Hyperoxia and mortality in conventional versus extracorporeal cardiopulmonary resuscitation

Association Between Arterial Hyperoxia and Mortality in Pediatric and Adult Patients Undergoing Extracorporeal Membrane Oxygenation: A Systematic Review and Meta-Analysis

BACKGROUND

In patients receiving extracorporeal membrane oxygenation (ECMO) support, the association between arterial hyperoxia and outcomes is unclear. We performed a systematic review and meta-analysis to determine the association between arterial Po2 (Pao2) and mortality in patients with ECMO.

METHODS

The meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement and registered in International Prospective Register of Systematic Reviews (PROSPERO; CRD42023467361). We systematically searched PubMed and Embase databases up to September 2023 for randomized trials or observational studies that investigated the association between Pao2 and mortality in pediatric and adult patients receiving venovenous ECMO (VV-ECMO), venoarterial ECMO (VA-ECMO), and extracorporeal cardiopulmonary resuscitation (ECPR). The predefined outcome was 28-day mortality. We synthesized the data using a random-effects model, calculating odds ratios (OR) and corresponding 95% confidence intervals (CI).

RESULTS

Thirteen cohort studies (17,766 participants) were included. All studies used categorical Pao2 cutoff, with varying thresholds ranging from ≥100 mm Hg to ≥300 mm Hg. When compared with patients with normoxia, elevated Pao2 levels at all studied thresholds were consistently associated with increased mortality (≥300 mm Hg: OR 1.56, 95% CI, 1.31-1.85, P < .01; ≥200 mm Hg: OR 1.43, 95% CI, 1.10-1.87, P < .01; ≥150 mm Hg: OR 1.51, 95% CI, 1.15-1.98, P < .01; and ≥100 mm Hg: OR 1.44, 95% CI, 1.03-2.02, P = .03). A sensitivity analysis focusing on studies reporting adjusted OR yielded similar results. We observed this association in both adult and pediatric populations.

CONCLUSIONS

In critically ill patients on VV- or VA-ECMO, increased Pao2 values were associated with increased 28-day mortality in ECMO patients. Our results should be interpreted with caution given observational nature of included studies. Further randomized trials are warranted to validate these results.

Associations of long-term hyperoxemia, survival, and neurological outcomes in extracorporeal cardiopulmonary resuscitation patients undergoing targeted temperature management: A retrospective observational analysis of the SAVE-J Ⅱ study

Background

Extracorporeal cardiopulmonary resuscitation (ECPR) can improve survival rates and neurological outcomes of patients with out-of-hospital cardiac arrest (OHCA). High levels of partial pressure of arterial oxygen (PaO2) negatively affect survival and neurological outcomes in patients with OHCA. However, research on associations of hyperoxemia with survival and neurological outcomes after ECPR remains limited, especially considering targeted temperature management (TTM) administration to patients. Additionally, few reports have examined the impact of hyperoxemia beyond 24 h. In this study, we aimed to examine the effect of prolonged hyperoxemia on survival and neurological outcomes after ECPR for OHCA in patients undergoing TTM.

Methods

We performed a secondary observational analysis of data from the SAVE-J Ⅱ study, a retrospective, multicenter registry study of ECPR of patients with OHCA. Data on arterial PaO2 after ECPR for intensive care unit days 2-4 were collected and averaged. Patients were divided into two groups: hyperoxic (PaO2 ≥ 300 mmHg) and non-hyperoxic (PaO2 < 300 mmHg). Each variable was compared between the groups. Additionally, survival and mortality rates at discharge were compared, and factors associated with survival (primary outcome) and neurological outcomes (secondary outcome) at discharge were examined.

Results

The multivariate analysis for survival at discharge showed that age, initial ventricular fibrillation/ventricular tachycardia (VF/VT) waveform, P = 0.0004), and hyperoxemia were significant factors. For neurological outcomes at discharge, significant factors included age, initial VF/VT waveform, hemoglobin level at presentation, and hyperoxemia.

Conclusions

Prolonged hyperoxemia was significantly associated with worse survival and neurological outcomes after ECPR for OHCA in patients who underwent TTM.

Determining the association of hyperoxia while on extracorporeal life support with mortality in neonates following Norwood operation

BACKGROUND

Patients requiring extracorporeal life support (ECLS) support post-Norwood operation constitute an extremely high-risk group.

MATERIALS AND METHODS

We retrospectively aimed to evaluate the relationship of hyperoxia with mortality and other clinical outcomes in patients who required ECLS following Norwood operation between January/2010 and December/2020 in a large volume center.

RESULTS

During the study period 65 patients required ECLS post-Norwood. Using receiver operating characteristic (ROC) curve analysis, mean PaO2 of 182 mmHg in the first 48-hour on ECLS was determined to have the optimal discriminatory ability for mortality (sensitivity 68%, specificity 70%). Of the 65 patients, 52% had PaO2 > 182 mmHg and were designated as hyperoxia group. Patients in the hyperoxia-group had longer cardiopulmonary bypass time (187 vs. 165 min, p = 0.023), shorter duration from CICU arrival to ECLS-cannulation (13.28 vs. 132.58 h, p = 0.003), higher serum lactate within 2-hours from ECLS-canulation (14.55 vs. 5.80, p = 0.01), higher ECLS flows in the first 4-hours (152.68 vs. 124.14, p = 0.006), and higher mortality (77% vs. 39%, p = 0.005). In the unadjusted-analysis, using a derived cut-point, patients in the hyperoxia-group had 5.15 higher odds of mortality (p = 0.003). However, this association was insignificant when adjusting for confounding variables (p = 0.104). Using a functional status scale, new morbidity (38% vs. 21%), and unfavorable outcomes (13% vs. 5%) were higher in the hyperoxia group. Despite being higher in the hyperoxia group, this did not reach statistical significance.

CONCLUSION

Neonates with hyperoxia (PaO2 > 182 Torr) during the first 48-hour of ECLS post-Norwood operation had 5 times higher odds of mortality in the unadjusted analysis, however, this was insignificant when adjusting for confounding variables. Patients in the hyperoxia group had shorter duration from CICU arrival to ECLS-cannulation, higher serum lactate prior to ECLS-canulation, and higher ECLS flows in the first 4-hours, (p < 0.05). Multicenter evaluation of this modifiable risk factor is imperative to improve the care of this high-risk cohort.

Oxygenation management during veno-arterial ECMO support for cardiogenic shock: a multicentric retrospective cohort study

BACKGOUND

Hyperoxemia is common and associated with poor outcome during veno-arterial extracorporeal membrane oxygenation (VA ECMO) support for cardiogenic shock. However, little is known about practical daily management of oxygenation. Then, we aim to describe sweep gas oxygen fraction (FSO2), postoxygenator oxygen partial pressure (PPOSTO2), inspired oxygen fraction (FIO2), and right radial arterial oxygen partial pressure (PaO2) between day 1 and day 7 of peripheral VA ECMO support. We also aim to evaluate the association between oxygenation parameters and outcome. In this retrospective multicentric study, each participating center had to report data on the last 10 eligible patients for whom the ICU stay was terminated. Patients with extracorporeal cardiopulmonary resuscitation were excluded. Primary endpoint was individual mean FSO2 during the seven first days of ECMO support (FSO2 mean (day 1-7)).

RESULTS

Between August 2019 and March 2022, 139 patients were enrolled in 14 ECMO centers in France, and one in Switzerland. Among them, the median value for FSO2 mean (day 1-7) was 70 [57; 79] % but varied according to center case volume. Compared to high volume centers, centers with less than 30 VA-ECMO runs per year were more likely to maintain FSO2 ≥ 70% (OR 5.04, CI 95% [1.39; 20.4], p = 0.017). Median value for right radial PaO2 mean (day 1-7) was 114 [92; 145] mmHg, and decreased from 125 [86; 207] mmHg at day 1, to 97 [81; 133] mmHg at day 3 (p < 0.01). Severe hyperoxemia (i.e. right radial PaO2 ≥ 300 mmHg) occurred in 16 patients (12%). PPOSTO2, a surrogate of the lower body oxygenation, was measured in only 39 patients (28%) among four centers. The median value of PPOSTO2 mean (day 1-7) value was 198 [169; 231] mmHg. By multivariate analysis, age (OR 1.07, CI95% [1.03-1.11], p < 0.001), FSO2 mean (day 1-3)(OR 1.03 [1.00-1.06], p = 0.039), and right radial PaO2 mean (day 1-3) (OR 1.03, CI95% [1.00-1.02], p = 0.023) were associated with in-ICU mortality.

CONCLUSION

In a multicentric cohort of cardiogenic shock supported by VA ECMO, the median value for FSO2 mean (day 1-7) was 70 [57; 79] %. PPOSTO2 monitoring was infrequent and revealed significant hyperoxemia. Higher FSO2 mean (day 1-3) and right radial PaO2 mean (day 1-3) were independently associated with in-ICU mortality.

Oxygenation During Venoarterial Extracorporeal Membrane Oxygenation: Physiology, Current Evidence, and a Pragmatic Approach to Oxygen Titration

OBJECTIVES

This review aims to: 1) identify the key circuit and patient factors affecting systemic oxygenation, 2) summarize the literature reporting the association between hyperoxia and patient outcomes, and 3) provide a pragmatic approach to oxygen titration, in patients undergoing peripheral venoarterial extracorporeal membrane oxygenation (ECMO).

DATA SOURCES

Searches were performed using PubMed, SCOPUS, Medline, and Google Scholar.

STUDY SELECTION

All observational and interventional studies investigating the association between hyperoxia, and clinical outcomes were included, as well as guidelines from the Extracorporeal Life Support Organization.

DATA EXTRACTION

Data from relevant literature was extracted, summarized, and integrated into a concise narrative review. For ease of reference a summary of relevant studies was also produced.

DATA SYNTHESIS

The extracorporeal circuit and the native cardiorespiratory circuit both contribute to systemic oxygenation during venoarterial ECMO. The ECMO circuit's contribution to systemic oxygenation is, in practice, largely determined by the ECMO blood flow, whereas the native component of systemic oxygenation derives from native cardiac output and residual respiratory function. Interactions between ECMO outflow and native cardiac output (as in differential hypoxia), the presence of respiratory support, and physiologic parameters affecting blood oxygen carriage also modulate overall oxygen exposure during venoarterial ECMO. Physiologically those requiring venoarterial ECMO are prone to hyperoxia. Hyperoxia has a variety of definitions, most commonly Pa o2 greater than 150 mm Hg. Severe hypoxia (Pa o2 > 300 mm Hg) is common, seen in 20%. Early severe hyperoxia, as well as cumulative hyperoxia exposure was associated with in-hospital mortality, even after adjustment for disease severity in both venoarterial ECMO and extracorporeal cardiopulmonary resuscitation. A pragmatic approach to oxygenation during peripheral venoarterial ECMO involves targeting a right radial oxygen saturation target of 94-98%, and in selected patients, titration of the fraction of oxygen in the mixture via the air-oxygen blender to target postoxygenator Pa o2 of 150-300 mm Hg.

CONCLUSIONS

Hyperoxia results from a range of ECMO circuit and patient-related factors. It is common during peripheral venoarterial ECMO, and its presence is associated with poor outcome. A pragmatic approach that avoids hyperoxia, while also preventing hypoxia has been described for patients receiving peripheral venoarterial ECMO.

Extracorporeal cardiopulmonary resuscitation in out-of-hospital cardiac arrest - current status

PURPOSE OF REVIEW

Extracorporeal cardiopulmonary resuscitation (ECPR) is an emerging treatment for refractory cardiac arrest. In recent years, several randomized controlled trials have been published that aimed to address the efficacy and effectiveness of ECPR for out-of-hospital cardiac arrest (OHCA). Despite the lack of high-quality evidence concerning clinical effectiveness and cost-effectiveness, ECPR is increasingly implemented throughout the world. In this review, we aim to provide an overview of the current status of ECPR for OHCA.

RECENT FINDINGS

Randomized controlled trials showed diverging results, largely due to differences in selection criteria and study design. Single-center studies, performed in centers with extraordinary expertise and dedication consistently achieve a low-flow time of around 60 min, but such achievements are rarely reproduced outside these centers. Strict patient selection can improve outcome but simultaneously limits the caseload. Preliminary data suggest that outcome may also be improved by avoiding hyperoxia postresuscitation.

SUMMARY

The potential of ECPR to increase survival in selected patients in highly dedicated systems seems to be proven, the question remains whether ECPR for OHCA can be widely implemented successfully and can develop into a sustainable, commonplace resource-effective treatment.

Blend to Limit OxygEN in ECMO: A RanDomised ControllEd Registry (BLENDER) Trial: Study Protocol and Statistical Analysis Plan

Introduction

Critically ill patients supported with venoarterial extracorporeal membrane oxygenation (VA ECMO) are at risk of developing severe arterial hyperoxia, which has been associated with increased mortality. Lower saturation targets in this population may lead to deleterious episodes of severe hypoxia. This manuscript describes the protocol and statistical analysis plan for the Blend to Limit OxygEN in ECMO: A RanDomised ControllEd Registry (BLENDER) Trial.

Design

The BLENDER trial is a pragmatic, multicentre, registry-embedded, randomised clinical trial., registered at ClinicalTrials.gov (NCT03841084) and approved by The Alfred Hospital Ethics Committee project ID HREC/50486/Alfred-2019.

Participants and setting

Patients supported by VA ECMO for cardiogenic shock or cardiac arrest who are enrolled in the Australian national ECMO registry.

Intervention

The study compares a conservative oxygenation strategy (target arterial saturations 92-96%) with a liberal oxygenation strategy (target 97-100%).

Main Outcome Measures

The primary outcome is the number of intensive care unit (ICU)-free days for patients alive at day 60. Secondary outcomes include duration of mechanical ventilation, ICU and hospital mortality, the number of hypoxic episodes, neurocognitive outcomes, and health economic analyses. The 300-patient sample size enables us to detect a 3-day difference in ICU-free days at day 60, assuming a mean ICU-free days of 11 days, with a risk of type 1 error of 5% and power of 80%. Data will be analysed according to a predefined analysis plan. Findings will be disseminated in peer-reviewed publications.

Conclusions

This paper details the protocol and statistical analysis plan for the BLENDER trial, a registry-embedded, multicentre interventional trial comparing liberal and conservative oxygenation strategies in VA ECMO.

Extracorporeal cardiopulmonary resuscitation for cardiac arrest: An updated systematic review

OBJECTIVES

To provide an updated systematic review on the use of extracorporeal cardiopulmonary resuscitation (ECPR) compared with manual or mechanical cardiopulmonary resuscitation during cardiac arrest.

METHODS

This was an update of a systematic review published in 2018. OVID Medline, Embase, and the Cochrane Central Register of Controlled Trials were searched for randomized trials and observational studies between January 1, 2018, and June 21, 2022. The population included adults and children with out-of-hospital or in-hospital cardiac arrest. Two investigators reviewed studies for relevance, extracted data, and assessed bias. The certainty of evidence was evaluated using GRADE.

RESULTS

The search identified 3 trials, 27 observational studies, and 6 cost-effectiveness studies. All trials included adults with out-of-hospital cardiac arrest and were terminated before enrolling the intended number of subjects. One trial found a benefit of ECPR in survival and favorable neurological status, whereas two trials found no statistically significant differences in outcomes. There were 23 observational studies in adults with out-of-hospital cardiac arrest or in combination with in-hospital cardiac arrest, and 4 observational studies in children with in-hospital cardiac arrest. Results of individual studies were inconsistent, although many studies favored ECPR. The risk of bias was intermediate for trials and critical for observational studies. The certainty of evidence was very low to low. Study heterogeneity precluded meta-analyses. The cost-effectiveness varied depending on the setting and the analysis assumptions.

CONCLUSIONS

Recent randomized trials suggest potential benefit of ECPR, but the certainty of evidence remains low. It is unclear which patients might benefit from ECPR.

Optimizing PO2 during peripheral veno-arterial ECMO: a narrative review

During refractory cardiogenic shock and cardiac arrest, veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is used to restore a circulatory output. However, it also impacts significantly arterial oxygenation. Recent guidelines of the Extracorporeal Life Support Organization (ELSO) recommend targeting postoxygenator partial pressure of oxygen (P_POSTO₂) around 150 mmHg. In this narrative review, we intend to summarize the rationale and evidence for this P_POSTO₂ target recommendation. Because this is the most used configuration, we focus on peripheral VA-ECMO. To date, clinicians do not know how to set the sweep gas oxygen fraction (F_SO₂). Because of the oxygenator's performance, arterial hyperoxemia is common during VA-ECMO support. Interpretation of oxygenation is complex in this setting because of the dual circulation phenomenon, depending on both the native cardiac output and the VA-ECMO blood flow. Such dual circulation results in dual oxygenation, with heterogeneous oxygen partial pressure (PO₂) along the aorta, and heterogeneous oxygenation between organs, depending on the mixing zone location. Data regarding oxygenation during VA-ECMO are scarce, but several observational studies have reported an association between hyperoxemia and mortality, especially after refractory cardiac arrest. While hyperoxemia should be avoided, there are also more and more studies in non-ECMO patients suggesting the harm of a too restrictive oxygenation strategy. Finally, setting F_SO₂ to target strict normoxemia is challenging because continuous monitoring of postoxygenator oxygen saturation is not widely available. The threshold of P_POSTO₂ around 150 mmHg is supported by limited evidence but aims at respecting a safe margin, avoiding both hypoxemia and severe hyperoxemia.