The dynamics and longevity of circulating CD4+ memory T cells depend on cell age and not the chronological age of the host.

Quantifying the kinetics with which memory T cell populations are generated and maintained is essential for identifying the determinants of the duration of immunity. The quality and persistence of circulating CD4 effector memory (TEM) and central memory (TCM) T cells in mice appear to shift with age, but it is unclear whether these changes are driven by the aging host environment, by cell age effects, or both. Here, we address these issues by combining DNA labelling methods, established fate-mapping systems, a novel reporter mouse strain, and mathematical models. Together, these allow us to quantify the dynamics of both young and established circulating memory CD4 T cell subsets, within both young and old mice. We show that that these cells and their descendents become more persistent the longer they reside within the TCM and TEM pools. This behaviour may limit memory CD4 T cell diversity by skewing TCR repertoires towards clones generated early in life, but may also compensate for functional defects in new memory cells generated in old age.

The changing landscape of text mining: a review of approaches for ecology and evolution.

In ecology and evolutionary biology, the synthesis and modelling of data from published literature are commonly used to generate insights and test theories across systems. However, the tasks of searching, screening, and extracting data from literature are often arduous. Researchers may manually process hundreds to thousands of articles for systematic reviews, meta-analyses, and compiling synthetic datasets. As relevant articles expand to tens or hundreds of thousands, computer-based approaches can increase the efficiency, transparency and reproducibility of literature-based research. Methods available for text mining are rapidly changing owing to developments in machine learning-based language models. We review the growing landscape of approaches, mapping them onto three broad paradigms (frequency-based approaches, traditional Natural Language Processing and deep learning-based language models). This serves as an entry point to learn foundational and cutting-edge concepts, vocabularies, and methods to foster integration of these tools into ecological and evolutionary research. We cover approaches for modelling ecological texts, generating training data, developing custom models and interacting with large language models and discuss challenges and possible solutions to implementing these methods in ecology and evolution.

Validating the safety of low-dose CTPA in pregnancy: results from the OPTICA (Optimised CT Pulmonary Angiography in Pregnancy) Study.

BACKGROUND: Pulmonary embolism (PE) is a leading cause of pregnancy-related mortality. CT pulmonary angiogram (CTPA) is the first-line advanced imaging modality for suspected PE in pregnancy at institutes offering low-dose techniques; however, a protocol balancing safety with low dose remains undefined. The wide range of CTPA doses reported in pregnancy suggests a lack of confidence in implementing low-dose techniques in this group. PURPOSE: To define and validate the safety, radiation dose and image quality of a low-dose CTPA protocol optimised for pregnancy. MATERIALS AND METHODS: The OPTICA study is a prospective observational study. Pregnant study participants with suspected PE underwent the same CTPA protocol between May 2018 and February 2022. The primary outcome, CTPA safety, was judged by the reference standard; the 3-month incidence of venous thromboembolism (VTE) in study participants with a negative index CTPA. Secondary outcomes defined radiation dose and image quality. Absorbed breast, maternal effective and fetal doses were estimated by Monte-Carlo simulation on gestation-matched phantoms. Image quality was assessed by signal-to-noise and contrast-to-noise ratios and a Likert score for pulmonary arterial enhancement. RESULTS: A total of 116 CTPAs were performed in 113 pregnant women of which 16 CTPAs were excluded. PE was diagnosed on 1 CTPA and out-ruled in 99. The incidence of recurrent symptomatic VTE was 0.0% (one-sided 95% CI, 2.66%) at follow-up. The mean absorbed breast dose was 2.9 ± 2.1mGy, uterine/fetal dose was 0.1 ± 0.2mGy and maternal effective dose was 1.4 ± 0.9mSv. Signal-to-noise ratio (SNR) was 11.9 ± 3.7. Contrast-to-noise ratio (CNR) was 10.4 ± 3.5. CONCLUSION: The OPTICA CTPA protocol safely excluded PE in pregnant women across all trimesters, with low fetal and maternal radiation. CLINICAL RELEVANCE: OPTICA (Optimised CT Pulmonary Angiography in Pregnancy) is the first prospective study to define the achievable radiation dose, image-quality and safety of a low-dose CT pulmonary angiogram protocol optimised for pregnancy (NCT04179487). It provides the current benchmark for safe and achievable CT pulmonary angiogram doses in the pregnant population. KEY POINTS: • Despite the increased use of CT pulmonary angiogram in pregnancy, an optimised low-dose protocol has not been defined and reported doses in pregnancy continue to vary widely. • The OPTICA (Optimised CT Pulmonary Angiography in Pregnancy) study prospectively defines the achievable dose, image quality and safety of a low-dose CT pulmonary angiogram protocol using widely available technology. • OPTICA provides a benchmark for safe and achievable CT pulmonary angiogram doses in the pregnant population.

Early bolus epinephrine administration during pediatric cardiopulmonary resuscitation for bradycardia with poor perfusion: an ICU-resuscitation study.

BACKGROUND: Half of pediatric in-hospital cardiopulmonary resuscitation (CPR) events have an initial rhythm of non-pulseless bradycardia with poor perfusion. Our study objectives were to leverage granular data from the ICU-RESUScitation (ICU-RESUS) trial to: (1) determine the association of early epinephrine administration with survival outcomes in children receiving CPR for bradycardia with poor perfusion; and (2) describe the incidence and time course of the development of pulselessness. METHODS: Prespecified secondary analysis of ICU-RESUS, a multicenter cluster randomized trial of children (< 19 years) receiving CPR in 18 intensive care units in the United States. Index events (October 2016-March 2021) lasting ≥ 2 min with a documented initial rhythm of bradycardia with poor perfusion were included. Associations between early epinephrine (first 2 min of CPR) and outcomes were evaluated with Poisson multivariable regression controlling for a priori pre-arrest characteristics. Among patients with arterial lines, intra-arrest blood pressure waveforms were reviewed to determine presence of a pulse during CPR interruptions. The temporal nature of progression to pulselessness was described and outcomes were compared between patients according to subsequent pulselessness status. RESULTS: Of 452 eligible subjects, 322 (71%) received early epinephrine. The early epinephrine group had higher pre-arrest severity of illness and vasoactive-inotrope scores. Early epinephrine was not associated with survival to discharge (aRR 0.97, 95%CI 0.82, 1.14) or survival with favorable neurologic outcome (aRR 0.99, 95%CI 0.82, 1.18). Among 186 patients with invasive blood pressure waveforms, 118 (63%) had at least 1 period of pulselessness during the first 10 min of CPR; 86 (46%) by 2 min and 100 (54%) by 3 min. Sustained return of spontaneous circulation was highest after bradycardia with poor perfusion (84%) compared to bradycardia with poor perfusion progressing to pulselessness (43%) and bradycardia with poor perfusion progressing to pulselessness followed by return to bradycardia with poor perfusion (62%) (p < 0.001). CONCLUSIONS: In this cohort of pediatric CPR events with an initial rhythm of bradycardia with poor perfusion, we failed to identify an association between early bolus epinephrine and outcomes when controlling for illness severity. Most children receiving CPR for bradycardia with poor perfusion developed subsequent pulselessness, 46% within 2 min of CPR onset.

Management of Extracorporeal Membrane Oxygenation Anticoagulation in the Perioperative Period: The Pediatric Extracorporeal Membrane Oxygenation Anticoagulation CollaborativE Consensus Conference.

OBJECTIVES: To derive systematic review-informed, modified Delphi consensus regarding the management of children on extracorporeal membrane oxygenation (ECMO) undergoing invasive procedures or interventions developed by the Pediatric Anticoagulation on ECMO CollaborativE (PEACE) Consensus Conference. DATA SOURCES: A structured literature search was performed using PubMed, EMBASE, and Cochrane Library (CENTRAL) databases from January 1988 to May 2021. STUDY SELECTION: ECMO anticoagulation and hemostasis management in the perioperative period and during procedures. DATA EXTRACTION: Two authors reviewed all citations independently, with a third independent reviewer resolving any conflicts. Seventeen references were used for data extraction and informed recommendations. Evidence tables were constructed using a standardized data extraction form. DATA SYNTHESIS: Risk of bias was assessed using the Quality in Prognosis Studies tool. The evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation system. Forty-eight experts met over 2 years to develop evidence-based recommendations and, when evidence was lacking, expert-based consensus statements for the management of bleeding and thrombotic complications in pediatric ECMO patients. A web-based modified Delphi process was used to build consensus via the Research And Development/University of California Appropriateness Method. Consensus was defined as greater than 80% agreement. Four good practice statements, 7 recommendations, and 18 consensus statements are presented. CONCLUSIONS: Although agreement among experts was strong, important future research is required in this population for evidence-informed recommendations.

Clinical Outcomes After Tracheostomy in Children With Single Ventricle Physiology: Collaborative Research From the Pediatric Cardiac Intensive Care Society Multicenter Cohort, 2010-2021.

OBJECTIVES: Multicenter studies reporting outcomes following tracheostomy in children with congenital heart disease are limited, particularly in patients with single ventricle physiology. We aimed to describe clinical characteristics and outcomes in a multicenter cohort of patients with single ventricle physiology who underwent tracheostomy before Fontan operation. DESIGN: Multicenter retrospective cohort study. SETTING: Twenty-one tertiary care pediatric institutions participating in the Collaborative Research from the Pediatric Cardiac Intensive Care Society. PATIENTS: We reviewed 99 children with single ventricle physiology who underwent tracheostomy before the Fontan operation at 21 institutions participating in Collaborative Research from the Pediatric Cardiac Intensive Care Society between January 2010 and December 2020, with follow-up through December 31, 2021. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Death occurred in 51 of 99 patients (52%). Cox proportional hazard analysis was performed to determine factors associated with death after tracheostomy. Results are presented as hazard ratio (HR) with 95% CIs. Nonrespiratory indication(s) for tracheostomy (HR, 2.21; 95% CI, 1.14-4.32) and number of weeks receiving mechanical ventilation before tracheostomy (HR, 1.06; 95% CI, 1.02-1.11) were independently associated with greater hazard of death. In contrast, diagnosis of tricuspid atresia or Ebstein's anomaly was associated with less hazard of death (HR, 0.16; 95% CI, 0.04-0.69). Favorable outcome, defined as survival to Fontan operation or decannulation while awaiting Fontan operation with viable cardiopulmonary physiology, occurred in 29 of 99 patients (29%). Median duration of mechanical ventilation before tracheostomy was shorter in patients who survived to favorable outcome (6.1 vs. 12.1 wk; p < 0.001), and only one of 16 patients with neurologic indications for tracheostomy and 0 of ten patients with cardiac indications for tracheostomy survived to favorable outcome. CONCLUSIONS: For children with single ventricle physiology who undergo tracheostomy, mortality risk is high and should be carefully considered when discussing tracheostomy as an option for these children. Favorable outcomes are possible, although thoughtful attention to patient selection and tracheostomy timing are likely necessary to achieve this goal.

Executive Summary: The Pediatric Extracorporeal Membrane Oxygenation Anticoagulation CollaborativE (PEACE) Consensus Conference.

OBJECTIVES: To present recommendations and consensus statements with supporting literature for the clinical management of neonates and children supported with extracorporeal membrane oxygenation (ECMO) from the Pediatric ECMO Anticoagulation CollaborativE (PEACE) consensus conference. DATA SOURCES: Systematic review was performed using PubMed, Embase, and Cochrane Library (CENTRAL) databases from January 1988 to May 2021, followed by serial meetings of international, interprofessional experts in the management ECMO for critically ill children. STUDY SELECTION: The management of ECMO anticoagulation for critically ill children. DATA EXTRACTION: Within each of eight subgroup, two authors reviewed all citations independently, with a third independent reviewer resolving any conflicts. DATA SYNTHESIS: A systematic review was conducted using MEDLINE, Embase, and Cochrane Library databases, from January 1988 to May 2021. Each panel developed evidence-based and, when evidence was insufficient, expert-based statements for the clinical management of anticoagulation for children supported with ECMO. These statements were reviewed and ratified by 48 PEACE experts. Consensus was obtained using the Research and Development/UCLA Appropriateness Method. Results were summarized using the Grading of Recommendations Assessment, Development, and Evaluation method. We developed 23 recommendations, 52 expert consensus statements, and 16 good practice statements covering the management of ECMO anticoagulation in three broad categories: general care and monitoring; perioperative care; and nonprocedural bleeding or thrombosis. Gaps in knowledge and research priorities were identified, along with three research focused good practice statements. CONCLUSIONS: The 91 statements focused on clinical care will form the basis for standardization and future clinical trials.

The emerging role of fatty acid binding protein 7 (FABP7) in cancers.

Fatty acid binding protein 7 (FABP7) is an intracellular protein involved in the uptake, transportation, metabolism, and storage of fatty acids (FAs). FABP7 is upregulated up to 20-fold in multiple cancers, usually correlated with poor prognosis. FABP7 silencing or pharmacological inhibition suggest FABP7 promotes cell growth, migration, invasion, colony and spheroid formation/increased size, lipid uptake, and lipid droplet formation. Xenograft studies show that suppression of FABP7 inhibits tumour formation and tumour growth, and improves host survival. The molecular mechanisms involve promotion of FA uptake, lipid droplets, signalling [focal adhesion kinase (FAK), proto-oncogene tyrosine-protein kinase Src (Src), mitogen-activated protein kinase kinase/p-extracellular signal-regulated kinase (MEK/ERK), and Wnt/ß-catenin], hypoxia-inducible factor 1-alpha (Hif1α), vascular endothelial growth factor A/prolyl 4-hydroxylase subunit alpha-1 (VEGFA/P4HA1), snail family zinc finger 1 (Snail1), and twist-related protein 1 (Twist1). The oncogenic capacity of FABP7 makes it a promising pharmacological target for future cancer treatments.

Notch2 controls developmental fate choices between germinal center and marginal zone B cells upon immunization.

Sustained Notch2 signals induce trans-differentiation of Follicular B (FoB) cells into Marginal Zone B (MZB) cells in mice, but the physiology underlying this differentiation pathway is still elusive. Here, we demonstrate that most B cells receive a basal Notch signal, which is intensified in pre-MZB and MZB cells. Ablation or constitutive activation of Notch2 upon T-cell-dependent immunization reveals an interplay between antigen-induced activation and Notch2 signaling, in which FoB cells that turn off Notch2 signaling enter germinal centers (GC), while high Notch2 signaling leads to generation of MZB cells or to initiation of plasmablast differentiation. Notch2 signaling is dispensable for GC dynamics but appears to be re-induced in some centrocytes to govern expansion of IgG1+ GCB cells. Mathematical modelling suggests that antigen-activated FoB cells make a Notch2 dependent binary fate-decision to differentiate into either GCB or MZB cells. This bifurcation might serve as a mechanism to archive antigen-specific clones into functionally and spatially diverse B cell states to generate robust antibody and memory responses.

What is the optimum post treatment surveillance imaging protocol for low-grade appendiceal mucinous neoplasms and pseudomyxoma peritoneii?

Appendiceal mucinous neoplasms are rare and can be associated with the development of disseminated peritoneal disease known as pseudomyxoma peritonei (PMP). Mucinous tumours identified on appendicectomy are therefore followed up to assess for recurrence and the development of PMP. In addition, individuals who initially present with PMP and are treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) are followed up to assess for recurrence. However, despite the concerted efforts of multiple expert groups, the optimal imaging follow-up protocol is yet to be established. The purpose of this article is to review the available evidence for imaging surveillance in these populations to identify the optimum post-resection imaging follow-up protocol.

Perioperative Evaluation of Arterial and Venous Whole Blood in the Lamb (Ovis aries) Fontan Model.

Whole blood analysis can evaluate numerous parameters, including pH, pCO2, pO2, HCO3 - , base excess, glucose, electrolytes, lactate, blood urea nitrogen, creatinine, bilirubin, and hemoglobin. This valuable tool enables clinicians to make more informed decisions about patient care. However, the current body of literature describing perioperative whole blood analysis in Dorset sheep (Ovis aries) is small, so clinicians lack adequate information to guide their decision-making when evaluating test results. We evaluated arterial and venous whole blood pH, bicarbonate, pCO2, lactate, creatinine, and blood urea nitrogen before and for the first 24 hours after surgery in 2 cohorts of male and female Ovis arie s undergoing one of 2 major cardiovascular procedures, a Single-Stage Fontan or an inferior vena cava to pulmonary artery extracardiac conduit implantation (IP-ECC). The cohort undergoing a Single-Stage Fontan, which is the more complex procedure, exhibited greater deviation from baseline measurements than did the cohort undergoing the IP-ECC for lactate, bicarbonate, and creatinine. The cohort undergoing the IP-ECC showed no significant deviation from baseline for any parameters, potentially indicating a better safety margin than expected when compared with the Single-Stage Fontan. Together, these results indicate the clinical value of arterial and venous whole blood measurements in perioperative management of sheep and can provide a reference for clinicians managing sheep after significant cardiovascular procedures.

The dynamics and longevity of circulating CD4+ memory T cells depend on cell age and not the chronological age of the host.

Quantifying the kinetics with which memory T cell populations are generated and maintained is essential for identifying the determinants of the duration of immunity. The quality and persistence of circulating CD4+ effector memory (TEM) and central memory (TCM) T cells in mice appear to shift with age, but it is unclear whether these changes are driven by the aging host environment, by cell age effects, or both. Here we address these issues by combining DNA labelling methods, established fate-mapping systems, a novel reporter mouse strain, and mathematical models. Together, these allow us to quantify the dynamics of both young and established circulating memory CD4+ T cell subsets, within both young and old mice. We show that that these cells and their descendents become more persistent the longer they reside within the TCM and TEM pools. This behaviour may limit memory CD4 T cell diversity by skewing TCR repertoires towards clones generated early in life, but may also compensate for functional defects in new memory cells generated in old age.

A linear ontogeny accounts for the development of naive, memory and tumour-infiltrating regulatory T cells in mice.

Foxp3 + Regulatory T cells (Treg) are a subset of CD4 + T cells that play critical functions in maintaining tolerance to self antigens and suppressing autoimmunity, regulating immune responses to pathogens and have a role in the pathophysiology of anti-tumoural immunity. Treg ontogeny is complex since they are generated following recognition of self antigens in the thymus during normal T cell development (thymic Treg), but are also induced from mature conventional T cells when activated by foreign antigen with appropriate additional cues (inducible Treg). How these distinct ontogenic pathways contribute to the maintenance and function of the mature Treg compartment in health and disease remains unclear. Here, we use a combination of fate mapping approaches in mice to map the ontogeny of Treg subsets throughout life and estimate rates of production, loss and self-renewal. We find that naive and effector/memory (EM) Treg subsets exhibit distinct dynamics but are both continuously replenished by de novo generation throughout life. Using an inducible Foxp3-dependent Cre fate reporter system, we show that naive Treg and not conventional T cells, are the predominant precursors of EM Treg in adults. Tonic development of new EM Treg is not influenced by foreign antigens from commensals, rather suggesting a role for self recognition. To investigate the ontogeny of Treg development in malignant disease, we used the same fate reporter systems to characterise the Treg infiltrate of three different model tumours. In all three cases, we found that Treg derived from pre-existing, EM Treg. Together, these results reveal a predominantly linear pathway of Treg development from thymic origin to EM Treg associated with pathophysiology of malignant disease, that is driven by self antigen recognition throughout.

An Optimized CT Protocol for Detecting Suspected Cauda Equina Syndrome: A Comparative Analysis with MRI.

BACKGROUND AND PURPOSE: Lumbar disc herniation, potentially leading to nerve root compression and cauda equina syndrome, is typically evaluated using MR imaging. However, the limited availability of MR imaging outside regular hours in certain health care systems poses considerable challenges. This purpose of this study was to prospectively evaluate the diagnostic accuracy of an optimized CT lumbar spine protocol as a potential alternative to MR imaging in assessing suspected neural compression. MATERIALS AND METHODS: Patients presenting to the emergency department with suspected cauda equina syndrome or acute radicular symptoms secondary to lumbar disc herniation referred for MR imaging were prospectively enrolled for an additional CT optimized to assess spinal stenosis. An expert radiologist, blinded to clinical data, graded canal stenosis at each lumbar level on CT. The same grading process was applied to MR imaging after a 4-week interval to maintain blinding. RESULTS: Fifty-nine individuals were included in the final analysis. In 22 (39%) cases, no significant stenosis was identified. In a further 22 (37%) cases, disc pathology was identified that was managed conservatively. Thirteen (22%) individuals proceeded to urgent surgical decompression. In 1 (2%) instance, an alternative diagnosis was identified. Compared with MR imaging, the sensitivity, specificity, and positive and negative predictive values for CT in detecting disc pathology in patients presenting with symptoms suggestive of acute neural compression were 97% (95% CI, 82%-99%), 97% (95% CI, 83%-99%), 97% (95% CI, 92%-99%), and 97% (95% CI, 83%-99%), respectively. CT accurately identified all cases requiring urgent decompression. CONCLUSIONS: CT accurately predicted MR imaging findings in patients with suspected cauda equina and nerve root compression, demonstrating its utility as an adjunct tool for patient triage in emergency settings with limited MR imaging access. This protocol could enhance the allocation of emergency resources by appropriately selecting patients for emergent MR imaging.

Discovery and Preclinical Evaluation of a Novel Inhibitor of FABP5, ART26.12, Effective in Oxaliplatin-Induced Peripheral Neuropathy.

Oxaliplatin-induced peripheral neuropathy (OIPN) is a dose-limiting toxicity characterised by mechanical allodynia and thermal hyperalgesia, without any licensed medications. ART26.12 is a fatty acid-binding protein (FABP) 5 inhibitor with antinociceptive properties, characterised here for the prevention and treatment of OIPN. ART26.12 binds selectively to FABP5 compared to FABP3, FABP4, and FABP7, with minimal off-target liabilities, high oral bioavailability, and a NOAEL of 1,000 mg/kg/day in rats and dogs. In an established preclinical OIPN model, acute oral dosing (25-100 mg/kg) showed a cannabinoid receptor type 1 (CB1)-dependent anti-allodynic effect lasting up to 8 hours (persisting longer than plasma exposure to ART26.12). Antagonists of cannabinoid receptor type 2 (CB2), peroxisome proliferator-activated receptor alpha, and transient receptor potential cation channel subfamily V member 1 (TRPV1) may have also been implicated. Twice daily oral dosing (25 mg/kg bis in die (BID) for 7 days) showed anti-allodynic effects in an established OIPN model without the development of tolerance. In a prevention paradigm, coadministration of ART26.12 (10 and 25 mg/kg BID for 15 days) with oxaliplatin prevented thermal hyperalgesia, mitigated mechanical allodynia, and attenuated OXA-induced weight loss. Multi-scale analyses revealed widespread lipid modulation, particularly among N-acyl amino acids in the spinal cord, including potential analgesic mediators. Additionally, ART26.12 administration led to upregulation of ion channels in the periaqueductal grey, and broad translational upregulation within the plasma proteome. These results show promise that ART26.12 is a safe and well-tolerated candidate for the treatment and prevention of OIPN through lipid modulation. PERSPECTIVE: Inhibition of fatty acid-binding protein 5 (FABP5) is a novel target for reducing pain associated with chemotherapy. ART26.12 is a safe and well-tolerated small molecule FABP5 inhibitor effective at preventing and reducing pain induced with oxaliplatin through lipid modulation and activation of cannabinoid receptors.

Tissue engineered vascular grafts are resistant to the formation of dystrophic calcification.

Advancements in congenital heart surgery have heightened the importance of durable biomaterials for adult survivors. Dystrophic calcification poses a significant risk to the long-term viability of prosthetic biomaterials in these procedures. Herein, we describe the natural history of calcification in the most frequently used vascular conduits, expanded polytetrafluoroethylene grafts. Through a retrospective clinical study and an ovine model, we compare the degree of calcification between tissue-engineered vascular grafts and polytetrafluoroethylene grafts. Results indicate superior durability in tissue-engineered vascular grafts, displaying reduced late-term calcification in both clinical studies (p < 0.001) and animal models (p < 0.0001). Further assessments of graft compliance reveal that tissue-engineered vascular grafts maintain greater compliance (p < 0.0001) and distensibility (p < 0.001) than polytetrafluoroethylene grafts. These properties improve graft hemodynamic performance, as validated through computational fluid dynamics simulations. We demonstrate the promise of tissue engineered vascular grafts, remaining compliant and distensible while resisting long-term calcification, to enhance the long-term success of congenital heart surgeries.

Association of Pediatric Postcardiac Arrest Ventilation and Oxygenation with Survival Outcomes.

Rationale: Adult and pediatric studies provide conflicting data regarding whether post-cardiac arrest hypoxemia, hyperoxemia, hypercapnia, and/or hypocapnia are associated with worse outcomes. Objectives: We sought to determine whether postarrest hypoxemia or postarrest hyperoxemia is associated with lower rates of survival to hospital discharge, compared with postarrest normoxemia, and whether postarrest hypocapnia or hypercapnia is associated with lower rates of survival, compared with postarrest normocapnia. Methods: An embedded prospective observational study during a multicenter interventional cardiopulmonary resuscitation trial was conducted from 2016 to 2021. Patients ⩽18 years old and with a corrected gestational age of ≥37 weeks who received chest compressions for cardiac arrest in one of the 18 intensive care units were included. Exposures during the first 24 hours postarrest were hypoxemia, hyperoxemia, or normoxemia-defined as lowest arterial oxygen tension/pressure (PaO2) <60 mm Hg, highest PaO2 ⩾200 mm Hg, or every PaO2 60-199 mm Hg, respectively-and hypocapnia, hypercapnia, or normocapnia, defined as lowest arterial carbon dioxide tension/pressure (PaCO2) <30 mm Hg, highest PaCO2 ⩾50 mm Hg, or every PaCO2 30-49 mm Hg, respectively. Associations of oxygenation and carbon dioxide group with survival to hospital discharge were assessed using Poisson regression with robust error estimates. Results: The hypoxemia group was less likely to survive to hospital discharge, compared with the normoxemia group (adjusted relative risk [aRR] = 0.71; 95% confidence interval [CI] = 0.58-0.87), whereas survival in the hyperoxemia group did not differ from that in the normoxemia group (aRR = 1.0; 95% CI = 0.87-1.15). The hypercapnia group was less likely to survive to hospital discharge, compared with the normocapnia group (aRR = 0.74; 95% CI = 0.64-0.84), whereas survival in the hypocapnia group did not differ from that in the normocapnia group (aRR = 0.91; 95% CI = 0.74-1.12). Conclusions: Postarrest hypoxemia and hypercapnia were each associated with lower rates of survival to hospital discharge.