Keywords

1. Cardiac arrest survival
2. Hyperoxia effects
3. Post-arrest treatment
4. Oxygen therapy in resuscitation
5. Systematic review cardiac arrest

A recent scientific correspondence has brought to light the evolving understanding of how hyperoxia, or elevated levels of oxygen, affects the mortality rates of adults who have suffered cardiac arrest. Authored by esteemed researchers from West China Hospital and Sichuan University, the letter sheds light on the association between intra- and post-arrest hyperoxia and mortality, expanding on findings reported in a comprehensive systematic review and meta-analysis published in the respected journal, ‘Resuscitation’. The letter, titled “Reply to ‘Association between intra-and post-arrest hyperoxia on mortality in adults with cardiac arrest: A systematic review and meta-analysis'”, represents a crucial discourse in the ongoing debate over optimal oxygen levels during and after resuscitation efforts.

The group of specialists, led by Fang Zhou from the Department of Emergency Medicine and Laboratory of Emergency Medicine at West China Hospital, Sichuan University, and including Li Qian from West China School of Medicine, Sichuan University, and He Yarong and Cao Yu from both the Medical Center and West China Hospital, have meticulously reviewed the available evidence on hyperoxia’s impact. Acknowledging the importance of their work, the authors have disclosed no conflicts of interest, affording their findings a level of impartiality that is invaluable for advancing medical practice.

DOI: 10.1016/j.resuscitation.2023.109959

The correspondence, which addresses the findings of previous research, contributes significant insights to the field of resuscitation science. Both hypoxia and hyperoxia are known to be harmful when they occur during medical emergencies, such as cardiac arrest. While the former involves a lack of sufficient oxygen reaching the body’s tissues, the latter involves an excess. The delicate balance of administering the correct amount of oxygen to patients during and after cardiac arrest is a subject of extensive research and debate within the medical community.

The contention hinges on whether the administration of high levels of oxygen—an established practice in resuscitation efforts for decades—is benefiting or potentially harming patients who have undergone cardiac arrest. Traditional protocols have called for high-flow oxygen to be administered during cardiac arrest in the belief that maximizing oxygen delivery can only help. However, an emerging body of evidence has cast doubt on this approach, suggesting that hyperoxia could, in fact, have adverse effects, including increased mortality.

The recent work by Zhou and colleagues discusses the influence of oxygen levels on mortality, not just during resuscitation (intra-arrest) but also in the critical post-resuscitation phase (post-arrest). Their analysis takes into account the myriad of variables that come into play when determining the outcome of cardiac arrest patients, including neurological status and overall survival.

The methodology of the systematic review and meta-analysis scrutinized by the authors of the letter includes a rigorous examination of the literature, pooling results from diverse studies, and presenting findings that instigate a re-evaluation of medical guidelines on oxygen therapy. Their examination underscores the need for precision in oxygen administration for cardiac arrest patients, tailored to individual physiological responses and conditions.

The correlation between hyperoxia and increased mortality is particularly notable in light of the age-old medical emphasis on oxygen’s life-sustaining properties. The findings indicate that there might be a threshold beyond which oxygen can switch from a life-saving to a life-threatening agent due to oxidative stress and subsequent cellular damage. These revelations are leading to calls for a paradigm shift in the approach to oxygen therapy in the immediate treatment phase of cardiac arrest, as well as in the intensive care settings thereafter.

The authors argue that targeted oxygenation—keeping oxygen levels within a safe range that avoids both hypoxia and hyperoxia—could become the cornerstone of enhanced resuscitation practices. They emphasize the importance of continuous monitoring and adjustment of oxygen levels, along with further research to fine-tune the exact parameters that optimize patient outcomes.

References

1. Wang, C. H., Chang, W. T., Huang, C. H., Tsai, M. S., Lu, T. C., & Chou, E. (2018). The effect of hyperoxia on survival following adult cardiac arrest: a systematic review and meta-analysis of observational studies. Resuscitation, 132, 15–21. https://doi.org/10.1016/j.resuscitation.2018.08.019

2. Helmerhorst, H. J., Roos-Blom, M. J., van Westerloo, D. J., & de Jonge, E. (2015). Association between arterial hyperoxia and outcome in subsets of critical illness: a systematic review, meta-analysis, and meta-regression of cohort studies. Critical Care Medicine, 43(7), 1508–1519. https://doi.org/10.1097/CCM.0000000000000998

3. Damiani, E., Adrario, E., Girardis, M., Romano, R., Pelaia, P., Singer, M., & Donati, A. (2014). Arterial hyperoxia and mortality in critically ill patients: a systematic review and meta-analysis. Critical Care, 18(6), 711. https://doi.org/10.1186/s13054-014-0711-x

4. Janz, D. R., Hollenbeck, R. D., Pollock, J. S., McPherson, J. A., & Rice, T. W. (2012). Hyperoxia is associated with increased mortality in patients treated with mild therapeutic hypothermia after sudden cardiac arrest. Circulation, 126(21), 2302–2308. https://doi.org/10.1161/CIRCULATIONAHA.112.124115

5. Kilgannon, J. H., Jones, A. E., Shapiro, N. I., Angelos, M. G., Milcarek, B., Hunter, K., … & Trzeciak, S. (2010). Association between arterial hyperoxia following resuscitation from cardiac arrest and in-hospital mortality. JAMA, 303(21), 2165–2171. https://doi.org/10.1001/jama.2010.707

The work outlined in the ‘Resuscitation’ letter emphasizes the requirement for individualized patient care that leverages the best available evidence to improve patient outcomes post cardiac arrest. It advances the conversation in a field that is at a critical juncture, faced with reassessing long-held beliefs and practices. As researchers, like Zhou and the team from Sichuan University, continue to scrutinize and test the boundaries of medical knowledge, the quest for improved survival rates for cardiac arrest patients will undoubtedly evolve, guided by rigorous science and compassionate care.