Carbon dioxide and cardiac output as major contributors to cerebral oxygenation during apnoeic oxygenation.

Apnoeic oxygenation has experienced a resurgence in interest in critical care and perioperative medicine. However, its effect on cerebral oxygenation and factors influencing it, have not yet been investigated in detail. By using near-infrared spectroscopy, we intended to provide further evidence for the safety of apnoeic oxygenation and to increase our understanding of the association between cerebral perfusion, haemodynamic, respiratory and demographic factors. In this secondary analysis of a prospective randomized controlled noninferiority trial, we recruited 125 patients, who underwent surgery under general anaesthesia with neuromuscular blockade. Arterial blood samples were taken every 2 min for a total of 15 min under apnoeic oxygenation with 100% oxygen. Near-infrared spectroscopy and cardiac output were continuously measured. Statistical analysis was performed using uni- and multivariable statistics. Ninety-one complete data sets were analysed. In six patients the SpO2 fell below 92% (predefined study termination criterion). The significant average increase of cerebral oxygenation was 0.5%/min and 2.1 mmHg/min for the arterial pressure of carbon dioxide (paCO2). The median cardiac output increased significantly from 5.0 l/min (IQR 4.5-6.0) to 6.5 l/min (IQR 5.7-7.5). The most significant effect on cerebral oxygenation was exhibited by the variable paCO2 and non-specific patient factors, followed by cardiac output and paO2. Apnoeic oxygenation proves to have a high safety profile while significantly increasing cerebral oxygenation, paCO2 and cardiac output. In reverse, NIRS might act as a reliable clinical surrogate of paCO2 and cardiac output during stable arterial oxygenation.

Lower alpha frequency of intraoperative frontal EEG is associated with postoperative delirium: A secondary propensity-matched analysis.

BACKGROUND: Postoperative delirium (POD) is a serious complication of surgery, especially in the elderly patient population. It has been proposed that decreasing the amount of anesthetics by titrating to an EEG index will lower POD rate, but clear evidence is missing. A strong age-dependent negative correlation has been reported between the peak oscillatory frequency of alpha waves and end-tidal anesthetic concentration, with older patients generating slower alpha frequencies. We hypothesized, that slower alpha oscillations are associated with a higher rate of POD. METHOD: Retrospective analysis of patients` data from a prospective observational study in cardiac surgical patients approved by the Bernese Ethics committee. Frontal EEG was recorded during Isoflurane effect-site concentrations of 0.7 to 0.8 and peak alpha frequency was measured at highest power between 6 and 17 Hz. Delirium was assessed by chart review. Demographic and clinical characteristics were compared between POD and non-POD groups. Selection bias was addressed using nearest neighbor propensity score matching (PSM) for best balance. This incorporated 18 variables, whereas patients with missing variable information or without an alpha oscillation were excluded. RESULT: Of the 1072 patients in the original study, 828 were included, 73 with POD, 755 without. PSM allowed 328 patients into the final analysis, 67 with, 261 without POD. Before PSM, 8 variables were significantly different between POD and non-POD groups, none thereafter. Mean peak alpha frequency was significantly lower in the POD in contrast to non-POD group before and after matching (7.9 vs 8.9 Hz, 7.9 vs 8.8 Hz respectively, SD 1.3, p < 0.001). CONCLUSION: Intraoperative slower frontal peak alpha frequency is independently associated with POD after cardiac surgery and may be a simple intraoperative neurophysiological marker of a vulnerable brain for POD. Further studies are needed to investigate if there is a causal link between alpha frequency and POD.

The (Pro)renin Receptor - A Regulatory Nodal Point in Disease Networks.

Experimental inhibition of the (pro)renin receptor [(P)RR] is a promising therapeutic strategy in different disease models ranging from cardiorenal to oncological entities. Here, we briefly review the direct protein-protein interaction partners of the (P)RR and the plethora of distinct diseases in which the (P)RR is involved. The first structural work on the (P)RR using AlphaFold, which was recently published by Ebihara et al., is the center of this mini-review since it can mechanistically link the protein-protein interaction level with the pathophysiological level. More detailed insights into the 3D structure of the (P)RR and its interaction domains might guide drug discovery on this novel target. Finally, antibody- and small molecule-based approaches to inhibit the (P)RR are shortly discussed.

The (pro)renin receptor as a pharmacological target in cardiorenal diseaes.

The (pro)renin receptor ((P)RR) is not only a member of the renin-angiotensin system (RAS) but also exerts several RAS-independent functions due to its multiple signal transductions pathways. In this mini-review, we shortly discuss the molecular functions of this receptor and its pathophysiological significance with a focus on cardiorenal diseases. Finally, we provide a short summary regarding a drug discovery and drug development program on small molecule-based renin/ prorenin receptor blockers (RERBs).

The nuts and bolts of multimodal anaesthesia in the 21st century: a primer for clinicians.

PURPOSE OF REVIEW: This review article explores the application of multimodal anaesthesia in general anaesthesia, particularly in conjunction with locoregional anaesthesia, specifically focusing on the importance of EEG monitoring. We provide an evidence-based guide for implementing multimodal anaesthesia, encompassing drug combinations, dosages, and EEG monitoring techniques, to ensure reliable intraoperative anaesthesia while minimizing adverse effects and improving patient outcomes. RECENT FINDINGS: Opioid-free and multimodal general anaesthesia have significantly reduced opioid addiction and chronic postoperative pain. However, the evidence supporting the effectiveness of these approaches is limited. This review attempts to integrate research from broader neuroscientific fields to generate new clinical hypotheses. It discusses the correlation between high-dose intraoperative opioids and increased postoperative opioid consumption and their impact on pain indices and readmission rates. Additionally, it explores the relationship between multimodal anaesthesia and pain processing models and investigates the potential effects of nonpharmacological interventions on preoperative anxiety and postoperative pain. SUMMARY: The integration of EEG monitoring is crucial for guiding adequate multimodal anaesthesia and preventing excessive anaesthesia dosing. Furthermore, the review investigates the impact of combining regional and opioid-sparing general anaesthesia on perioperative EEG readings and anaesthetic depth. The findings have significant implications for clinical practice in optimizing multimodal anaesthesia techniques (Supplementary Digital Content 1: Video Abstract, http://links.lww.com/COAN/A96 ).

Association Between Risk of Stroke and Delirium After Cardiac Surgery and a New Electroencephalogram Index of Interhemispheric Similarity.

OBJECTIVES: Neurologic complications after surgery (stroke, delirium) remain a major concern despite advancements in surgical and anesthetic techniques. The authors aimed to evaluate whether a novel index of interhemispheric similarity, the lateral interconnection ratio (LIR), between 2 prefrontal electroencephalogram (EEG) channels could be associated with stroke and delirium following cardiac surgery. DESIGN: Retrospective observational study. SETTING: Single university hospital. PARTICIPANTS: A total of 803 adult patients without documentation of a previous stroke, who underwent cardiac surgery with cardiopulmonary bypass (CPB) between July 2016 and January 2018. INTERVENTIONS: The LIR index was calculated retrospectively from the patients' EEG database. MEASUREMENTS AND MAIN RESULTS: LIR was analyzed intraoperatively every 10 seconds and compared among patients with postoperative stroke, patients with delirium, and patients without documented neurologic complications, during 5 key periods, each lasting10 minutes: (1) surgery start, (2) before CPB, (3) on CPB, (4) after CPB, and (5) surgery end. After cardiac surgery, 31 patients suffered from stroke; 48 patients were diagnosed with delirium; and 724 had no documented neurologic complications. Patients with stroke demonstrated a decrease in LIR index between the start of surgery and the postbypass period of 0.08 (0.01, 0.36 [21]; median and [interquartile range {IQR}]; valid EEG samples); whereas there was no similar decrease in the no-dysfunction group (-0.04 [-0.13, 0.04; {551}], p < 0.0001). Patients with delirium showed a decrease in LIR index between the start of surgery and the end of the surgery by 0.15 (0.02, 0.30 [12]), compared with no such decrease in the no-dysfunction group (-0.02 [-0.12, 0.08 {376}], p ≈ 0.001). CONCLUSIONS: After improvement of SNR, it might be of value to further study the index decrease as an indication for risk for brain injury after surgery. The timing of decrease (after CPB or end of surgery) may provide hints regarding the injury pathophysiology and its onset.

Limitations of transcutaneous carbon dioxide monitoring in apneic oxygenation.

BACKGROUND: High-flow nasal oxygenation is increasingly used during sedation procedures and general anesthesia in apneic patients. Transcutaneous CO2 (ptcCO2)-monitoring is used to monitor hypercapnia. This study investigated ptcCO2-monitoring during apneic oxygenation. METHODS: We included 100 patients scheduled for elective surgery under general anesthesia in this secondary analysis of a randomized controlled trial. Before surgery, we collected ptcCO2 measured by TCM4 and TCM5 monitors and arterial blood gas (ABG) measurements every two minutes during 15 minutes of apnea. Bland-Altman plots analyzed agreement between measurement slopes; linear mixed models estimated the different measuring method effect, and outlined differences in slope and offset between transcutaneous and arterial CO2 partial pressures. RESULTS: Bland-Altman plots showed a bias in slope (95% confidence intervals) between ABG and TCM4-measurements of 0.05mmHg/min (-0.05 to 0.15), and limits of agreement were -0.88mmHg/min (-1.06 to -0.70) and 0.98mmHg/min (0.81 to 1.16). Bias between ABG and TCM5 was -0.14mmHg/min (-0.23 to -0.04), and limits of agreement were -0.98mmHg/min (-1.14 to -0.83) and 0.71mmHg/min (0.55 to 0.87). A linear mixed model (predicting the CO2-values) showed an offset between arterial and transcutaneous measurements of TCM4 (-15.2mmHg, 95%CI: -16.3 to -14.2) and TCM5 (-19.1mmHg, -20.1 to -18.0). Differences between the two transcutaneous measurements were statistically significant. CONCLUSIONS: Substantial differences were found between the two transcutaneous measurement systems, and between them and ABG. Transcutaneous CO2 monitoring cannot replace arterial CO2-monitoring during apneic oxygenation. In clinical settings with rapidly changing CO2-values, arterial blood gas measurements are needed to reliably assess the CO2-partial pressure in blood. TRIAL REGISTRATION: ClinicalTrials.gov (NCT03478774).

A Pilot Investigation Evaluating Relative Changes in Fronto-Occipital Alpha and Beta Spectral Power as Measurement of Anesthesia Hypnotic Depth.

BACKGROUND: Other than clinical observation of a patient's vegetative response to nociception, monitoring the hypnotic component of general anesthesia (GA) and unconsciousness relies on electroencephalography (EEG)-based indices. These indices exclusively based on frontal EEG activity neglect an important observation. One of the main hallmarks of transitions from wakefulness to GA is a shift in alpha oscillations (7.5-12.5 Hz activity) from occipital brain regions toward anterior brain regions ("alpha anteriorization"). Monitoring the degree of this alpha anteriorization may help to guide induction and maintenance of hypnotic depth and prevent intraoperative awareness. However, the occipital region of the brain is completely disregarded and occipital alpha as characteristic of wakefulness and its posterior-to-anterior shift during induction are missed. Here, we propose an application of Narcotrend's reduced power alpha beta (RPAB) index, originally developed to monitor differences in hemispheric perfusion, for determining the ratio of alpha and beta activity in the anterior-posterior axis. METHODS: Perioperative EEG data of 32 patients undergoing GA in the ophthalmic surgery department of Bern University Hospital were retrospectively analyzed. EEG was recorded with the Narcotrend® monitor using a frontal (Fp1-Fp2) and a posterior (T9-Oz) bipolar derivation with reference electrode over A2. The RPAB index was computed between both bipolar signals, defining the fronto-occipital RPAB (FO-RPAB). FO-RPAB was analyzed during wakefulness, GA maintenance, and emergence, as well as before and after the intraoperative administration of a ketamine bolus. FO-RPAB was compared with a classical quantitative EEG measure-the spectral edge frequency 95% (SEF-95). RESULTS: A significant shift of the FO-RPAB was observed during both induction of and emergence from GA ( P < .001). Interestingly, the additional administration of ketamine during GA did not lead to a significant change in FO-RPAB ( P = 0.81). In contrast, a significant increase in the SEF-95 in the frontal channel was observed during the 10-minute period after ketamine administration ( P < .001). CONCLUSIONS: FO-RPAB appears to qualify as a marker of unconsciousness, reflecting physiological fronto-occipital activity differences during GA. In contrast to frontal SEF-95, it is not disturbed by additional administration of ketamine for analgesia.

Five commercial 'depth of anaesthesia' monitors provide discordant clinical recommendations in response to identical emergence-like EEG signals.

BACKGROUND: 'Depth of anaesthesia' monitors claim to measure hypnotic depth during general anaesthesia from the EEG, and clinicians could reasonably expect agreement between monitors if presented with the same EEG signal. We took 52 EEG signals showing intraoperative patterns of diminished anaesthesia, similar to those that occur during emergence (after surgery) and subjected them to analysis by five commercially available monitors. METHODS: We compared five monitors (BIS, Entropy-SE, Narcotrend, qCON, and Sedline) to see if index values remained within, or moved out of, each monitors' recommended index range for general anaesthesia for at least 2 min during a period of supposed lighter anaesthesia, as observed by changes in the EEG spectrogram obtained in a previous study. RESULTS: Of the 52 cases, 27 (52%) had at least one monitor warning of potentially inadequate hypnosis (index above range) and 16 of the 52 cases (31%) had at least one monitor signifying excessive hypnotic depth (index below clinical range). Of the 52 cases, only 16 (31%) showed concordance between all five monitors. Nineteen cases (36%) had one monitor discordant compared with the remaining four, and 17 cases (33%) had two monitors in disagreement with the remaining three. CONCLUSIONS: Many clinical providers still rely on index values and manufacturer's recommended ranges for titration decision making. That two-thirds of cases showed discordant recommendations given identical EEG data, and that one-third signified excessive hypnotic depth where the EEG would suggest a lighter hypnotic state, emphasizes the importance of personalised EEG interpretation as an essential clinical skill.

Changes in lung volume estimated by electrical impedance tomography during apnea and high-flow nasal oxygenation: A single-center randomized controlled trial.

BACKGROUND: Previous studies concerning humidified, heated high-flow nasal oxygen delivered in spontaneously breathing patients postulated an increase in functional residual capacity as one of its physiological effects. It is unclear wheter this is also true for patients under general anesthesia. METHODOLOGY: The sincle-center noninferiority trial was registered at ClinicalTrials.gov (NCT NCT03478774). This secondary outcome analysis shows estimated differences in lung volume changes using electrical impedance tomography between different flow rates of 100% oxygen in apneic, anesthetized and paralyzed adults prior to intubation. One hundred and twenty five patients were randomized to five groups with different flow rates of 100% oxygen: i) minimal-flow: 0.25 l.min-1 via endotracheal tube; ii) low-flow: 2 l.min-1 + continuous jaw thrust; iii) medium-flow: 10 l.min-1 + continuous jaw thrust; iv) high-flow: 70l.min-1 + continuous jaw thrust; and v) control: 70 l.min-1 + continuous video-laryngoscopy. After standardized anesthesia induction with non-depolarizing neuromuscular blockade, the 15-minute apnea period and oxygen delivery was started according to the randomized flow rate. Continuous electrical impedance tomography measurements were performed during the 15-minute apnea period. Total change in lung impedance (an estimate of changes in lung volume) over the 15-minute apnea period and times to 25%, 50% and 75% of total impedance change were calculated. RESULTS: One hundred and twenty five patients completed the original study. Six patients did not complete the 15-minute apnea period. Due to maloperation, malfunction and artefacts additional 54 measurements had to be excluded, resulting in 65 patients included into this secondary outcome analysis. We found no differences between groups with respect to decrease in lung impedance or curve progression over the observation period. CONCLUSIONS: Different flow rates of humidified 100% oxygen during apnea result in comparable decreases in lung volumes. The demonstrated increase in functional residual capacity during spontaneous breathing with high-flow nasal oxygenation could not be replicated during apnea under general anesthesia with neuromuscular blockade.

The First Derivative of the Electroencephalogram Facilitates Tracking of Electroencephalographic Alpha Band Activity During General Anesthesia.

BACKGROUND: Intraoperative neuromonitoring can help to navigate anesthesia. Pronounced alpha oscillations in the frontal electroencephalogram (EEG) appear to predict favorable perioperative neurocognitive outcomes and may also provide a measure of intraoperative antinociception. Monitoring the presence and strength of these alpha oscillations can be challenging, especially in elderly patients, because the EEG in these patients may be dominated by oscillations in other frequencies. Hence, the information regarding alpha oscillatory activity may be hidden and hard to visualize on a screen. Therefore, we developed an effective approach to improve the detection and presentation of alpha activity in the perioperative setting. METHODS: We analyzed EEG records of 180 patients with a median age of 60 years (range, 18-90 years) undergoing noncardiac, nonneurologic surgery under general anesthesia with propofol induction and sevoflurane maintenance. We calculated the power spectral density (PSD) for the unprocessed EEG as well as for the time-discrete first derivative of the EEG (diffPSD) from 10-second epochs. Based on these data, we estimated the power-law coefficient κ of the PSD and diffPSD, as the EEG coarsely follows a 1/fκ distribution when displayed in double logarithmic coordinates. In addition, we calculated the alpha (7.8-12.1 Hz) to delta (0.4-4.3 Hz) ratio from the PSD as well as diffPSD. RESULTS: The median κ was 0.899 [first and third quartile: 0.786, 0.986] for the unaltered PSD, and κ = -0.092 [-0.202, -0.013] for the diffPSD, corresponding to an almost horizontal PSD of the differentiated EEG. The alpha-to-delta ratio of the diffPSD was strongly increased (median ratio = -8.0 dB [-10.5, -4.7 dB] for the unaltered PSD versus 30.1 dB [26.1, 33.8 dB] for the diffPSD). A strong narrowband oscillatory alpha power component (>20% of total alpha power) was detected in 23% using PSD, but in 96% of the diffPSD. CONCLUSIONS: We demonstrated that the calculation of the diffPSD from the time-discrete derivative of the intraoperative frontal EEG is a straightforward approach to improve the detection of alpha activity by eliminating the broadband background noise. This improvement in alpha peak detection and visualization could facilitate the guidance of general anesthesia and improve patient outcome.

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.

Carbon Dioxide Changes during High-flow Nasal Oxygenation in Apneic Patients: A Single-center Randomized Controlled Noninferiority Trial.

BACKGROUND: Anesthesia studies using high-flow, humidified, heated oxygen delivered via nasal cannulas at flow rates of more than 50 l · min-1 postulated a ventilatory effect because carbon dioxide increased at lower levels as reported earlier. This study investigated the increase of arterial partial pressure of carbon dioxide between different flow rates of 100% oxygen in elective anesthetized and paralyzed surgical adults before intubation. METHODS: After preoxygenation and standardized anesthesia induction with nondepolarizing neuromuscular blockade, all patients received 100% oxygen (via high-flow nasal oxygenation system or circuit of the anesthesia machine), and continuous jaw thrust/laryngoscopy was applied throughout the 15-min period. In this single-center noninferiority trial, 25 patients each, were randomized to five groups: (1) minimal flow: 0.25 l · min-1, endotracheal tube; (2) low flow: 2 l · min-1, continuous jaw thrust; (3) medium flow: 10 l · min-1, continuous jaw thrust; (4) high flow: 70 l · min-1, continuous jaw thrust; and (5) control: 70 l · min-1, continuous laryngoscopy. Immediately after anesthesia induction, the 15-min apnea period started with oxygen delivered according to the randomized flow rate. Serial arterial blood gas analyses were drawn every 2 min. The study was terminated if either oxygen saturation measured by pulse oximetry was less than 92%, transcutaneous carbon dioxide was greater than 100 mmHg, pH was less than 7.1, potassium level was greater than 6 mmol · l-1, or apnea time was 15 min. The primary outcome was the linear rate of mean increase of arterial carbon dioxide during the 15-min apnea period computed from linear regressions. RESULTS: In total, 125 patients completed the study. Noninferiority with a predefined noninferiority margin of 0.3 mmHg · min-1 could be declared for all treatments with the following mean and 95% CI for the mean differences in the linear rate of arterial partial pressure of carbon dioxide with associated P values regarding noninferiority: high flow versus control, -0.0 mmHg · min-1 (-0.3, 0.3 mmHg · min-1, P = 0.030); medium flow versus control, -0.1 mmHg · min-1 (-0.4, 0.2 mmHg · min-1, P = 0.002); low flow versus control, -0.1 mmHg · min-1 (-0.4, 0.2 mmHg · min-1, P = 0.003); and minimal flow versus control, -0.1 mmHg · min-1 (-0.4, 0.2 mmHg · min-1, P = 0.004). CONCLUSIONS: Widely differing flow rates of humidified 100% oxygen during apnea resulted in comparable increases of arterial partial pressure of carbon dioxide, which does not support an additional ventilatory effect of high-flow nasal oxygenation.

Ventricular assist device for Fontan: who, when and why?

PURPOSE OF REVIEW: Since the advent of the Fontan palliation, survival of patients with univentricular congenital heart disease has increased significantly. These patients will, however, ultimately develop heart failure requiring advanced therapies such as heart transplantation. As wait times are long, mechanical circulatory support (MCS) is an attractive therapy, both for bridge to transplantation and destination therapy in patients not suitable for transplantation. This review aims to summarize current thinking about how to determine which patients would benefit from a ventricular assist device (VAD), the optimal time for implantation and which device should be considered. RECENT FINDINGS: VAD implantation in end-stage Fontan is still in its infancy; however, case reports and research interest have increased extensively in the past few years. Mortality is significantly higher than in noncongenital heart disease patients. Implantation in patients with primarily systolic dysfunction is indicated, whereas patients with increased transpulmonary gradient may not benefit from a single-VAD solution. When possible, implantation should occur prior to clinical decompensation with evidence of end-organ damage, as outcomes at this point are worse. SUMMARY: Fontan patients demonstrating signs of heart failure should be evaluated early and often for feasibility and optimal timing of VAD implantation. The frequency of this procedure will likely increase significantly in the future.

A 3-hour fast-track extubation protocol for early extubation after cardiac surgery.

Objectives: Early extubation after cardiac surgery improves outcomes and reduces cost. We investigated the effect of a multidisciplinary 3-hour fast-track protocol on extubation, intensive care unit length of stay time, and reintubation rate after a wide range of cardiac surgical procedures. Methods: We performed an observational study of 472 adult patients undergoing cardiac surgery at a large academic institution. A multidisciplinary 3-hour fast-track protocol was applied to a wide range of cardiac procedures. Data were collected 4 months before and 6 months after protocol implementation. Cox regression model assessed factors associated with extubation time and intensive care unit length of stay. Results: A total of 217 patients preprotocol implementation and 255 patients postprotocol implementation were included. Baseline characteristics were similar except for the median procedure time and dexmedetomidine use. The median extubation time was reduced by 44% (4:43 hours vs 3:08 hours; P < .001) in the postprotocol group. Extubation within 3 hours was achieved in 49.4% of patients in the postprotocol group compared with 25.8% patients in the preprotocol group; P < .001. There was no statistically significant difference in the intensive care unit length of stay after controlling for other factors. Early extubation was associated with only 1 patient requiring reintubation in the postprotocol group. Conclusions: The multidisciplinary 3-hour fast-track extubation protocol is a safe and effective tool to further reduce the duration of mechanical ventilation after a wide range of cardiac surgical procedures. The protocol implementation did not decrease the intensive care unit length of stay.

Continuing professional development module : An updated introduction to electroencephalogram-based brain monitoring during intended general anesthesia.

The electroencephalogram (EEG) provides a reliable reflection of the brain's electrical state, so it can reassure us that the anesthetic agents are actually reaching the patient's brain, and are having the desired effect. In most patients, the EEG changes somewhat predictably in response to propofol and volatile agents, so a frontal EEG channel can guide avoidance of insufficient and excessive administration of general anesthesia. Persistent alpha-spindles (around 10 Hz) phase-amplitude coupled with slow delta waves (around 1 Hz) are commonly seen during an "appropriate hypnotic state of general anesthesia". Such patterns can be appreciated from the EEG waveform or from the spectrogram (a colour-coded display of how the power in the various EEG frequencies changes with time). Nevertheless, there are exceptions to this. For example, administration of ketamine and nitrous oxide is generally not associated with the aforementioned alpha-spindle coupled with delta wave pattern. Also, some patients, including older adults and those with neurodegenerative disorders, are less predisposed to generate a strong electroencephalographic "alpha-spindle" pattern during general anesthesia. There might also be some rare instances when the frontal EEG shows a pattern suggestive of general anesthesia, while the patient has some awareness and is able to follow simple commands, albeit this is typically without obvious distress or memory formation. Thus, the frontal EEG alone, as currently analyzed, is an imperfect but clinically useful mirror, and more scientific insights will be needed before we can claim to have a reliable readout of brain "function" during general anesthesia.

RéSUMé: L'électroencéphalogramme (EEG) procure une image fiable de l'état électrique du cerveau, de telle sorte qu'il peut nous rassurer que les agents anesthésiques atteignent bien le cerveau du patient et ont l'effet désiré. Chez la plupart des patients, le tracé de l'EEG change de façon relativement prévisible en réponse au propofol et aux agents volatils; ainsi, une analyse d'EEG frontal peut prévenir l'administration insuffisante ou excessive d'anesthésique générale. Pendant « un état hypnotique adéquat de l'anesthésie générale ¼, on remarquera fréquemment une phase-amplitude de fuseaux alpha (alpha-spindles phase amplitude) (d'environ 10 Hz) couplée à des ondes lentes delta (d'environ 1 Hz). De tels tracés peuvent être observés à partir de l'EEG ou sur un spectrogramme (un affichage par code couleur de la façon dont la puissance dans les diverses fréquences d'EEG se modifie au fil du temps). Toutefois, il existe des exceptions. Par exemple, l'administration de kétamine et de protoxyde d'azote n'est généralement pas associée au tracé de fréquence alpha couplé à l'onde delta susmentionné. En outre, certains patients, notamment des personnes plus âgées et les personnes souffrant de maladies neurodégénératives, sont moins prédisposés à générer un fort tracé électroencéphalographique de 'fréquence alpha' pendant une anesthésie générale. Dans de rares cas, le tracé de l'EEG frontal pourrait évoquer une anesthésie générale alors que le patient est encore quelque peu conscient et capable de suivre des ordres simples, mais ces situations surviennent habituellement sans détresse ni rétention de mémoire évidente. Par conséquent, l'EEG frontal seul tel qu'il est analysé à l'heure actuelle est un miroir clinique utile mais imparfait, et des recherches scientifiques seront nécessaires avant de pouvoir affirmer que nous disposons d'une mesure fiable de la « fonction ¼ cérébrale pendant l'anesthésie générale.

Comorbidity-dependent changes in alpha and broadband electroencephalogram power during general anaesthesia for cardiac surgery.

BACKGROUND: Age and comorbidities are reported to induce neurobiological transformations in the brain. Whilst the influence of ageing on anaesthesia-induced electroencephalogram (EEG) changes has been investigated, the effect of comorbidities has not yet been explored. We hypothesised that certain diseases significantly affect frontal EEG alpha and broadband power in cardiac surgical patients. METHODS: We analysed the frontal EEGs of 589 patients undergoing isoflurane general anaesthesia from a prospective observational study. We used multi- and uni-variable regression to analyse the relationships between comorbidities and age as independent with peak and oscillatory alpha, and broadband power as dependent variables. A score of comorbidities and minimum alveolar concentration (MAC) was built to interrogate the combined effect of age and score on alpha and broadband power. RESULTS: At the univariable level, many comorbidities were associated with lower EEG alpha or broadband power. Multivariable regression indicated the independent association of numerous comorbidities and MAC with peak alpha (R2=0.19) and broadband power (R2=0.31). The association with peak alpha power is markedly reduced when the underlying broadband effect is subtracted (R2=0.09). Broadband measures themselves are more strongly correlated with comorbidities and MAC (R2=0.31) than age (R2=0.15). CONCLUSIONS: Comorbidities and age are independently associated with decreasing frontal EEG alpha and broadband power during general anaesthesia. For alpha power, the association is highly dependent on the underlying broadband effect. These findings might have significant clinical consequences for automated computation for depth of anaesthesia in comorbid patients, because misclassification might pose the risk of under- or over-dosing of anaesthetics. CLINICAL TRIAL REGISTRATION: NCT02976584.

Point-of-care ultrasound in the preoperative setting.

Point-of-care ultrasound (POCUS) is a widely used diagnostic tool, especially in emergency and critical care medicine, and it is increasingly being used in the perioperative setting. Its specific role in preoperative assessment of patients, however, has not yet been defined. While some data show innovative use of the technique in the preoperative setting, higher-level evidence to underscore potential advantages is still limited. We review and discuss a range of POCUS examinations which can potentially help anaesthesiologists in the preoperative clinic decide whether to perform additional testing, can assist in selecting the best anaesthetic approach, and can support perioperative and postoperative monitoring.