Elsevier

Resuscitation

Volume 181, December 2022, Pages 173-181
Resuscitation

Clinical paper
Outcomes associated with intra-arrest hyperoxaemia in out-of-hospital cardiac arrest: A registry-based cohort study

https://doi.org/10.1016/j.resuscitation.2022.11.008Get rights and content

Abstract

Background

An association between post-arrest hyperoxaemia and worse outcomes has been reported for out-of-hospital cardiac arrest (OHCA) patients, but little is known about the relationship between intra-arrest hyperoxaemia and clinically relevant outcomes. This study aimed to investigate the association between intra-arrest hyperoxaemia and outcomes for OHCA patients.

Methods

This was an observational study using a registry database of OHCA cases that occurred between 2014 and 2017 in Japan. We included adult, non-traumatic OHCA patients who were in cardiac arrest at the time of hospital arrival and for whom partial pressure of arterial oxygen (PaO2) levels was measured during resuscitation. Main exposure was intra-arrest PaO2 level, which was divided into three categories: hypoxaemia, PaO2 < 60 mmHg; normoxaemia, 60–300; or hyperoxaemia, ≥300. Primary outcome was favourable functional survival at one month or at hospital discharge. Multivariable logistic regression was performed to adjust for clinically relevant variables.

Results

Among 16,013 patients who met the eligibility criteria, the proportion of favourable functional survival increased as the PaO2 categories became higher: 0.5 % (57/11,484) in hypoxaemia, 1.1 % (48/4243) in normoxaemia, and 5.2 % (15/286) in hyperoxaemia (p-value for trend < 0.001). Higher PaO2 categories were associated with favourable functional survival and the adjusted odds ratios increased as the PaO2 categories became higher: 2.09 (95 % CI: 1.39–3.14) in normoxaemia and 5.04 (95 % CI: 2.62–9.70) in hyperoxaemia when compared to hypoxaemia as a reference.

Conclusion

In this observational study of adult OHCA patients, intra-arrest normoxaemia and hyperoxaemia were associated with better functional survival, compared to hypoxaemia.

Introduction

Out-of-hospital cardiac arrest (OHCA) is a major public health burden throughout the world.1 While cardiopulmonary resuscitation (CPR) without rescue breathing allows civilian rescuers to perform basic life support for OHCA victims,2 provision of oxygen by healthcare workers during CPR is still beneficial to patients according to current guidelines.3, 4 To provide a high concentration of oxygen, bag-valve-mask ventilation and advanced airway management are essential procedures for clinical practitioners, including emergency medical services (EMS) personnel, nurses and physicians involved in acute care medicine.

There is no doubt about the importance of oxygen supply in acute care settings, but there is emerging evidence regarding the potential harmful effects of oxygen.5 A systematic review and meta-analysis of previous observational studies showed that post-arrest hyperoxaemia, commonly defined as partial pressure of arterial oxygen (PaO2) of ≥ 300 mmHg, among post-cardiac arrest patients after the return of spontaneous circulation (ROSC) was associated with higher hospital mortality compared to normoxaemia.6 On the other hand, there have been few studies that examined the association between patients’ outcomes and PaO2 levels during CPR, i.e., during the period when ROSC is not yet achieved, with the exception of two studies which showed that intra-arrest hyperoxaemia was associated with better short-term outcomes such as subsequent ROSC and following hospital admission.7, 8 In addition, it is uncertain whether more clinically relevant outcomes like longer-term survival and neurological or functional outcomes are associated with PaO2 levels during CPR.

In Japan, the Japanese Association of Acute Medicine (JAAM) launched a prospective OHCA registry database that combined an existing nationwide prehospital OHCA database with newly obtained individual data taken from emergency rooms, including intra-arrest blood gas analysis data. In this study, we aimed to investigate the association between intra-arrest hyperoxaemia and favourable functional survival. The null hypothesis is that there was no difference in favourable functional survival of OHCA patients between intra-arrest hyperoxaemia and hypoxaemia.

Section snippets

Study design and setting

We conducted a retrospective observational study using the JAAM-OHCA Registry database. Details of the registry have been described previously.9 Cardiac arrest was defined as the cessation of cardiac mechanical activity as confirmed by the absence of signs of circulation.10 Each EMS authority submitted anonymized data. The medical institutional review board of Kyoto University as the corresponding institution approved this study and waived the need for informed consent because we used only

Subjects

We screened all 30,855 cases of OHCA from the JAAM-OHCA Registry that occurred between 2014 and 2017 (Fig. 1). The number of patients who were in cardiac arrest at the time of hospital arrival was 21,019. Data of intra-arrest PaO2 levels sampled during CPR were available for 16,125 (76.7 %) of these patients. After applying our eligibility criteria, 16,013 patients remained. Of these, 11,484 (71.7 %) were classified as hypoxaemia (PaO2 during CPR < 60 mmHg), 4243 (26.5 %) as normoxaemia

Relation to previous studies

Several observational studies that examined post-arrest hyperoxaemia reported an association between post-arrest hyperoxaemia and worse survival or neurological outcome.12, 13, 17, 18, 19, 20. In addition, a recent randomized controlled trial in critically ill ventilated patients demonstrated increased survival and ventilator-free days in the group with aggressive avoidance of hyperoxaemia in their subgroup of post-arrest patients.21 Based on these results, current resuscitation guidelines

Conclusions

In this large multi-center observational study of adult OHCA patients in whom arterial gas analysis was performed during CPR after arriving at the hospital, intra-arrest normoxaemia (PaO2 60–300 mmHg) and hyperoxaemia (>300 mmHg) were favourably associated with better functional survival, compared to hypoxaemia (<60 mmHg). Further investigations are needed to investigate the effect of interventions that affect oxygen administration during cardiac arrest.

Ethical approval and consent to participate

The medical institutional review board of Kyoto University as the corresponding institution approved this study and waived the need for informed consent because we used only de-identified data.

Funding

This study was supported by a scientific research grant from the JSPS KAKENHI of Japan (22H03313 to Iwami and 22K09139 to Kitamura).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We are deeply grateful to all of the EMS personnel for collecting Utstein data. This article was supported by the Clinical Investigator’s Research Project in Osaka University Graduate School of Medicine, Osaka, Japan.

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