An update on anesthetics and impact on the brain

Incidence of psychiatric disorders after total knee or hip arthroplasty by anesthesia type: A nationwide cohort study

BACKGROUND

Evidence is lacking of an association between anesthetic choice and the risk of psychiatric disorders. Therefore, this study aimed to examine the impact of regional anesthesia (R/A) versus general anesthesia (G/A) on the occurrence of psychiatric disorders in patients undergoing total knee arthroplasty (TKA) or total hip arthroplasty (THA).

METHODS

Data for this population-based cohort study were sourced from the National Health Insurance Service of South Korea. The study included adult patients who underwent TKA or THA between January 1, 2016, and December 31, 2021. The endpoint was the diagnosis of postoperative psychiatric disorders within 1 year postoperative.

RESULTS

This study included 411,967 patients who underwent THA or TKA. Among them, 290,476 (70.5 %) underwent THA or TKA under R/A (R/A group), while 121,491 (29.5 %) underwent THA or TKA under G/A (G/A group). In multivariate logistic regression, the R/A group had an 8 % lower incidence of postoperative psychiatric disorders (odds ratio [OR], 0.92; 95 % confidence interval [CI], 0.90-0.94; P < 0.001) than the G/A group. Specifically, a lower incidence of postoperative psychiatric disorder for depression (OR, 0.89; 95 % CI, 0.86-0.92; P < 0.001), bipolar disorder (OR, 0.88; 95 % CI, 0.83-0.94; P < 0.001), anxiety disorder (OR, 0.95; 95 % CI, 0.92-0.98; P = 0.001), and insomnia disorder (OR, 0.95; 95 % CI, 0.80-1.11; P = 0.496) was observed in the R/A versus G/A group.

CONCLUSIONS

Among these South Korean patients who underwent TKA or THA, the R/A group had a lower incidence of postoperative psychiatric disorders than the G/A group.

Perioperative impact of ultrasound-guided ilioinguinal and iliohypogastric nerve blocks in patients undergoing pelvic fracture surgery

Pelvic fractures present a severe and complex clinical challenge. This study aimed to compare ultrasound-guided ilioinguinal (IIN) and iliohypogastric nerve (IHN) blocks with conventional general anesthesia (GA) in patients undergoing internal fixation surgery for pelvic fractures. A retrospective analysis was conducted on 100 patients equally divided into ultrasound-guided and control groups. The study monitored hemodynamics, intraoperative anesthesia drug usage, postoperative pain levels, and the incidence of adverse reactions between the 2 groups. The ultrasound-guided group underwent ultrasound-guided IHN and IIN blocks combined with GA. The ultrasound-guided group exhibited significant advantages for hemodynamic measurements at specific time points, lower consumption of Propofol and Remifentanil, and reduced pain intensity across all evaluated time intervals (P < .05). The incidence rate of adverse reactions was significantly lower in the ultrasound group (P = .016). Ultrasound-guided anesthesia is a superior alternative to conventional GA for managing pelvic fractures through internal fixation surgery. It offers advantages in terms of hemodynamic stability, drug consumption, postoperative pain management, and adverse reaction reduction.

Effect of different anesthetic modalities on postoperative delirium in elderly hip fractures: A meta-analysis

BACKGROUND

Previous findings on the effect of general versus spinal anesthesia on postoperative delirium in elderly people with hip fractures are somewhat controversial. This article included the latest randomized controlled study for meta-analysis to evaluate the effect of general anesthesia (GA) and spinal anesthesia (SA) on delirium after hip fracture surgery in the elderly, so as to guide the clinical.

METHODS

Cochrane Library, PubMed, Web Of Science, and Embase were searched from inception up to January 16, 2024. Randomized controlled trial (RCT) was included to evaluate the postoperative results of GA and SA in elderly patients (≥50 years old) undergoing hip fracture surgery. Two researchers independently screened for inclusion in the study and extracted data. Heterogeneity was assessed by the I²and Chi-square tests, and P < .1 or I² ≥ 50% indicated marked heterogeneity among studies. The Mantel-Haenszel method was used to estimate the combined relative risk ratio (RR) and the corresponding 95% confidence interval (CI) for the binary variables.

RESULTS

Nine randomized controlled trials were included. There was no significant difference (RR = 0.93, 95% CI = 0.774-1.111, P > .05) in the incidence of postoperative delirium between the GA group and the SA group. In intraoperative blood transfusion (RR = 1.0, 95% CI = 0.77-1.28, Z = 0.04, P = .971), pulmonary embolism (RR = 0.795, 95% CI = 0.332-1.904, Z = 0.59, P = .606), pneumonia (RR = 1.47, 95% CI = 0.75-2.87, P = .675), myocardial infarction (RR = 0.97, 95% CI = 0.24-3.86, Z = 0.05, P = .961), heart failure (RR = 0.80, 95% CI = 0.26-2.42, Z = 0.40, P = .961), urinary retention (RR = 1.42, 95% CI = 0.77-2.61, Z = 1.11, P = .267) were similar between the 2 anesthetic techniques.

CONCLUSION

There is no significant difference in the effect of GA and SA on postoperative delirium in elderly patients with hip fracture, and their effects on postoperative complications are similar.

Machine Learning Technology for EEG-Forecast of the Blood-Brain Barrier Leakage and the Activation of the Brain's Drainage System during Isoflurane Anesthesia

Anesthesia enables the painless performance of complex surgical procedures. However, the effects of anesthesia on the brain may not be limited only by its duration. Also, anesthetic agents may cause long-lasting changes in the brain. There is growing evidence that anesthesia can disrupt the integrity of the blood-brain barrier (BBB), leading to neuroinflammation and neurotoxicity. However, there are no widely used methods for real-time BBB monitoring during surgery. The development of technologies for an express diagnosis of the opening of the BBB (OBBB) is a challenge for reducing post-surgical/anesthesia consequences. In this study on male rats, we demonstrate a successful application of machine learning technology, such as artificial neural networks (ANNs), to recognize the OBBB induced by isoflurane, which is widely used in surgery. The ANNs were trained on our previously presented data obtained on the sound-induced OBBB with an 85% testing accuracy. Using an optical and nonlinear analysis of the OBBB, we found that 1% isoflurane does not induce any changes in the BBB, while 4% isoflurane caused significant BBB leakage in all tested rats. Both 1% and 4% isoflurane stimulate the brain's drainage system (BDS) in a dose-related manner. We show that ANNs can recognize the OBBB induced by 4% isoflurane in 57% of rats and BDS activation induced by 1% isoflurane in 81% of rats. These results open new perspectives for the development of clinically significant bedside technologies for EEG-monitoring of OBBB and BDS.

The Crosstalk between the Blood–Brain Barrier Dysfunction and Neuroinflammation after General Anaesthesia

As we know, with continuous medical progress, the treatment of many diseases can be conducted via surgery, which often relies on general anaesthesia for its satisfactory performance. With the widespread use of general anaesthetics, people are beginning to question the safety of general anaesthesia and there is a growing interest in central nervous system (CNS) complications associated with anaesthetics. Recently, abundant evidence has suggested that both blood–brain barrier (BBB) dysfunction and neuroinflammation play roles in the development of CNS complications after anaesthesia. Whether there is a crosstalk between BBB dysfunction and neuroinflammation after general anaesthesia, and whether this possible crosstalk could be a therapeutic target for CNS complications after general anaesthesia needs to be clarified by further studies.

Implication of microglia in ketamine-induced long-term cognitive impairment in murine pups

BACKGROUND

Ketamine, a non-competitive N-methyl-D-aspartate receptor (NMDAR) antagonist, is widely applicable to anesthesia, analgesia, and sedation. However, the function and mechanisms of ketamine in the long-term learning and memory function of neonatal mice are unclear.

OBJECTIVE

The present study aims to investigate whether long-term learning and memory function will be affected by multiple ketamine exposures in the early development period.

METHODS

The mRNA and protein levels were measured by RT-qPCR and western blot, respectively. The Morris Water Maze test was performed to assess spatial learning and memory.

RESULTS

We identified that neonatal exposure to ketamine downsized the positive neurons for microtubule-associated protein doublecortin (DCX) and Ki67 in hippocampal dentate gyrus at the juvenile and late adolescence stages. Double-labeling tests demonstrated that the counts of Iba1⁺ cells and Ki67⁺ cells were pronouncedly diminished with exposure to ketamine. Further, qPCR assays to screen the key factors predisposing the populations and maturation of microglia exhibited remarkable decline of CX3CR1 mRNA levels in ketamine group versus the control group. The close relation of microglia to synaptic plasticity was depicted by the significantly downregulated synaptic plasticity-related proteins NR2B and PSD-95 subsequent to multiple exposures to ketamine. Finally, we found that both the protein and mRNA levels of BDNF were markedly decreased in ketamine group versus the control group.

CONCLUSION

We found that multiple exposures to ketamine in neonatal mice lead to spatial learning and memory dysfunction. The alterations of microglial development and function are the possible mechanisms of long-term learning and memory impairment.

Emerging Role of Long Noncoding RNAs in Perioperative Neurocognitive Disorders and Anesthetic-Induced Developmental Neurotoxicity

Preclinical investigations in animal models have consistently demonstrated neurobiological changes and life-long cognitive deficits following exposure to widely used anesthetics early in life. However, the mechanisms by which these exposures affect brain function remain poorly understood, therefore, limiting the efficacy of current diagnostic and therapeutic options in human studies. The human brain exhibits an abundant expression of long noncoding RNAs (lncRNAs). These biologically active transcripts play critical roles in a diverse array of functions, including epigenetic regulation. Changes in lncRNA expression have been linked with brain development, normal CNS processes, brain injuries, and the development of neurodegenerative diseases, and many lncRNAs are known to have brain-specific expression. Aberrant lncRNA expression has also been implicated in areas of growing importance in anesthesia-related research, including anesthetic-induced developmental neurotoxicity (AIDN), a condition defined by neurological changes occurring in patients repeatedly exposed to anesthesia, and the related condition of perioperative neurocognitive disorder (PND). In this review, we detail recent advances in PND and AIDN research and summarize the evidence supporting roles for lncRNAs in the brain under both normal and pathologic conditions. We also discuss lncRNAs that have been linked with PND and AIDN, and conclude with a discussion of the clinical potential for lncRNAs to serve as diagnostic and therapeutic targets for the prevention of these neurocognitive disorders and the challenges facing the identification and characterization of associated lncRNAs.

Develop a Clinical Prediction Model for Postoperative Cognitive Dysfunction after Major Noncardiac Surgery in Elderly Patients: A Protocol for a Prospective Observational Study

Perioperative neurocognitive disorders (PNDs) refer to cognitive decline identified in the preoperative or postoperative period. It has been reported that the incidence of postoperative neurocognitive impairment after noncardiac surgery in patients older than 65 at 1 week was 25.8∼41.4%, and at 3 months 9.9∼12.7%. PNDs will last months or even develop to permanent dementia, leading to prolonged hospital stays, reduced quality of life, and increased mortality within 1 year. Despite the high incidence and poor prognosis of PNDs in the aged population, no effective clinical prediction model has been established to predict postoperative cognitive decline preoperatively. To develop a clinical prediction model for postoperative neurocognitive dysfunction, a prospective observational study (Clinical trial registration number: ChiCTR2000036304) will be performed in the Shanghai General Hospital during January 2021 to October 2022. A sample size of 675 patients aged >65 years old, male or female, and scheduled for elective major noncardiac surgery will be recruited. A battery of neuropsychological tests will be used to test the cognitive function of patients at 1 week, 1 month, and 3 months postoperatively. We will evaluate the associations of PNDs with a bunch of candidate predictors including general characteristics of patients, blood biomarkers, indices associated with anesthesia and surgery, retinal nerve-fiber layer thickness, and frailty index to develop the clinical prediction model by using multiple logistic regression analysis and least absolute shrinkage and the selection operator (LASSO) method. The k-fold cross-validation method will be utilized to validate the clinical prediction model. In conclusion, this study was aimed to develop a clinical prediction model for postoperative cognitive dysfunction of old patients. It is anticipated that the knowledge gained from this study will facilitate clinical decision-making for anesthetists and surgeons managing the aged patients undergoing noncardiac surgery.

Biochanin A protects SH-SY5Y cells against isoflurane-induced neurotoxicity by suppressing oxidative stress and apoptosis

Biochanin A (BCA) is a natural organic O-methylated isoflavone with a variety of pharmacological effects, and has been reported to have neuroprotective properties. Here, we explored whether BCA protects neurocytes against isoflurane-induced neurotoxicity and investigated the underlying mechanism. Cell viability was tested by cell counting kit-8 and lactate dehydrogenase release assays. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and caspase-3/7 activity assays. Superoxide dismutase (SOD) and catalase (CAT) activities and levels of glutathione (GSH) and malondialdehyde (MDA) were measured to assess oxidative stress. Expression of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase (NQO1) was determined by western blotting. Treatment with BCA significantly attenuated the reduction of cell viability induced by isoflurane in SH-SY5Y cells. In addition, BCA treatment reversed isoflurane-induced SOD and CAT activity reduction, GSH level decline and MDA level increase. Isoflurane-induced apoptosis was also attenuated by treatment with BCA. The increase in nuclear Nrf2, HO-1 and NQO1 expression induced by isoflurane was amplified by treatment with BCA. These inhibitory effects of BCA on isoflurane-induced oxidative stress, viability reduction and cell apoptosis were attenuated in Nrf2 knockdown SH-SY5Y cells. Our findings indicate that BCA protects SH-SY5Y cells against isoflurane-induced neurotoxicity via inducing the Nrf2/ARE pathway.

The Effects of Propofol and Sevoflurane on Postoperative Delirium in Older Patients: A Randomized Clinical Trial Study

BACKGROUND

Postoperative delirium is associated with adverse postoperative outcomes. However, whether intravenous and inhalation anesthetics are associated with different risks of postoperative delirium remains unknown.

OBJECTIVE

We set up to determine the incidence and duration of postoperative delirium in older patients who had surgery under the intravenous anesthetic propofol or the inhalational anesthetic sevoflurane.

METHODS

Participants were patients who had total hip/knee replacements and were randomized to propofol (N = 106) or sevoflurane (N = 103) anesthesia group. The Confusion Assessment Method was employed by investigators who were blinded to the anesthesia regimen to assess the incidence and duration (days of postoperative delirium per person) of postoperative delirium on postoperative days 1, 2, and 3.

RESULTS

A total of 209 participants (71.2±6.7 years old, 29.2% male) were included in the final data analysis. The incidence of postoperative delirium was 33.0% with propofol anesthesia and 23.3% with sevoflurane anesthesia (p = 0.119, Chi-square test), and we estimated that we would need 316 participants in each arm to detect a potential statistically significant difference. Days of postoperative delirium per person were higher in the propofol (0.5±0.8) anesthesia group compared to the sevoflurane anesthesia group (0.3±0.5, p = 0.049, Student's t-test).

CONCLUSION

This pilot study established a system to compare effects of different anesthetics and generated a hypothesis that propofol trended to have a higher incidence and had longer duration of postoperative delirium than sevoflurane. Additional studies with a larger sample size are needed to test this hypothesis.

MiR-191 downregulation protects against isoflurane-induced neurotoxicity through targeting BDNF

BACKGROUND

Isoflurane inhalation can cause nerve damage, and miR-191 is abnormally expressed in nerve crush injuries. This study aimed to explore the effect of miR-191 on isoflurane-induced cognition impairment and neurotoxicity in vivo and in vitro, as well as its potential mechanism.

METHODS

Sprague-Dawley male rats and primary hippocampal neurons were applied and exposed to 2% isoflurane. The level of miR-191 was regulated both in vitro and in vivo to investigate the role of miR-191 in isoflurane-induced neurotoxicity. Morris water maze assay was used to evaluate the neurological function of rats. The level of miR-191 was measured by qRT-PCR. CCK-8 assay and Flow cytometry were applied to detect the cell viability and apoptosis. Dual luciferase reporter gene detection was used for the target gene analysis.

RESULTS

miR-191 was up-regulated in the hippocampal tissues of rats exposed to isoflurane. Downregulation of miR-191 ameliorated isoflurane-induced cognition impairment, including the increase of the neurological score and the escape latency, and the decrease of the time spent in the original quadrant for the rats exposed to isoflurane. Isoflurane exposure inhibited hippocampal neuron viability and promoted cell apoptosis, which was reversed by down-regulation of miR-191. BDNF is a target gene of miR-191.

CONCLUSIONS

Isoflurane causes some neurotoxic effect which is mediated through miR-191 abnormal expression targeting BDNF. Downregulation of miR-191 has a protective role against isoflurane-induced neurotoxicity, regulates the vitality and slows down neuronal cell apoptosis.

Predictors of swallowing outcomes in patients with combat-injury related dysphagia

BACKGROUND

Traumatic injuries, such as those from combat-related activities, can lead to complicated clinical presentations that may include dysphagia.

METHODS

This retrospective observational database study captured dysphagia-related information for 215 US military service members admitted to the first stateside military treatment facility after sustaining combat-related or combat-like traumatic injuries. A multidimensional relational database was developed to document the nature, course, and management for dysphagia in this unique population and to explore variables predictive of swallowing recovery using Bayesian statistical modeling and inferential statistical methods.

RESULTS

Bayesian statistical modeling revealed the importance of maxillofacial fractures and soft tissue loss as primary predictors of poor swallowing outcomes. The presence of traumatic brain injury (TBI), though common, did not further complicate dysphagia outcomes. A more detailed examination and rating of videofluoroscopic swallow studies from a subset of 161 participants supported greater impairment for participants with maxillofacial trauma and no apparent relationship between having sustained a TBI and swallow functioning.

CONCLUSION

These analyses revealed that maxillofacial trauma is a stronger indicator than TBI of dysphagia severity and slower or incomplete recovery following combat-related injuries.

LEVEL OF EVIDENCE

Therapeutic/Care Management study, level IV.

Research progress and treatment strategies for anesthetic neurotoxicity

Every year, a large number of infants and young children worldwide are administered general anesthesia. Whether general anesthesia adversely affects the intellectual development and cognitive function of children at a later date remains controversial. Many animal experiments have shown that general anesthetics can cause nerve damage during development, affect synaptic plasticity, and induce apoptosis, and finally affect learning and memory function in adulthood. The neurotoxicity of pediatric anesthetics (PAN) has received extensive attention in the field of anesthesia, which has been listed as a potential problem affecting public health by NFDA of the United States. Previous studies on rodents and non-human primates indicate that inhalation of anesthetics early after birth can induce long-term and sustained impairment of learning and memory function, as well as changes in brain function. Many anti-oxidant drugs, dexmedetomidine, as well as a rich living environment and exercise have been proven to reduce the neurotoxicity of anesthetics. In this paper, we summarize the research progress, molecular mechanisms and current intervention measures of anesthetic neurotoxicity.

The role of Bag2 in neurotoxicity induced by the anesthetic sevoflurane

Sevoflurane is the most commonly used general anesthetic in pediatric patients. But preclinical studies indicate that sevoflurane could have neurotoxicity in newborn and old animals, and this raises concern regarding its safety. In this study, we explored the potential mechanisms of sevoflurane-induced neurotoxicity in human SH-SY5Y neuronal cells. We showed that prolonged exposure to 2% sevoflurane caused a significant increase in the Bag family protein Bag2 in a time- and dose-dependent manner. We investigated the possible role of Bag2 upon exposure to sevoflurane by silencing Bag2 in neuronal cells. Knockdown of Bag2 caused increased overall reactive oxygen species (ROS) and generation of lipid peroxidation products 4-hydroxynonenal (4-HNE). Upon sevoflurane exposure, Bag2-silent cells have reduced glutathione (GSH) and glutathione peroxidase activity. Under the sevoflurane treatment, Bag2-deficient cells have reduced mitochondrial membrane potential (MMP) and adenosine triphosphate (ATP) production, while knockdown cells have less viability and higher lactic dehydrogenase (LDH) release as well as a higher percentage of apoptotic cells. The knockdown cells also had higher levels of mitochondrial cytochrome C release, a higher ratio of Bax/Bcl-2 and increased caspase cleavage by sevoflurane. Overall, our data support an important role of Bag2 in sevoflurane-induced neurotoxicity.

Effects of Sevoflurane Exposure During Mid-Pregnancy on Learning and Memory in Offspring Rats: Beneficial Effects of Maternal Exercise

Fetal exposure to general anesthetics may pose significant neurocognitive risks but methods to mitigate against these detrimental effects are still to be determined. We set out, therefore, to assess whether single or repeated in utero exposure to sevoflurane triggers long-term cognitive impairments in rat offspring. Since maternal exercise during pregnancy has been shown to improve cognition in offspring, we hypothesized that maternal treadmill exercise during pregnancy would protect against sevoflurane-induced neurotoxicity. In the first experiment, pregnant rats were exposed to 3% sevoflurane for 2 h on gestational (G) day 14, or to sequential exposure for 2 h on G13, G14 and G15. In the second experiment, pregnant rats in the exercise group were forced to run on a treadmill for 60 min/day during the whole pregnancy. The TrkB antagonist ANA-12 was used to investigate whether the brain-derived neurotrophic factor (BDNF)/TrkB/Akt signaling pathway is involved in the neuroprotection afforded by maternal exercise. Our data suggest that repeated, but not single, exposure to sevoflurane caused a reduction in both histone acetylation and BDNF expression in fetal brain tissues and postnatal hippocampus. This was accompanied by decreased numbers of dendritic spines, impaired spatial-dependent learning and memory dysfunction. These effects were mitigated by maternal exercise but the TrkB antagonist ANA-12 abolished the beneficial effects of maternal exercise. Our findings suggest that repeated, but not single, exposure to sevoflurane in pregnant rats during the second trimester caused long-lasting learning and memory dysfunction in the offspring. Maternal exercise ameliorated the postnatal neurocognitive impairment by enhancing histone acetylation and activating downstream BDNF/TrkB/Akt signaling.

Changes in the metabolome and microRNA levels in biological fluids might represent biomarkers of neurotoxicity: A trimethyltin study

Neurotoxicity has been linked with exposure to a number of common drugs and chemicals, yet efficient, accurate, and minimally invasive methods to detect it are lacking. Fluid-based biomarkers such as those found in serum, plasma, urine, and cerebrospinal fluid have great potential due to the relative ease of sampling but at present, data on their expression and translation are lacking or inconsistent. In this pilot study using a trimethyl tin rat model of central nervous system toxicity, we have applied state-of-the-art assessment techniques to identify potential individual biomarkers and patterns of biomarkers in serum, plasma, urine or cerebral spinal fluid that may be indicative of nerve cell damage and degeneration. Overall changes in metabolites and microRNAs were observed in biological fluids that were associated with neurotoxic damage induced by trimethyl tin. Behavioral changes and magnetic resonance imaging T₂ relaxation and ventricle volume changes served to identify animals that responded to the adverse effects of trimethyl tin. Impact statement These data will help design follow-on studies with other known neurotoxicants to be used to assess the broad applicability of the present findings. Together this approach represents an effort to begin to develop and qualify a set of translational biochemical markers of neurotoxicity that will be readily accessible in humans. Such biomarkers could prove invaluable for drug development research ranging from preclinical studies to clinical trials and may prove to assist with monitoring of the severity and life cycle of brain lesions.

The role of general anesthetics and the mechanisms of hippocampal and extra-hippocampal dysfunctions in the genesis of postoperative cognitive dysfunction

Postoperative cognitive dysfunction (POCD) is a multifactorial process with a huge number of predisposing, causal, and precipitating factors. In this scenario, the neuroinflammation and the microglial activation play a pivotal role by triggering and amplifying a complex cascade involving the immuno-hormonal activation, the micro circle alterations, the hippocampal oxidative stress activation and, finally, an increased blood-brain barrier's permeability. While the role of anesthetics in the POCD's genesis in humans is debated, a huge number of preclinical studies have been conducted on the topic and many mechanisms have been proposed to explain the potential neurodegenerative effects of general anesthetics. Probably, the problem concerns on what we are searching for and how we are searching and, surprisingly, preclinical studies showed that anesthetics may also manifest neuroprotective properties. The aim of this paper is to offer an overview on the potential impact of general anesthetics on POCD. Mechanisms of hippocampal and extra-hippocampal dysfunction due to neuroinflammation are discussed, whereas further research perspectives are also given.