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COVID-19-associated respiratory failure offers the unprecedented opportunity to evaluate the differential host response to a uniform pathogenic insult. Understanding whether there are distinct subphenotypes of severe COVID-19 may offer insight into its pathophysiology. Sequential Organ Failure Assessment (SOFA) score is an objective and comprehensive measurement that measures dysfunction severity of six organ systems, i.e., cardiovascular, central nervous system, coagulation, liver, renal, and respiration. Our aim was to identify and characterize distinct subphenotypes of COVID-19 critical illness defined by the post-intubation trajectory of SOFA score. Intubated COVID-19 patients at two hospitals in New York city were leveraged as development and validation cohorts. Patients were grouped into mild, intermediate, and severe strata by their baseline post-intubation SOFA. Hierarchical agglomerative clustering was performed within each stratum to detect subphenotypes based on similarities amongst SOFA score trajectories evaluated by Dynamic Time Warping. Distinct worsening and recovering subphenotypes were identified within each stratum, which had distinct 7-day post-intubation SOFA progression trends. Patients in the worsening suphenotypes had a higher mortality than those in the recovering subphenotypes within each stratum (mild stratum, 29.7% vs. 10.3%, p = 0.033; intermediate stratum, 29.3% vs. 8.0%, p = 0.002; severe stratum, 53.7% vs. 22.2%, p

Vascular injury is a menacing element of acute respiratory distress syndrome (ARDS) pathogenesis. To better understand the role of vascular injury in COVID-19 ARDS, we used lung autopsy immunohistochemistry and blood proteomics from COVID-19 subjects at distinct timepoints in disease pathogenesis, including a hospitalized cohort at risk of ARDS development (“at risk”, N=59), an intensive care unit cohort with ARDS (“ARDS”, N=31), and a cohort recovering from ARDS (“recovery”, N=12). COVID-19 ARDS lung autopsy tissue revealed an association between vascular injury and platelet-rich microthrombi. This link guided the derivation of a protein signature in the at risk cohort characterized by lower expression of vascular proteins in subjects who died, an early signal of vascular limitation termed the maladaptive vascular response. These findings were replicated in COVID-19 ARDS subjects, as well as when bacterial and influenza ARDS patients (N=29) were considered, hinting at a common final pathway of vascular injury that is more disease (ARDS) then cause (COVID-19) specific, and may be related to vascular cell death. Among recovery subjects, our vascular signature identified patients with good functional recovery one year later. This vascular injury signature could be used to identify ARDS patients most likely to benefit from vascular targeted therapies.

BACKGROUND Antibiotic use can result in reduced efficacy of immune checkpoint blockade (ICB), presumably because of dysbiosis of the intestinal microbiome. We sought to determine the precise temporal relation between antibiotic therapy and its possible effects on ICB efficacy. We also investigated the histologic changes in the tumor microenvironment secondary to antibiotics use. METHODS AND OBJECTIVES This was a single institution retrospective study that evaluated the impact of antibiotics on outcomes of patients with advanced or metastatic malignancy who were treated with ICB. Use of antibiotics among patients treated with ICB was assessed during a 12-week period before and after initiation of ICB. The primary outcome was response to ICB. Histologic changes in the tumor microenvironment following antibiotics use were also examined. RESULTS Between January 1, 2011 and December 31, 2018, 414 patients were identified who received ICB, and 207 patients (50%) received antibiotics within 12 weeks (before/after) of initiation of ICB. In univariate analysis, antibiotic use following initiation of ICB was associated with a significantly reduced response (odds ratio [OR]: 0.33, 95% confidence interval [CI]: 0.2-0.52, P

COVID-19 has proven to be a metabolic disease resulting in adverse outcomes in individuals with diabetes or obesity. Patients infected with SARS-CoV-2 and hyperglycemia suffer from longer hospital stays, higher risk of developing acute respiratory distress syndrome (ARDS), and increased mortality compared to those who do not develop hyperglycemia. We find the prevalence of hyperglycemia in patients with COVID-19 ARDS to be equal to those with non-COVID-19 ARDS. Nevertheless, the pathophysiological mechanism(s) of hyperglycemia in COVID-19 remains poorly characterized. Here we show that insulin resistance rather than pancreatic beta cell failure is the prevalent cause of hyperglycemia in COVID-19 patients with ARDS, independent of glucocorticoid treatment. A screen of protein hormones that regulate glucose homeostasis reveals that the insulin sensitizing adipokine adiponectin is reduced in hyperglycemic COVID-19 patients. Hamsters infected with SARS-CoV-2 also have diminished expression of adiponectin. Together these data suggest that adipose tissue dysfunction may be a driver of insulin resistance and adverse outcomes in acute COVID-19. Funding Information: This work was supported by the following grants: NIH R01 DK121140 (J.C.L.) and R01 DK121844 (J.C.L.), NCI R01 CA234614 (R.E.S), NIAID 2R01 AI107301 (R.E.S), and NIDDK R01 DK121072 (R.E.S). R.E.S. and J.C.L are supported as Irma Hirschl Trust Research Award Scholars. In addition, this study received support from NewYork-Presbyterian Hospital (NYPH) and Weill Cornell Medical College (WCMC), including the Clinical and Translational Science Center (CTSC) (UL1 TR 0002384). Declaration of Interests: R.E.S. is on the scientific advisory board of Miromatrix Inc. R.E.S. is a speaker and consultant for Alnylam Inc. The other authors have no conflict of interest. Ethics Approval Statement: The registry was approved by the institutional review board of WCMC (1405015116, 20-05022072, 20-03021681). All animal experiment procedures, breeding, and ethical use were performed in accordance with the guidelines set by the Institutional Animal Care and Use Committee at Mount Sinai School of Medicine.

COVID-19 outcomes like mortality have been associated with albumin alteration. However, it is unclear whether albumin changes in COVID-19 are pathogen specific or not. To this end, we characterized the kinetics of serum albumin in mechanically ventilated patients with COVID-19 compared to mechanically ventilated patients with sepsis-induced Acute Respiratory Distress Syndrome (ARDS). We discovered two phases of alterations in albumin levels during the course of Covid-19 critical illness, but not for the sepsis-induced ARDS. Our findings suggest the metabolic effects of COVID-19 are pathogen-specific and albumin recovery may signal the cessation of a deleterious immune response in this disease.

Background There is a lack of mechanism-driven, clinically relevant biomarkers in chronic obstructive pulmonary disease (COPD). Mitochondrial dysfunction, a proposed disease mechanism in COPD, is associated with the release of mitochondrial DNA (mtDNA), but plasma cell-free mtDNA has not been previously examined prospectively for associations with clinical COPD measures. Methods P-mtDNA, defined as copy number of mitochondrially-encoded NADH dehydrogenase-1 (MT-ND1) gene, was measured by real-time quantitative PCR in 700 plasma samples from participants enrolled in the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) cohort. Associations between p-mtDNA and clinical disease parameters were examined, adjusting for age, sex, smoking status, and for informative loss to follow-up. Results P-mtDNA levels were higher in participants with mild or moderate COPD, compared to smokers without airflow obstruction, and to participants with severe COPD. Baseline increased p-mtDNA levels were associated with better CAT scores in female smokers without airflow obstruction and female participants with mild or moderate COPD on 1-year follow-up, but worse 6MWD in females with severe COPD. Higher p-mtDNA levels were associated with better 6MWD in male participants with severe COPD. These associations were no longer significant after adjusting for informative loss to follow-up. Conclusion In this study, p-mtDNA levels associated with baseline COPD status but not future changes in clinical COPD measures after accounting for informative loss to follow-up. To better characterize mitochondrial dysfunction as a potential COPD endotype, these results should be confirmed and validated in future studies. Trial Registration: ClinicalTrials.gov NCT01969344 (SPIROMICS)

Background Patients who have undergone solid organ transplants (SOT) have an increased risk for sepsis compared with the general population. Paradoxically, studies suggest that SOT patients with sepsis may experience better outcomes compared with those without a SOT. However, these analyses used previous definitions of sepsis. It remains unknown whether the more recent definitions of sepsis and modern analytic approaches demonstrate a similar relationship. Methods Using the Weill Cornell-Critical Care Database for Advanced Research, we analyzed granular physiologic, microbiologic, comorbidity, and therapeutic data in patients with and without SOT admitted to intensive care units (ICUs). We used a survival analysis with a targeted minimum loss-based estimation, adjusting for within-group (SOT and non-SOT) potential confounders to ascertain whether the effect of sepsis, defined by sepsis-3, on 28-day mortality was modified by SOT status. We performed additional analyses on restricted populations. Results We analyzed 28 431 patients: 439 with SOT and sepsis, 281 with SOT without sepsis, 6793 with sepsis and without SOT, and 20 918 with neither. The most common SOT types were kidney (475) and liver (163). Despite a higher severity of illness in both sepsis groups, the adjusted sepsis-attributable effect on 28-day mortality for non-SOT patients was 4.1% (95% confidence interval [CI], 3.8–4.5) and −14.4% (95% CI, −16.8 to −12) for SOT patients. The adjusted SOT effect modification was −18.5% (95% CI, −21.2 to −15.9). The adjusted sepsis-attributable effect for immunocompromised controls was −3.5% (95% CI, −4.5 to −2.6). Conclusions Across a large database of patients admitted to ICUs, the sepsis-associated 28-day mortality effect was significantly lower in SOT patients compared with controls.

BACKGROUND: Mitochondrial dysfunction, a proposed mechanism of chronic obstructive pulmonary disease (COPD) pathogenesis, is associated with the leakage of mitochondrial DNA (mtDNA), which may be detected extracellularly in various bodily fluids. Despite evidence for the increased prevalence of chronic kidney disease in COPD subjects and for mitochondrial dysfunction in the kidneys of murine COPD models, whether urine mtDNA (u-mtDNA) associates with measures of disease severity in COPD is unknown. METHODS: Cell-free u-mtDNA, defined as copy number of mitochondrially encoded NADH dehydrogenase-1 (MTND1) gene, was measured by quantitative PCR and normalized to urine creatinine in cell-free urine samples from participants in the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) cohort. Urine albumin/creatinine ratios (UACR) were measured in the same samples. Associations between u-mtDNA, UACR, and clinical disease parameters — including FEV(1) % predicted, clinical measures of exercise tolerance, respiratory symptom burden, and chest CT measures of lung structure — were examined. RESULTS: U-mtDNA and UACR levels were measured in never smokers (n = 64), smokers without airflow obstruction (n = 109), participants with mild/moderate COPD (n = 142), and participants with severe COPD (n = 168). U-mtDNA was associated with increased respiratory symptom burden, especially among smokers without COPD. Significant sex differences in u-mtDNA levels were observed, with females having higher u-mtDNA levels across all study subgroups. U-mtDNA associated with worse spirometry and CT emphysema in males only and with worse respiratory symptoms in females only. Similar associations were not found with UACR. CONCLUSION: U-mtDNA levels may help to identify distinct clinical phenotypes and underlying pathobiological differences in males versus females with COPD. TRIAL REGISTRATION: This study has been registered at ClinicalTrials.gov ( NCT01969344). FUNDING: US NIH, National Heart, Lung and Blood Institute, supplemented by contributions made through the Foundation for the NIH and the COPD Foundation from AstraZeneca/MedImmune, Bayer, Bellerophon Therapeutics, Boehringer-Ingelheim Pharmaceuticals Inc., Chiesi Farmaceutici S.p.A., Forest Research Institute Inc., GlaxoSmithKline, Grifols Therapeutics Inc., Ikaria Inc., Novartis Pharmaceuticals Corporation, Nycomed GmbH, ProterixBio, Regeneron Pharmaceuticals Inc., Sanofi, Sunovion, Takeda Pharmaceutical Company, and Theravance Biopharma and Mylan.

Background: Estimated glomerular filtration rate (eGFR) based on serum creatinine (sCr) improves early after left ventricular assist device (LVAD) implantation but subsequently declines. Although sCr is a commonly accepted clinical standard, cystatin C (CysC) has shown superiority in assessment of renal function in disease states characterized by muscle wasting. Among patients with an LVAD, we aimed to (1) longitudinally compare CysC-eGFR and sCr-eGFR, (2) assess their predictive value for early postoperative outcomes, and (3) investigate mechanisms which might explain potential discrepancies. Methods: A prospective cohort (n=116) with CysC and sCr concurrently measured at serial time points, and a retrospective cohort (n=91) with chest computed tomography performed within 40 days post-LVAD were studied. In the prospective cohort, the primary end point was a composite of in-hospital mortality, renal replacement therapy, or severe right ventricular failure. In the retrospective cohort, muscle mass was estimated using pectoralis muscle area indexed to body surface area (pectoralis muscle index). Results: In the prospective cohort, sCr-eGFR significantly improved early post-LVAD and subsequently declined, whereas CysC-eGFR remained stable. CysC-eGFR but not sCr-eGFR predicted the primary end point: odds ratio per 5 mL/(min·1.73 m 2 ) decrease 1.16 (1.02–1.31) versus 0.99 (0.94–1.05). In retrospective cohort, for every 5 days post-LVAD, a 6% decrease in pectoralis muscle index was observed (95% CI, 2%–9%, P =0.003). After adjusting for time on LVAD, for every 1 cm 2 /m 2 decrease in pectoralis muscle index, there was a 4% decrease in 30-day post-LVAD sCr (95% CI, 1%–6%, P =0.004). Conclusions: Initial improvement in sCr-eGFR is likely due to muscle wasting following LVAD surgery. CysC may improve assessment of renal function and prediction of early postoperative outcomes in patients with an LVAD.

Individuals infected with SARS-CoV-2 who also display hyperglycemia suffer from longer hospital stays, higher risk of developing acute respiratory distress syndrome (ARDS), and increased mortality. Nevertheless, the pathophysiological mechanism of hyperglycemia in COVID-19 remains poorly characterized. Here, we show that hyperglycemia is similarly prevalent among patients with ARDS independent of COVID-19 status. Yet, among patients with ARDS and COVID-19, insulin resistance is the prevalent cause of hyperglycemia, independent of glucocorticoid treatment, which is unlike patients with ARDS but without COVID-19, where pancreatic beta cell failure predominates. A screen of glucoregulatory hormones revealed lower levels of adiponectin in patients with COVID-19. Hamsters infected with SARS-CoV-2 demonstrated a strong antiviral gene expression program in the adipose tissue and diminished expression of adiponectin. Moreover, we show that SARS-CoV-2 can infect adipocytes. Together these data suggest that SARS-CoV-2 may trigger adipose tissue dysfunction to drive insulin resistance and adverse outcomes in acute COVID-19., Graphical Abstract, Here, Reiterer et al. report that hyperglycemia in critically ill patients with COVID-19 is caused mainly by insulin resistance and is associated with decreased circulating adiponectin. SARS-CoV-2 is shown to directly infect human adipocytes, trigger an inflammatory antiviral response in the adipose tissue and cause its dysfunction.

Background Hypercalcemia of malignancy (HCM) is a common complication of advanced cancer. PTH-independent HCM may be mediated through different mechanisms: (1) humoral HCM, caused by the secretion of PTH-related peptide (PTHrP), (2) local osteolysis resulting from metastatic lesions, and (3) calcitriol-mediated hypercalcemia. Calcitriol-mediated HCM in patients with nonlymphomatous solid tumors is thought to be rare. Methods We performed a retrospective chart review from 2008 to 2017 to characterize further patients at our institution with solid tumors who had HCM with concomitant elevations in calcitriol. Patients with PTH-dependent hypercalcemia and patients with evidence of granulomatous disease were excluded, as were patients with hematologic malignancies. We hypothesized that patients with HCM and elevated calcitriol levels would respond less favorably to treatment with antiresorptive therapy compared with patients with HCM but without calcitriol elevation. We also aimed to assess mortality and determine if PTHrP and phosphorus levels correlate with calcitriol because both factors may alter calcitriol levels. Results Of 101 eligible patients, calcitriol was elevated in 45 (45%). PTHrP was elevated in 76% of patients with elevated calcitriol compared with 52% of patients without calcitriol elevation. The mean PTHrP value did not differ between patients with HCM and elevated calcitriol (36.3 ± 22 pg/mL) and those without calcitriol elevation (37.4 ± 19 pg/mL). Those with elevated calcitriol levels generally did not respond completely to antiresorptive treatment (80% incomplete response rate), whereas most patients without an elevation in calcitriol responded well to antiresorptive treatment (78% response rate: P < .001). There was no significant difference in the percentage of patients with metastatic bone disease among the 2 groups (49% vs. 55%, respectively). There was no difference in mortality between the 2 groups (P = .14). A weak but significant negative correlation was found between phosphorus and calcitriol (Pearson r = -0.261, P = .016). This correlation was only significant in patients without calcitriol elevation (Pearson r = -0.4, P = .0082). Also, a significant negative correlation was found between PTHrP and phosphorus, again only in patients without calcitriol elevation. Discussion In the setting of HCM, patients with calcitriol elevation are much less likely to respond to antiresorptive therapy than patients without calcitriol elevation. Because calcitriol elevation did not appear to be correlated with hypophosphatemia or elevated PTHrP, it would appear that calcitriol production under these conditions is autonomous, and not subject to normal physiological controls. These observations indicate that calcitriol elevations in patients with HCM have clinical significance.

ObjectiveTo investigate sex differences in late-onset Alzheimer disease (AD) risks by means of multimodality brain biomarkers (β-amyloid load via 11C-Pittsburgh compound B [PiB] PET, neurodegeneration via 18F-fluorodeoxyglucose [FDG] PET and structural MRI).MethodsWe examined 121 cognitively normal participants (85 women and 36 men) 40 to 65 years of age with clinical, laboratory, neuropsychological, lifestyle, MRI, FDG- and PiB-PET examinations. Several clinical (e.g., age, education, APOE status, family history), medical (e.g., depression, diabetes mellitus, hyperlipidemia), hormonal (e.g., thyroid disease, menopause), and lifestyle AD risk factors (e.g., smoking, diet, exercise, intellectual activity) were assessed. Statistical parametric mapping and least absolute shrinkage and selection operator regressions were used to compare AD biomarkers between men and women and to identify the risk factors associated with sex-related differences.ResultsGroups were comparable on clinical and cognitive measures. After adjustment for each modality-specific confounders, the female group showed higher PiB β-amyloid deposition, lower FDG glucose metabolism, and lower MRI gray and white matter volumes compared to the male group (p < 0.05, family-wise error corrected for multiple comparisons). The male group did not show biomarker abnormalities compared to the female group. Results were independent of age and remained significant with the use of age-matched groups. Second to female sex, menopausal status was the predictor most consistently and strongly associated with the observed brain biomarker differences, followed by hormone therapy, hysterectomy status, and thyroid disease.ConclusionHormonal risk factors, in particular menopause, predict AD endophenotype in middle-aged women. These findings suggest that the window of opportunity for AD preventive interventions in women is early in the endocrine aging process.

Background Direct oral anticoagulants (DOACs) are effective alternatives to warfarin for stroke prevention in patients with atrial fibrillation (AF) including patients with CKD III. However, data on patient outcomes with DOACs for advanced CKD are limited, while warfarin use is controversial. Methods A retrospective study of patients with AF using DOACs and CKD stages III-V was conducted. The primary outcomes were stroke or systemic embolism and major bleeding while on DOAC therapy among CKD IV and V patients. Rates of outcomes from the DOAC trials and from previous studies of warfarin in CKD were referenced. Results Of 316 patients reviewed, 152 were included with mean CrCl of 38.8 mL/min. Stroke and systemic embolism occurred at a rate of 1.17 per 100 person-years, with no significant difference between CKD IV/V and CKD III (P = .567). Rates were comparable to DOAC use from the DOAC trials, and lower than rates in studies of warfarin in CKD IV/V patients. There was a nonstatistically significant trend toward increased major bleeding in CKD IV/V patients. Rates of major bleeding in CKD III to V subjects were comparable to published rates for warfarin users with similar levels of renal impairment. Conclusions In our study, DOACs appeared to be as efficacious and safe in CKD IV and V as in CKD III. In addition, DOACs appeared to be more effective than, and as safe as warfarin when compared with reference studies of patients with advanced CKD. Our findings support the use of DOACs for thromboembolism prevention in patients with advanced CKD and AF.

Purpose The HeartMate 3 (HM3) is superior to HMII in survival free from disabling stroke and pump exchange, however, rates of GIB remain high. Prior studies show a protective effect of digoxin and ACEi/ARB on risk for GIB, whereas phosphodiesterase 5 inhibitors (PDE5i) have opposite effect in HMII using Cox Proportional Hazard (PH) models with inverse probability weighting (IPW). Compared to this approach, marginal structural modeling (MSM) accounts for time-dependent confounding thereby producing results closer to true causal effect. Targeted Maximum Likelihood Estimation (TMLE) can help estimate MSM effects making minimal assumptions on data distribution. We studied the impact of outpt medications on survival free from GIB in HM3 pts using TMLE-MSM. Methods Data were retrospectively collected in HM3 pts up to 18 mo after discharge from implant and summarized in 3-mo time intervals. Medication status was defined as receiving vs. not ACEi/ARB/ARNi, PDE5i and digoxin at each time-node. Medication use was calculated by summarizing duration in days within each time node. Creatinine, potassium, INR and mean arterial pressure of each node were averaged. We fit TMLE-MSMs and compared results to IPW Cox PH models using both time variant and invariant covariates. Endpoint was survival free from GIB. Results 128 HM3 pts (60±13 y, 16% F) were studied. 5 deaths and 19 first GIB events occurred in 22 (17.2%) pts during follow up. 60 pts were exposed to ACEi/ARB/ARNi, 43 to digoxin and 39 to PDEi5. There was no effect of ACEi/ARB/ARNi, PDE5i or digoxin on the endpoint when using IPW Cox PH model. When using TMLE-MSM a statistically significant effect between ACEi/ARB/ARNi and the endpoint was observed (Table). Conclusion ACEi/ARB/ARNi improves survival free from GIB in HM3 pts using TMLE-MSM. Prospective randomized studies are needed to further test the impact of pharmacotherapy on outcomes in HM3 pts.

Purpose Trimethylamine N-oxide (TMAO) is a novel, gut microbe-derived metabolite that directly contributes to platelet activation and thrombosis, and is associated with increased cardiovascular risk. Gastrointestinal bleeding (GIB) is the most common complication during LVAD support and is related to acquired coagulopathy. We hypothesized that higher levels of TMAO might have a protective effect against the risk of GIB in LVAD patients. Methods We prospectively enrolled 123 heart failure (HF) patients undergoing LVAD surgery at our institution between Jan 2011 and Aug 2016. TMAO was measured in blood at three time points pre- and post-LVAD: baseline (pre-LVAD), 3-6 mo post-LVAD, and >6 mo post-LVAD. Patients were categorized by > median vs ≤median TMAO level. We assessed time to GIB occurrence for each time point separately. Univariable Cox proportional hazard models were constructed, along with multivariable models adjusted for (i) age and sex and (ii) age, sex, and estimated glomerular filtration rate (eGFR). Results Among 123 pts (age 57.5 ± 14.8, 86% male, 59% white), TMAO levels were measured at baseline in 77 pts, 3-6 mo post-LVAD in 54 pts, and >6 mo post-LVAD in 60 pts. Median (IQR) TMAO levels were 7.67 (3.86, 13.80) for pre-LVAD, 5.38 (3.21, 9.82) for 3-6 mo, 5.97 (4.44, 10.78) >6 mo. In univariable analysis, there was no significant difference in time to GIB for above vs below median TMAO levels at all time points. These findings were similar in each of the multivariable models (Table). Conclusion Although TMAO levels have been associated with pro-thrombotic potentials, no association was found between pre- and post-LVAD levels of TMAO and the risk of GIB in our cohort of LVAD patients.

Objective: In this study, available medical literature were reviewed to determine whether brain hypoxia as measured by brain tissue oxygen (Bto 2 ) levels is associated with increased risk of poor outcome after traumatic brain injury (TBI). A secondary objective was to examine the safety profile of a direct BtO 2 probe. Data Source and Extraction: Clinical studies published between 1993 and 2008 were identified from electronic databases, Index Medicus, bibliographies of pertinent articles, and expert consultation. The following inclusion criteria were applied for outcome analysis: 1) more than 10 patients described, 2) use of a direct Bto 2 monitor, 3) brain hypoxia defined as Bto 2 15 or 30 minutes, 4) 6-month outcome data, and 5) clear reporting of patient outcome associated with Bto 2 . For the analysis, each selected article had to have adequate data to determine odds ratios (ORs) and confidence intervals (Cls). Thirteen studies met the initial inclusion criteria and three were included in the final outcome analysis. Safety data were abstracted from any report where it was mentioned. Data Synthesis: The three studies included 150 evaluable patients with severe TBI (Glasgow Coma Scale ≤8). Brain hypoxia was identified in 71 (47%) of these patients. Among the patients with brain hypoxia, 52 (73%) had unfavorable outcome including 39 (55%) who died. In the absence of brain hypoxia, 34 (43%) patients had an unfavorable outcome, including 17 (22%) who died. Overall brain hypoxia (Bto 2 15 minutes) was associated with worse outcome (OR 4.0; 95% CI 1.9-8.2) and increased mortality (OR 4.6; 95% CI 2.2-9.6). We reviewed published safety data; in 292 patients monitored with a Bto 2 probe, only two adverse events were reported. Conclusion: Summary results indicate that brain hypoxia (