Extreme Hyperoxia Worsens ECMO-Assisted CPR Neurologic Outcomes

The study covered in this summary was published on ResearchSquare.com as a preprint and has not yet been peer reviewed.

Key Takeaways

• Extreme hyperoxia was associated with less favorable short-term neurologic outcomes in patients who underwent extracorporeal membrane oxygenation (ECMO)-assisted cardiopulmonary resuscitation (ECPR) for out-of-hospital cardiac arrest (OHCA).

• Survival at 30 days after cardiac arrest was also significantly decreased in patients with extreme hyperoxia.

Why This Matters

• Survival is generally poor for patients with OHCA, but ECPR has been associated with improved clinical outcomes. However, there are limited data on the effect of hyperoxia on ECPR results.

• The findings support previous studies showing an association between hyperoxia and poor clinical outcomes. But this study, in contrast to previous studies, included a larger sample and adjusted for various confounding factors, including age, sex, and etiology of cardiac arrest.

• The results suggest that extreme hyperoxia should be avoided during ECPR to improve neurologic outcomes after OHCA.

• Because they looked at initial blood gas levels after starting ECMO, study investigators suggested that clinical outcomes might be improved after adjustment of the fraction of oxygen in the sweep gas (FDO₂) at ECMO initiation.

Study Design

• The retrospective analysis involved 847 adults (79% male) entering the Japanese Association for Acute Medicine Out-of-Hospital Cardiac Arrest (JAAM-OHCA) nationwide registry between June 2014 and December 2017 who underwent ECPR as part of their resuscitation and for whom there were complete data.

• Patients were grouped according to their initial partial pressure of oxygen in arterial blood (PaO₂) level after starting ECMO: normoxia (PaO₂ ≤ 200 mm Hg), moderate hyperoxia (PaO₂ > 200 mm Hg and ≤ 400 mm Hg), and extreme hyperoxia (PaO₂ > 400 mm Hg).

• Patients with good cerebral recovery or moderate cerebral disability were categorized as having favorable neurologic outcomes at evaluation 30 days after cardiac arrest. Unfavorable neurologic outcomes included severe cerebral disability, coma or vegetative state, and death or brain death.

Key Results

• The median PaO₂ level was 300 mm Hg.

• At 30 days, 16.5% had favorable neurologic outcomes and 33.1% had survived.

• Patients in the extreme hyperoxia group (n = 257), compared with the normoxia group (n = 277), were significantly less likely to experience favorable neurologic outcomes in adjusted analysis (odds ratio [OR], 0.48; 95% CI, 0.29 – 0.82; P = .007) or to be alive 30 days after cardiac arrest (OR, 0.66; 95% CI, 0.44 – 1.00; P = .048).

• Neither mortality nor neurologic outcomes differed significantly between the moderate hyperoxia group (n = 313) and the normoxia group.

Limitations

• Differences in ECPR protocols among centers could have influenced the overall study results.

• The registry did not include data on ECMO duration or length of hospital or intensive care unit stay.

• Blood gas data were missing for two-thirds of the registry’s patients who underwent ECPR; exclusion of these patients might have distorted the results.

• Investigators did not have data on cardiac function, which can affect PaO₂ levels.

• There is no standard definition of extreme hyperoxia; the cutoff PaO₂ value of 400 mm Hg was chosen arbitrarily.

• Further research is needed to address the limitations and to determine the optimal PaO₂ level for improvement of neurologic outcomes in patients with OHCA who receive ECPR.

Disclosures

• The study received no commercial funding.

• Author Hiroyuki Tsutsui, MD, is president of the Japanese Heart Failure Society and discloses receiving grants from Daiichi Sankyo, Mitsubishi Tanabe Pharma, Nippon Boehringer Ingelheim, IQVIA Services Japan, Omron Healthcare, and MEDINET; and personal fees from Daiichi Sankyo, Mitsubishi Tanabe Pharma, Nippon Boehringer Ingelheim, AstraZeneca, Ono Pharmaceutical, Otsuka Pharmaceutical, Novartis Pharma, Bayer Yakuhin, Pfizer Japan, Bristol-Myers Squibb, Kowa, and Nippon Rinsho.

• The other authors declare they have no conflicts of interest.

This is a summary of a preprint research study, Association Between Short-term Neurological Outcomes and Extreme Hyperoxia in Patients With Out-of-Hospital Cardiac Arrest Who Underwent Extracorporeal Cardiopulmonary Resuscitation: A Retrospective Observational Study From a Multicenter Registry, written by Masahiro Kashiura, MD, from Saitama Medical Center, Jichi Medical University, Japan, and colleagues on ResearchSquare.com provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on ResearchSquare.com.

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