Inflammatory cytokines in relation to adrenal response following total hip replacement

Serum proteomic analysis in esophagectomy patients with postoperative delirium: A case-control study

BACKGROUND

Postoperative delirium occurs in up to 80% of patients undergoing esophagectomy. We performed an exploratory proteomic analysis to identify protein pathways that may be associated with delirium post-esophagectomy.

OBJECTIVES

Identify proteins associated with delirium and delirium severity in a younger and higher-risk surgical population.

METHODS

We performed a case-control study using blood samples collected from patients enrolled in a negative, randomized, double-blind clinical trial. English speaking adults aged 18 years or older, undergoing esophagectomy, who had blood samples obtained were included. Cases were defined by a positive delirium screen after surgery while controls were patients with negative delirium assessments. Delirium was assessed using Richmond Agitation Sedation Scale and Confusion Assessment Method for the Intensive Care Unit, and delirium severity was assessed by Delirium Rating Scale-Revised-98. Blood samples were collected pre-operatively and on post-operative day 1, and discovery proteomic analysis was performed. Between-group differences in median abundance ratios were reported using Wilcoxon-Mann-Whitney Odds (WMWodds1) test.

RESULTS

52 (26 cases, 26 controls) patients were included in the study with a mean age of 64 (SD 9.6) years, 1.9% were females and 25% were African American. The median duration of delirium was 1 day (IQR: 1-2), and the median delirium/coma duration was 2.5 days (IQR: 2-4). Two proteins with greater relative abundance ratio in patients with delirium were: Coagulation factor IX (WMWodds: 1.89 95%CI: 1.0-4.2) and mannosyl-oligosaccharide 1,2-alpha-mannosidase (WMWodds: 2.4 95%CI: 1.03-9.9). Protein abundance ratios associated with mean delirium severity at postoperative day 1 were Complement C2 (Spearman rs = -0.31, 95%CI [-0.55, -0.02]) and Mannosyl-oligosaccharide 1,2-alpha-mannosidase (rs = 0.61, 95%CI = [0.29, 0.81]).

CONCLUSIONS

We identified changes in proteins associated with coagulation, inflammation, and protein handling; larger, follow-up studies are needed to confirm our hypothesis-generating findings.

A nomogram for predicting sepsis-associated delirium: a retrospective study in MIMIC III

OBJECTIVE

To develop a nomogram for predicting the occurrence of sepsis-associated delirium (SAD).

MATERIALS AND METHODS

Data from a total of 642 patients were retrieved from the Medical Information Mart for Intensive Care (MIMIC III) database to build a prediction model. Multivariate logistic regression was performed to identify independent predictors and establish a nomogram to predict the occurrence of SAD. The performance of the nomogram was assessed in terms of discrimination and calibration by bootstrapping with 1000 resamples.

RESULTS

Multivariate logistic regression identified 4 independent predictors for patients with SAD, including Sepsis-related Organ Failure Assessment(SOFA) (p = 0.004; OR: 1.131; 95% CI 1.040 to 1.231), mechanical ventilation (P < 0.001; OR: 3.710; 95% CI 2.452 to 5.676), phosphate (P = 0.047; OR: 1.165; 95% CI 1.003 to 1.358), and lactate (P = 0.023; OR: 1.135; 95% CI 1.021 to 1.270) within 24 h of intensive care unit (ICU) admission. The area under the curve (AUC) of the predictive model was 0.742 in the training set and 0.713 in the validation set. The Hosmer - Lemeshow test showed that the model was a good fit (p = 0.471). The calibration curve of the predictive model was close to the ideal curve in both the training and validation sets. The DCA curve also showed that the predictive nomogram was clinically useful.

CONCLUSION

We constructed a nomogram for the personalized prediction of delirium in sepsis patients, which had satisfactory performance and clinical utility and thus could help clinicians identify patients with SAD in a timely manner, perform early intervention, and improve their neurological outcomes.

Postoperative Delirium in Neurosurgical Patients: Recent Insights into the Pathogenesis

Postoperative delirium (POD) is a complication characterized by disturbances in attention, awareness, and cognitive function that occur shortly after surgery or emergence from anesthesia. Since it occurs prevalently in neurosurgical patients and poses great threats to the well-being of patients, much emphasis is placed on POD in neurosurgical units. However, there are intricate theories about its pathogenesis and limited pharmacological interventions for POD. In this study, we review the recent insights into its pathogenesis, mainly based on studies within five years, and the five dominant pathological theories that account for the development of POD, with the intention of furthering our understanding and boosting its clinical management.

Reducing opioid usage in total knee arthroplasty postoperative pain management: a literature review and future directions

Total knee arthroplasty (TKA) is a common orthopedic surgery performed with a projected 3.5 million procedures to be done by 2030. Current postoperative pain management for TKA is insufficient, as it results in extensive opioid consumption and functional decline postoperatively. This study identifies the best practices for postoperative TKA pain management through a literature review of the last three years. Studies utilizing interventional techniques (local infiltration analgesia, nerve blocks) and pharmacologic options were reviewed on PubMed, Embase, Ovid Medline and Scopus. Primary outcomes analyzed were the effect of different analgesic approaches on pain reduction, opioid use reduction and improvements in functional mobility or quadriceps strength postoperatively. Additionally, this paper explores the use of cooled radiofrequency ablation, a minimally invasive therapy, for preoperative and postoperative TKA pain management.

Phenotypes and subphenotypes of delirium: a review of current categorisations and suggestions for progression

Delirium is a clinical syndrome occurring in heterogeneous patient populations. It affects 45-87% of critical care patients and is often associated with adverse outcomes including acquired dementia, institutionalisation, and death. Despite an exponential increase in delirium research in recent years, the pathophysiological mechanisms resulting in the clinical presentation of delirium are still hypotheses. Efforts have been made to categorise the delirium spectrum into clinically meaningful subgroups (subphenotypes), using psychomotor subtypes such as hypoactive, hyperactive, and mixed, for example, and also inflammatory and non-inflammatory delirium. Delirium remains, however, a constellation of symptoms resulting from a variety of risk factors and precipitants with currently no successful targeted pharmacological treatment. Identifying specific clinical and biological subphenotypes will greatly improve understanding of the relationship between the clinical symptoms and the putative pathways and thus risk factors, precipitants, natural history, and biological mechanism. This will facilitate risk factor mitigation, identification of potential methods for interventional studies, and informed patient and family counselling. Here, we review evidence to date and propose a framework to identify subphenotypes. Endotype identification may be done by clustering symptoms with their biological mechanism, which will facilitate research of targeted treatments. In order to achieve identification of delirium subphenotypes, the following steps must be taken: (1) robust records of symptoms must be kept at a clinical level. (2) Global collaboration must facilitate large, heterogeneous research cohorts. (3) Patients must be clustered for identification, validation, and mapping of subphenotype stability.

Impact of Acute Inflammation on Cytochromes P450 Activity Assessed by the Geneva Cocktail

Cytochromes P450 (CYP) are subject to important interindividual variability in their activity due to genetic and environmental factors and some diseases. Limited human data support the idea that inflammation downregulates CYP activities. Our study aimed to evaluate the impact of orthopedic surgery (acute inflammation model) on the activity of six human CYP. This prospective observational study was conducted in 30 patients who underwent elective hip surgery at the Geneva University Hospitals in Switzerland. The Geneva phenotyping cocktail containing caffeine, bupropion, flurbiprofen, omeprazole, dextromethorphan, and midazolam as probe drugs respectively assessing CYP1A2, 2B6, 2C9, 2C19, 2D6, and 3A activities was administered orally before surgery, day 1 (D1) and 3 (D3) postsurgery and at discharge. Capillary blood samples were collected 2 hours after cocktail intake to assess metabolic ratios (MRs). Serum inflammatory markers (CRP, IL‐6, IL‐1β, TNF‐α, and IFN‐γ) were also measured in blood. CYP1A2 MRs decreased by 53% (P < 0.0001) between baseline and the nadir at D1. CYP2C19 and CYP3A activities (MRs) decreased by 57% (P = 0.0002) and 61% (P < 0.0001), respectively, with the nadir at D3. CYP2B6 and CYP2C9 MRs increased by 120% (P < 0.0001) and 79% (P = 0.018), respectively, and peaked at D1. Surgery did not have a significant impact on CYP2D6 MR. Hip surgery was a good acute inflammation model as CRP, IL‐6, and TNF‐α peak levels were reached between D1 and day 2 (D2). Acute inflammation modulated CYP activity in an isoform‐specific manner, with different magnitudes and kinetics. Acute inflammation may thus have a clinically relevant impact on the pharmacokinetics of these CYP substrates.

A Systematic Pharmacology and In Vitro Study to Identify the Role of the Active Compounds of Achyranthes bidentata in the Treatment of Osteoarthritis

Backgrounds

Achyranthes bidentata is a Chinese traditional herbal medicine widely used to treat osteoarthritis (OA). This study aimed to identify active compounds from Achyranthes bidentata through systematic pharmacology and in vitro experiments to find the targets of Achyranthes bidentata in the treatment of OA.

Material/Methods

We screened the active compounds of Achyranthes bidentata from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database. Then, we used STITCH and Open Targets Platform databases to screen the active components and predict the potential targets of Achyranthes bidentata in the treatment of OA. Subsequently, we studied the compound-target network and protein interaction network and analyzed the enrichment of potential target proteins. Finally, we used Western blot analysis to verify the therapeutic effect of Achyranthes bidentata extract on the expression of OA-related target proteins.

Results

There were 7 active components in Achyranthes bidentata, which were strongly related to the 74 targets of OA. Quercetin, baicalein, and berberine are the critical active compounds of Achyranthes bidentata in the treatment of OA. Protein interaction analysis and in vitro experiments suggested that TNF, IL-6, and TP53 are the critical targets of Achyranthes bidentata in the treatment of OA. Functional enrichment analysis showed that Achyranthes bidentata plays a pharmacological role in OA through apoptosis, inflammation, and immune regulation.

Conclusions

Quercetin, baicalein, and berberine are the critical active compounds of Achyranthes bidentata in the treatment of OA. TNF, IL-6, and TP53 may be potential targets for the treatment of OA.

Biomarkers of Delirium Duration and Delirium Severity in the ICU

OBJECTIVES

Both delirium duration and delirium severity are associated with adverse patient outcomes. Serum biomarkers associated with delirium duration and delirium severity in ICU patients have not been reliably identified. We conducted our study to identify peripheral biomarkers representing systemic inflammation, impaired neuroprotection, and astrocyte activation associated with delirium duration, delirium severity, and in-hospital mortality.

DESIGN

Observational study.

SETTING

Three Indianapolis hospitals.

PATIENTS

Three-hundred twenty-one critically ill delirious patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We analyzed the associations between biomarkers collected at delirium onset and delirium-/coma-free days assessed through Richmond Agitation-Sedation Scale/Confusion Assessment Method for the ICU, delirium severity assessed through Confusion Assessment Method for the ICU-7, and in-hospital mortality. After adjusting for age, gender, Acute Physiology and Chronic Health Evaluation II score, Charlson comorbidity score, sepsis diagnosis and study intervention group, interleukin-6, -8, and -10, tumor necrosis factor-α, C-reactive protein, and S-100β levels in quartile 4 were negatively associated with delirium-/coma-free days by 1 week and 30 days post enrollment. Insulin-like growth factor-1 levels in quartile 4 were not associated with delirium-/coma-free days at both time points. Interleukin-6, -8, and -10, tumor necrosis factor-α, C-reactive protein, and S-100β levels in quartile 4 were also associated with delirium severity by 1 week. At hospital discharge, interleukin-6, -8, and -10 retained the association but tumor necrosis factor-α, C-reactive protein, and S-100β lost their associations with delirium severity. Insulin-like growth factor-1 levels in quartile 4 were not associated with delirium severity at both time points. Interleukin-8 and S-100β levels in quartile 4 were also associated with higher in-hospital mortality. Interleukin-6 and -10, tumor necrosis factor-α, and insulin-like growth factor-1 were not found to be associated with in-hospital mortality.

CONCLUSIONS

Biomarkers of systemic inflammation and those for astrocyte and glial activation were associated with longer delirium duration, higher delirium severity, and in-hospital mortality. Utility of these biomarkers early in delirium onset to identify patients at a higher risk of severe and prolonged delirium, and delirium related complications during hospitalization needs to be explored in future studies.

A Systematic Review and Meta-Analysis Examining the Impact of Sleep Disturbance on Postoperative Delirium

OBJECTIVES

Basic science and clinical studies suggest that sleep disturbance may be a modifiable risk factor for postoperative delirium. We aimed to assess the association between preoperative sleep disturbance and postoperative delirium.

DATA SOURCES

We searched PubMed, Embase, CINAHL, Web of Science, and Cochrane from inception until May 31, 2017.

STUDY SELECTION

We performed a systematic search of the literature for all studies that reported on sleep disruption and postoperative delirium excluding cross-sectional studies, case reports, and studies not reported in English language.

DATA EXTRACTION

Two authors independently performed study selection and data extraction. We calculated pooled effects estimates with a random-effects model constructed in Stata and evaluated the risk of bias by formal testing (Stata Corp V.14, College Station, TX), DATA SYNTHESIS:: We included 12 studies, from 1,238 citations that met our inclusion criteria. The pooled odds ratio for the association between sleep disturbance and postoperative delirium was 5.24 (95% CI, 3.61-7.60; p < 0.001 and I = 0.0%; p = 0.76). The pooled risk ratio for the association between sleep disturbance and postoperative delirium in prospective studies (n = 6) was 2.90 (95% CI, 2.28-3.69; p < 0.001 and I = 0.0%; p = 0.89). The odds ratio associated with obstructive sleep apnea and unspecified types of sleep disorder were 4.75 (95% CI, 2.65-8.54; p < 0.001 and I = 0.0%; p = 0.85) and 5.60 (95% CI, 3.46-9.07; p < 0.001 and I = 0.0%; p = 0.41), respectively. We performed Begg's and Egger's tests for publication bias and confirmed a null result for publication bias (p = 0.371 and 0.103, respectively).

CONCLUSIONS

Preexisting sleep disturbances are likely associated with postoperative delirium. Whether system-level initiatives targeting patients with preoperative sleep disturbance may help reduce the prevalence, morbidity, and healthcare costs associated with postoperative delirium remains to be determined.

Suitability of serum cytokine profiling for early diagnosis of implant-associated infections after orthopaedic surgery: A preliminary prospective study

The C-reactive protein (CRP) is still the conventional marker used to diagnose implant-associated infections (IAI) after orthopaedic surgery. However, the CRP level can lead to misdiagnosis since it is up-regulated not only during bacterial infection. In this prospective study, we evaluated the serum cytokine profile before (pre-OP) and after orthopaedic surgery (post-OP) as well as after confirmation of a developed infection (COI) to identify candidate biomarkers for diagnosis of IAI. Sera from 10 controls 7 to 1 days pre-OP and 0 to 22 days post-OP as well as from 5 patients who developed IAI 5 to 1 days pre-OP, 0 to 197 days post-OP and after COI were analyzed for 27 different cytokines using a multiplex cytokine assay. In addition to CRP, 14 cytokines IL-1ra, IL-4, IL-5, IL-6, IL-8, IL-12(p70), IL-13, IL-17, eotaxin, G-CSF, IFN-γ, IP-10, MCP-1, and MIP-1β were significantly altered (P ≤ 0.05) during the study although some differences were low-fold elevations compared to the pre-OP levels. IL-6 as well as IL-12(p70) were consistently elevated in infected patients. Surgery influenced cytokine production with some overlap of cytokines in both groups, implying that the use of cytokines is maximized when the cytokines are not or no longer affected by surgical trauma. To lend more robustness to the selection of candidate cytokines, in addition to the statistical differences, we applied a threshold cut-off of approximately 2-fold elevations when comparisons were made. This resulted in the selection of 8 cytokines, namely IL-6, IL-1ra, IL-8, IL-12(p70), eotaxin, IP-10, MCP-1, and MIP-1β, which may be used in a multiplex assay for detection of IAI after surgery. Furthermore, IL-1ra and IL-8 may be used as prognostic cytokines prior to surgery. The present results imply that the use of cytokines may be a suitable alternative to CRP for IAI diagnosis.

Preventing Postoperative Delirium After Major Noncardiac Thoracic Surgery-A Randomized Clinical Trial

OBJECTIVES

To assess the efficacy of haloperidol in reducing postoperative delirium in individuals undergoing thoracic surgery.

DESIGN

Randomized double-blind placebo-controlled trial.

SETTING

Surgical intensive care unit (ICU) of tertiary care center.

PARTICIPANTS

Individuals undergoing thoracic surgery (N=135).

INTERVENTION

Low-dose intravenous haloperidol (0.5 mg three times daily for a total of 11 doses) administered postoperatively.

MEASUREMENTS

The primary outcome was delirium incidence during hospitalization. Secondary outcomes were time to delirium, delirium duration, delirium severity, and ICU and hospital length of stay. Delirium was assessed using the Confusion Assessment Method for the ICU and delirium severity using the Delirium Rating Scale-Revised.

RESULTS

Sixty-eight participants were randomized to receive haloperidol and 67 placebo. No significant differences were observed between those receiving haloperidol and those receiving placebo in incident delirium (n=15 (22.1%) vs n=19 (28.4%); p = .43), time to delirium (p = .43), delirium duration (median 1 day, interquartile range (IQR) 1-2 days vs median 1 day, IQR 1-2 days; p = .71), delirium severity, ICU length of stay (median 2.2 days, IQR 1-3.3 days vs median 2.3 days, IQR 1-4 days; p = .29), or hospital length of stay (median 10 days, IQR 8-11.5 days vs median 10 days, IQR 8-12 days; p = .41). In the esophagectomy subgroup (n = 84), the haloperidol group was less likely to experience incident delirium (n=10 (23.8%) vs n=17 (40.5%); p = .16). There were no differences in time to delirium (p = .14), delirium duration (median 1 day, IQR 1-2 days vs median 1 day, IQR 1-2 days; p = .71), delirium severity, or hospital length of stay (median 11 days, IQR 10-12 days vs median days 11, IQR 10-15 days; p = .26). ICU length of stay was significantly shorter in the haloperidol group (median 2.8 days, IQR 1.1-3.8 days vs median 3.1 days, IQR 2.1-5.1 days; p = .03). Safety events were comparable between the groups.

CONCLUSION

Low-dose postoperative haloperidol did not reduce delirium in individuals undergoing thoracic surgery but may be efficacious in those undergoing esophagectomy. J Am Geriatr Soc 66:2289-2297, 2018.

Postoperative delirium in the elderly: the potential neuropathogenesis

Postoperative delirium (POD) is a neurobehavioral syndrome caused by dysfunction of neural activity mainly in elderly people. POD is not uncommon, but under-recognized, and often serious. Multifactorial causes including aging, acetylcholine deficiency, sleep deprivation and intraoperative hypoxia have been proposed attempting to explain the processes leading to the development of POD. To date, however, no specific pathophysiologic mechanism has been identified. Here, we summarize the five most prominent theories (neuronal aging, neuroinflammation, neurotransmitter imbalance, neuroendocrine activation, and network connectivity change) to explain the development of delirium. Understanding of the neuropathogenesis of delirium will help focus future research, and assist in developing prophylactic and treatment strategies.

Transcutaneous electrical acupoint stimulation for prevention of postoperative delirium in geriatric patients with silent lacunar infarction: a preliminary study

Purpose

This study aims to investigate the effect of transcutaneous electrical acupoint stimulation (TEAS) on postoperative delirium (POD) in elderly patients with silent lacunar infarct and preliminarily to determine the relationship among TEAS, blood–brain barrier (BBB), neuroinflammation, and POD.

Patients and methods

Sixty-four-old patients with silent lacunar infarct were randomly divided into two groups: group TEAS and control group (group C). Patients in the group TEAS received TEAS (disperse-dense waves; frequency, 2/100 Hz) on acupoints Hegu and Neiguan of both sides starting from 30 minutes before induction of anesthesia until the end of surgery, and the intensity was the maximum current that could be tolerated. In group C, electrodes were placed on the same acupoints before anesthesia induction, but no current was given. At 0 minute before the treatment of TEAS, 30 minutes after skin incision, and after completion of surgery (T_1–3), blood samples were extracted to detect the concentration of serum tumor necrosis factor (TNF)-α, interleukin-6 (IL-6), matrix metalloproteinase-9 (MMP-9), and S100β. We assessed patients for delirium and coma twice daily in the first 3 postoperative days using the Confusion Assessment Method for the intensive care unit and the Richmond Agitation-Sedation Scale.

Results

This study preliminarily suggests that TEAS can reduce the development of POD in elderly patients with silent lacunar infarction (6.3% vs 25.0%; P=0.039). Compared with the baseline value at T₁, the serum concentrations of IL-6, TNF-α, MMP-9, and S100β were significantly increased at T_2–3 in both the groups (P<0.05). Compared with group TEAS, serum levels of TNF-α and IL-6 were higher at T_2–3 and serum levels of MMP-9 and S100β were higher at T₃ in group C (P<0.05). The intraoperative anesthetic consumptions were less in group TEAS than group C.

Conclusion

TEAS can alleviate POD in older patients with silent lacunar infarction and may be related to reduce the neuroinflammation by lowering the permeability of BBB.

A meta-analysis of dexamethasone for pain management in patients with total knee arthroplasty

BACKGROUND

Pain management after a total-knee arthroplasty (TKA) has become an important issue in the field of medicine. This study conducted a meta-analysis from randomized controlled trials (RCTs) to assess the efficacy and safety of dexamethasone for pain management after TKA.

METHODS

PubMed, Medline, Embase, ScienceDirect, and the Cochrane Library were searched up to December 2017 for comparative RCTs involving dexamethasone and placebo for pain control after TKA. Primary outcomes were postoperative pain scores and opioid consumption. Secondary outcomes were length of hospital stay, adverse effects, and postoperative complications. We assessed statistical heterogeneity for each RCT with the use of a standard Chi-squared test and the I statistic. All data were carried out with Stata 14.0 software.

RESULTS

A total of 6 RCTs were included. The present meta-analysis indicated that there were significant differences between dexamethasone-treated groups and placebo groups regarding postoperative pain scores at 12, 24, and 48 hours after TKA. Administering dexamethasone could significantly reduce opioid consumption at 12 hours after TKA. However, no significant difference was found in opioid consumption at 24 and 48 hours after TKA. There was a decreased risk of adverse effects in dexamethasone groups.

CONCLUSION

Use of dexamethasone could result in a significant reduction in postoperative pain while minimizing adverse effects after TKA. Based on the current evidence available, more RCTs are needed for further investigation.

Minimizing ICU Neurological Dysfunction with Dexmedetomidine-induced Sleep (MINDDS): protocol for a randomised, double-blind, parallel-arm, placebo-controlled trial

INTRODUCTION

Delirium, which is prevalent in postcardiac surgical patients, is an acute brain dysfunction characterised by disturbances in attention, awareness and cognition not explained by a pre-existing neurocognitive disorder. The pathophysiology of delirium remains poorly understood. However, basic science and clinical studies suggest that sleep disturbance may be a modifiable risk factor for the development of delirium. Dexmedetomidine is a α-2A adrenergic receptor agonist medication that patterns the activity of various arousal nuclei similar to sleep. A single night-time loading dose of dexmedetomidine promotes non-rapid eye movement sleep stages N2 and N3 sleep. This trial hypothesises dexmedetomidine-induced sleep as pre-emptive therapy for postoperative delirium.

METHODS AND ANALYSIS

The MINDDS (Minimizing ICU Neurological Dysfunction with Dexmedetomidine-induced Sleep) trial is a 370-patient block-randomised, placebo-controlled, double-blinded, single-site, parallel-arm superiority trial. Patients over 60 years old, undergoing cardiac surgery with planned cardiopulmonary bypass, will be randomised to receive a sleep-inducing dose of dexmedetomidine or placebo. The primary outcome is the incidence of delirium on postoperative day 1, assessed with the Confusion Assessment Method by staff blinded to the treatment assignment. To ensure that the study is appropriately powered for the primary outcome measure, patients will be recruited and randomised into the study until 370 patients receive the study intervention on postoperative day 0. Secondary outcomes will be evaluated by in-person assessments and medical record review for in-hospital end points, and by telephone interview for 30-day, 90-day and 180-day end points. All trial outcomes will be evaluated using an intention-to-treat analysis plan. Hypothesis testing will be performed using a two-sided significance level (type I error) of α=0.05. Sensitivity analyses using the actual treatment received will be performed and compared with the intention-to-treat analysis results. Additional sensitivity analyses will assess the potential impact of missing data due to loss of follow-up.

ETHICS AND DISSEMINATION

The Partners Human Research Committee approved the MINDDS trial. Recruitment began in March 2017. Dissemination plans include presentations at scientific conferences, scientific publications and popular media.

TRIAL REGISTRATION NUMBER

NCT02856594.

Postoperative Myocardial Injury and Inflammation Is Not Blunted by a Trial of Atorvastatin in Orthopedic Surgery Patients

BACKGROUND

Orthopedic patients are at risk for adverse postoperative cardiovascular outcomes.

QUESTIONS/PURPOSES

This pilot randomized controlled trial (RCT) of atorvastatin vs. placebo in orthopedic surgery patients was performed in order to assess: (1) the prevalence of perioperative myocardial injury; (2) the effect of atorvastatin on perioperative inflammation; and (3) the feasibility of performing a large RCT of statin therapy in orthopedic patients.

METHODS

Hip fracture (hip Fx) and total hip and knee replacement (THR and TKR) patients were randomized 1:1 to atorvastatin 40 mg daily vs. placebo, starting preoperatively and continuing until postoperative day (POD) 45. High-sensitivity cardiac troponin I (hs-cTnI), high-sensitivity C-reactive protein (hs-CRP), and interleukin-6 (IL-6) were measured preoperatively and on POD 2. Patients were monitored for adverse events until POD 90.

RESULTS

Five hundred fifty-six patients were screened, 22 were recruited (4 hip Fx, 11 THR, 7 TKR), and 2 withdrew. Most (80%) had detectable hs-cTnI (> 1.1 pg/mL) preoperatively. Twenty percent had a perioperative rise in hs-cTnI (≥ 10 pg/mL), which was not blunted by atorvastatin. Hs-CRP rose in 19/20 patients, and IL-6 rose in all patients. However, atorvastatin did not blunt the rise in these inflammatory biomarkers. On POD 2, IL-6 and hs-cTnI levels correlated (ρ = 0.59, p = 0.02). Recruitment was limited by the high prevalence of statin use in the screened population and a high prevalence of exclusions among hip fracture patients.

CONCLUSION

Perioperative myocardial injury and inflammation are common in orthopedic patients and do not appear to be reduced in those randomized to atorvastatin.

TRIAL REGISTRATION

NCT02197065.

Preoperative intravenous glucocorticoids can reduce postoperative acute pain following total knee arthroplasty: A meta-analysis

BACKGROUND

The ability of preoperative intravenous glucocorticoids to control pain after total knee arthroplasty (TKA) has been examined in many studies, but it remains controversial. Therefore, we undertook a meta-analysis of randomized controlled trials (RCTs) to evaluate the efficacy and safety of preoperative intravenous glucocorticoids for postoperative pain management after TKA.

METHODS

We systematically searched RCTs from electronic databases, including PubMed, Embase, Web of Science, the Cochrane Library, the Chinese Wanfang Database, and the China National Knowledge Infrastructure database. The outcomes included visual analogue scale (VAS) scores at 6, 12, 24, 48, and 72 hours after TKA; the occurrence of postoperative nausea and vomiting (PONV); blood glucose at 6 and 24 hours after TKA; and the occurrence of infection.

RESULTS

Of the identified studies, a total of 11 RCTs involving 1000 patients (glucocorticoids = 501, control = 499) were included in this meta-analysis. Compared with a placebo, preoperative intravenous glucocorticoids significantly reduced VAS scores at 6, 12, 24, and 48 hours, with decreases of 3.63 points, 6.81 points, 10.40 points, and 3.15 points, respectively, on a 110-point VAS. Moreover, intravenous glucocorticoids were associated with significant decreases of 19.4% and 16.8% in the occurrence of nausea and vomiting, respectively. However, intravenous glucocorticoids were also associated with increased blood glucose with no clinical importance at 6 hours after TKA. No significant difference was found in the occurrence of infection or in blood glucose at 24 hours after TKA.

CONCLUSION

Preoperative intravenous glucocorticoids are an effective and safe method to reduce postoperative pain and PONV in patients following TKA. More studies are necessary to identify the optimal dose and type of glucocorticoids for maximal pain control.

Can intravenous steroid administration reduce postoperative pain scores following total knee arthroplasty?: A meta-analysis

BACKGROUND

The purpose of this systematic review and meta-analysis of randomized controlled trials (RCTs) was to evaluate whether intravenous steroids would result in reduced acute pain and postoperative nausea and vomiting (PONV) among patients undergoing total knee arthroplasty (TKA).

METHODS

Electronic databases, including PubMed, Embase, Web of Science, and the Cochrane Library, were searched to identify articles published from database inception to July 2016. RCTs that compared the effects of intravenous steroids with the effects of placebo among patients undergoing TKA were included in this meta-analysis. The primary outcomes were visual analogue scale (VAS) scores after 12, 24, and 48 hours of rest and PONV incidence. The secondary outcomes were blood glucose levels and incidence of infection. We calculated the risk ratio (RR) with its corresponding 95% confidence interval (CI) for dichotomous outcomes and the mean difference (MD) with its corresponding 95% CI for continuous outcomes.

RESULTS

Seven clinical trials involving 434 patients were included in the final meta-analysis. The pooled results indicated that intravenous steroids were associated with decreased VAS scores after 24 hours (MD = -10.21, 95%CI = -18.80 to -1.63, P = .020) and 48 hours (MD = -2.60, 95%CI = -4.70 to -0.50, P = .015) of rest. Moreover, intravenous steroids were also associated with decreased risk of nausea (RR = 0.58, 95% CI 0.44-0.77, P = .000) and vomiting (RR = 0.46, 95% CI = 0.24-0.88, P = .019). However, intravenous steroids were also associated with increased blood glucose levels. No significant difference in the risk of infection was identified between the 2 groups.

CONCLUSION

Intravenous steroids may be associated with decreased pain intensity and decreased risk of nausea and vomiting during the early period following TKA. However, evidence supporting its use is limited by the low quality of and variations in dosing regimens between the included RCTs. Thus, more high-quality RCTs are needed to identify the optimal drug administration intervals for maximal pain control.

Factors Affecting Measurement of Salivary Cortisol and Secretory Immunoglobulin A in Field Studies of Athletes

AIMS

Biological and lifestyle factors, such as daily rhythm, caffeine ingestion, recent infection, and antibiotic intake, have been shown to influence measurements of salivary cortisol (SC) and secretory immunoglobulin A (sIgA). Current methodology in unsynchronized, field-based biomarker studies does not take these effects into account. Moreover, very little is known about the combined effects of biological and lifestyle factors on SC and sIgA. This study supports development of a protocol for measuring biomarkers from saliva collected in field studies by examining the individual and combined effects of these factors on SC and sIgA.

METHOD

At three time points (start of the pre-season; start of playing season; and end of playing season), saliva samples were collected from the entire squad of 45 male players of an elite Australian Football club (mean age 22.8 ± 3.5 years). At each time, point daily rhythm and lifestyle factors were determined via a questionnaire, and concentrations of both SC and sIgA via an enzyme linked immuno-sorbent (ELISA) assay of saliva samples. In addition, player times to produce 0.5 mL of saliva were recorded.

RESULTS

Analysis of covariance of the data across the three time points showed that daily rhythm had a more consistent effect than the lifestyle factors of caffeine ingestion, recent infection, and antibiotic intake on SC, but not on sIgA. Data for sIgA and SC concentrations were then adjusted for the effects of daily rhythm and lifestyle factors, and correlational analysis of the pooled data was used to examine the relative effects of these two sources of influence on sIgA and SC. With the exception of time to produce saliva, the biological measures of stress were affected by players' daily rhythms. When daily rhythm was taken into account the group of lifestyle factors did not have an additional effect.

DISCUSSION

It is recommended that future studies measuring SC and sIgA make additional adjustments for the daily rhythm, in particular time since first sight of daylight, as small measurement errors of biomarkers can confound discrimination among study participants.

Peripheral surgical wounding may induce cognitive impairment through interlukin-6-dependent mechanisms in aged mice

Post-operative cognitive dysfunction (POCD) is associated with morbidity, mortality and increased cost of medical care. However, the neuropathogenesis and targeted interventions of POCD remain largely to be determined. We have found that the peripheral surgical wounding induces an age-dependent Aβ accumulation, neuroinflammation and cognitive impairment in aged mice. Pro-inflammatory cytokine interlukin-6 (IL-6) has been reported to be associated with cognitive impairment in rodents and humans. However, the role of IL-6 in the neuropathogenesis of POCD is unknown. We therefore employed pharmacological (IL-6 antibody) and genetic (knockout of IL-6) approach to investigate whether IL-6 contributed to the peripheral surgical wounding-induced cognitive impairment in aged mice. Abdominal surgery under local anesthesia (peripheral surgical wounding) was established in 18-month-old wild-type and IL-6 knockout mice (n = 6 to 10 in each group). Brain level of IL-6 and cognitive function in the mice were determined by western blot, ELISA at the end of procedure, and Fear Conditioning System at 7 days after the procedure. The peripheral surgical wounding increased the level of IL-6 in the hippocampus of aged wild-type, but not IL-6 knockout mice. IL-6 antibody ameliorated the peripheral surgical wounding-induced cognitive impairment in the aged wild-type mice. Finally, the peripheral surgical wounding did not induce cognitive impairment in the aged IL-6 knockout mice. These data suggested that IL-6 would be a required pro-inflammatory cytokine for the peripheral surgical wounding-induced cognitive impairment. Given this, further studies are warranted to investigate the role of IL-6 in the neuropathogenesis and targeted interventions of POCD.

Spatiotemporal Dynamics of Dexmedetomidine-Induced Electroencephalogram Oscillations

An improved understanding of the neural correlates of altered arousal states is fundamental for precise brain state targeting in clinical settings. More specifically, electroencephalogram recordings are now increasingly being used to relate drug-specific oscillatory dynamics to clinically desired altered arousal states. Dexmedetomidine is an anesthetic adjunct typically administered in operating rooms and intensive care units to produce and maintain a sedative brain state. However, a high-density electroencephalogram characterization of the neural correlates of the dexmedetomidine-induced altered arousal state has not been previously accomplished. Therefore, we administered dexmedetomidine (1mcg/kg bolus over 10 minutes, followed by 0.7mcg/kg/hr over 50 minutes) and recorded high-density electroencephalogram signals in healthy volunteers, 18–36 years old (n = 8). We analyzed the data with multitaper spectral and global coherence methods. We found that dexmedetomidine was associated with increased slow-delta oscillations across the entire scalp, increased theta oscillations in occipital regions, increased spindle oscillations in frontal regions, and decreased beta oscillations across the entire scalp. The theta and spindle oscillations were globally coherent. During recovery from this state, these electroencephalogram signatures reverted towards baseline signatures. We report that dexmedetomidine-induced electroencephalogram signatures more closely approximate the human sleep onset process than previously appreciated. We suggest that these signatures may be targeted by real time visualization of the electroencephalogram or spectrogram in clinical settings. Additionally, these signatures may aid the development of control systems for principled neurophysiological based brain-state targeting.

Activation of Complement Following Total Hip Replacement

The aim of this study was to investigate whether complement activation, via the classical and alternative pathways, occurs following a cemented total hip replacement (THR) surgery due to osteoarthritis. Blood samples were collected systematically from 12 patients - six male and six women, with a median age of 75 (range: 59-90 years) - preoperatively, 6 h post-operatively and on the first, second and third post-operative day. Total function of classical (CH50) and alternative pathways (AH50) was evaluated, along with the determination of serum concentrations of the complement proteins C3, C4, C3d, the soluble terminal complement complex (sTCC) sC5b-9, as well as C-reactive protein (CRP) and albumin. Measurements of CRP and albumin levels elucidated a marked inflammatory response following the operation. The CH50, AH50 and C3 and C4 levels were significantly lower 6 h after the surgery compared with the preoperative levels, but elevated above the preoperative levels during the following 3 days. The complement activation product C3d levels increased continually during the whole observation period, from 13.5 AU/ml (range: 8-19 AU/ml) preoperative to 20 AU/ml (range: 12-34 AU/ml) on the third post-operative day. Furthermore, we observed an increase in the sC5b-9 levels between the preoperative and the third post-operative day. These results demonstrate a significant activation of the complement system following cemented THR. Further studies are needed to elucidate the time frame and the pathogenic role of this observed complement activation.

Routine clinical markers of the magnitude of the systemic inflammatory response after elective operation: a systematic review

BACKGROUND

Operative injury to the body from all procedures causes a stereotypical cascade of neuroendocrine, cytokine, myeloid, and acute phase responses. This response has been examined commonly by the use of cortisol, interleukin-6 (IL-6), white cell count, and C-reactive protein (CRP). We aimed to determine which markers of the systemic inflammatory response were useful in determining the magnitude of injury after elective operations.

METHODS

A systematic review of the literature was performed using surgery, endocrine response, systemic inflammatory response, cortisol, IL-6, white cell count, and CRP. For each analyte the studies were grouped according to whether the operative injury was considered to be minor, moderate, or major and then by the operative procedure.

RESULTS

A total of 164 studies were included involving 14,362 patients. The IL-6 and CRP responses clearly were associated with the magnitude of operative injury and the invasiveness of the operative procedure. For example, the peak CRP response increased from 52 mg/L with cholecystectomy to 123 mg/L with colorectal cancer resection, 145 mg/L with hip replacement, 163 mg/L after abdominal aortic aneurysm repair, and 189 mg/L after open cardiac surgery. There also appeared to be a difference between minimally invasive/laparoscopic and open procedures such as cholecystectomy (27 vs 80 mg/L), colorectal cancer resection (97 vs 133 mg/L), and aortic aneurysm repair (132 vs 180 mg/L).

CONCLUSION

Peak IL-6 and CRP concentrations consistently were associated with the magnitude of operative injury and operative procedure. These markers may be useful in the objective assessment of which components of Enhanced Recovery after Surgery are likely to improve patient outcome and to assess the possible impact of operative injury on immune function.

Investigation of Effects of Epidural Anaesthesia Combined with General Anaesthesia on the Stress Response in Patients Undergoing Hip and Knee Arthroplasty

OBJECTIVE

To investigate the effects of general anaesthesia and general+epidural anaesthesia on the stress response which was evaluated with the adrenocorticotrophic hormone (ACTH), cortisol, insulin, and glucose levels and the haemodynamic parameters.

METHODS

Forty two, American Society of Anesthesiologists physiologic status I-II, patients undergoing hip and knee arthroplasty were randomized into two groups; general anaesthesia (Group G) and general anaesthesia+epidural anaesthesia (Group E). Epidural anaesthesia: patients in Group E received epidural anaesthesia with 0.5% bupivacaine, a lumbar epidural catheter was placed and after achieving sensorial block at T10 dermatome, general anaesthesia was commenced. General anaesthesia was standardized in both groups. Further, plasma ACTH, cortisol, insulin and glucose levels were determined at preoperative=t1, after the surgical incision=t2, postoperative 2(nd) hour=t3 and postoperative 24(th) hour=t4. Perioperative heart rate, blood pressures, pain scores and morphine consumption were also determined.

RESULTS

ACTH levels were higher in Group G than Group E [Group G, t2: 71.4±39.9 pg mL(-1), t3: 578.6±566.1 pg mL(-1), Group E, t2: 20.2±16.2 pg mL(-1), t3: 56.3±73.6 pg mL(-1) (p<0.001)]. Cortisol, was higher in Group G compared with Group E [Group G, t3: 33.4±13.1 μg dL(-1), t4: 34.1±22.5 μg dL(-1), Group E, t3: 19.1±10.3 μg dL(-1), t4: 21.3±8.1 μg dL(-1) (p=0.001 and p=0.002)]. The insulin levels were higher compared with the baseline values at t3, and glucose was higher at t3 and t4 in both groups. Haemodynamic parameters were stable in Group E, and pain scores and morphine consumption were higher in Group G than in Group E.

CONCLUSION

Our results suggest that epidural anaesthesia combined with general anaesthesia suppressed the stress response, which was evaluated with ACTH, cortisol levels and haemodynamic parameters; however, this method was ineffective to attenuate the increase in glucose and insulin levels.

Steroid modulation of cytokine release and desmosine levels in bilateral total knee replacement: a prospective, double-blind, randomized controlled trial

BACKGROUND

The perioperative inflammatory response as measured by elevated levels of interleukin-6 (IL-6) has been linked to acute respiratory distress syndrome, postoperative confusion, and fever. Because of the extent of surgery,patients undergoing bilateral total knee arthroplasty may be at high risk of complications. We had found a significant decrease in IL-6 in patients having bilateral total knee replacement who received two doses of 100 mg of hydrocortisone eight hours apart; however, by twenty-four hours, IL-6 levels were equal to those in the group that received a placebo. In the present study, we investigated whether the administration of three doses would reduce IL-6 levels at twenty-four hours and affect other outcomes such as desmosine level, a marker of lung injury.

METHODS

After institutional review board approval, a total of thirty-four patients (seventeen patients and seventeen control subjects) were enrolled in this double-blind, randomized, placebo-controlled study. Three doses of intravenous hydrocortisone (100 mg) or placebo were given eight hours apart. Urinary desmosine levels were obtained at baseline and at one and three days postoperatively. The level of IL-6 was measured at baseline and at six, ten, twenty-four, and forty-eight hours postoperatively. Pain scores, presence of fever, and functional outcomes were recorded.

RESULTS

The level of IL-6 increased in both groups, but was significantly higher in the control group, peaking at twenty-four hours (mean and standard deviation, 623.74 ± 610.35 pg/mL versus 148.13 ± 119.35 pg/mL; p = 0.006). Urinary desmosine levels significantly increased by twenty-four hours in the control group, but remained unchanged in the study group (134.75 ± 67.88 pmol/mg and 79.45 ± 46.30 pmol/mg, respectively; p = 0.006). Pain scores at twenty-four hours were significantly lower in the study group (1.4 ± 0.9 versus 2.4 ± 1.2; p = 0.01) as was the presence of fever (11.8%versus 47.1%; p = 0.03). Range of motion at the knee was significantly greater in the study group (81.6 ± 11.6 versus 70.6 ± 14.0 in the right knee [p = 0.02] and 81.4 ± 11.3 versus 73.4 ± 9.4 in the left knee [p = 0.03]).

CONCLUSIONS

Hydrocortisone (100 mg) given over three doses, each eight hours apart, decreased and maintained a lower degree of inflammation with bilateral total knee replacement as measured by IL-6 level. Corticosteroids decreased the prevalence of fever, lowered visual analog pain scores, and improved knee motion. The significantly lower values of desmosine in the study group suggest that this treatment may be protective against lung injury.

Interleukin-18-induced inflammatory responses in synoviocytes and chondrocytes from osteoarthritic patients

The major pathological changes of osteoarthritis (OA) include cartilage degeneration and synovial inflammation. Previous studies confirmed that interleukin-1 (IL-1) stimulates the secretion of multiple inflammatory factors in synoviocytes and chondrocytes. IL-18 is a member of the IL-1 superfamily. In this study, the pro-inflammatory effects of IL-18 on synoviocytes and chondrocytes in patients with OA were investigated. Knee synovial membrane and cartilage samples were obtained from OA patients, then primary cells were cultured. Synoviocytes and primary chondrocytes at different generations (primary, secondary and tertiary), were stimulated with IL-18, then inflammatory marker levels, including tumor necrosis factor-α (TNF-α), prostaglandin E2 (PGE₂) and cyclooxygenase-2 (COX-2), were measured using reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay. IL-1 receptor antagonist (IL-1Ra) was applied to interfere with the IL-18 stimulation of chondrocytes, and then the COX-2 expression in chondrocytes and the PGE2 levels in the medium were measured. The expression of IL-18 receptor α (IL-18Rα) and IL-18 receptor β (IL-18Rβ) in synoviocytes and chondrocytes was assessed, using RT-PCR. Our results showed that IL-18 stimulated the COX-2 and TNF-α expressions in primary synoviocytes, while increasing PGE₂ and TNF-α levels in the supernatant (P<0.05) of the culture medium in primary synoviocytes. IL-18 also induced high PGE₂ level production in second-generation synoviocytes (P<0.05). Moreover, IL-18 upregulated COX-2 and TNF-α mRNA in chondrocytes, while promoting PGE₂ and TNF-α (P<0.05) secretions in a dose-dependent manner. The induced effects were not attenuated by the addition of IL-1Ra (P<0.05). IL-18Rα was expressed in the chondrocytes and synoviocytes of 4/8 patients, while IL-18Rβ was expressed in the chondrocytes of 4/8 patients and in the synoviocytes of 2/8 patients. We conclude that IL-18 induces inflammatory responses in synoviocytes and chondrocytes and that this effect was correlated with, although not entirely dependent on, IL-1β.

Use of low-dose steroids in decreasing cytokine release during bilateral total knee replacement

BACKGROUND

Interleukin 6 (IL-6), a marker of inflammation, is one of the major cytokines released during joint replacement. In the orthopedic patient population, high levels have been linked to many adverse effects including acute respiratory distress syndrome, postoperative mental status changes, and fever. We looked to assess the efficacy of low-dose steroids on the postinflammatory response as measured by IL-6 in patients undergoing bilateral total knee replacement (BTKR). The role of steroids has never been evaluated before in that setting.

METHODS

Double-blind, randomized, placebo-controlled study of 30 patients undergoing BTKR. The study was powered in order to detect at least a 25% decrease in IL-6 from control. Hydrocortisone (100 mg) or placebo was given at 2 doses 8 hrs apart to the study and control group respectively. Clinical outcome was assessed as well.

RESULTS

Levels of IL-6 were 40% lower in the study group by 10 hrs (P = 0.0037) but were similar to the control group at 24 hrs. Greater hemodynamic stability was noted in the study group with fewer episodes of hypotension postoperatively (P = 0.031). Range of motion gained on discharge was also greatest in the study group (P = 0.049). Absence of infection and normal wound healing were noted in all patients.

CONCLUSIONS

The use of hydrocortisone significantly decreased the inflammatory response in patients undergoing BTKR as measured by IL-6 production. Further studies looking at clinical implications of such findings in a larger patient population and with a longer course of steroids are warranted.

LBP and sCD14 patterns in total hip replacement surgery performed during combined spinal/epidural anaesthesia

BACKGROUND

Danger patterns and pattern recognition receptors have been targets in the investigation and treatment of systemic inflammatory response syndrome and sepsis. Lipopolysaccharide (LPS)-binding protein (LBP) presents LPS and gram-positive bacterial cell wall products to the receptors TLR4/MD-2 and TLR2, respectively. Low concentrations of LBP stimulate responses to LPS and peptidoglycan, whereas higher concentrations inhibit these responses. Soluble CD14 (sCD14) presents the LBP-LPS complex to CD14-negative cells, and it modulates the biological activity of circulating LPS. In this study, we aimed to elucidate the physiological reactions to LBP and sCD14 after total hip replacement surgery during spinal/epidural anaesthesia.

METHODS

Seven patients with coxarthrosis were operated upon with a total hip replacement, which is a defined trauma to bone and muscles in conjunction with a certain amount of blood loss. Venous blood samples were taken before the operation and at 1 h, 3 days and 6 days after surgery. LBP and sCD14 were measured by conventional ELISA. To correct for hemodilution, each parameter was adjusted for hematocrit. A panel of cytokines was measured using Luminex technology to evaluate the trauma reaction.

RESULTS

IL-6 levels peaked 24 h after the operation, whereas IL-1β and IL-10 levels remained unchanged. Systemic levels of LBP were increased 24 h after surgery, whereas sCD14 remained steady. However, the dilution-corrected sCD14 values increased significantly, and the levels of both LBP and sCD14 peaked at day 3 after surgery.

CONCLUSION

Aseptic trauma primes the innate immune system for the posttraumatic release of LBP and sCD14.

Antimicrobial anxiety: the impact of stress on antimicrobial immunity

Leukocytes and epithelial cells are fundamental to antimicrobial immunity. Their antimicrobial responses are an evolutionarily conserved component of the innate immune system and are influenced by the host's response to external stimuli. The efficacy of host defense via antimicrobial responses derives from the ability of AMPs to rapidly identify and eradicate foreign microbes and activate proinflammatory pathways, and from the capacity of later innate and adaptive immune responses to amplify protection through distinct biochemical mechanisms. Recent advances in neuroimmunology have identified a direct link between the neuroendocrine and immune systems, where environmental stimuli are generally believed to promote a transient effect on the immune system in response to environmental challenges and are presumably brought back to baseline levels via neuroendocrine pathways. Stress is an environmental stimulus that flares from a variety of circumstances and has become engrained in human society. Small bouts of stress are believed to enhance the host's immune response; however, prolonged periods of stress can be detrimental through excess production of neuroendocrine-derived mediators that dampen immune responses to invasive pathogens. Elucidation of the mechanisms behind stress-induced immune modulation of antimicrobial responses will ultimately lead to the development of more effective therapeutic interventions for pathologic conditions. It is the intent of this review to broaden the existing paradigm of how stress-related molecules dampen immune responses through suppression of antimicrobial mechanisms, and to emphasize that bacteria can use these factors to enhance microbial pathogenesis during stress.

The neuroinflammatory hypothesis of delirium

Delirium is a neuropsychiatric syndrome characterized by a sudden and global impairment in consciousness, attention and cognition. It is particularly frequent in elderly subjects with medical or surgical conditions and is associated with short- and long-term adverse outcomes. The pathophysiology of delirium remains poorly understood as it involves complex multi-factorial dynamic interactions between a diversity of risk factors. Several conditions associated with delirium are characterized by activation of the inflammatory cascade with acute release of inflammatory mediators into the bloodstream. There is compelling evidence that acute peripheral inflammatory stimulation induces activation of brain parenchymal cells, expression of proinflammatory cytokines and inflammatory mediators in the central nervous system. These neuroinflammatory changes induce neuronal and synaptic dysfunction and subsequent neurobehavioural and cognitive symptoms. Furthermore, ageing and neurodegenerative disorders exaggerate microglial responses following stimulation by systemic immune stimuli such as peripheral inflammation and/or infection. In this review we explore the neuroinflammatory hypothesis of delirium based on recent evidence derived from animal and human studies.