Tonic Downward Movement of Eyes and Its Eccentric Positioning in Downgaze Under General Anaesthesia

Objectives. To summarize abrupt eccentric eye positioning in downgaze following the downward movement of eyes encountered in patients undergoing ophthalmic surgeries under general anesthesia (GA) and analyze the relationship between the fluctuation in the depth of anesthesia (DOA) and eccentric eye positioning in downgaze. Subjects and Methods. Patients undergoing ophthalmic surgeries under GA without nondepolarizing muscle relaxant between January 2018-December 2019 in a tertiary-eye-care who witnessed a sudden tonic hypo-tropic movement of eyes were included in the retrospective, cross-sectional study. Results. A total of 8 patients out of 199 were enrolled in this study with an average age of 1.13±0.40years. All cases (3 pediatric cataracts, 4 strabismus, and 1 pseudophakia with posterior capsular opacification) were performed under GA with sevoflurane as an inducing agent. Downward movement was seen before the start of surgery in 4 cases and during surgery in 4 cases. Downward drift of eyes appeared tonic as the strong tug was felt in an extreme downward eccentric position. It was preceded by an eccentric upward drift of eyes following which sevoflurane concentration was increased to optimize DOA when this downward drift was encountered (mean minimal alveolar concentration/MAC 1.63±0.25). Downward movement was quick but return movement of eyes to the central position was gradual (mean 1.55±0.48minutes) when DOA was decreased (mean MAC 1.3±0.09).Conclusions. Tonic-downward movement of eyes or its eccentric positioning in downgaze is not an uncommon entity in children under GA without muscle-relaxant and fluctuations in DOA should be avoided to circumvent inadvertent complications during ocular surgery.

Polyspikes and Rhythmic Polyspikes During Volatile Induction of General Anesthesia With Sevoflurane Result in Bispectral Index Variations

Background Although electroencephalography (EEG)-based indices may show artifactual values, raw EEG signal is seldom used to monitor the depth of volatile induction of general anesthesia (VIGA). The current analysis aimed to identify whether bispectral index (BIS) variations reliably reflect the actual depth of general anesthesia during presence of different types of epileptiform patterns (EPs) in EEGs during induction of general anesthesia. Methods Sixty patients receiving either VIGA with sevoflurane using increasing concentrations (group VIMA) or vital capacity (group VCRII) technique or intravenous single dose of propofol (group PROP) were included. Monitoring included facial electromyography (fEMG), fraction of inspired sevoflurane (FiAA), fraction of expired sevoflurane (FeAA), minimal alveolar concentration (MAC) of sevoflurane, BIS, standard EEG, and hemodynamic parameters. Results In the PROP group no EPs were observed. During different stages of VIGA with sevoflurane in the VIMA and VCRII groups, presence of polyspikes and rhythmic polyspikes in patients’ EEGs resulted in artifactual BIS values indicating a false awareness/wakefulness from anesthesia, despite no concomitant change of FiAA, FeAA, and MAC of sevoflurane. Periodic epileptiform discharges did not result in aberrant BIS values. Conclusion Our results suggest that raw EEG correlate it with values of BIS, FiAA, FeAA, and MAC of sevoflurane during VIGA. It seems that because artifactual BIS values indicating false awareness/wakefulness as a result of presence of polyspikes and rhythmic polyspikes in patients’ EEGs may be misleading to an anesthesiologist, leading to unintentional administration of toxic concentration of sevoflurane in ventilation gas.

Effects of isoflurane, remifentanil and dexmedetomidine on selected EEG parameters derived from a Narcotrend Monitor before and after nociceptive stimulation at different MAC multiples in cats

Background The aim of this prospective and complete cross-over study was to evaluate the effects of isoflurane, remifentanil and dexmedetomidine on EEG parameters derived from the Narcotrend® Monitor before and after nociceptive stimulation at different isoflurane MAC (minimal alveolar concentration) multiples. Seven adult European Domestic Short Hair cats were used. Each cat went through 3 experimental treatments. Group I received isoflurane, group IR received isoflurane and a constant rate infusion (CRI) of remifentanil (18 μg/kg/h IV), and group ID received isoflurane and a CRI of dexmedetomidine (3 μg/kg/h IV). The isoflurane MAC in each group was determined via supramaximal electrical stimulation. The EEG parameters were derived by a Narcotrend Monitor at specific time points before and after nociceptive stimulation at 0.75, 1.0 and 1.5 MAC. The depth of anaesthesia was also assessed by a clinical score. Results The mean MAC sparing effects in group IR and group ID were 9.8 and 55.2%, respectively. The best correlation of EEG and MAC multiples was found for the Narcotrend Index (NI) in group I (r = − 0.67). The NI was also able to differentiate between 0.75 MAC and 1.5 MAC in group IR. Spectral edge frequency had a lower correlation with MAC multiples in group I (r = − 0.62) but was able to differentiate between 0.75 MAC and 1.5 MAC in groups I and IR, and between 1.0 MAC and 1.5 MAC in group IR. Narcotrend Index, SEF 95 and MF increased significantly after nociceptive stimulation at 1.0 MAC in group I, and SEF 95 increased significantly at 0.75 MAC in group ID. The clinical score correlated closer than any of the EEG parameters with MAC in all groups, with highest correlation values in group I (r = − 0.89). Noxious stimulation led to a significant increase of the clinical score at 0.75 MAC and 1.0 MAC in group I. Conclusions The EEG parameters derived from the Narcotrend Monitor show correlation to isoflurane MAC multiples in cats, but the anaesthetic protocol and especially the addition of dexmedetomidine have great influence on the reliability. The Narcotrend Monitor can be used as an additional tool to assess anesthetic depth in cats.

Perioperative brain health: strategies to prevent perioperative neurocognitive disorders

Cognitive changes in patients after anesthesia and surgery have been recognized for over 100 years. Research on postoperative cognitive changes accelerated in the 1980s and the term postoperative cognitive dysfunction emerged, which was used until recently. Postoperative cognitive dysfunction has been used in research to describe an objectively measurable decline in cognitive function using neuropsychological tests. This dysfunction had significant heterogeneity in the type, number of tests, timing of tests, and the criteria for change. Therefore, a recent article recommended a new nomenclature for perioperative neurocognitive disorders including neurocognitive disorder, postoperative delirium, delayed neurocognitive recovery, and postoperative neurocognitive disorder. Since old age and baseline cognitive impairment are important risk factors for these perioperative neurocognitive disorders, routine preoperative cognitive assessment in all elderly patients is recommended. A preventive strategy is important, since effective modality for the treatment of perioperative neurocognitive disorders is not yet known. Intraoperative monitoring of age-adjusted end-tidal minimal alveolar concentration fraction, electroencephalography-based anesthetic management, and perioperative non-pharmacological methods are recommended for effective prevention.

Variability of anesthetic depth in total intravenous anesthesia vs balanced anesthesia using entropy indices: a randomized, crossover, controlled clinical trial

Introduction: Total intravenous anesthesia (TIVA) and balanced anesthesia (BA) are the most commonly used anesthetic techniques. The differences are the variability of the depth of anesthesia between these techniques that might predict which one is safer for patients and presents a lower risk of intraoperative awakening. Objective: To determine whether a difference exists in the variability of depth of anesthesia obtained by response entropy (RE). Methods: A crossover clinical trial was conducted on 20 healthy patients receiving upper or lower limb ambulatory orthopedic surgery. Patients were randomly assigned to (a) target-controlled infusion of propofol using the Schnider model at a target concentration of 2.5mg/mL for 15minutes and a 10-minute washout, followed by sevoflurane administration at 0.8 minimal alveolar concentration (MAC) for the reminder of the surgery, or (b) the reverse sequence. Differences in the variability of the depth of anesthesia using RE were evaluated using paired t test. Results: The treatment effect showed no significant difference in the average values of RE, during TIVA=97.23 vs BA 97.04 (P=0.39). Carry Over (-4.98 vs 4.08) and Period (100.3 vs 94.68) effects were not significantly different. Conclusion: The present study suggests that both anesthetic techniques are equivalent in terms of the stability of the depth of anesthesia. It is important to keep testing the determinants of the efficacy of different populations because the individual behaviors of patients might ultimately tip the scale.

Variations in Values of State, Response Entropy and Haemodynamic Parameters Associated with Development of Different Epileptiform Patterns during Volatile Induction of General Anaesthesia with Two Different Anaesthetic Regimens Using Sevoflurane in Comparison with Intravenous Induct: A Comparative Study

Background and Objectives: Raw electroencephalographic (EEG) signals are rarely used to monitor the depth of volatile induction of general anaesthesia (VIGA) with sevoflurane, even though EEG-based indices may show aberrant values. We aimed to identify whether response (RE) and state entropy (SE) variations reliably reflect the actual depth of general anaesthesia in the presence of different types of epileptiform patterns (EPs) in EEGs during induction of general anaesthesia. Materials and Methods: A randomized, prospective clinical study was performed with 60 patients receiving VIGA using sevoflurane with the increasing concentrations (group VIMA) or the vital capacity (group VCRII) technique or an intravenous single dose of propofol (group PROP). Facial electromyography (fEMG), fraction of inspired sevoflurane (FiAA), fraction of expired sevoflurane (FeAA), minimal alveolar concentration (MAC) of sevoflurane, RE and SE, and standard electroencephalographic evaluations were performed in these patients. Results: In contrast to periodic epileptiform discharges, erroneous SE and RE values in the patients’ EEGs were associated with the presence of polyspikes (PS) and rhythmic polyspikes (PSR), which were more likely to indicate toxic depth rather than false emergence from anaesthesia with no changes in the FiAA, FeAA, and MAC of sevoflurane. Conclusion: Calculated RE and SE values may be misleading during VIGA when EPs are present in patients’ EEGs. During VIGA with sevoflurane, we recommend monitoring raw EEG data in scientific studies to correlate it with potentially erroneous RE and SE values and the end-tidal concentration of sevoflurane in everyday clinical practice, when monitoring raw EEG is not available, because they can mislead anaesthesiologists to reduce sevoflurane levels in the ventilation gas and result in unintentional true emergence from anaesthesia. Further studies are required to investigate the behaviour of EEG-based indices during rapid changes in sevoflurane concentrations at different stages of VIGA and the influence of polyspikes and rhythmic polyspikes on the transformation of EEG signals into a digital form.

Sevoflurane inhibits Human umbilical vein endothelial cells migration by up-regulating VE-cadherin expression

Background Sevoflurane is a commonly used inhalation anesthesia and is famous for rapid onset of action, less metabolism in vivo and fast recovery. The aim of this study is to elaborate whether sevoflurane inhibits Human umbilical vein endothelial cells (HUVECs) migration function. Methods In vitro experiments, the HUVECs were divided into four groups randomly, and were exposed to 2% sevoflurane, refer to 1.6 minimal alveolar concentration (MAC), respectively for 0.5h, 1h, 2h and the first group was the control group which exposed to the same gas environment with other three groups but only without sevoflurane. After sevoflurane exposure, HUVECs were conducted the scratch assay. Results The results suggested that the HUVECs exposed to 2% sevoflurane for 2 h were more obviously inhibited on the migration distance during 12 h after scratched than the control group. Quantitative PCR results suggested that the HUVECs exposed to 2% sevoflurane for 2 h expressed more vascular endothelial cadherin (VE-cadherin) than the control group, with statistic difference. However, other scratch assay and quantitative trials suggested that the HUVECs which were transfected with VE-cadherin siRNA and exposed to 2% sevoflurane for 2 h had no significant difference with the control group on the migration distance and the expression of VE-cadherin. Conclusion These results suggested that sevoflurane inhibited the HUVECs migration function by up-regulating VE-cadherin expression, and may have an adverse effect on the normal functions of vascular endothelial cells.