Optimal ventilator settings after return of spontaneous circulation:

Nicotinamide mononucleotide mitigates hyperoxia-aggravated septic lung injury via the GPx4-mediated anti-ferroptosis signaling pathway in alveolar epithelial cells

BACKGROUND

The molecular mechanisms and optimal treatment strategies underlying hyperoxia-aggravated septic lung injury remain elusive. We explored the effects and mechanisms of nicotinamide mononucleotide (NMN) on hyperoxia-aggravated septic lung injury.

METHODS

The rat and cellular models of sepsis-induced lung injury were established and subjected to hyperoxygenation treatment, followed by treatment with NMN, ferroptosis promoter, or inhibitor separately. The extent of lung injury was assessed based on histological examination, lung histological injury scores, wet/dry weight ratio of lung tissues, oxygenation indexes, TNF-ɑ and IL-6 levels, and cell viability. Meanwhile, ferroptosis was assessed through various methods. The levels of glutathione peroxidase 4 (GPx4) and 4-hydroxynonenal (4-HNE) in lung tissues were determined by immunohistochemistry, while iron deposition was evaluated using Prussian blue staining. Fe2+, MDA, and GSH levels were also detected with the respective kits. The reactive oxygen species (ROS) level was measured by flow cytometry and immunofluorescence techniques. The protein and mRNA levels of GPx4 and ACSL4 were also detected. The relationship between sirtuin 6 (SIRT6) and GPx4 was clarified by using SIRT6 inhibitor and activator, as well as in combination with sh-GPx4.

RESULTS

Hyperoxia exacerbated lung injury in rats subjected to cecal ligation and puncture (CLP). Hyperoxia also intensified damage to alveolar epithelial cells (AECs) in a lipopolysaccharide (LPS) model. However, NMN ameliorated these detrimental effects. Furthermore, LPS+Hyperoxia treatment significantly upregulated Fe2+, MDA, ROS, and ACSL4 levels, exacerbating oxidative damage. Also, LPS+Hyperoxia treatment downregulated GSH and GPx4 levels, thereby reducing antioxidant capacity. Additionally, Erastin, a ferroptosis promoter, further intensified oxidative stress damage and inflammatory response. However, ferroptosis inhibitor Fer-1 alleviated this damage. Similarly, NMN inhibited ferroptosis in hyperoxia-aggravated septic lung injury. Co-treatment with NMN and sh-GPx4 reversed the protective effect of NMN against LPS-stimulated injury exacerbated by hyperoxia in AECs. NMN supplementation increased SIRT6 expression in AECs. SIRT6 inhibition decreased GPx4 expression and raised ferroptosis markers, while SIRT6 activation had opposite effects. Co-treatment with SIRT6 activator and sh-GPx4 reversed the inhibitory effect on ferroptosis.

CONCLUSION

Hyperoxia aggravates septic lung injury by inducing ferroptosis of AECs. NMN can mitigate hyperoxia-aggravated septic lung injury by up-regulating GPx4 through increasing SIRT6 and inhibiting ferroptosis of AECs.

Impact of normocapnia vs. mild hypercapnia on prognosis after cardiac arrest: A systematic review and meta-analysis

OBJECTIVE

To explore the impact of mild hypercapnia or normocapnia on the prognosis of patients after the return of spontaneous circulation (ROSC) following cardiac arrest (CA).

METHODS

This systematic review and meta-analysis followed the guidelines in the PROSPERO report. Information was retrieved in PubMed, Cochrane Library, Embase, and Web of Science to collect all publications in English from January 1, 2000, to March 1, 2024, involving post-CA with mild hypercapnia. Study selection and data extraction were performed by two authors using Review Manager 5.4 software. The primary/secondary outcomes, including overall or ICU mortality, were evaluated.

RESULTS

6 studies, including 4 observational studies, were ultimately enrolled in this study. A total of 19,025 patients were included in the studies, with 6899 receiving therapeutic mild hypercapnia and 12,126 maintaining normocapnia. Three studies focused on out-of-hospital patients, one study on in-hospital patients, one study on both in-hospital and out-of-hospital patients, and one study not specifying the type of CA. Compared to normocapnia, there was no significant difference in overall mortality among patients with mild hypercapnia (P = 0.51, OR = 1.13, 95 % CI: 0.93-1.38) and the proportion of patients with favorable neurological prognosis was not altered (OR:0.95, 95 % CI:0.80-1.14, P = 0.52). The overall ICU mortality rate was not significantly different between mild hypercapnia and normocapnia (OR:1.08,95 % CI:0.89-1.32, P = 0.42), and subgroup analysis showed that the results of randomized controlled trials and observational studies were consistent.

CONCLUSION

The presented meta-analysis suggests that mild hypercapnia is not associated with improvements in overall survival, ICU survival, or neurological prognosis compared to normocapnia in patients with CA.

IMPLICATIONS FOR CLINICAL PRACTICE

This is the first meta-analysis specifically to compare the clinical outcome of CA with mild hypercapnia or normocapnia and find that mild hypercapnia may not be detrimental to the prognosis of patients after CA. It is unnecessary to control the mild hypercapnia intensively to normal range of PaCO2 in clinics.

Optimizing brain protection after cardiac arrest: advanced strategies and best practices

Cardiac arrest (CA) is associated with high incidence and mortality rates. Among patients who survive the acute phase, brain injury stands out as a primary cause of death or disability. Effective intensive care management, including targeted temperature management, seizure treatment and maintenance of normal physiological parameters, plays a crucial role in improving survival and neurological outcomes. Current guidelines advocate for neuroprotective strategies to mitigate secondary brain injury following CA, although certain treatments remain subjects of debate. Clinical examination and neuroimaging studies, both invasive and non-invasive neuromonitoring methods and serum biomarkers are valuable tools for predicting outcomes in comatose resuscitated patients. Neuromonitoring, in particular, provides vital insights for identifying complications, personalizing treatment approaches and forecasting prognosis in patients with brain injury post-CA. In this review, we offer an overview of advanced strategies and best practices aimed at optimizing brain protection after CA.

Ventilatory settings in the initial 72 h and their association with outcome in out-of-hospital cardiac arrest patients: a preplanned secondary analysis of the targeted hypothermia versus targeted normothermia after out-of-hospital cardiac arrest (TTM2) trial

PURPOSE

The optimal ventilatory settings in patients after cardiac arrest and their association with outcome remain unclear. The aim of this study was to describe the ventilatory settings applied in the first 72 h of mechanical ventilation in patients after out-of-hospital cardiac arrest and their association with 6-month outcomes.

METHODS

Preplanned sub-analysis of the Target Temperature Management-2 trial. Clinical outcomes were mortality and functional status (assessed by the Modified Rankin Scale) 6 months after randomization.

RESULTS

A total of 1848 patients were included (mean age 64 [Standard Deviation, SD = 14] years). At 6 months, 950 (51%) patients were alive and 898 (49%) were dead. Median tidal volume (V_T) was 7 (Interquartile range, IQR = 6.2-8.5) mL per Predicted Body Weight (PBW), positive end expiratory pressure (PEEP) was 7 (IQR = 5-9) cmH₂0, plateau pressure was 20 cmH₂0 (IQR = 17-23), driving pressure was 12 cmH₂0 (IQR = 10-15), mechanical power 16.2 J/min (IQR = 12.1-21.8), ventilatory ratio was 1.27 (IQR = 1.04-1.6), and respiratory rate was 17 breaths/minute (IQR = 14-20). Median partial pressure of oxygen was 87 mmHg (IQR = 75-105), and partial pressure of carbon dioxide was 40.5 mmHg (IQR = 36-45.7). Respiratory rate, driving pressure, and mechanical power were independently associated with 6-month mortality (omnibus p-values for their non-linear trajectories: p < 0.0001, p = 0.026, and p = 0.029, respectively). Respiratory rate and driving pressure were also independently associated with poor neurological outcome (odds ratio, OR = 1.035, 95% confidence interval, CI = 1.003-1.068, p = 0.030, and OR = 1.005, 95% CI = 1.001-1.036, p = 0.048). A composite formula calculated as [(4*driving pressure) + respiratory rate] was independently associated with mortality and poor neurological outcome.

CONCLUSIONS

Protective ventilation strategies are commonly applied in patients after cardiac arrest. Ventilator settings in the first 72 h after hospital admission, in particular driving pressure and respiratory rate, may influence 6-month outcomes.

Ventilation management and outcomes in out-of-hospital cardiac arrest: a protocol for a preplanned secondary analysis of the TTM2 trial

INTRODUCTION

Mechanical ventilation is a fundamental component in the management of patients post cardiac arrest. However, the ventilator settings and the gas-exchange targets used after cardiac arrest may not be optimal to minimise post-anoxic secondary brain injury. Therefore, questions remain regarding the best ventilator management in such patients.

METHODS AND ANALYSIS

This is a preplanned analysis of the international randomised controlled trial, targeted hypothermia versus targeted normothermia after out-of-hospital cardiac arrest (OHCA)-target temperature management 2 (TTM2). The primary objective is to describe ventilatory settings and gas exchange in patients who required invasive mechanical ventilation and included in the TTM2 trial. Secondary objectives include evaluating the association of ventilator settings and gas-exchange values with 6 months mortality and neurological outcome. Adult patients after an OHCA who were included in the TTM2 trial and who received invasive mechanical ventilation will be eligible for this analysis. Data collected in the TTM2 trial that will be analysed include patients' prehospital characteristics, clinical examination, ventilator settings and arterial blood gases recorded at hospital and intensive care unit (ICU) admission and daily during ICU stay.

ETHICS AND DISSEMINATION

The TTM2 study has been approved by the regional ethics committee at Lund University and by all relevant ethics boards in participating countries. No further ethical committee approval is required for this secondary analysis. Data will be disseminated to the scientific community by abstracts and by original articles submitted to peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT02908308.

Optimizing Physiology During Prehospital Airway Management: An NAEMSP Position Statement and Resource Document

Airway management is a critical component of resuscitation but also carries the potential to disrupt perfusion, oxygenation, and ventilation as a consequence of airway insertion efforts, the use of medications, and the conversion to positive-pressure ventilation. NAEMSP recommends:Airway management should be approached as an organized system of care, incorporating principles of teamwork and operational awareness.EMS clinicians should prevent or correct hypoxemia and hypotension prior to advanced airway insertion attempts.Continuous physiological monitoring must be used during airway management to guide the timing of, limit the duration of, and inform decision making during advanced airway insertion attempts.Initial and ongoing confirmation of advanced airway placement must be performed using waveform capnography. Airway devices must be secured using a reliable method.Perfusion, oxygenation, and ventilation should be optimized before, during, and after advanced airway insertion.To mitigate aspiration after advanced airway insertion, EMS clinicians should consider placing a patient in a semi-upright position.When appropriate, patients undergoing advanced airway placement should receive suitable pharmacologic anxiolysis, amnesia, and analgesia. In select cases, the use of neuromuscular blocking agents may be appropriate.

Cerebral Oximetry during Out-of-Hospital Resuscitation: Pilot Study of First Responder Implementation

Background: Anoxic brain injury is a common mode of death following out-of-hospital cardiac arrest (OHCA). We assessed the course of regional cerebral oxygen saturation (rSO₂) at the outset and during first responder resuscitation to understand its relationship with return of spontaneous circulation (ROSC) and functional survival. Methods: We undertook a prospective observational investigation of adult OHCA patients treated by a first-responder EMS agency in King County, WA. Cerebral oximetry was performed using the SenSmart® Model X-100 Universal Oximetry System (Nonin Medical, Inc). We determined cerebral oximetry rSO₂ overall and stratified according to ROSC and favorable survival status defined by Cerebral Performance Category (CPC) of 1-2. Results: Among the 59 OHCA cases enrolled, 47% (n = 28) achieved ROSC and 14% (n = 8) survived with CPC 1-2. On average, initial rSO₂ cerebral oximetry was 41% and was not different at the outset according to return of spontaneous circulation (ROSC) or survival status. Within 5 minutes of first responder resuscitation, those who would subsequently achieve ROSC had a higher rSO₂ than those who would not achieve ROSC (51% vs. 43%, p = 0.03). Among patients who achieved ROSC, those who would survive with CPC 1-2 had a higher rSO₂ cerebral oximetry following ROSC than nonsurvivors (74% vs. 60%, p = 0.04 at 5 minutes post ROSC), a difference that was not evident in the minutes prior to ROSC (55% vs. 51% at 3 minutes prior to ROSC, p = 0.5). Conclusion: In this observational study, where first responders applied cerebral oximetry, higher rSO₂ during the course of care predicted ROSC among all patients and predicted favorable survival among those who achieved ROSC. Future investigation should evaluate whether and how treatments might modify rSO₂ and in turn may influence prognosis.

The effect of mild hypercapnia on hospital mortality after cardiac arrest may be modified by chronic obstructive pulmonary disease

BACKGROUND

The main objective was to evaluate the effect of carbon dioxide on hospital mortality in chronic obstructive pulmonary disease (COPD) and non-COPD patients with out-of-hospital cardiac arrest (OHCA).

METHODS

We conducted a retrospective observational study in OHCA patients from the eICU database (eicu-crd.mit.edu). The main exposure was the partial pressure of arterial carbon dioxide (PaCO₂). The proportion of time spent (PTS) within four predefined PaCO₂ ranges (hypocapnia: <35 mmHg, normocapnia: 35-45 mmHg, mild hypercapnia: 46-55 mmHg, and severe hypercapnia: >55 mmHg) were calculated respectively. The primary outcome was hospital mortality. Multivariable logistic regression models were performed to assess the independent relationship between PTS within PaCO₂ range and hospital mortality, and the interaction between PTS within PaCO₂ range and COPD was explored.

RESULTS

A total of 1721 OHCA patients were included, of which 272 (15.8%) had COPD. After adjusted for the confounders, the PTS within mild hypercapnia was associated with lower odds ratio for hospital mortality in COPD patients (OR 0.923; 95% CI 0.857-0.992; P = 0.036); however, it was associated with higher odds ratio for hospital mortality in non-COPD patients (OR 1.053; 95% CI 1.012-1.097; P = 0.012; P_interaction = 0.008). The PTS within normocapnia was not associated with hospital mortality in COPD patients (OR 0.987; 95% CI 0.914-1.067; P = 0.739); however, it was associated with lower odds ratio for hospital mortality in non-COPD patients (OR 0.944; 95% CI 0.916-0.973; P < 0.001; P_interaction = 0.113).

CONCLUSIONS

The effect of carbon dioxide on hospital mortality differed between COPD and non-COPD patients. Mild hypercapnia was associated with increased hospital mortality for non-COPD patients but reduced hospital mortality for COPD patients. It would be reasonable to adjust PaCO₂ targets in OHCA patients with COPD.