Supranormal arterial oxygen tension only during the first six hours after cardiac arrest is associated with unfavourable outcomes

Abstract

Background: Multiple studies have investigated the association between hyperoxaemia following cardiac arrest (CA) and unfavourable outcomes; however, they have yielded inconsistent results. Most previous studies quantified oxygen exposure without considering its timing or duration. We investigated the relationship between unfavourable outcomes and supranormal arterial oxygen tension (PaO₂ ), commonly defined as PaO₂ > 100 mmHg, at specific time intervals within 24 h following CA.

Methods: This retrospective observational study included 838 adult non-traumatic patients with CA. The first 24 h following CA were divided into four 6-h time intervals, and the first 6-h period was further divided into three 2-h segments. Multivariable logistic regression analyses were conducted to assess associations of the highest PaO₂ and time-weighted average PaO₂ (TWA-PaO₂ ) values at each time interval with unfavourable outcomes at hospital discharge (cerebral performance categories 3-5).

Results: The highest PaO₂ (p = .028) and TWA-PaO₂ (p = .022) values during the 0-6-h time interval were significantly associated with unfavourable outcomes, whereas those at time intervals beyond 6 h were not. The association was the strongest at supranormal PaO₂ values within the 0-2-h time interval, becoming significant at PaO₂ values ≥ 150 mmHg. During the first 6 h, longer time spent at ≥150 mmHg of PaO₂ was associated with an increased risk of unfavourable outcomes (p = .038). The results were consistent across several sensitivity analyses.

Conclusion: Supranormal PaO₂ during but not after the first 6 h following cardiac arrest was independently associated with unfavourable outcomes.

Keywords: heart arrest; hyperoxia; prognosis.