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Hyperoxemia during the hyperacute phase of aneurysmal subarachnoid hemorrhage is associated with delayed cerebral ischemia and poor outcome: a retrospective observational study.

OBJECTIVE
The harmful effects of hyperoxemia have been reported in critically ill patients with various disorders, including those with brain injuries. However, the effect of hyperoxemia on aneurysmal subarachnoid hemorrhage (aSAH) patients is unclear. In this study the authors aimed to determine whether hyperoxemia during the hyperacute or acute phase in patients with aSAH is associated with delayed cerebral ischemia (DCI) and poor neurological outcome.


METHODS
In this single-center retrospective study, data from patients with aSAH treated between January 2011 and June 2017 were reviewed. The patients were classified into groups according to whether they experienced DCI (DCI group and non-DCI group) and whether they had a poor outcome at discharge (poor outcome group and favorable outcome group). The background characteristics and time-weighted average (TWA) PaO2 during the first 24 hours after arrival at the treatment facility (TWA24h-PaO2) and between the first 24 hours after arrival and day 6 (TWA6d-PaO2), the hyperacute and acute phases, respectively, were compared between the groups. Factors related to DCI and poor outcome were evaluated with logistic regression analyses.


RESULTS
Of 197 patients with aSAH, 42 patients experienced DCI and 82 patients had a poor outcome at discharge. TWA24h-PaO2 was significantly higher in the DCI group than in the non-DCI group (186 [141-213] vs 161 [138-192] mm Hg, p = 0.029) and in the poor outcome group than in the favorable outcome group (176 [154-205] vs 156 [136-188] mm Hg, p = 0.004). TWA6d-PaO2 did not differ significantly between the groups. Logistic regression analyses revealed that higher TWA24h-PaO2 was an independent risk factor for DCI (OR 1.09, 95% CI 1.01-1.17, p = 0.037) and poor outcome (OR 1.17, 95% CI 1.06-1.29, p = 0.002).


CONCLUSIONS
Hyperoxemia during the first 24 hours was associated with DCI and a poor outcome in patients with aSAH. Excessive oxygen therapy might have an adverse effect in the hyperacute phase of aSAH.