Integrating rSO2 and EEG monitoring in cardiopulmonary resuscitation: A novel methodology.

Despite improvements in cardiopulmonary resuscitation (CPR), survival and neurologic recovery after cardiac arrest remain poor due to ischemia and subsequent reperfusion injury. As the likelihood of survival and favorable neurologic outcome decreases with increasing severity of ischemia during CPR, developing methods to measure the magnitude of ischemia during resuscitation is critical for improving overall outcomes. Cerebral oximetry, which measures regional cerebral oxygen saturation (rSO2) by near-infrared spectroscopy, has emerged as a potentially beneficial marker of cerebral ischemia during CPR. In numerous preclinical and clinical studies, higher rSO2 during CPR has been associated with improved cardiac arrest survival and neurologic outcome. There is also emerging evidence that this can be integrated with electroencephalogram (EEG) monitoring to provide a bimodal system of brain monitoring during CPR. In this method's review, we discuss the feasibility, application, and implications of this integrated monitoring approach, highlighting its significance for improving clinical outcomes in cardiac arrest management and guiding future research directions.

Wolf Creek XVII Part 6: Physiology-Guided CPR.

Introduction: Physiology-guided cardiopulmonary resuscitation (CPR) offers the potential to optimize resuscitation and enable early prognosis. Methods: Physiology-Guided CPR was one of six focus topic for the Wolf Creek XVII Conference held on June 14-17, 2023 in Ann Arbor, Michigan, USA. International thought leaders and scientists in the field of cardiac arrest resuscitation from academia and industry were invited. Participants submitted via online survey knowledge gaps, barriers to translation and research priorities for each focus topic. Expert panels used the survey results and their own perspectives and insights to create and present a preliminary unranked list for each category, which was then debated, revised and ranked by all attendees to identify the top 5 for each category. Results: Top knowledge gaps include identifying optimal strategies for the evaluation of physiology-guided CPR and the optimal values for existing patients using patient outcomes. The main barriers to translation are the limited usability outside of critical care environments and the training and equipment required for monitoring. The top research priorities are the development of clinically feasible and reliable methods to continuously and non-invasively monitor physiology during CPR and prospective human studies proving targeting parameters during CPR improves outcomes. Conclusion: Physiology-guided CPR has the potential to provide individualized resuscitation and move away from a one-size-fits-all approach. Current understanding is limited, and clinical trials are lacking. Future developments need to consider the clinical application and applicability of measurement to all healthcare settings. Therefore, clinical trials using physiology-guided CPR for individualisation of resuscitation efforts are needed.

Association of Arterial Carbon Dioxide Tension Following In-Hospital Cardiac Arrest With Survival and Favorable Neurologic Outcome.

BACKGROUND: In-hospital cardiac arrest (IHCA) continues to be associated with high morbidity and mortality. The objective of this study was to study the association of arterial carbon dioxide tension (PaCO2) on survival to discharge and favorable neurologic outcomes in adults with IHCA. METHODS: The study population included 353 adults who underwent resuscitation from 2011 to 2019 for IHCA at an academic tertiary care medical center with arterial blood gas testing done within 24 hours of arrest. Outcomes of interest included survival to discharge and favorable neurologic outcome, defined as Glasgow outcome score of 4-5. RESULTS: Of the 353 patients studied, PaCO2 classification included: hypocapnia (PaCO2 <35 mm Hg, n = 89), normocapnia (PaCO2 35-45 mm Hg, n = 151), and hypercapnia (PaCO2 >45 mm Hg, n = 113). Hypercapnic patients were further divided into mild (45 mm Hg < PaCO2 ≤55 mm Hg, n = 62) and moderate/severe hypercapnia (PaCO2 > 55 mm Hg, n = 51). Patients with normocapnia had the highest rates of survival to hospital discharge (52.3% vs. 32.6% vs. 30.1%, P < 0.001) and favorable neurologic outcome (35.8% vs. 25.8% vs. 17.9%, P = 0.005) compared those with hypocapnia and hypercapnia respectively. In multivariable analysis, compared to normocapnia, hypocapnia [odds ratio (OR), 2.06; 95% confidence interval (CI), 1.15-3.70] and hypercapnia (OR, 2.67; 95% CI, 1.53-4.66) were both found to be independently associated with higher rates of in-hospital mortality. Compared to normocapnia, while mild hypercapnia (OR, 2.53; 95% CI, 1.29-4.97) and moderate/severe hypercapnia (OR, 2.86; 95% CI, 1.35-6.06) were both independently associated with higher in-hospital mortality compared to normocapnia, moderate/severe hypercapnia was also independently associated with lower rates of favorable neurologic outcome (OR, 0.28; 95% CI, 0.11-0.73), while mild hypercapnia was not. CONCLUSIONS: In this prospective registry of adults with IHCA, hypercapnia noted within 24 hours after arrest was independently associated with lower rates of survival to discharge and favorable neurologic outcome.

AWAreness during REsuscitation - II: A multi-center study of consciousness and awareness in cardiac arrest.

INTRODUCTION: Cognitive activity and awareness during cardiac arrest (CA) are reported but ill understood. This first of a kind study examined consciousness and its underlying electrocortical biomarkers during cardiopulmonary resuscitation (CPR). METHODS: In a prospective 25-site in-hospital study, we incorporated a) independent audiovisual testing of awareness, including explicit and implicit learning using a computer and headphones, with b) continuous real-time electroencephalography(EEG) and cerebral oxygenation(rSO2) monitoring into CPR during in-hospital CA (IHCA). Survivors underwent interviews to examine for recall of awareness and cognitive experiences. A complementary cross-sectional community CA study provided added insights regarding survivors' experiences. RESULTS: Of 567 IHCA, 53(9.3%) survived, 28 of these (52.8%) completed interviews, and 11(39.3%) reported CA memories/perceptions suggestive of consciousness. Four categories of experiences emerged: 1) emergence from coma during CPR (CPR-induced consciousness [CPRIC]) 2/28(7.1%), or 2) in the post-resuscitation period 2/28(7.1%), 3) dream-like experiences 3/28(10.7%), 4) transcendent recalled experience of death (RED) 6/28(21.4%). In the cross-sectional arm, 126 community CA survivors' experiences reinforced these categories and identified another: delusions (misattribution of medical events). Low survival limited the ability to examine for implicit learning. Nobody identified the visual image, 1/28(3.5%) identified the auditory stimulus. Despite marked cerebral ischemia (Mean rSO2 = 43%) normal EEG activity (delta, theta and alpha) consistent with consciousness emerged as long as 35-60 minutes into CPR. CONCLUSIONS: Consciousness. awareness and cognitive processes may occur during CA. The emergence of normal EEG may reflect a resumption of a network-level of cognitive activity, and a biomarker of consciousness, lucidity and RED (authentic "near-death" experiences).

Toward harmonization of strategies for investigating lucidity in AD/ADRD: A preliminary research framework.

Episodes of lucidity (ELs) in Alzheimer's disease and Alzheimer's disease-related dementias (AD/ADRD), have garnered increasing attention as an important area of research. Efforts to study lucidity suffer from a lack of clear definitional criteria, inconsistent conceptualization, and diverse approaches to operationalizing features of these events. To advance systematic investigation of ELs in AD/ADRD, there is a need for clarity and precision in labeling event attributes, markers, and specific measurement strategies that enable operational harmonization across distinct approaches to investigating the relatively broad and nascent phenomenon. To that end, we propose a preliminary research framework to guide harmonization of approaches to investigating ELs in AD/ADRD. Our goal is to provide an initial schematic that encourages uniform labeling of operational decisions about ELs.

A Randomized Trial of Mesenchymal Stromal Cells for Moderate to Severe Acute Respiratory Distress Syndrome from COVID-19.

Rationale: There are limited therapeutic options for patients with coronavirus disease (COVID-19)-related acute respiratory distress syndrome with inflammation-mediated lung injury. Mesenchymal stromal cells offer promise as immunomodulatory agents. Objectives: Evaluation of efficacy and safety of allogeneic mesenchymal cells in mechanically-ventilated patients with moderate or severe COVID-19-induced respiratory failure. Methods: Patients were randomized to two infusions of 2 million cells/kg or sham infusions, in addition to the standard of care. We hypothesized that cell therapy would be superior to sham control for the primary endpoint of 30-day mortality. The key secondary endpoint was ventilator-free survival within 60 days, accounting for deaths and withdrawals in a ranked analysis. Measurements and Main Results: At the third interim analysis, the data and safety monitoring board recommended that the trial halt enrollment as the prespecified mortality reduction from 40% to 23% was unlikely to be achieved (n = 222 out of planned 300). Thirty-day mortality was 37.5% (42/112) in cell recipients versus 42.7% (47/110) in control patients (relative risk [RR], 0.88; 95% confidence interval, 0.64-1.21; P = 0.43). There were no significant differences in days alive off ventilation within 60 days (median rank, 117.3 [interquartile range, 60.0-169.5] in cell patients and 102.0 [interquartile range, 54.0-162.5] in control subjects; higher is better). Resolution or improvement of acute respiratory distress syndrome at 30 days was observed in 51/104 (49.0%) cell recipients and 46/106 (43.4%) control patients (odds ratio, 1.36; 95% confidence interval, 0.57-3.21). There were no infusion-related toxicities and overall serious adverse events over 30 days were similar. Conclusions: Mesenchymal cells, while safe, did not improve 30-day survival or 60-day ventilator-free days in patients with moderate and/or severe COVID-19-related acute respiratory distress syndrome.

CPR-related cognitive activity, consciousness, awareness and recall, and its management: A scoping review.

Background: There are increasing numbers of reports of cognitive activity, consciousness, awareness and recall related to cardiopulmonary resuscitation (CPR) and interventions such as the use of sedative and analgesic drugs during CPR. Objectives: This scoping review aims to describe the available evidence concerning CPR-related cognitive activity, consciousness, awareness and recall and interventions such as the use of sedative and analgesic drugs during CPR. Methods: A literature search was conducted of Medline, Embase and CINAHL from inception to 21 October 2021. We included case studies, observational studies, review studies and grey literature. Results: We identified 8 observational studies including 40,317 patients and 464 rescuers, and 26 case reports including 33 patients. The reported prevalence of CPR-induced consciousness was between 0.23% to 0.9% of resuscitation attempts, with 48-59% of experienced professional rescuers surveyed estimated to have observed CPR-induced consciousness. CPR-induced consciousness is associated with professional rescuer CPR, witnessed arrest, a shockable rhythm, increased return of spontaneous circulation (ROSC), and survival to hospital discharge when compared to patients without CPR-induced consciousness. Few studies of sedation for CPR-induced consciousness were identified. Although local protocols for treating CPR-induced consciousness exist, there is no widely accepted guidance. Conclusions: CPR-related cognitive activity, consciousness, awareness and recall is uncommon but increasingly reported by professional rescuers. The data available was heterogeneous in nature and not suitable for progression to a systematic review process. Although local treatment protocols exist for management of CPR-induced consciousness, there are no widely accepted treatment guidelines. More studies are required to investigate the management of CPR-induced consciousness.

Guidelines and standards for the study of death and recalled experiences of death--a multidisciplinary consensus statement and proposed future directions.

An inadvertent consequence of advances in stem cell research, neuroscience, and resuscitation science has been to enable scientific insights regarding what happens to the human brain in relation to death. The scientific exploration of death is in large part possible due to the recognition that brain cells are more resilient to the effects of anoxia than assumed. Hence, brain cells become irreversibly damaged and "die" over hours to days postmortem. Resuscitation science has enabled life to be restored to millions of people after their hearts had stopped. These survivors have described a unique set of recollections in relation to death that appear universal. We review the literature, with a focus on death, the recalled experiences in relation to cardiac arrest, post-intensive care syndrome, and related phenomena that provide insights into potential mechanisms, ethical implications, and methodologic considerations for systematic investigation. We also identify issues and controversies related to the study of consciousness and the recalled experience of cardiac arrest and death in subjects who have been in a coma, with a view to standardize and facilitate future research.

Cerebral oximetry: a developing tool for monitoring cerebral oxygenation during cardiopulmonary resuscitation.

Despite improvements in cardiopulmonary resuscitation (CPR), survival and neurologic recovery after cardiac arrest remain very poor because of the impact of severe ischemia and subsequent reperfusion injury. As the likelihood of survival and favorable neurologic outcome decreases with increasing severity of ischemia during CPR, developing methods to measure the magnitude of ischemia during resuscitation, particularly cerebral ischemia, is critical for improving overall outcomes. Cerebral oximetry, which measures regional cerebral oxygen saturation (rSO2 ) by near-infrared spectroscopy, has emerged as a potentially beneficial marker of cerebral ischemia during CPR. In numerous preclinical and clinical studies, higher rSO2 during CPR has been associated with improved cardiac arrest survival and neurologic outcome. In this narrative review, we summarize the scientific rationale and validation of cerebral oximetry across populations and pathophysiologic states, discuss the evidence surrounding its use to predict return of spontaneous circulation, rearrest, and neurologic outcome, and provide suggestions for incorporation of cerebral oximetry into CPR practice.

Low-Dose Tocilizumab With High-Dose Corticosteroids in Patients Hospitalized for COVID-19 Hypoxic Respiratory Failure Improves Mortality Without Increased Infection Risk.

BACKGROUND: Severe hypoxic respiratory failure from COVID-19 pneumonia carries a high mortality risk. There is uncertainty surrounding which patients benefit from corticosteroids in combination with tocilizumab and the dosage and timing of these agents. The balance of controlling inflammation without increasing the risk of secondary infection is difficult. At present, dexamethasone 6 mg is the standard of care in COVID-19 hypoxia; whether this is the ideal choice of steroid or dosage remains to be proven. OBJECTIVES: The primary objective was to assess the impact on mortality of tocilizumab only, corticosteroids only, and combination therapy in patients with COVID-19 respiratory failure. METHODS: A multihospital, retrospective study of adult patients with severe respiratory failure from COVID-19 who received supportive therapy, corticosteroids, tocilizumab, or combination therapy were assessed for 28-day mortality, biomarker improvement, and relative risk of infection. Propensity-matched analysis was performed between corticosteroid alone and combination therapies to further assess mortality benefit. RESULTS: The steroid-only, tocilizumab-only, and combination groups showed hazard reduction in mortality at 28 days when compared with supportive therapy. In a propensity-matched analysis, the combination group (daily equivalent dexamethasone 10 mg and tocilizumab 400 mg) had an improved 28-day mortality compared with the steroid-only group (daily equivalent dexamethasone 10 mg; hazard ratio (95% CI) = 0.56 (0.38-0.84), P = 0.005] without increasing the risk of infection. CONCLUSION AND RELEVANCE: Combination of tocilizumab and corticosteroids was associated with improved 28-day survival when compared with corticosteroids alone. Modification of steroid dosing strategy as well as steroid type may further optimize therapeutic effect of the COVID-19 treatment.

Pharmacologic neuroprotection in ischemic brain injury after cardiac arrest.

Cardiac arrest has many implications for morbidity and mortality. Few interventions have been shown to improve return of spontaneous circulation (ROSC) and long-term outcomes after cardiac arrest. Ischemic-reperfusion injury upon achieving ROSC creates an imbalance between oxygen supply and demand. Multiple events occur in the postcardiac arrest period, including excitotoxicity, mitochondrial dysfunction, and oxidative stress and inflammation, all of which contribute to ongoing brain injury and cellular death. Given that complex pathophysiology underlies global brain hypoxic ischemia, neuroprotective strategies targeting multiple stages of the neuropathologic cascade should be considered as a means of mitigating secondary neuronal injury and improving neurologic outcomes and survival in cardiac arrest victims. In this review article, we discuss a number of different pharmacologic agents that may have a potential role in targeting these injurious pathways following cardiac arrest. Pharmacologic therapies most relevant for discussion currently include memantine, perampanel, magnesium, propofol, thiamine, methylene blue, vitamin C, vitamin E, coenzyme Q10 , minocycline, steroids, and aspirin.

The impact of extracorporeal membrane oxygenation on cerebral oxygen delivery during cardiac arrest: a case series.

AIM: To describe the impact of extracorporeal membrane oxygenation (ECMO) assisted CPR (E-CPR) on cerebral oxygen delivery during in-hospital cardiac arrest (IHCA). METHODS: Retrospective case series from a tertiary academic medical center. Regional cerebral oxygen saturation (rSO2) was measured continuously using cerebral oximetry in six patients who experienced IHCA. During CPR, the time of E-CPR initiation was recorded, and rSO2 values were subsequently analyzed for a period beginning 5 min before and ending 2.5 min after the initiation of E-CPR. RESULTS: The average rSO2 value in the 2.5 min period following E-CPR initiation increased by 20.8% as compared to the 5-min period before E-CPR initiation. CONCLUSIONS: ECMO can be employed in parallel with cerebral rSO2 monitoring during CPR for adult IHCA patients. E-CPR is associated with rapid and significant increases in brain oxygen delivery.

Decreasing Incidence of Acute Kidney Injury in Patients with COVID-19 Critical Illness in New York City.

INTRODUCTION: Reports from the United States suggest that acute kidney injury (AKI) frequently complicates coronavirus disease 2019 (COVID-19), but understanding of AKI risks and outcomes is incomplete. In addition, whether kidney outcomes have evolved during the course of the pandemic is unknown. METHODS: We used electronic medical records to identify patients with COVID-19 with and without AKI admitted to 3 New York Hospitals between March 2 and August 25, 2020. Outcomes included AKI overall and according to admission week, AKI stage, the requirement for new renal replacement therapy (RRT), mortality, and recovery of kidney function. Logistic regression was used to assess associations of patient characteristics and outcomes. RESULTS: Of 4732 admissions, 1386 (29.3%) patients had AKI. Among those with AKI, 717 (51.7%) had stage 1 disease, 132 (9.5%) had stage 2 disease, 537 (38.7%) had stage 3 disease, and 237 (17.1%) required RRT initiation. In March, 536 of 1648 (32.5%) patients developed AKI compared with 15 of 87 (17.2%) in August (P < 0.001 for monthly trend), whereas RRT initiation was required in 6.9% and 0% of admissions in March and August, respectively. Mortality was higher with than without AKI (51.6% vs. 8.6%) and was 71.9% in individuals requiring RRT. However, most patients with AKI who survived hospitalization (77%) recovered to within 0.3 mg/dl of baseline creatinine. Among those surviving to discharge, 62% discontinued RRT. CONCLUSIONS: AKI impacts a high proportion of admitted patients with COVID-19 and is associated with high mortality, particularly when RRT is required. AKI incidence appears to be decreasing over time and kidney function frequently recovers in those who survive.

Association of post-resuscitation inflammatory response with favorable neurologic outcomes in adults with in-hospital cardiac arrest.

BACKGROUND: Early prediction of mortality in adults after in-hospital cardiac arrest (IHCA) remains vital to optimizing treatment strategies. Inflammatory cytokines specific to early prognostication in this population have not been well studied. We evaluated whether novel inflammatory cytokines obtained from adults with IHCA helped predict favorable neurologic outcome. METHODS: The study population included adults with IHCA who underwent ACLS-guided resuscitation between March 2014 and May 2019 at an academic tertiary medical center. Peripheral blood samples were obtained within 6, 24, 48, 72, and 96 h of IHCA and analysis of 15 cytokines were performed. The primary outcome of interest was presence of favorable neurologic outcome at hospital discharge, defined as a Glasgow Outcome Score of 4 or 5. RESULTS: Of the 105 adults with IHCA studied, 27 (25.7%) were noted to have survival with a favorable neurologic outcome while 78 (74.3%) did not. Patients who survived with favorable neurologic outcome were more often men (88.9% vs 61.5%, p = 0.008) and had higher rates of ventricular tachyarrhythmias as their initial rhythm (34.6% vs 11.7%, p = 0.018). Levels of interleukin (IL)-6, IL-8, IL-10, and Tumor Necrosis Factor (TNF)-R1 within 6 or 24 h were significantly lower in patients with favorable neurologic outcome compared with those who had unfavorable neurologic outcome. In multivariable analysis, IL-10 levels within 6 h was the only independent predictor of favorable neurologic outcomes [odds ratio (OR) 0.895, 95% confidence interval 0.805-0.996, p = 0.041]. CONCLUSION: In this contemporary observational study of adults with IHCA receiving ACLS-guided resuscitative and post-resuscitative care, inflammatory cytokines specific to early prognostication in adults with IHCA exist. Further larger scale studies examining the association of these inflammatory cytokines with prognosis are warranted.

Outcomes among Hospitalized Chronic Kidney Disease Patients with COVID-19.

Background: Patients with CKD ha ve impaired immunity, increased risk of infection-related mortality, and worsened COVID-19 outcomes. However, data comparing nondialysis CKD and ESKD are sparse. Methods: Patients with COVID-19 admitted to three hospitals in the New York area, between March 2 and August 27, 2020, were retrospectively studied using electronic health records. Patients were classified as those without CKD, those with nondialysis CKD, and those with ESKD, with outcomes including hospital mortality, ICU admission, and mortality rates. Results: Of 3905 patients, 588 (15%) had nondialysis CKD and 128 (3%) had ESKD. The nondialysis CKD and ESKD groups had a greater prevalence of comorbidities and higher admission D-dimer levels, whereas patients with ESKD had lower C-reactive protein levels at admission. ICU admission rates were similar across all three groups (23%-25%). The overall, unadjusted hospital mortality was 25%, and the mortality was 24% for those without CKD, 34% for those with nondialysis CKD, and 27% for those with ESKD. Among patients in the ICU, mortality was 56%, 64%, and 56%, respectively. Although patients with nondialysis CKD had higher odds of overall mortality versus those without CKD in univariate analysis (OR, 1.58; 95% CI, 1.31 to 1.91), this was no longer significant in fully adjusted models (OR, 1.11; 95% CI, 0.88 to 1.40). Also, ESKD status did not associate with a higher risk of mortality compared with non-CKD in adjusted analyses, but did have reduced mortality when compared with nondialysis CKD (OR, 0.57; 95% CI, 0.33 to 0.95). Mortality rates declined precipitously after the first 2 months of the pandemic, from 26% to 14%, which was reflected in all three subgroups. Conclusions: In a diverse cohort of patients with COVID-19, we observed higher crude mortality rates for patients with nondialysis CKD and, to a lesser extent, ESKD, which were not significant after risk adjustment. Moreover, patients with ESKD appear to have better outcom es than those with nondialysis CKD.

Prevalence and Outcomes of D-Dimer Elevation in Hospitalized Patients With COVID-19.

OBJECTIVE: To determine the prevalence of D-dimer elevation in coronavirus disease 2019 (COVID-19) hospitalization, trajectory of D-dimer levels during hospitalization, and its association with clinical outcomes. Approach and Results: Consecutive adults admitted to a large New York City hospital system with a positive polymerase chain reaction test for SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) between March 1, 2020 and April 8, 2020 were identified. Elevated D-dimer was defined by the laboratory-specific upper limit of normal (>230 ng/mL). Outcomes included critical illness (intensive care, mechanical ventilation, discharge to hospice, or death), thrombotic events, acute kidney injury, and death during admission. Among 2377 adults hospitalized with COVID-19 and ≥1 D-dimer measurement, 1823 (76%) had elevated D-dimer at presentation. Patients with elevated presenting baseline D-dimer were more likely than those with normal D-dimer to have critical illness (43.9% versus 18.5%; adjusted odds ratio, 2.4 [95% CI, 1.9-3.1]; P<0.001), any thrombotic event (19.4% versus 10.2%; adjusted odds ratio, 1.9 [95% CI, 1.4-2.6]; P<0.001), acute kidney injury (42.4% versus 19.0%; adjusted odds ratio, 2.4 [95% CI, 1.9-3.1]; P<0.001), and death (29.9% versus 10.8%; adjusted odds ratio, 2.1 [95% CI, 1.6-2.9]; P<0.001). Rates of adverse events increased with the magnitude of D-dimer elevation; individuals with presenting D-dimer >2000 ng/mL had the highest risk of critical illness (66%), thrombotic event (37.8%), acute kidney injury (58.3%), and death (47%). CONCLUSIONS: Abnormal D-dimer was frequently observed at admission with COVID-19 and was associated with higher incidence of critical illness, thrombotic events, acute kidney injury, and death. The optimal management of patients with elevated D-dimer in COVID-19 requires further study.

The association between post-cardiac arrest cerebral oxygenation and survival with favorable neurological outcomes: A multicenter study.

OBJECTIVE: Cerebral oximetry is a non-invasive system that uses near infrared spectroscopy to measure regional cerebral oxygenation (rSO2) in the frontal lobe of the brain. Post-cardiac arrest rSO2 may be associated with survival and neurological outcomes in out-of-hospital cardiac arrest patients; however, no studies have examined relationships between rSO2 and neurological outcomes following in-hospital cardiac arrest (IHCA). We tested the hypothesis that rSO2 following IHCA is associated with survival and favorable neurological outcomes. DESIGN: Prospective study from nine acute care hospital in the United States and United Kingdom. PATIENTS: Convenience sample of IHCA patients admitted to the intensive care unit with post-cardiac arrest syndrome. INTERVENTIONS: Cerebral oximetry monitoring (Equanox 7600, Nonin Medical, MN, USA) during the first 48 h after IHCA. MEASUREMENTS AND MAIN RESULTS: Subject's rSO2 was calculated as the mean of collected data at different time intervals: hourly between 1-6 h, 6-12 h, 12-18 h, 18-24 h and 24-48 h. Demographic data pertaining to possible confounding variables for rSO2 and primary outcome were collected. The primary outcome was survival with favorable neurological outcomes (cerebral performance scale [CPC] 1-2) vs severe neurological injury or death (CPC 3-5) at hospital discharge. Univariate and multivariate statistical analyses were performed to correlate cerebral oximetry values and other variables with the primary outcome. Among 87 studied patients, 26 (29.9%) achieved CPC 1-2. A significant difference in mean rSO2 was observed during hours 1-2 after IHCA in CPC 1-2 vs CPC 3-5 (73.08 vs. 66.59, p = 0.031) but not at other time intervals. There were no differences in age, Charlson comorbidity index, APACHE II scores, CPR duration, mean arterial pressure, PaO2, PaCO2, and hemoglobin levels between two groups. CONCLUSIONS: There may be a significant physiological difference in rSO2 in the first two hours after ROSC in IHCA patients who achieve favorable neurological outcomes, however, this difference may not be clinically significant.