review recent studies proposing that the radical pair mechanism provides explanations for isotope effects in xenon anaesthesia and lithium treatment of hyperactivity, magnetic field effects on the circadian clock, and hypomagnetic field effects on neurogenesis and microtubule assembly. We conclude by discussing future lines of investigation in this exciting new area of quantum biology.

Performance of the bispectral index and electroencephalograph derived parameters of anesthetic depth during emergence from xenon and sevoflurane anesthesia

Many processed EEG monitors (pEEG) are unreliable when non-GABAergic anesthetic agents are used. The primary aim of the study was to compare the response of the Bispectral Index (BIS) during emergence from anesthesia maintained by xenon and sevoflurane. To better understand the variation in response of pEEG to these agents, we also compared several EEG derived parameters relevant to pEEG monitoring during emergence. Twenty-four participants scheduled for lithotripsy were randomized to receive xenon or sevoflurane anesthesia. Participants were monitored with the BIS and had simultaneous raw EEG collected. BIS index values were compared at three key emergence timepoints: first response, eyes open and removal of airway. Two sets of EEG derived parameters, three related to the BIS: relative beta ratio, SynchFastSlow and SynchFastSlow biocoherence, and two unrelated to the BIS: spectral edge frequency and the composite cortical state, were calculated for comparison. BIS index values were significantly lower in the xenon group than the sevoflurane group at each emergence timepoint. The relative beta ratio parameter increased significantly during emergence in the sevoflurane group but not in the xenon group. The spectral edge frequency and composite cortical state parameters increased significantly in both groups during emergence. The BIS index is lower at equivalent stages of behavioural response during emergence from xenon anesthesia when compared to sevoflurane anesthesia, most likely due to differences in how these two agents influence the relative beta ratio. The spectral edge frequency and composite cortical state might better reflect emergence from xenon anaesthesia.Clinical trial number and registry Australia New Zealand Clinical Trials Registry Number: ACTRN12618000916246.

Radical pairs can explain magnetic field and lithium effects on the circadian clock

Drosophila’s circadian clock can be perturbed by magnetic fields, as well as by lithium administration. Cryptochromes are critical for the circadian clock. Further, the radical pairs in cryptochrome also can explain magnetoreception in animals. Based on a simple radical pair mechanism model of the animal magnetic compass, we show that both magnetic fields and lithium can influence the spin dynamics of the naturally occurring radical pairs and hence modulate the circadian clock’s rhythms. Using a simple chemical oscillator model for the circadian clock, we show that the spin dynamics influence a rate in the chemical oscillator model, which translates into a change in the circadian period. Our model can reproduce the results of two independent experiments, magnetic field and lithium effects on the circadian clock. Our model predicts that stronger magnetic fields would shorten the clock’s period. We also predict that lithium influences the clock in an isotope-dependent manner. Furthermore, our model also predicts that magnetic fields and hyperfine interactions modulate oxidative stress. The findings of this work suggest that the quantum nature of radical pairs might play roles in the brain, as another piece of evidence in addition to recent results on xenon anesthesia and lithium effects on hyperactivity.

Assessment of xenon-induced depth of hypnosis according to Kugler’s scale in elderly and senile patients undergoing knee replacement surgery: a prospective open-label cohort study

INTRODUCTION. Anesthesia with xenon is characterized by stable hemodynamic parameters, cardio- and neuroprotection preferable in elderly. Assessment of the depth of hypnosis remains challenging. The Kugler classification based on electroencephalogram has been suggested for such assessment. OBJECTIVES. To assess the feasibility of Kugler scale for objective assessment of the depth of hypnosis induced by xenon alone or in combination with narcotics and regional anesthesia during knee arthroplasty in elderly. MATERIALS AND METHODS. The study included 57 patients divided into 2 groups. In group 1, general anesthesia with xenon was performed, fentanyl and femoral nerve block were used for pain control. In group 2, xenon anesthesia was performed in combination with femoral and sciatic nerve block. The depth of hypnosis was monitored using EEG and matched with the Kugler scale. Also, the bispectral index (BIS) was recorded. RESULTS. At xenon concentration of 40 %, the depth of hypnosis reached D2 stage in group 1 and D1 in group 2 patients, while at 55 % and above it was D2 in both groups. Fentanyl increased the δ-rhythm by 19.08 %, which corresponded to reduction in the effective xenon concentration by 20 %. A correlation between δ-rhythm decrease and BIS was seen in groups 1 (r = –0.78; R2 = 60 %) and 2 (r = –0.61; R2 = 37 %). The differences could be related to the use of fentanyl in group 1. The intergroup difference between the reduction of BIS was not significant. CONCLUSIONS. In elderly patients undergoing knee arthroplasty under combined anesthesia, stage D2 according to Kugler scale (proportion of δ-rhythm more than 50 %) is achieved at xenon concentration of 55 % without narcotics and at concentration of 40 % with fentanyl. The diminished correlation between δ-rhythm and BIS in group 2 and no difference in decrease of BIS suggests that BIS is less accurate for determining the depth of hypnosis during xenon monoanesthesia.

Comparing the effect of xenon and sevoflurane anesthesia on postoperative neural injury biomarkers: a randomized controlled trial.

General anesthesia and surgery are associated with an increase in neural injury biomarkers. Elevations of these neural injury biomarkers in the perioperative period are associated with postoperative delirium. Xenon has been shown to be protective against a range of neurological insults in animal models. It remains to be seen if xenon anesthesia is neuroprotective in the perioperative setting in humans. Twenty-four participants scheduled for lithotripsy were randomized to receive either xenon or sevoflurane general anesthesia. There was no statistically significant difference in the concentrations of postoperative neural injury biomarkers between the xenon and sevoflurane group. Following the procedure there was a significant increase in the concentration from baseline of all three biomarkers at 1 hour post-induction with a return to baseline at 5 hours. General anesthesia for lithotripsy was associated with a significant increase at 1 hour post-induction in the neural injury biomarkers total tau, neurofilament light and tau phosphorylated at threonine 181, a marker of tau phosphorylation. The protocol was approved by the St. Vincent’s Hospital Melbourne Ethics Committee (approval No. HREC/18/SVHM/221) on July 20, 2018 and was registered with the Australia New Zealand Clinical Trials Registry (registration No. ACTRN12618000916246) on May 31, 2018.

Observational Study of Dynamic Ventilation Parameters during Xenon Anesthesia

Background: The aim of this study was to observe dynamic pressure and flow measurements during the breathing cycle with different concentrations of xenon in patients without pulmonary disease to provide a better understanding of the mechanical-physiological effects of gas mixtures for anesthesia and other potential applications. Ventilation and respiratory data monitoring of flow rate, pressure at the Y-piece of the ventilator circuit, inhaled volume, and concentration of oxygen, xenon, and carbon dioxide for three concentrations of xenon (0, 30, and 60%) were recorded on the anesthetic ventilator station and downloaded to a portable computer. Main Findings: The overall effects of gas concentration are compared in the superimposed flow and pressure curves recorded from the ventilator. Airway resistance increases with xenon concentration for both inspiration (p=0.0028) and expiration (p=0.0007) as expected. The compliance increased with increasing xenon concentration, but only to statistical significance between 100% oxygen and 60% xenon (p=0.0344). The percentage of pressure drop due to the breathing circuit were about 70% for all the groups (no differences statistically, p=0.8161). Conclusions: The results show that the dominant source of the pressure loss is from the breathing circuit compared to the respiratory tract in patients without respiratory disease during inspiration.

Applications and Perspectives of Ultrasonic Multi-Gas Analysis with Simultaneous Flowmetry

We have developed ultrasonic instrumentation for simultaneous flow and composition measurement in a variety of gas mixtures. Flow and composition are respectively derived from measurements of the difference and average of sound transit times in opposite directions in a flowing process gas. We have developed a sound velocity-based algorithm to compensate for the effects of additional gases, allowing the concentrations of a pair of gases of primary interest to be acoustically measured on top of a varying baseline from ‘third party’ gases whose concentrations in the multi-gas mixture are measured by other means. Several instruments are used in the CERN ATLAS experiment. Three monitor C3F8, (R218), and CO2 coolant leaks into N2-purged environmental envelopes. Precision in molar concentration of better than 2 × 10−5 is routinely seen in mixtures of C3F8 in N2 in the presence of varying known concentrations of CO2. Further instruments monitor air ingress and C3F8 vapor flow (at high mass flows around 1.1 kg s−1) in the 60 kW thermosiphon C3F8 evaporative cooling recirculator. This instrumentation and analysis technique, targeting binary pairs of gases of interest in multi-gas mixtures, is promising for mixtures of anesthetic gases, particularly in the developing area of xenon anesthesia.

Efficacy of xenon anesthesia in preventing postoperative cognitive dysfunction after cardiac and major non-cardiac surgeries in elderly patients: a topical review.

Elderly patients undergoing major cardiac and non-cardiac surgeries have a high propensity (up to 40–60%) of developing postoperative cognitive dysfunction, which are caused by patient’s factors, type of surgery, intraoperative and postoperative factors. All these pose a challenge to the clinicians. The noble gas xenon does not undergo metabolism or any kind of biotransformation in the body owing to its inert nature. Xenon confers excellent hemodynamic stability and provides excellent recovery at the end of surgery. This topical review discusses advantages of xenon anesthesia in elderly patients undergoing major cardiac and non-cardiac surgeries and whether it is worth using a costly anesthetic in elderly patients for preventing postoperative cognitive dysfunction.

Inhalation anesthesia in children in outpatient dentistry: xenon or sevoflurane?

Abstract. The choice of optimal anesthetic in outpatient dental practice is an important stage in treatment plan preparation for children who need oral sanitation under general anesthesia. Few works were devoted to the comparative characterization of sevoflurane and xenon, especially in conditions of outpatient dental practice.&#x0D; Aim. This study aimed to compare the characteristics of xenon and sevoflurane inhalation anesthesia at the stage of maintaining anesthesia in outpatient dental practice.&#x0D; Materials and methods. This is an open, comparative, and randomized study, in parallel groups with random sampling. A total of 103 patients of both sexes aged 212 years were included. Children were divided into 2 groups: group 1 (35 children), with sevoflurane anesthesia and group 2 (68 children), with xenon anesthesia. In each and between groups at stages of anesthesia, data from the bispectral (BIS) index, heart rate, blood pressure, lung ventilation, glucose, acid-base status, and ionic composition of venous blood were monitored.&#x0D; Results. Significant differences between groups were observed in the BIS-index values at the end of anesthesia, indicating a faster awakening of patients under xenon anesthesia. Blood pressure and heart rate indicators in the xenon group at the beginning and end of the study are not statistically significant compared to the sevoflurane group. Remaining indicators did not show significant differences between groups.&#x0D; Conclusion. The use of sevoflurane and xenon during general anesthesia in outpatient dental practice characterized by the stability of the acid-base state, ion composition, and glucose concentration allows adequate conditions for spontaneous ventilation with pressure support. However, a faster awakening of the patient at the end was observed when using xenon. Diastolic blood pressure and heart rate in the xenon group after the end of anesthesia are close to baseline values.

Source-level Cortical Power Changes for Xenon and Nitrous Oxide-induced Reductions in Consciousness in Healthy Male Volunteers.

Investigations of the electrophysiology of gaseous anesthetics xenon and nitrous oxide are limited revealing inconsistent frequency-dependent alterations in spectral power and functional connectivity. Here, the authors describe the effects of sedative, equivalent, stepwise levels of xenon and nitrous oxide administration on oscillatory source power using a crossover design to investigate shared and disparate mechanisms of gaseous xenon and nitrous oxide anesthesia. Twenty-one healthy males underwent simultaneous magnetoencephalography and electroencephalography recordings. In separate sessions, sedative, equivalent subanesthetic doses of gaseous anesthetic agents nitrous oxide and xenon (0.25, 0.50, and 0.75 equivalent minimum alveolar concentration-awake [MACawake]) and 1.30 MACawake xenon (for loss of responsiveness) were administered. Source power in various frequency bands were computed and statistically assessed relative to a conscious/pre-gas baseline. Observed changes in spectral-band power (P < 0.005) were found to depend not only on the gas delivered, but also on the recording modality. While xenon was found to increase low-frequency band power only at loss of responsiveness in both source-reconstructed magnetoencephalographic (delta, 208.3%, 95% CI [135.7, 281.0%]; theta, 107.4%, 95% CI [63.5, 151.4%]) and electroencephalographic recordings (delta, 260.3%, 95% CI [225.7, 294.9%]; theta, 116.3%, 95% CI [72.6, 160.0%]), nitrous oxide only produced significant magnetoencephalographic high-frequency band increases (low gamma, 46.3%, 95% CI [34.6, 57.9%]; high gamma, 45.7%, 95% CI [34.5, 56.8%]). Nitrous oxide-not xenon-produced consistent topologic (frontal) magnetoencephalographic reductions in alpha power at 0.75 MACawake doses (44.4%; 95% CI [-50.1, -38.6%]), whereas electroencephalographically nitrous oxide produced maximal reductions in alpha power at submaximal levels (0.50 MACawake, -44.0%; 95% CI [-48.1,-40.0%]). Electromagnetic source-level imaging revealed widespread power changes in xenon and nitrous oxide anesthesia, but failed to reveal clear universal features of action for these two gaseous anesthetics. Magnetoencephalographic and electroencephalographic power changes showed notable differences which will need to be taken into account to ensure the accurate monitoring of brain state during anaesthesia.

Combined Xenon and Epidural Anesthesia During Surgical Correction of Joint Deformities in the Lower Extremities of Children with Cerebral Palsy

Objectives. The objective of this study is to compare different methods of combination general and regional anesthesia based on xenon.Materials and methods. Xenon anesthesia combined with epidural block was performed in 50 children with cerebral palsy aged 3–17 years. In 30 patients xenon was used to maintain anesthesia, in 20 children xenon was combined with sevoflurane. We compared the process of anesthesia, the intraoperative hemodynamic parameters and cognitive status before surgery and after it.Results. The use of xenon in all studied anesthesia methods increased the cardiac performance and was associated with a stable hemodynamic profile at all stages of anesthesia despite the depressive effect of epidural blockade on hemodynamics. Psychological testing revealed that xenon anesthesia has no negative effect on cognitive functions in children with cerebral palsy.Conclusion. Xenon anesthesia is a promising trend in anesthesia care for children with cerebral palsy. Xenon can compensate the hemodynamic depression caused by epidural anesthesia due to its cardiac stimulant property, with no neurotoxicity being a significant benefit for children with initial damage of CNS. However, anesthesia with xenon turned out to have some disadvantages. In our study, xenon showed insufficient analgesic properties, had emetic properties and was associated with spirometric abnormalities. It was more difficult to maintain normal ventilation parameters in young children when using xenon. Several adverse events were noted in the recovery period. These disadvantages can be partially reduced by using a combination of xenon and sevoflurane.

Intraoperative xenon for prevention of delirium after on-pump cardiac surgery: a randomised, observer-blind, controlled clinical trial

BackgroundOlder patients undergoing cardiac surgery have a 40–60% risk of developing postoperative delirium (POD), which is associated with increased morbidity and mortality. In animals, xenon has been found to be neuroprotective. Little is known about its neuroprotective effects in humans. We evaluated whether xenon anaesthesia prevents POD in patients undergoing cardiac surgery. MethodsWe conducted a randomised, observer-blind, controlled trial in which 190 patients 65 yr or older undergoing on-pump cardiac surgery were randomly allocated to xenon or sevoflurane anaesthesia. During cardiopulmonary bypass, propofol infusion was used for anaesthetic maintenance. Subjects were screened for POD daily during the first 5 postoperative days using the 3-Minute Diagnostic Interview for Confusion Assessment Method (CAM) or with a CAM version for patients in ICU (CAM-ICU). Other methods to detect delirium, such as chart review, were also used. Secondary outcomes included the duration and severity of POD, and postoperative cognitive function. ResultsThe overall incidence of POD was 41% (78/190). There was no statistically significant difference in the POD incidence between the xenon and sevoflurane groups (42.7% [41/96] vs 39.4% [37/94], P=0.583). The odds ratio for POD when comparing xenon with sevoflurane was 1.18 (95% confidence interval, 0.65–2.16). ConclusionsIn older patients undergoing cardiac surgery, xenon anaesthesia did not result in a significant reduction in POD. Based on these results alone, use of xenon cannot be recommended for this purpose. Clinical trial registrationEudraCT: 2014-005370-11 (May 13, 2015; https://www.clinicaltrialsregister.eu/ctr-search/search?query=2014-005370-11).

Better haemodynamic stability under xenon anaesthesia than under isoflurane anaesthesia during partial nephrectomy \u2013 a secondary analysis of a randomised controlled trial

BackgroundRenal dysfunction following intraoperative arterial hypotension is mainly caused by an insufficient renal blood flow. It is associated with higher mortality and morbidity rates. We hypothesised that the intraoperative haemodynamics are more stable during xenon anaesthesia than during isoflurane anaesthesia in patients undergoing partial nephrectomy.MethodsWe performed a secondary analysis of the haemodynamic variables collected during the randomised, single-blinded, single-centre PaNeX study, which analysed the postoperative renal function in 46 patients who underwent partial nephrectomy. The patients received either xenon or isoflurane anaesthesia with 1:1 allocation ratio. We analysed the duration of the intraoperative systolic blood pressure decrease by > 40% from baseline values and the cumulative duration of a mean arterial blood pressure (MAP) of < 65 mmHg as primary outcomes. The secondary outcomes were related to other blood pressure thresholds, the amount of administered norepinephrine, and the analysis of confounding factors on the haemodynamic stability.ResultsThe periods of an MAP of < 65 mmHg were significantly shorter in the xenon group than in the isoflurane group. The medians [interquartile range] were 0 [0–10.0] and 25.0 [10.0–47.5] minutes, for the xenon and isoflurane group, respectively (P = 0.002). However, the cumulative duration of a systolic blood pressure decrease by > 40% did not significantly differ between the groups (P = 0.51). The periods with a systolic blood pressure decrease by 20% from baseline, MAP decrease to values < 60 mmHg, and the need for norepinephrine, as well as the cumulative dose of norepinephrine were significantly shorter and lower, respectively, in the xenon group. The confounding factors, such as demographic data, surgical technique, or anaesthesia data, were similar in the two groups.ConclusionThe patients undergoing xenon anaesthesia showed a better haemodynamic stability, which might be attributed to the xenon properties. The indirect effect of xenon anaesthesia might be of importance for the preservation of renal function during renal surgery and needs further elaboration.Trial registrationClinicalTrials.gov: NCT01839084. Registered 24 April 2013.

The spectral exponent of the resting EEG indexes the presence of consciousness during unresponsiveness induced by propofol, xenon, and ketamine

Despite the absence of responsiveness during anesthesia, conscious experience may persist. However, reliable, easily acquirable and interpretable neurophysiological markers of the presence of consciousness in unresponsive states are still missing. A promising marker is based on the decay-rate of the power spectral density (PSD) of the resting EEG.We acquired resting electroencephalogram (EEG) in three groups of healthy participants (n = 5 each), before and during anesthesia induced by either xenon, propofol or ketamine. Dosage of each anesthetic agent was tailored to yield unresponsiveness (Ramsay score = 6). Delayed subjective reports assessed whether conscious experience was present (‘Conscious report’) or absent/inaccessible to recall (‘No Report’). We estimated the decay of the PSD of the resting EEG—after removing oscillatory peaks—via the spectral exponent β, for a broad band (1–40 Hz) and narrower sub-bands (1–20 Hz, 20–40 Hz). Within-subject anesthetic changes in β were assessed. Furthermore, based on β, ‘Conscious report’ states were discriminated against ‘no report’ states. Finally, we evaluated the correlation of the resting spectral exponent with a recently proposed index of consciousness, the Perturbational Complexity Index (PCI), derived from a previous TMS-EEG study.The spectral exponent of the resting EEG discriminated states in which consciousness was present (wakefulness, ketamine) from states where consciousness was reduced or abolished (xenon, propofol). Loss of consciousness substantially decreased the (negative) broad-band spectral exponent in each subject undergoing xenon or propofol anesthesia—indexing an overall steeper PSD decay. Conversely, ketamine displayed an overall PSD decay similar to that of wakefulness—consistent with the preservation of consciousness—yet it showed a flattening of the decay in the high-frequencies (20–40 Hz)—consistent with its specific mechanism of action. The spectral exponent was highly correlated to PCI, corroborating its interpretation as a marker of the presence of consciousness. A steeper PSD of the resting EEG reliably indexed unconsciousness in anesthesia, beyond sheer unresponsiveness.

Current trends in the development of neuroanesthesiology

The paper presents the author's analysis of the main trends in the development of modern neuroanesthesiology over the past five to ten years. These, in the author\s opinion, include the introduction and elaboration of blood-sparing techniques, monitoring the depth of anesthesia, fast track concept, applying regional (conduction) anesthesia techniques, xenon anesthesia, development of effective and safe protocols for DVT and PTE prophylaxis for neurosurgical patients, study of the hemostatic system using bedside methods for assessing hemostasis (thromboelastogram) and correcting hypocoagulation by activated recombinant VII factor.