Postoperative delirium, neuroinflammation, and influencing factors of postoperative delirium: A review

ML365 ameliorates postoperative cognitive impairment in aged mice by inhibiting NLRP3 inflammasome activation in the hippocampus

The aim of this study was to examine the effects of ML365, a two-pore potassium channel (K2P) inhibitor, on postoperative cognitive impairment (POCD). A mouse model of POCD was constructed by subjecting aged C57BL/6 mice to exploratory laparotomy. Changes in cognitive function were assessed using the Morris water maze test. Western blotting and qPCR were used to detect hippocampal NLRP3, Caspase-1 and IL-1β expression levels on days 3 and 7 post-surgery. Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) expression level was also assessed by western blotting. Pathological changes and nerve damage in the hippocampal CA1 and CA3 regions were detected by H&E staining, while the concentration of malondialdehyde (MDA) in the plasma was measured. We found that pretreatment with ML365 (administered intraperitoneally at a dose of 10 mg/kg) 30 min prior to exploratory laparotomy effectively ameliorated POCD in mice. ML365 pretreatment also reduced NLRP3, Caspase-1, ASC and IL-1β expression levels in the hippocampus, improved POCD-induced pathological changes in the hippocampal CA1 and CA3 areas of aged mice, and decreased levels of plasma MDA and oxidative stress. Together, our findings indicate that ML365 can alleviate POCD in mice by inhibiting NLRP3 inflammasome activation in the hippocampus.

Impact of intraoperative dexmedetomidine on postoperative delirium and pro-inflammatory cytokine levels in elderly patients undergoing thoracolumbar compression fracture surgery: A prospective, randomized, placebo-controlled clinical trial

BACKGROUND

This study evaluates the efficacy of dexmedetomidine (DEX) in reducing postoperative delirium (POD) and modulating pro-inflammatory cytokines in elderly patients undergoing thoracolumbar compression fracture surgery.

METHODS

In this randomized, double-blind, placebo-controlled trial conducted from October 2022 to January 2023 at Anting Hospital in Shanghai, 218 elderly patients were randomized into DEX (n = 110) and normal saline (NS, n = 108) groups. The DEX group received 0.5 µg/kg/h DEX, and delirium incidence was assessed using the Confusion Assessment Method (CAM) on days 1 to 3 post-surgery. Levels of interleukins IL-1β, IL-6, and tumor necrosis factor-α (TNF-α) were measured pre-operation (T0) and on postoperative days 1 (T1) and 3 (T3). Preoperative (T0) and postoperative day 1 (T1) cerebrospinal fluid (CSF) samples were treated with varying concentrations of olanzapine or DEX to observe their regulatory effects on the expression of Phospho-ERK1/2 and Phospho-JNK.

RESULTS

Dexmedetomidine significantly lowered the incidence of POD to 18.2%, compared to 30.6% in the NS group (P = .033). While all patients showed an initial increase in cytokine levels after surgery, by T3, IL-6 and TNF-α levels notably decreased in the DEX group, with no significant change in IL-1β levels across groups. The adverse events rate was similar between groups, demonstrating the safety of DEX in this population. In postoperative CSF samples, treatment with 0.5 mM DEX significantly downregulated Phospho-JNK and upregulated Phospho-ERK1/2 expression, demonstrating a dose-dependent modulation of inflammatory responses.

CONCLUSION

Dexmedetomidine is effective in reducing early POD in elderly patients post-thoracolumbar compression fracture surgery. It also decreases IL-6 and TNF-α levels, indicating its potential in managing postoperative inflammatory responses. Treatment with 0.5 mM DEX significantly modulated Phospho-ERK1/2 and Phospho-JNK expressions in postoperative CSF samples, indicating a dose-dependent effect on reducing inflammation. This study contributes to understanding DEX's role in improving postoperative outcomes in elderly patients.

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.

An exploratory study on the heterogeneity of postoperative delirium: Preoperative cognitive screening does not detect hallucinatory delirium risk

INTRODUCTION

This study compared the clinical characteristics of patients who had hallucinations and those who did not during delirium after elective cancer surgery.

MATERIALS AND METHODS

This study retrospectively observed 1137 consecutive patients who had preoperative screening by a trained nurse before elective major urologic cancer surgery in our department. We compared the patient characteristics, including mini-cognitive assessment instrument (Mini-Cog) and Geriatric-8 (G8) scores, between those who developed postoperative delirium and those who did not, and also between those who had hallucinations and those who did not during delirium.

RESULTS

Out of 1137 patients, 68 developed postoperative delirium, and 12 of them had hallucinations. A hierarchical cluster analysis based on the G8 and Mini-Cog scores divided the patients into two groups: one with high G8 and cognitive function (36 patients) and one with low G8 and cognitive function (32 patients). Hallucinations during delirium were more frequent in the high G8 and cognitive function group (11 out of 36 patients) than in the low G8 and cognitive function group (one out of 32 patients). Patients who had hallucinations during delirium also had higher preoperative Mini-Cog scores (P = 0.002) and G8 scores (P = 0.03) than those who did not, indicating better cognitive function and less frailty.

DISCUSSIONS

We identified a patient population that is prone to hallucinations that preoperative screening tools cannot detect. This suggests the heterogeneity of postoperative delirium and the need for further research.

Former smoking, but not active smoking, is associated with delirium in postoperative ICU patients: a matched case-control study

Objective

To examine the relationship between current and former smoking and the occurrence of delirium in surgical Intensive Care Unit (ICU) patients.

Methods

We conducted a single center, case-control study involving 244 delirious and 251 non-delirious patients that were admitted to our ICU between 2018 and 2022. Using propensity score analysis, we obtained 115 pairs of delirious and non-delirious patients matched for age and Simplified Acute Physiology Score II (SAPS II). Both groups of patients were further stratified into non-smokers, active smokers and former smokers, and logistic regression was performed to further investigate potential confounders.

Results

Our study revealed a significant association between former smoking and the incidence of delirium in ICU patients, both in unmatched (adjusted odds ratio (OR): 1.82, 95% confidence interval (CI): 1.17-2.83) and matched cohorts (OR: 3.0, CI: 1.53-5.89). Active smoking did not demonstrate a significant difference in delirium incidence compared to non-smokers (unmatched OR = 0.98, CI: 0.62-1.53, matched OR = 1.05, CI: 0.55-2.0). Logistic regression analysis of the matched group confirmed former smoking as an independent risk factor for delirium, irrespective of other variables like surgical history (p = 0.010). Notably, also respiratory and vascular surgeries were associated with increased odds of delirium (respiratory: OR: 4.13, CI: 1.73-9.83; vascular: OR: 2.18, CI: 1.03-4.59). Medication analysis showed that while Ketamine and Midazolam usage did not significantly correlate with delirium, Morphine use was linked to a decreased likelihood (OR: 0.27, 95% CI: 0.13-0.55).

Discussion

Nicotine's complex neuropharmacological impact on the brain is still not fully understood, especially its short-term and long-term implications for critically ill patients. Although our retrospective study cannot establish causality, our findings suggest that smoking may induce structural changes in the brain, potentially heightening the risk of postoperative delirium. Intriguingly, this effect seems to be obscured in active smokers, potentially due to the recognized neuroprotective properties of nicotine. Our results motivate future prospective studies, the results of which hold the potential to substantially impact risk assessment procedures for surgeries.

Ketofol versus Dexmedetomidine for preventing postoperative delirium in elderly patients undergoing intestinal obstruction surgeries: a randomized controlled study

PURPOSE

Postoperative delirium (POD) is considered the most common postoperative neurological complication in elderly patients. The aim of this study was to evaluate the efficacy of the administration of ketofol versus dexmedetomidine (DEX) for minimizing POD in elderly patients undergoing urgent exploration for intestinal obstruction.

METHODS

This prospective double-blinded randomized clinical trial was conducted on 120 elderly patients undergoing urgent exploration for intestinal obstruction. Patients were randomly allocated to one of the three groups: Group C (control group) patients received normal saline 0.9%, group D received dexmedetomidine, and group K received ketofol (ketamine: propofol was 1:4). The primary outcome was the incidence of POD. Secondary outcomes were incidence of emergence agitation, postoperative pain, consumption of rescue opioids, hemodynamics, and any side effects.

RESULTS

The incidence of POD was statistically significantly lower in ketofol and DEX groups than in the control group at all postoperative time recordings. Additionally, VAS scores were statistically significantly decreased in the ketofol and DEX groups compared to the control group at all time recordings except at 48 and 72 h postoperatively, where the values of the three studied groups were comparable. The occurrence of emergence agitation and high-dose opioid consumption postoperatively were found to be significant predictors for the occurrence of POD at 2 h and on the evening of the 1st postoperative day.

CONCLUSION

The administration of ketofol provides a promising alternative option that is as effective as DEX in reducing the incidence of POD in elderly patients undergoing urgent exploration for intestinal obstruction.

TRIAL REGISTRATION

This clinical trial was approved by the Institutional Review Board (IRB) at Zagazig University (ZU-IRB# 6704// 3/03/2021) and ClinicalTrials.gov (NCT04816162, registration date 22/03/ 2021). The first research participant was enrolled on 25/03/2021).

Thoracic delirium index for predicting postoperative delirium in elderly patients following thoracic surgery: A retrospective case-control study

BACKGROUND

Postoperative delirium (POD) is an acute neurological complication in the elderly undergoing thoracic surgery and can result in serious adverse consequences.

AIMS

This study aimed to identify the related risk factors for POD following thoracic surgery, primarily focusing on preoperative serum biomarkers, and further to establish a novel delirium index to better predict POD.

METHODS

A total of 279 patients aged ≥60 years who underwent elective thoracic surgery from August 2021 to August 2022 were enrolled in this observational study. The platelet-to-white blood cell ratio (PWR) was calculated as number the of platelets divided by the number of white blood cells. POD was defined by the confusion assessment method twice daily during the postoperative first 3 days. Multivariate regression analysis was performed to identify all potential variables for POD. Moreover, a novel thoracic delirium index (TDI) was developed based on the related risk factors. The accuracy of TDI and its component factors in predicting POD was determined by the curve of receiver operating characteristic (ROC).

RESULTS

In total, 25 of 279 patients developed POD (8.96%). Age, PWR, and average pain scores within the first 3 days after surgery were regarded as the independent risk factors for POD. Moreover, the ROC analysis showed the TDI, including age, PWR, and average pain scores within the first 3 days after surgery, can more accurately predict POD with the largest area under the curve of 0.790 and the optimal cutoff value of 9.072, respectively.

CONCLUSION

The TDI can scientifically and effectively predict POD to provide optimal clinical guidance for older patients after thoracic surgery.

Effect of Intraoperative Intravenous Lidocaine on Postoperative Delirium in Elderly Patients with Hip Fracture: A Prospective Randomized Controlled Trial

Purpose

This study was performed to evaluate the effects of intraoperative intravenous lidocaine on postoperative delirium in elderly patients with hip fracture.

Patients and methods

In total, 100 elderly patients undergoing hip fracture surgery were randomized to the lidocaine group (Group L) or saline (control) group (Group C). Before anesthetic induction, Group L received lidocaine at 1 mg/kg for more than 10 minutes followed by continuous infusion at 1.5 mg/kg/h until the end of surgery. Group C received normal saline, and the injection methods were consistent with those in Group L. General anesthesia was induced with propofol, sufentanil, and cis-atracurium. Anesthesia was maintained by propofol and remifentanil. The primary outcome was the incidence of postoperative delirium in the first 7 postoperative days. The secondary outcomes included the severity of delirium, onset and duration of delirium, emergence agitation, adverse events, total propofol dose, intraoperative opioid dosage, length of post-anesthesia care unit stay, extubation time, and patient satisfaction with postoperative pain management.

Results

All 100 patients completed the study. The incidence of postoperative delirium was lower in Group L than in Group C (14% vs 36%, P = 0.011). The delirium severity scores were lower in Group L (3 [3-4]) than in Group C (4 [4-5]) (P = 0.017). In addition, the incidences of hypertension, tachycardia, and emergence agitation were significantly lower in Group L than in Group C. No cases of local anesthetic toxicity occurred in either group.

Conclusion

Patients received lidocaine at 1 mg/kg for more than 10 minutes followed by continuous infusion at 1.5 mg/kg/h until the end of surgery, which can reduce the incidence of postoperative delirium in elderly patients undergoing hip fracture. In addition, the used regimen of lidocaine would not increase the risk of local anesthetic toxicity.

Gene networks for use in metabolomic data analysis of blood plasma from patients with postoperative delirium

Postoperative delirium (POD) is considered one of the most severe complications, resulting in impaired cognitive function, extended hospitalization, and higher treatment costs. The challenge of early POD diagnosis becomes particularly significant in cardiac surgery cases, as the incidence of this complication exceeds 50 % in certain patient categories. While it is known that neuroinflammation, neurotransmitter imbalances, disruptions in neuroendocrine regulation, and interneuronal connections contribute significantly to the development of POD, the molecular, genetic mechanisms of POD in cardiac surgery patients, along with potential metabolomic diagnostic markers, remain inadequately understood. In this study, blood plasma was collected from a group of patients over 65 years old after cardiac surgery involving artificial circulation. The collected samples were analyzed for sphingomyelin content and quantity using high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS/MS) methods. The analysis revealed four significantly different sphingomyelin contents in patients with POD compared to those who did not develop POD (control group). Employing gene network reconstruction, we perceived a set of 82 regulatory enzymes affiliated with the genetic coordination of the sphingolipid metabolism pathway. Within this set, 47 are assumed to be regulators of gene expression, governing the transcription of enzymes pivotal to the metabolic cascade. Complementing this, an additional assembly of 35 regulators are considered to be regulators of activity, degradation, and translocation dynamics of enzymes integral to the aforementioned pathway. Analysis of the overrepresentation of diseases with which these regulatory proteins are associated showed that the regulators can be categorized into two groups, associated with cardiovascular pathologies (CVP) and neuropsychiatric diseases (NPD), respectively. The regulators associated with CVP are expectedly related to the effects on myocardial tissue during surgery. It is hypothesized that dysfunction of NPD-associated regulators may specifically account for the development of POD after cardiac surgery. Thus, the identified regulatory genes may provide a basis for planning further experiments, in order to study disorders at the level of expression of these genes, as well as impaired function of proteins encoded by them in patients with POD. The identified significant sphingolipids can be considered as potential markers of POD.

Molecular-genetic pathways of hepatitis C virus regulation of the expression of cellular factors PREB and PLA2G4C, which play an important role in virus replication

The participants of Hepatitis C virus (HCV) replication are both viral and host proteins. Therapeutic approaches based on activity inhibition of viral non-structural proteins NS3, NS5A, and NS5B are undergoing clinical trials. However, rapid mutation processes in the viral genome and acquisition of drug resistance to the existing drugs remain the main obstacles to fighting HCV. Identifying the host factors, exploring their role in HCV RNA replication, and studying viral effects on their expression is essential for understanding the mechanisms of viral replication and developing novel, effective curative approaches. It is known that the host factors PREB (prolactin regulatory element binding) and PLA2G4C (cytosolic phospholipase A2 gamma) are important for the functioning of the viral replicase complex and the formation of the platforms of HCV genome replication. The expression of PREB and PLA2G4C was significantly elevated in the presence of the HCV genome. However, the mechanisms of its regulation by HCV remain unknown. In this paper, using a text-mining technology provided by ANDSystem, we reconstructed and analyzed gene networks describing regulatory effects on the expression of PREB and PLA2G4C by HCV proteins. On the basis of the gene network analysis performed, we put forward hypotheses about the modulation of the host factors functions resulting from protein-protein interaction with HCV proteins. Among the viral proteins, NS3 showed the greatest number of regulatory linkages. We assumed that NS3 could inhibit the function of host transcription factor (TF) NOTCH1 by protein-protein interaction, leading to upregulation of PREB and PLA2G4C. Analysis of the gene networks and data on differential gene expression in HCV-infected cells allowed us to hypothesize further how HCV could regulate the expression of TFs, the binding sites of which are localized within PREB and PLA2G4C gene regions. The results obtained can be used for planning studies of the molecular-genetic mechanisms of viral-host interaction and searching for potential targets for anti-HCV therapy.