ReviewThe effect of hyperoxia on survival following adult cardiac arrest: A systematic review and meta-analysis of observational studies☆
Introduction
Cardiac arrest, either out-of-hospital or in-hospital, is a common and lethal emergency condition.1, 2 Even if return of spontaneous circulation (ROSC) is achieved, most patients do not survive to hospital discharge.1, 2 The high post-ROSC mortality may be attributed to post-cardiac arrest syndrome, which includes anoxic neurological injury, myocardial dysfunction, and systemic ischemic/reperfusion response.3
The 2010 European Resuscitation Council (ERC) Guidelines integrates the post-resuscitation care into the new chain of survival.4 The ERC recommends rapid application of therapeutic hypothermia for post-ROSC patients to improve survival to hospital discharge and neurological outcome because therapeutic hypothermia is thought to mitigate this systemic inflammatory response after ROSC.5
In the search for other modifiable post-ROSC factors that can improve outcomes, the role of supplemental oxygen in the pathogenesis of post-cardiac arrest syndrome has gained increasing attention recently. A meta-analysis of animal studies concluded that administration of 100% oxygen in the early post-ROSC period was associated with adverse neurological outcome.6
The only human randomized controlled trial compared the effects of administering 30% and 100% oxygen to post-ROSC patients.7 Although this study was not powered to show differences in long-term outcomes, subgroup analysis showed that 100% oxygen was associated with an increased level of neuron-specific enolase, a serum marker of neuronal injury.
It might be difficult to conduct a large-scale randomized controlled trial for examining the influence of high oxygen concentration on post-ROSC patients because of logistical and ethical difficulties. To maximize the value of existing evidence in the literature, we performed a meta-analysis of human observational studies to examine the effects of hyperoxia on outcomes of post-ROSC patients.
Section snippets
Data sources and searches
We performed this meta-analysis in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses8 and the Meta-Analysis of Observational Studies in Epidemiology.9 We searched PubMed and Embase from the inception through October 2013. We did not set any restrictions on publication year or language. We used 2 sets of search terms to represent the primary variable and population of interest. The search terms for the primary variable included “normox*,”
Search results and study characteristics
In the systematic review, we identified 14 observational studies, including 8 full-text articles18, 19, 20, 21, 22, 23, 24, 25 and 6 abstract-only articles26, 27, 28, 29, 30, 31 (Fig. 1 and Table 1). All studies were cohort studies and included patients between the years 2000 and 2012, encompassing a total of 49,951 patients.
Six studies used multicenter databases for analysis.18, 19, 20, 22, 25, 28 Two studies18, 20 utilized the Project IMPACT database; the later study20 was a secondary
Discussion
The systematic review identified 14 observational studies examining the relationship between hyperoxia and adverse outcomes in post-ROSC patients. The meta-analysis indicated that hyperoxia might be associated with increased in-hospital mortality (OR, 1.40; 95% CI, 1.02–1.93; I2, 69.27%). However, because of the great heterogeneity among studies, this conclusion should be interpreted with caution.
The timing and duration of exposure to hyperoxia were not controlled in each study, which might
Conclusions
Hyperoxia appears to be correlated with increased in-hospital mortality of post-ROSC patients. This result should be interpreted cautiously because of the significant heterogeneity and limited number of studies included in the analysis. However, because exposure to hyperoxia had no obvious benefits, clinicians should monitor PaO2 closely and titrate the oxygen administration cautiously.
Conflict of interest statement
The authors declare no conflicts of interest or sources of funding for this study.
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2022, Journal of Cardiothoracic and Vascular AnesthesiaCitation Excerpt :The hyperoxia after I/R exacerbates this process by enhanced oxidation of hypoxanthine, leading to excessive production of ROS. These processes overwhelm the body's defense mechanisms, leading to tissue injury, cell death, and multiple organ dysfunction syndrome.18,19,79 Three risk factors for cardiovascular diseases are hypercholesterolemia, diabetes, and hypertension.
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A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.05.021.