Development of a 3D Brain Model to Study Sex-Specific Neuroinflammation After Hemorrhagic Stroke.

Subarachnoid hemorrhage (SAH) accounts for 5% of stroke, with women having a decreased inflammatory response compared to men; however, this mechanism has yet to be identified. One hurdle in SAH research is the lack of human brain models. Studies in murine models are helpful, but human models should be used in conjunction for improved translatability. These observations lead us to develop a 3D system to study the sex-specific microglial and neuroglial function in a novel in vitro human SAH model and compare it to our validated in vivo SAH model. Our lab has developed a 3D, membrane-based in vitro cell culture system with human astrocytes, microglia, and neurons from both sexes. The 3D cultures were incubated with male and female cerebrospinal fluid from SAH patients in the Neuro-ICU. Furthermore, microglial morphology, erythrophagocytosis, microglial inflammatory cytokine production, and neuronal apoptosis were studied and compared with our murine SAH models. The human 3D system demonstrated intercellular interactions and proportions of the three cell types similar to the adult human brain. In vitro and in vivo models of SAH showed concordance in male microglia being more inflammatory than females via morphology and flow cytometry. On the contrary, both in vitro and in vivo models revealed that female microglia were more phagocytic and less prone to damaging neurons than males. One possible explanation for the increased phagocytic ability of female microglia was the increased expression of CD206 and MerTK. Our in vitro, human, 3D cell culture SAH model showed similar results to our in vivo murine SAH model with respect to microglial morphology, inflammation, and phagocytosis when comparing the sexes. A human 3D brain model of SAH may be a useful adjunct to murine models to improve translation to SAH patients.

Brain FADE syndrome: the final common pathway of chronic inflammation in neurological disease.

Importance: While the understanding of inflammation in the pathogenesis of many neurological diseases is now accepted, this special commentary addresses the need to study chronic inflammation in the propagation of cognitive Fog, Asthenia, and Depression Related to Inflammation which we name Brain FADE syndrome. Patients with Brain FADE syndrome fall in the void between neurology and psychiatry because the depression, fatigue, and fog seen in these patients are not idiopathic, but instead due to organic, inflammation involved in neurological disease initiation. Observations: A review of randomized clinical trials in stroke, multiple sclerosis, Parkinson's disease, COVID, traumatic brain injury, and Alzheimer's disease reveal a paucity of studies with any component of Brain FADE syndrome as a primary endpoint. Furthermore, despite the relatively well-accepted notion that inflammation is a critical driving factor in these disease pathologies, none have connected chronic inflammation to depression, fatigue, or fog despite over half of the patients suffering from them. Conclusions and relevance: Brain FADE Syndrome is important and prevalent in the neurological diseases we examined. Classical "psychiatric medications" are insufficient to address Brain FADE Syndrome and a novel approach that utilizes sequential targeting of innate and adaptive immune responses should be studied.

Single-cell analysis reveals diversity of tumor-associated macrophages and their interactions with T lymphocytes in glioblastoma.

Glioblastoma (GBM) is an aggressive primary CNS malignancy and clinical outcomes have remained stagnant despite introduction of new treatments. Understanding the tumor microenvironment (TME) in which tumor associated macrophages (TAMs) interact with T cells has been of great interest. Although previous studies examining TAMs in GBM have shown that certain TAMs are associated with specific clinical and/or pathologic features, these studies used an outdated M1/M2 paradigm of macrophage polarization and failed to include the continuum of TAM states in GBM. Perhaps most significantly, the interactions of TAMs with T cells have yet to be fully explored. Our study uses single-cell RNA sequencing data from adult IDH-wildtype GBM, with the primary aim of deciphering the cellular interactions of the 7 TAM subtypes with T cells in the GBM TME. Furthermore, the interactions discovered herein are compared to IDH-mutant astrocytoma, allowing for focus on the cellular ecosystem unique to GBM. The resulting ligand-receptor interactions, signaling sources, and global communication patterns discovered provide a framework for future studies to explore methods of leveraging the immune system for treating GBM.

In Vitro and In Vivo Drug-Response Profiling Using Patient-Derived High-Grade Glioma.

BACKGROUND: Genomic profiling cannot solely predict the complexity of how tumor cells behave in their in vivo microenvironment and their susceptibility to therapies. The aim of the study was to establish a functional drug prediction model utilizing patient-derived GBM tumor samples for in vitro testing of drug efficacy followed by in vivo validation to overcome the disadvantages of a strict pharmacogenomics approach. METHODS: High-throughput in vitro pharmacologic testing of patient-derived GBM tumors cultured as 3D organoids offered a cost-effective, clinically and phenotypically relevant model, inclusive of tumor plasticity and stroma. RNAseq analysis supplemented this 128-compound screening to predict more efficacious and patient-specific drug combinations with additional tumor stemness evaluated using flow cytometry. In vivo PDX mouse models rapidly validated (50 days) and determined mutational influence alongside of drug efficacy. We present a representative GBM case of three tumors resected at initial presentation, at first recurrence without any treatment, and at a second recurrence following radiation and chemotherapy, all from the same patient. RESULTS: Molecular and in vitro screening helped identify effective drug targets against several pathways as well as synergistic drug combinations of cobimetinib and vemurafenib for this patient, supported in part by in vivo tumor growth assessment. Each tumor iteration showed significantly varying stemness and drug resistance. CONCLUSIONS: Our integrative model utilizing molecular, in vitro, and in vivo approaches provides direct evidence of a patient's tumor response drifting with treatment and time, as demonstrated by dynamic changes in their tumor profile, which may affect how one would address that drift pharmacologically.

Upregulation of the Oct3/4 Network in Basal Breast Cancer Is Associated with Its Metastatic Potential and Shows Tissue Dependent Variability.

Adaptive plasticity of Breast Cancer stem cells (BCSCs) is strongly correlated with cancer progression and resistance, leading to a poor prognosis. In this study, we report the expression profile of several pioneer transcription factors of the Oct3/4 network associated with tumor initiation and metastasis. In the triple negative breast cancer cell line (MDA-MB-231) stably transfected with human Oct3/4-GFP, differentially expressed genes (DEGs) were identified using qPCR and microarray, and the resistance to paclitaxel was assessed using an MTS assay. The tumor-seeding potential in immunocompromised (NOD-SCID) mice and DEGs in the tumors were also assessed along with the intra-tumor (CD44+/CD24-) expression using flow cytometry. Unlike 2-D cultures, the Oct3/4-GFP expression was homogenous and stable in 3-D mammospheres developed from BCSCs. A total of 25 DEGs including Gata6, FoxA2, Sall4, Zic2, H2afJ, Stc1 and Bmi1 were identified in Oct3/4 activated cells coupled with a significantly increased resistance to paclitaxel. In mice, the higher Oct3/4 expression in tumors correlated with enhanced tumorigenic potential and aggressive growth, with metastatic lesions showing a >5-fold upregulation of DEGs compared to orthotopic tumors and variability in different tissues with the highest modulation in the brain. Serially re-implanting tumors in mice as a model of recurrence and metastasis highlighted the sustained upregulation of Sall4, c-Myc, Mmp1, Mmp9 and Dkk1 genes in metastatic lesions with a 2-fold higher expression of stem cell markers (CD44+/CD24-). Thus, Oct3/4 transcriptome may drive the differentiation and maintenance of BCSCs, promoting their tumorigenic potential, metastasis and resistance to drugs such as paclitaxel with tissue-specific heterogeneity.

Feasibility Study of Cord Tissue Derived Mesenchymal Stromal Cells in COVID-19-Related Acute Respiratory Distress Syndrome.

BACKGROUND: Treatment options for patients with COVID-19-related acute respiratory distress syndrome (ARDS) are desperately needed. Allogeneic human umbilical cord derived mesenchymal stromal cells (hCT-MSCs) have potential therapeutic benefits in these critically ill patients, but feasibility and safety data are lacking. MATERIALS AND METHODS: In this phase I multisite study, 10 patients with COVID-19-related ARDS were treated with 3 daily intravenous infusions of hCT-MSCs (1 million cells/kg, maximum dose 100 million cells). The primary endpoint assessed safety. RESULTS: Ten patients (7 females, 3 males; median age 62 years (range 39-79)) were enrolled at 2 sites and received a total of 30 doses of study product. The average cell dose was 0.93 cells/kg (range 0.56-1.45 cells/kg and total dose range 55-117 million cells) with 5/30 (17%) of doses lower than intended dose. Average cell viability was 85% (range 63%-99%) with all but one meeting the >70% release criteria. There were no infusion-related reactions or study-related adverse events, 28 non-serious adverse events in 3 unique patients, and 2 serious adverse events in 2 unique patients, which were expected and unrelated to the study product. Five patients died: 3 by day 28 and 5 by day 90 of the study (median 27 days, range 7-76 days). All deaths were determined to be unrelated to the hCT-MSCs. CONCLUSION: We were able to collect relevant safety outcomes for the use of hCT-MSCs in patients with COVID-19-related ARDS. Future studies to explore their safety and efficacy are warranted.

Gender differences in Alzheimer's may be associated with TLR4-LYN expression in damage associated microglia and neuronal phagocytosis.

The role of Aß plaques and neurofibrillary tangles in Alzheimer's disease (AD) pathogenesis have recently come into question due to failure of many pharmaceutical agents targeting these deposits and detection of these misfolded proteins in normal human brains. Therefore, we investigated correlations between microglial activation and toll like receptor 4 (TLR4) and Lck/Yes novel tyrosine (LYN) kinase signaling in an AD mouse model. In this study, we used 5-6-month-old 5XFAD and wild type (WT) male and female mice. Immunohistochemistry (IHC) and flow cytometry (FC) were performed on their brains. Cognitive performance was assessed with the Barnes-Maze. IHC showed more Ab aggregation in microglia of female 5XFAD mice compared to their male counterparts. Increased co-localization of microglial TLR4 and LYN was also observed in AD more than WT and females more than males. IHC also suggests microglial phagocytosis of neurons in AD mice, which is supported by FC data. Our FC data also support the involvement of disease associated microglia (DAMs) in this process based on cytokine secretion. Cognitive assessment by the Barnes maze showed 5XFAD females performed worse than males. In this study, we investigated the relationship between microglial TLR4 and LYN kinase in 5XFAD male and females. Our data reveals a correlation between microglial TLR4 and LYN co-localization and AD pathogenesis, more in females than males. Targeting microglial TLR4 and Lyn in DAMs may offer new therapeutic opportunities in the treatment of AD.

Acute subdural hematoma due to acute myeloid leukemia and B-cell lymphoma.

Chloroma, is an rare malignant tumor characterized by the extramedullary blast proliferation of myeloid lineages that subsequently change the normal architecture of surrounding tissues. Because this is very rare disease, primary central nervous system myeloid sarcoma has not been widely reported. Myeloid sarcoma, as a group of heterogenetic diseases, presents with differential clinical and histological pictures depending upon the primary affected site. We are presenting a 77-year-old gentleman, with past medical history of chronic lymphoblastic leukemia that was not on any treatment and who presented with complaints of lethargy, disorientation, and weakness. CT scan of the head showed left-sided subdural hematoma with significant mass effect with left-to-right shift. Craniotomy and hematoma evacuation was performed and hematoma and subdural lesion was sent for pathological evaluation. Histologic examination of the hematoma revealed solid sheets of small-medium sized atypical hematopoietic cells that was imbedded in an acute and chronic hematoma. To confirm the final diagnosis, flow cytometry was performed and showed two neoplastic clones, consistent with acute myeloid leukemia with monocytic differentiation and a separate mature B-cell lymphoma. To our knowledge we are presenting the first case in the literature of the Intracranial acute myeloid leukemia/myeloid sarcoma and B-cell lymphoma that was found in the same brain lesion.

Posterior reversible encephalopathy syndrome due to unilateral renal artery stenosis: A case report.

A tricenarian female with a past medical history of status epilepticus secondary to posterior reversible encephalopathy syndrome (PRES) of unknown etiology presented with a 2-week history of double vision, dizziness, elevated blood pressure, and altered mental status. On hospital day 2, she experienced status epilepticus, during which her blood pressure rose to 240/160 from her baseline of around 140/90. The patient was subsequently intubated for airway protection and transferred to the intensive care unit, where she was started on a nicardipine drip. Due to her history of thrombotic microangiopathy, empiric treatment with plasma exchange and prednisone was started but discontinued when ADAMTS13 came back negative. Urine metanephrines also were found to be negative. Computed tomography angiography of the abdomen showed left renal artery stenosis and stent was placed. Remarkably, over the coming days, her blood pressure normalized, and her neurologic symptoms significantly improved. As a result, antihypertensive medications were titrated down, and the patient was finally provided with a cause of her repetitive, life-threatening episodes of PRES.

Microglial TLR4 is Critical for Neuronal Injury and Cognitive Dysfunction in Subarachnoid Hemorrhage.

BACKGROUND: Toll-like receptor 4 (TLR4) activation causes excessive production of proinflammatory mediators and an increased expression of costimulatory molecules that leads to neuroinflammation after subarachnoid hemorrhage (SAH). Although TLR4-mediated inflammatory pathways have long been studied in neuroinflammation, the specific glia implicated in initiation and propagation of neuroinflammation in SAH have not been well elucidated. In this study, we investigated the involvement of glial TLR4 including microglia and astrocytes in brain damage and poor neurological outcome. METHODS: In this study, global TLR4 knockout, cell-specific TLR4 knockout, and floxxed control male and female mice were used. The mice were injected with 60 µl autologous blood near the mesencephalon to induce SAH; animals were euthanized on postoperative day 7 for immunohistochemistry of glia and apoptotic cells. Microglial morphology was evaluated by using immunofluorescence density quantification to determine correlations between morphology and neuroinflammation. Microglial depletion was accomplished with the intracerebroventricular administration of clodronate liposomes. Cognitive function was assessed with Barnes maze. RESULTS: On postoperative day 7 after SAH induction, neuronal apoptosis was markedly reduced in the clodronate liposome group compared with phosphate-buffered saline control liposomes, and cognitive performance in the clodronate group was improved, as well. Differences in microglial activation, assessed by morphometric analysis, and neuronal apoptosis were significantly greater in wildtype knockouts compared with cell-specific and global TLR4 knockouts. The mice lacking TLR4 on astrocytes and neurons showed no differences compared with wildtype mice on any end points. CONCLUSIONS: Our data suggest that microglial depletion with the intracerebroventricular administration of clodronate can improve the cognitive function in an SAH mouse model, and TLR4 is critical for microglial activation and neuronal injury. Only microglial TLR4 is necessary for brain damage and poor cognitive outcome rather than astrocyte or neuronal TLR4. Thus, microglial TLR4 could be a potent therapeutic target to treat SAH-associated neuronal injury and protect against cognitive dysfunction.

An overview on microglial origin, distribution, and phenotype in Alzheimer's disease.

Alzheimer's disease (AD) is the most common neurodegenerative disease that is responsible for about one-third of dementia cases worldwide. It is believed that AD is initiated with the deposition of Ab plaques in the brain. Genetic studies have shown that a high number of AD risk genes are expressed by microglia, the resident macrophages of brain. Common mode of action by microglia cells is neuroinflammation and phagocytosis. Moreover, it has been discovered that inflammatory marker levels are increased in AD patients. Recent studies advocate that neuroinflammation plays a major role in AD progression. Microglia have different activation profiles depending on the region of brain and stimuli. In different activation, profile microglia can generate either pro-inflammatory or anti-inflammatory responses. Microglia defend brain cells from pathogens and respond to injuries; also, microglia can lead to neuronal death along the way. In this review, we will bring the different roles played by microglia and microglia-related genes in the progression of AD.

Multiple watershed and cardioembolic strokes in 84-year-old male after cardiac ablation procedure: Case report.

Current guidelines do not include radiologic assessment of the carotid arteries before catheter ablation procedures. There are multiple studies describing the risks of periprocedural cardioembolic strokes during cardiac ablation procedure but none describing the risks of periprocedural watershed strokes due to hypoperfusion during cardiac ablation. It is critically important for neurologists, cardiologists, and all other associated health-care workers to recognize the risks of neurologic complications, such as watershed strokes, before cardiac procedures are performed. We are presenting an 84-year-old male who presented to the emergency room with complaints of vision changes after a cardiac ablation procedure for atrial fibrillation. He described spotty vision with decreased visual acuity in both eyes. Magnetic resonance imaging of the brain showed multiple strokes bilaterally. Based on the radiologic features, all the strokes happened at approximately the same time. Of note, subsequent computed tomography angiography of the head and neck showed 65%-70% bilateral stenosis of the internal carotid arteries.

Post-stroke recrudescence-a possible connection to autoimmunity?

Early recanalization of the occluded vessel is the only efficient intervention that improves outcome after ischemic stroke. In contrast, interventions for chronic issues facing stroke patients are limited. Recent clinical and preclinical studies have shown a correlation between upregulated immune responses to brain antigens and post-stroke recrudescence (PSR), post-stroke fatigue (PSF), and dementia (PSD); all of which are associated with poor long-term stroke outcome. Recent retrospective studies have demonstrated a strong correlation between the onset of PSR and acute infection during acute stroke, suggesting some adaptive immune system mediated pathology. This review will discuss the mechanisms and epidemiology of PSR based on the current clinical and pre-clinical evidence. Accordingly, PSR does appear correlated with populations that are prone to autoimmunity, infection, and subsequent triggers, which corroborate autoimmune responses to self-brain antigens as an underlying mechanism. Moreover, PSR as well as PSF and PSD seem to be partly explained by the development of a neuro-inflammatory response to brain antigens. Therefore, the future of improving long-term stroke outcome could be bright with more accurate pre-clinical models focusing on the role of adaptive immune-mediated post stroke neuroinflammation and more clinical studies of PSR.

Sodium Variability and Probability of Vasospasm in Patients with Aneurysmal Subarachnoid Hemorrhage.

OBJECTIVES: Vasospasm is a well-known complication of aneurysmal subarachnoid hemorrhage (aSAH) that generally occurs 4-14 days post-hemorrhage. Based on American Heart Association guidelines, the current understanding is that hyponatremic episodes may lead to vasospasm. Therefore, we sought to determine the association between repeated serum sodium levels of aSAH patients and its relationship to radiographic vasospasm. MATERIALS AND METHODS: A single-center retrospective analysis from 2007-2016 was conducted of aSAH patients. Daily serum sodium levels were recorded up to day 14 post-admission. Hyponatremia was defined as a serum sodium value of < 135 mEq/L. We evaluated the relationship to radiologic vasospasm, neurologic deterioration, functional status at discharge, and mortality. A repeated measures analysis using a mixed-effect regression model was performed to assess the interindividual relationship between serum sodium trends and outcomes. RESULTS: A total of 271 aSAH patients were included. There were no significant differences in interindividual serum sodium values over time and occurrence of radiographic vasospasm, neurologic deterioration, functional, or mortality outcomes (p = .59, p = .42, p = .94, p = .99, respectively) using the mixed-effect regression model. However, overall mean serum sodium levels were significantly higher in patients who had neurologic deterioration, poor functional outcome (mRS 3-6), and mortality. CONCLUSIONS: Serum sodium level variations are not associated with subsequent development of cerebral vasospasm in aSAH patients. These findings indicate that serum sodium may not have an impact on vasospasm, and avoiding hypernatremia may provide a neurologic, functional and survival benefit.

Gliomagenesis is orchestrated by the Oct3/4 regulatory network.

Glioblastoma multiforme (GBM) is a lethal brain tumor characterized by developmental hierarchical phenotypic heterogeneity, therapy resistance and recurrent growth. Neural stem cells (NSCs) from human central nervous system (CNS), and glioblastoma stem cells from patient-derived GBM (pdGSC) samples and cultured in both 2D well-plate and 3D monoclonal neurosphere culture system (pdMNCS). The pdMNCS model shows promise to establish a relevant 3D-tumor environment that maintains GBM cells in the stem cell phase within suspended neurospheres. Utilizing the pdMNCS, we examined GBM cell-lines for a wide spectrum of developmental cancer stem cell markers, including the early blastocyst inner-cell mass (ICM)-specific Nanog, Oct3/4,B, and CD133. We observed that MNCS epigenotype is recapitulated using gliomasphere-derived cells. CD133, the marker of GSC is robustly expressed in 3D-gliomaspheres and localized within the plasma membrane compartment. Conversely, gliomasphere cultures grown in conventional 2D culture quickly lost CD133 expression, indicating its variable expression is dependent on cell-culture conditions. Critically, this experiment demonstrates incomplete differentiation of cytoskeleton microtubules and intermediate filaments (IFs) of patient derived cells, similar to commercially available GBM cell lines. Subsequently, in order to determine whether Oct3/4 it was necessary for CD133 expression and cancer stemness, we transfected 2D and 3D culture with siRNA against Oct3/4 and found a significant reduction in gliomasphere formation. These results suggest that expression of Oct3/4,Aand CD133 suppress differentiation of GSCs.

Effects of Volatile Anesthetics on Postoperative Ischemic Stroke Incidence.

Background Preclinical studies suggest that volatile anesthetics decrease infarct volume and improve the outcome of ischemic stroke. This study aims to determine their effect during noncardiac surgery on postoperative ischemic stroke incidence. Methods and Results This was a retrospective cohort study of surgical patients undergoing general anesthesia at 2 tertiary care centers in Boston, MA, between October 2005 and September 2017. Exclusion criteria comprised brain death, age <18 years, cardiac surgery, and missing covariate data. The exposure was defined as median age-adjusted minimum alveolar concentration of all intraoperative measurements of desflurane, sevoflurane, and isoflurane. The primary outcome was postoperative ischemic stroke within 30 days. Among 314 932 patients, 1957 (0.6%) experienced the primary outcome. Higher doses of volatile anesthetics had a protective effect on postoperative ischemic stroke incidence (adjusted odds ratio per 1 minimum alveolar concentration increase 0.49, 95% CI, 0.40-0.59, P<0.001). In Cox proportional hazards regression, the effect was observed for 17 postoperative days (postoperative day 1: hazard ratio (HR), 0.56; 95% CI, 0.48-0.65; versus day 17: HR, 0.85; 95% CI, 0.74-0.99). Volatile anesthetics were also associated with lower stroke severity: Every 1-unit increase in minimum alveolar concentration was associated with a 0.006-unit decrease in the National Institutes of Health Stroke Scale (95% CI, -0.01 to -0.002, P=0.002). The effects were robust throughout various sensitivity analyses including adjustment for anesthesia providers as random effect. Conclusions Among patients undergoing noncardiac surgery, volatile anesthetics showed a dose-dependent protective effect on the incidence and severity of early postoperative ischemic stroke.

Defining the Mechanism of Subarachnoid Hemorrhage-Induced Pyrexia.

Fever can affect the majority of patients with subarachnoid hemorrhage (SAH) and many times no identifiable source is found for the fever whether infectious or sterile, like deep vein thrombosis. We hypothesized that fever in SAH is mediated by a NON-cyclo-oxygenase-dependent mechanism, which we neologized as subarachnoid hemorrhage-induced pyrexia (SAHiP). This hypothesis was investigated using genetically modified mice, pharmacological manipulation, cerebrospinal fluid from SAH patients, and a large cohort of SAH patients. Mice with deletions of neuronal prostaglandin EP3 receptor, global toll-like receptor 4 (TLR4), myeloid TLR4, and microglial TLR4 were subjected to SAH after being implanted with thermometers. Pathways necessary for SAHiP were identified. In SAH patients, cerebrospinal fluid was examined by flow cytometry and correlated with SAHiP. From a large cohort of SAH patients, independent associations with SAHiP were determined using logistic regression analysis. In our mouse model of SAH, microglial TLR4 is necessary for SAHiP, but independent of the neuronal prostaglandin EP3 receptor, cyclo-oxygenase, and prostaglandins. Macrophages from the cerebrospinal fluid of SAH patients with SAHiP expressed more TLR4-co-receptor than SAH patients without SAHiP. In a large cohort of SAH patients, SAHiP was found to be independently, yet inversely, associated with acetaminophen administration. SAHiP is independent of the neuronal prostaglandin EP3 receptor, cyclo-oxygenase, and prostaglandins, but dependent on microglial/macrophage TLR4 with evidence from both SAH mouse models and SAH patients.

Incidence and Risk Model Development for Severe Tachypnea Following Terminal Extubation.

BACKGROUND: Palliative ventilator withdrawal (PVW) in the ICU is a common occurrence. RESEARCH QUESTION: The goal of this study was to measure the rate of severe tachypnea as a proxy for dyspnea and to identify characteristics associated with episodes of tachypnea. STUDY DESIGN AND METHODS: This study assessed a retrospective cohort of ICU patients from 2008 to 2012 mechanically ventilated at a single academic medical center who underwent PVW. The primary outcome of at least one episode of severe tachypnea (respiratory rate > 30 breaths/min) within 6 h after PVW was measured by using detailed physiologic and medical record data. Multivariable logistic regression was used to examine the association between patient and treatment characteristics with the occurrence of a severe episode of tachypnea post extubation. RESULTS: Among 822 patients undergoing PVW, 19% and 30% had an episode of severe tachypnea during the 1-h and 6-h postextubation period, respectively. Within 1 h postextubation, patients with the following characteristics were more likely to experience tachypnea: no pre-extubation opiates (adjusted OR [aOR], 2.08; 95% CI, 1.03-4.19), lung injury (aOR, 3.33; 95% CI, 2.19-5.04), Glasgow Coma Scale score > 8 (aOR, 2.21; 95% CI, 1.30-3.77), and no postextubation opiates (aOR, 1.90; 95% CI, 1.19-3.00). INTERPRETATION: Up to one-third of ICU patients undergoing PVW experience severe tachypnea. Administration of pre-extubation opiates (anticipatory dosing) represents a key modifiable factor that may reduce poor symptom control.