Objective: Circadian rhythms are frequently disrupted in patients in the intensive care unit (ICU), potentially worsening clinical outcomes. Continuous enteral nutrition throughout the day and night is common in the ICU, but eliminates feeding-fasting cycles that serve as important timing cues for the circadian system. The objective of this study was to determine the effect of providing enteral nutrition in a cyclic daytime pattern, compared with continuous administration, on circadian rhythmicity in critically ill patients in the ICU. Design: Single-center randomized controlled trial Setting: Mixed medical-surgical tertiary intensive care unit in the Netherlands Patients: Adult ICU patients (≥18 yr) receiving enteral nutrition. Intervention: Patients were randomized to receive either continuous, or cyclic daytime enteral feeding (08:00-20:00), initiated from the start of nutritional support. Measurements and Main Results: Sixty-two ICU patients were enrolled, of whom 51 were included in the per-protocol analysis. While the amplitude of the 24-hour rhythm in core body temperature did not differ significantly between the cyclic daytime and continuous feeding groups (0.17 [interquartile range: 0.09-0.24] vs. 0.20 [0.13-0.30], p=0.182), the 24-hour rhythm in heart rate was enhanced in patients receiving cyclic daytime feeding, as reflected by significantly higher amplitudes and more synchronized peak times. No significant differences in 24-hour rhythmicity were observed between groups for the other vital signs or melatonin. Conclusions: Our findings suggest that cyclic daytime feeding may strengthen circadian rhythms in critically ill patients. Further studies are warranted to evaluate its impact on clinical outcomes. ### Competing Interest Statement Hassan S. Dashti is a scientific consultant for Eli Lilly & Co, which is unrelated to this work. All other authors declare that no conflict of interest exists. ### Clinical Trial NCT05795881 ### Clinical Protocols ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethical approval for the trial has been granted by the local medical ethics committee of Leiden, Den Haag, and Delft in the Netherlands (P22.080; date of approval: 9 December 2022). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Deidentified individual participant data that underlie the results reported in this article and the statistical code are available from the corresponding author upon reasonable request, subject to approval and a data sharing agreement. ZonMw, The Dutch Organisation for knowledge and innovation in health, healthcare and well-being, 2020–09150161910128 Dutch Research Council, 1292.19.077 Dutch Society for Intensive Care, Research Grant 2022 Leiden University Medical Center, PhD project grant

BACKGROUND:Circadian rhythms and sleep are often disrupted in critically ill patients in the intensive care unit (ICU), which has been linked to poor clinical outcomes. Feeding-fasting cycles serve as a synchronizing cue for the circadian timing system, indicating that optimizing these cycles in the ICU could reinforce circadian rhythms. The CIRCLES trial evaluates whether cyclic daytime enteral nutrition improves 24-h rhythms in critically ill patients compared to continuous enteral nutrition. OBJECTIVE:To describe the study protocol for the CIRCLES study. STUDY DESIGN:The CIRCLES study is an investigator-initiated randomized controlled trial in a tertiary care ICU in the Netherlands. Patients (aged ≥18 years) admitted to the ICU with an expected stay ≥48 h receiving or with intention to start enteral nutrition are eligible for inclusion. Patients (n = 60) are randomized to the continuous enteral nutrition (nutrition around the clock) or cyclic daytime enteral nutrition group (nutrition between 08:00 h to 20:00 h). MAIN OUTCOME MEASURES:The primary outcome is the amplitude of 24-h rhythms in core body temperature. Secondary outcomes include 24-h rhythms in heart rate, mean blood pressure heart rate variability, melatonin and gene expression, glucose regulation, insulin administration, caloric intake and feeding intolerance. CONCLUSION:We hypothesize that a cyclic daytime feeding strategy will result in a higher amplitude of 24-h rhythms in vital signs, heart rate variability, and melatonin, compared to continuous feeding, thereby suggesting improved circadian rhythm strength. This study aims to provide insight into strategies to optimize circadian rhythms in ICU patients. TRIAL REGISTRATION:Registered at ClinicalTrials.gov (NCT05795881), April 2023.

BACKGROUND:Circadian rhythms are often severely disrupted in critically ill patients in the ICU. The ICU environment, characterized by irregular light-dark signals, continuous nutrition, and round-the-clock interventions, contributes to this disruption by providing weak and conflicting timing cues to the circadian system. Extensive scientific research has demonstrated that circadian rhythms play a vital role in regulating physiology and maintaining overall health. Therefore, integrating circadian principles into critical care may represent a promising strategy to improve patient outcomes in the ICU. RESEARCH QUESTION:What are the key challenges of integrating circadian medicine into critical care, what steps can address these challenges, and which recommendations can guide future study designs and clinical implementation? STUDY DESIGN AND METHODS:We convened a 5-day workshop in September 2024 that brought together 24 international experts with backgrounds in circadian biology, critical care, and implementation science. Each day was organized around a predefined theme, with morning presentations and plenary discussions, and afternoons dedicated to drafting a list of Propositions and Recommendations in breakout groups. Propositions and Recommendations were finalized via a post-workshop survey requiring ≥ 75% agreement. RESULTS:This roadmap summarizes the discussions and outcomes of the workshop, structured around a set of Propositions and Recommendations, and provides a framework for building a robust evidence base for integrating circadian principles into ICU practice. Key recommendations include the development of circadian outcome measures tailored for use in the ICU and using standardized frameworks for evaluating the effect of circadian interventions in clinical trials. INTERPRETATION:Altogether, this roadmap provides an interdisciplinary framework resulting from a collaborative effort of ICU clinicians, circadian biologists, and implementation specialists, for building a robust evidence base for integrating circadian principles into ICU research and practice.

Objectives To investigate which patient characteristics, ultrasound operator certification level, and thoracic ultrasound (TUS) examination findings are associated with a TUS-induced change in clinical management in adult intensive care unit (ICU) patients.Design Post hoc analysis of a prospective international observational study (UltraMan study) on the impact of thoracic ultrasound on clinical management of critically ill patients. The first TUS examinations of each patient included in the study were included in this analysis. Multivariable logistic regression was performed to identify which patient characteristic(s), operator certification level, or TUS-related factors were significantly associated with a change in management.Interventions None.Measurements and Main Results The first TUS examinations of each of the 534 patients were included in this analysis. TUS led to management changes in almost half of the patients in whom a TUS was performed (44.6%). TUS-induced management changes were significantly associated with patient characteristics. Specifically, a medical history of cardiovascular disease demonstrated a significant association (OR: 1.73; 95% CI: 1.12-2.68). In terms of TUS examination findings, hypovolemia demonstrated a significant association with a change in management (OR: 2.05; 95% CI: 1.10-3.80). No significant association was found between ultrasound operator certification level and changes in management driven by TUS.Conclusions This study indicates that TUS was associated with management changes in 44.6% of ICU patients, with stronger associations in those with cardiovascular disease and hypovolemia, and no detectable effect of operator certification in adjusted analyses. As a post hoc analysis of an observational cohort, these findings warrant cautious interpretation and underscore the importance of competency-based training and quality assurance.

BACKGROUND:Vivid dream experiences in the intensive care unit (ICU) are common, but poorly understood. AIM:We investigated the occurrence, vividness, content, emotional impact and associated factors of dream experiences in the ICU. STUDY DESIGN:Retrospective mixed methods study with subjects ≥ 18 years, previously admitted to the ICU for ≥ 4 days and/or due to COVID-19, who were not sedated for ≥ 24 h during their stay (n = 80). Participants answered a retrospective questionnaire by telephone. Clinical data were collected from electronic health records. RESULTS:The questionnaires were taken a median of 9 months post-discharge. Dream experiences were reported by 79%. Of participants who recollected dream experiences, 73% reported "life-like" dreams, 49% associated their dreams with negative emotions and 54% said their dreams impacted them even after awaking. Some participants (28.6%) continued to have similar dreams at home. After being asked if they had additional comments, some participants suggest receiving information during their hospital stay about the potential for vivid dream experiences could be beneficial. The dream content was often related to the ICU admission. Younger age and longer length of stay were related to vivid dream experiences. Of participants with dream experiences 62.5% had experienced delirium during their ICU stay. Perceptual disturbances were also frequently reported by participants (50%) and only 45% could clearly distinguish them from dream experiences. There was an overlap between participants reporting perceptual disturbances and confirmed delirium (70%). CONCLUSIONS:Vivid dream experiences are common in ICU patients and often have a negative emotional impact. Future studies should dive deeper into effective ways to distinguish dreams, delirium and perceptual disturbances and how to reduce their impact. RELEVANCE TO CLINICAL PRACTICE:ICU nurses should be aware of the occurrence and psychological burden of vivid negative dreams in ICU patients. Providing anticipatory support may help patients process these experiences during recovery.

Continuous venovenous hemofiltation (CVVH) with citrate anticoagulation has been shown to be associated with substantial losses of calcium and negative calcium balance in ICU patients, which may lead to excessive bone loss and osteoporosis. The aim of this study is to investigate whether plasma parathormone monitoring can identify patients with negative calcium balance during CVVH. This is a retrospective single-center study of all adult ICU patients treated with citrate CVVH from 2021 to 2023. PTH was measured routinely once per week. Calcium excretion in ultrafiltrate fluid and CVVH calcium balance were measured daily. In total, 274 PTH measurements were performed in 111 patients. In 61 measurements (22%), PTH was higher than the upper limit of normal (>8 pmol/L). If PTH was higher than normal, plasma ionized calcium was less than 1.16 mmol/L in 77% of cases and hypercalcemia was never present. In a subgroup of patients treated with CVVH for at least 36 h in the preceding 72 h, PTH values were similar for quartiles by cumulative calcium balance. Increased plasma concentrations of PTH are frequently found in ICU patients treated with citrate CVVH, but no association was found between PTH and the CVVH calcium balance over the last 72 h.

BACKGROUND: Estimating central venous pressure (CVP) is essential in the diagnostic evaluation and treatment guidance of most hospitalized patients. It is unknown how different noninvasive bedside methods to estimate CVP correlate with each other and which method has the best accuracy. RESEARCH QUESTION: Which noninvasive bedside method to estimate CVP has the best accuracy to detect elevated CVP? STUDY DESIGN AND METHODS: During this prospective, single-center, observational study, we included patients admitted to the ward or ICU who already had an indwelling central venous catheter and who did not undergo positive pressure ventilation. We measured height of the fl fluid column in the external jugular vein (EJV) according to the Lewis and Borst method (EJV height), maximum and minimum diameters and height of the fl fluid column of the internal jugular vein (IJV; IJV height) using ultrasound, and diameters of the inferior vena cava (IVC) throughout a respiratory cycle and sniffing. We then compared these measurements with intravenously measured CVP. RESULTS: Ninety patients were included. Twenty-seven patients (30%) showed CVP of >= 10 mm Hg. All measurements had a significant correlation with CVP, except for the diameter of the IJV. Areas under the receiver operating characteristic curve for IJV height, EJV height, maximum diameter, and collapsibility on inspiration of the IVC were 0.85, 0.80, 0.78, and 0.76 respectively. The interobserver agreement was good to excellent. We estimated continuous likelihood ratios for the measurements to aid clinical decision-making. INTERPRETATION: Our results indicated that EJV height, IJV height, IVC diameter, and IVC collapsibility can be used to identify an elevated CVP in hospitalized patients. Among these, ultrasonographic estimation of the height of the fl fluid column in the IJV is quick and easy and allows identification of an elevated CVP with the best reproducibility and accuracy. CLINICAL TRIAL REGISTRATION: National Trial Register; ID: NL-OMON22937; URL: https:// onderzoekmetmensen.nl/en/trial/22937

Background The circadian timing system coordinates daily cycles in physiological functions, including glucose metabolism and insulin sensitivity. Here, the aim was to characterise the 24-h variation in glucose levels in critically ill patients during continuous enteral nutrition after controlling for potential sources of bias. Methods Time -stamped clinical data from adult patients who stayed in the Intensive Care Unit (ICU) for at least 4 days and received enteral nutrition were extracted from the Medical Information Mart for Intensive Care (MIMIC) -IV database. Linear mixed -effects and XGBoost modelling were used to determine the effect of time of day on blood glucose values. Findings In total, 207,647 glucose measurements collected during enteral nutrition were available from 6,929 ICU patients (3,948 males and 2,981 females). Using linear mixed -effects modelling, time of day had a significant effect on blood glucose levels (p < 0.001), with a peak of 9.6 [9.5 - 9.6; estimated marginal means, 95% CI] mmol/L at 10:00 in the morning and a trough of 8.6 [8.5 - 8.6] mmol/L at 02:00 at night. A similar impact of time of day on glucose levels was found with the XGBoost regression model. Interpretation These results revealed marked 24-h variation in glucose levels in ICU patients even during continuous enteral nutrition. This 24-h pattern persists after adjustment for potential sources of bias, suggesting it may be the result of endogenous biological rhythmicity.

Aim of the study: The primary purpose was to examine sleep difficulties and delirium in the Intensive and Intermediate Care Unit. Secondarily, factors impacting night -time sleep duration and quality, mortality, and the impact of benzodiazepine use on sleep outcomes were investigated. Materials and methods: This retrospective study encompassed data from 323 intensive and intermediate care unit admissions collected in the Netherlands, spanning from November 2018 to May 2020. Sleep quality was measured using the Richards-Campbell Sleep Questionnaire. Night -time sleep duration was nurse-reported. We investigated associations of these sleep outcomes with age, sex, length-of-stay, natural daylight, disease severity, mechanical ventilation, benzodiazepine use, and delirium using Generalized Estimating Equations models. Associations with one-year post-discharge mortality were analyzed using Cox regression. Results: Night -time sleep duration was short (median 4.5 hours) and sleep quality poor (mean score 4.9/10). Benzodiazepine use was common (24 % of included nights) and was negatively associated with night -time sleep duration and quality (B = -0.558 and -0.533, p <.001). Delirium and overnight transfers were negatively associated with sleep quality (B = -0.716 and -1.831, p <.05). The day -to -night sleep ratio was higher in the three days before delirium onset than in non-delirious individuals (p <.05). Age, disease severity and female sex were associated with increased one-year mortality. Sleep quality was negatively, but not-significantly, associated with mortality (p =.070). Conclusions: Night -time sleep in the critical care environment has a short duration and poor quality. Benzodiazepine use was not associated with improved sleep. Sleep patterns change ahead of delirium onset. Implications for clinical practice: Consistent sleep monitoring should be part of routine nursing practice, using a validated instrument like the Richards-Campbell Sleep Questionnaire. Given the lack of proven efficacy of benzodiazepines in promoting sleep in critical care settings, it is vital to develop more effective sleep treatments that include non-benzodiazepine medication and sleep hygiene strategies.

The primary aim of this study was to evaluate computed tomography (CT)-based bone density analysis at the level of thoracic vertebra 12 (Th12) as a screening method for decreased bone density in patients admitted to the intensive care unit (ICU). Interobserver variability was analyzed. Secondary aims were to assess the prevalence of CT-based low bone density upon ICU admission in a cohort of COVID-19 patients and to assess the potential effect of long-term ICU stay on bone density in these patients. Retrospective single-center cohort study. ICU of the Leiden University Medical Center (LUMC), the Netherlands. Patients admitted to the ICU of the LUMC between March 1st, 2020 and February 1st, 2022 with a diagnosis of COVID-19, and a length of ICU stay of ≥ 21 days. In the included patients both baseline chest CT scans (obtained upon ICU admission) and follow-up chest CT scans (obtained ≥ 21 days after ICU admission) were available for analysis. A total of 118 CT scans in 38 patients were analyzed. There was a good interobserver variability, with an overall mean absolute difference (between measurements of three observers) of 9.7 Hounsfield Units (HU) and an intraclass correlation coefficient (ICC) of 0.93 (95% CI 0.88-0.96). The effect of intravenous contrast administration on bone density measurements was small (+ 7.5 HU (95% CI 3.4-11.5 HU)) higher in contrast enhanced CT images compared to non contrast enhanced CT images). Thirty-seven percent of patients had a bone density < 140 HU, suggestive of osteoporosis. No significant difference was found between bone density upon ICU admission and bone density at follow-up (≥ 21 days after ICU admission). Vertebral CT-based bone density analysis using routine CT scans is an easily applicable method to identify ICU patients with decreased bone density, which could enable enrollment in osteoporosis prevention programs. A high prevalence of low bone density was found in our cohort of ICU patients. There were no changes observed in bone density between baseline and follow-up measurements.

OBJECTIVES: Deferred consent enables research to be conducted in the ICU when patients are unable to provide consent themselves, and there is insufficient time to obtain consent from surrogates before commencing (trial) treatment. The aim of this study was to evaluate how former ICU patients reflect on their participation in a study with deferred consent and examine whether their opinions are influenced by the quality of life (QoL) following hospital discharge. DESIGN: Survey study by questionnaire. SETTING: Eight ICUs in The Netherlands. PATIENTS: Former ICU patients who participated in the ICONIC trial, a multicenter randomized clinical trial that evaluated oxygenation targets in mechanically ventilated ICU patients. INTERVENTIONS: Participants enrolled in the ICONIC trial in one of the eight participating centers in The Netherlands received a questionnaire 6 months after randomization. The questionnaire included 12 close-ended questions on their opinion about the deferred consent procedure. QoL was measured using the EQ-5D-5L questionnaire. By calculating the EQ-5D index, patients were divided into four QoL quartiles, where Q1 reflects the lowest and Q4 is the highest. MEASUREMENTS AND MAIN RESULTS: Of 362 participants who were contacted, 197 responded (54%). More than half of the respondents (59%) were unaware of their participation in the ICONIC study. In total 61% were content with the deferred consent procedure, 1% were not content, 25% neutral, 9% did not know, and 9% answered “other.” Those with a higher QoL were more likely to be content (p = 0.02). In all QoL groups, the legal representative was the most often preferred individual to provide consent. CONCLUSIONS: Former ICU patients who participated in the ICONIC study often did not remember their participation but were predominantly positive regarding the use of deferred consent. Those with a higher QoL were most likely to be content.

OBJECTIVES:To investigate the impact of thoracic ultrasound (TUS) examinations on clinical management in adult ICU patients.DESIGN:A prospective international observational study.SETTING:Four centers in The Netherlands and Italy.PATIENTS:Adult ICU patients (> 18 yr) that received a clinically indicated lung ultrasound examination.INTERVENTIONS:None.MEASUREMENTS AND MAIN RESULTS:Clinicians performing TUS completed a pre- and post-examination case report form. Patient characteristics, TUS, and resulting clinical effects were recorded. First, change of management, defined as a TUS-induced change in clinical impression leading to a change in treatment plan, was reported. Second, execution of intended management changes within 8 hours was verified. Third, change in fluid balance after 8 hours was calculated. A total of 725 TUS performed by 111 operators across 534 patients (mean age 63 ± 15.0, 70% male) were included. Almost half of TUS caused a change in clinical impression, which resulted in change of management in 39% of cases. The remainder of TUS confirmed the clinical impression, while a minority (4%) did not contribute. Eighty-nine percent of management changes indicated by TUS were executed within 8 hours. TUS examinations that led to a change in fluid management also led to distinct and appropriate changes in patient's fluid balance.CONCLUSIONS:In this international observational study in adult ICU patients, use of TUS had a major impact on clinical management. These results provide grounds for future randomized controlled trials to determine if TUS-induced changes in decision-making also lead to improved health outcomes.

Background Fluid therapy is a common intervention in critically ill patients. It is increasingly recognised that deresuscitation is an essential part of fluid therapy and delayed deresuscitation is associated with longer invasive ventilation and length of intensive care unit (ICU) stay. However, optimal timing and rate of deresuscitation remain unclear. Lung ultrasound (LUS) may be used to identify fluid overload. We hypothesise that daily LUS-guided deresuscitation is superior to deresuscitation without LUS in critically ill patients expected to undergo invasive ventilation for more than 24 h in terms of ventilator free-days and being alive at day 28. Methods The “effect of lung ultrasound-guided fluid deresuscitation on duration of ventilation in intensive care unit patients” (CONFIDENCE) is a national, multicentre, open-label, randomised controlled trial (RCT) in adult critically ill patients that are expected to be invasively ventilated for at least 24 h. Patients with conditions that preclude a negative fluid balance or LUS examination are excluded. CONFIDENCE will operate in 10 ICUs in the Netherlands and enrol 1000 patients. After hemodynamic stabilisation, patients assigned to the intervention will receive daily LUS with fluid balance recommendations. Subjects in the control arm are deresuscitated at the physician’s discretion without the use of LUS. The primary endpoint is the number of ventilator-free days and being alive at day 28. Secondary endpoints include the duration of invasive ventilation; 28-day mortality; 90-day mortality; ICU, in hospital and total length of stay; cumulative fluid balance on days 1–7 after randomisation and on days 1–7 after start of LUS examination; mean serum lactate on days 1–7; the incidence of reintubations, chest drain placement, atrial fibrillation, kidney injury (KDIGO stadium ≥ 2) and hypernatremia; the use of invasive hemodynamic monitoring, and chest-X-ray; and quality of life at day 28. Discussion The CONFIDENCE trial is the first RCT comparing the effect of LUS-guided deresuscitation to routine care in invasively ventilated ICU patients. If proven effective, LUS-guided deresuscitation could improve outcomes in some of the most vulnerable and resource-intensive patients in a manner that is non-invasive, easy to perform, and well-implementable. Trial registration ClinicalTrials.gov NCT05188092. Registered since January 12, 2022

Rationale Supplemental oxygen is widely administered to ICU patients, but appropriate oxygenation targets remain unclear. Objectives This study aimed to determine whether a low-oxygenation strategy would lower 28-day mortality compared with a high-oxygenation strategy. Methods This randomized multicenter trial included mechanically ventilated ICU patients with an expected ventilation duration of at least 24 hours. Patients were randomized 1:1 to a low-oxygenation (PaO2, 55–80 mm Hg; or oxygen saturation as measured by pulse oximetry, 91–94%) or high-oxygenation (PaO2, 110–150 mm Hg; or oxygen saturation as measured by pulse oximetry, 96–100%) target until ICU discharge or 28 days after randomization, whichever came first. The primary outcome was 28-day mortality. The study was stopped prematurely because of the COVID-19 pandemic when 664 of the planned 1,512 patients were included. Measurements and Main Results Between November 2018 and November 2021, a total of 664 patients were included in the trial: 335 in the low-oxygenation group and 329 in the high-oxygenation group. The median achieved PaO2 was 75 mm Hg (interquartile range, 70–84) and 115 mm Hg (interquartile range, 100–129) in the low- and high-oxygenation groups, respectively. At Day 28, 129 (38.5%) and 114 (34.7%) patients had died in the low- and high-oxygenation groups, respectively (risk ratio, 1.11; 95% confidence interval, 0.9–1.4; P = 0.30). At least one serious adverse event was reported in 12 (3.6%) and 17 (5.2%) patients in the low- and high-oxygenation groups, respectively. Conclusions Among mechanically ventilated ICU patients with an expected mechanical ventilation duration of at least 24 hours, using a low-oxygenation strategy did not result in a reduction of 28-day mortality compared with a high-oxygenation strategy. Clinical trial registered with the National Trial Register and the International Clinical Trials Registry Platform (NTR7376).

Background: Systemic infection is an important risk factor for delirium, associated with neurodegeneration and subsequent cognitive impairment in older people. Microglial cell response is a known key player in this process and we hypothesize that the triggering receptor expressed on myeloid cells 2 (TREM2) plays an important role in the regulation of this response. Methods: 8- to 10-week old male wild-type (WT) and TREM2 knock-out (Trem2-/-) mice were intraperitoneally inoculated with live Escherichia coli (E. coli) or saline. After inoculation, all mice were treated with ceftriaxone (an antimicrobial drug) at 12 and 24 h and were sacrificed after 2 and 3 days. Microglial response was determined by immunohistochemical staining with an ionized calcium-binding adaptor molecule 1 (Iba-1) antibody and flow cytometry. mRNA expression of pro- and anti-inflammatory mediators was measured to quantify the inflammatory response. Results: We observed increased Iba-1 positive cells number in thalamus of Trem2-/- mice at 3d after inoculation compared to WT mice (mean 120 cell/mm2 [SD 8] vs 105 cell/mm2 [SD 11]; p = 0.03). Flow cytometry showed no differences in forward scatter or expression of CD11b, CD45 and CD14 between WT and Trem2-/- mice. The brain mRNA expression levels of tumor necrosis factor alpha (TNF-alpha) of Trem2-/- mice at 2d were higher compared to WT mice (p = 0.003). Higher mRNA expression of interleukin 1 beta (IL-1 beta), Iba-1, CD11b and mitogen-activated protein kinase 1 (MAPK-1) was found in brain of WT mice at 2d compared to Trem2-/- mice (respectively p = 0.02; p = 0.001; p = 0.03 and p = 0.02). In spleen there were no differences in inflammatory mediators, between WT and Trem2-/- mice. Interpretation: Although the loss of function of TREM2 during systemic infection led to an increased number of activated microglia in the thalamus, we did not observe a consistent increase in expression of inflammatory genes in the brain. The role of TREM2 in the neuro-inflammatory response following systemic infection therefore appears to be limited.

PURPOSE Oxygen therapy is vital in adult intensive care unit (ICU) patients, but it is indistinct whether higher or lower oxygen targets are favorable. Our aim was to update the findings of randomized controlled trials (RTCs) comparing higher and lower oxygen strategies. MATERIALS AND METHODS MEDLINE, EMBASE, and Web of Science were searched. RCTs comparing higher (liberal, hyperoxia) and lower (conservative, normoxia) oxygen in adult mechanically ventilated ICU patients were included. The main outcome was 90-day mortality; other outcomes include serious adverse events (SAE), support free days and length of stay (LOS). RESULTS No significant difference was observed for 90-day mortality. A lower incidence was found for SAEs, favoring lower oxygenation (OR, 0.86; 95%CI, 0.77-0.96; I 2 13%). No differences were observed in either support free days at day 28 or ICU and hospital LOS. CONCLUSIONS No difference was found for 90-day mortality, support free days and ICU and hospital LOS. However, a lower incidence of SAEs was found for lower oxygenation. These findings may have clinical implications for practice guidelines, yet it remains of paramount importance to continue conducting clinical trials, comparing groups with a clinically relevant contrast and focusing on the impact of important side effects.

Abstract Background Development of neurodegeneration in older people has been associated with microglial cell activation triggered by systemic infection. We hypothesize that α7 nicotinic acetylcholine receptor (α7nAChR) plays an important role in regulation of this process. Methods 8- to 10-week-old male wild-type (WT) and α7nAChR knock-out (α7nAChR −/−) mice were intraperitoneally inoculated with live Escherichia (E.) coli or saline. After inoculation, all mice were treated with ceftriaxone (an antimicrobial drug) at 12 and 24 h and killed at 2 or 3 days. The microglial response was characterized by immunohistochemical staining with an ionized calcium-binding adaptor molecule 1 (Iba-1) antibody and flow cytometry. To quantify inflammatory response, mRNA expression of pro- and anti-inflammatory mediators was measured in brain and spleen. Results We observed no differences in Iba-1 positive cell number or morphology and flow cytometry (CD11b, CD45 and CD14) of microglial cells between WT and α7nAChR −/− mice after systemic infection. Infected α7nAChR −/− mice showed significantly higher mRNA expression in brain for tumor necrosis factor alpha (TNF-α) at day 2 and 3, interleukin 6 (IL-6) at day 2 and monocyte chemotactic protein 1 (MCP-1) and suppressor of cytokine signaling 1 (SOCS1) at day 3, there was significantly lower mRNA expression in brain for mitogen-activated protein kinase 1 (MAPK1) at day 2 and 3, high-mobility group 1 (HMGB-1) and CD11b at day 2, and deubiquitinase protein A20 (A20) at day 3 compared to infected WT mice. Interpretation Loss of function of α7nAChR during systemic infection led to an increased expression of TNF-α and IL-6 in brain after systemic infection with E. coli, but not to distinct differences in microglial cell number or morphological activation of microglia.

ABSTRACTBackgroundTocilizumab improves outcome, including survival, in intensive care unit (ICU) admitted COVID-19 patients. The currently applied dosage of 8 mg/kg is based on use of this drug for other indications, however is has not formally been investigated for COVID-19. In this study pharmacokinetics and dynamics of tocilizumab were investigated in ICU admitted COVID-19 patients.MethodsThis was an open-label, single-center observational pharmacokinetic and -dynamic evaluation study. Enrolled patients, with polymerase chain reaction confirmed Covid-19 were admitted to the ICU for mechanical ventilation or high flow nasal canula oxygen support. All patients were 18 years of age or older and received tocilizumab within 24 hours after admission to the ICU and received 6 mg dexamethasone daily as concomitant therapy.Results29 patients were enrolled between 15 December 2020 and 15 March 2021. A total of 139 tocilizumab plasma samples were obtained covering the pharmacokinetic curve of day 0 up to day 20 after tocilizumab initiation. A population pharmacokinetic model with parallel linear and non-linear clearance was developed and validated. Average AUC0-inf 1stDOSEwas 938 [±190] ug/mL*days. Tocilizumab half-life was estimated to be 4·15 [±0·24] days. All patients had tocilizumab exposure above 1 ug/ml for at least 15 days.ConclusionThis study provides evidence to support a fixed dose of 600 mg tocilizumab in COVID-19 patients. Furthermore our findings suggest that alternative cost saving regimens with even lower doses are likely to be as effective as the current 8 mg/kg recommendation.FundingNo external funding was received for this workBackgroundIn the randomized controlled trial REMAP-CAP, the IL-6 receptor antagonist tocilizumab was shown to improve outcome, including survival in ICU admitted COVID-19 patients. Because obesity is a risk factor for development of severe COVID-19, concerns have been raised about overtreatment as well as undertreatment through weight-based dosing of tocilizumab. Furthermore pharmacokinetic and pharmacodynamic parameters of medications are often found to be different in severely ill patients when compared to mild or moderately ill patients. However, the effects of different dosing schedules were only investigated to a very limited extent in non-randomized observational studies. Hence, evaluation of the PK/PD parameters of tocilizumab in severely ill patients – is warranted.Added value of this studyThis study provides valuable information about the population pharmacokinetics and dynamics of tocilizumab in dexamethasone cotreated ICU admitted COVID-19 patients. This research shows that there is no rationale for the 8 mg/kg dosing recommendation in ICU patients. Fixed dosing of 600 mg tocilizumab is a cost saving, logistically attractive and safe alternative without losing efficacy.Implications of all the evidenceDue to the ongoing pandemic, shortages of tocilizumab and other IL-6 receptor antagonists may be anticipated. A fixed tocilizumab dose regimen has many practical and safety advantages, e.g. it will reduce dosing errors and avoid unnecessary wastage of medication. More importantly, according to the data presented in this study, relative underdosing of patients with low, or low-normal bodyweight compared to patients with high bodyweight will be avoided. Last but not least, in view of the large number of patients currently being treated with these agents, a significant cost saving can also be expected.