Clinical paperOutcomes associated with intra-arrest hyperoxaemia in out-of-hospital cardiac arrest: A registry-based cohort study
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.
References (24)
- et al.
Out-of-hospital cardiac arrest: current concepts
Lancet
(2018) - et al.
European Resuscitation Council Guidelines 2021: Adult advanced life support
Resuscitation
(2021) - et al.
Association between intra- and post-arrest hyperoxia on mortality in adults with cardiac arrest: a systematic review and meta-analysis
Resuscitation
(2018) - et al.
Increasing arterial oxygen partial pressure during cardiopulmonary resuscitation is associated with improved rates of hospital admission
Resuscitation
(2013) - et al.
Cardiac arrest and cardiopulmonary resuscitation outcome reports: update and simplification of the Utstein templates for resuscitation registries. A statement for healthcare professionals from a task force of the international liaison committee on resuscitation (American Heart Association, European Resuscitation Council, Australian Resuscitation Council, New Zealand Resuscitation Council, Heart and Stroke Foundation of Canada, InterAmerican Heart Foundation, Resuscitation Council of Southern Africa)
Resuscitation
(2004) - et al.
Post-resuscitation arterial oxygen and carbon dioxide and outcomes after out-of-hospital cardiac arrest
Resuscitation
(2017) - et al.
European Resuscitation Council and European Society of Intensive Care Medicine Guidelines 2021: Post-resuscitation care
Resuscitation
(2021) - et al.
Brain tissue oxygen pressure and cerebral metabolism in an animal model of cardiac arrest and cardiopulmonary resuscitation
Resuscitation
(2006) - et al.
Mechanisms linking advanced airway management and cardiac arrest outcomes
Resuscitation
(2015) - et al.
Part 6: Resuscitation Education Science: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care
Circulation
(2020)