Association between post-procedural hyperoxia and poor functional outcome after mechanical thrombectomy for ischemic stroke: an observational study

Abstract

Background: The actual effects of oxygen therapy on patients who have suffered a stroke are still unknown, and its recommendation as a routine measure in emergency services remains controversial. The aim of this study is to determine the effect of hyperoxia in functional recovery in patients with ischemic stroke who underwent intra-arterial mechanical thrombectomy (IAMT).

Methods: A prospective observational cohort study that included all adult patients consecutively admitted to the intensive care unit (ICU) due to an ischemic stroke in the anterior cerebral circulation and following an IAMT intervention, between 2010 and 2015. All patients were intubated and connected to mechanical ventilation for the intra-arterial therapy, receiving supplementary oxygen to achieve saturations above 94%. Two groups were established regarding oxygen partial pressure (paO₂) reached. It was based on a single ICU admission blood gas analysis. The hyperoxia group was defined as paO₂ > 120 mmHg. We measured functional recovery in each of the groups according to the modified Rankin scale after 90 days.

Results: For the analysis, a total of 333 patients were included. High levels of paO₂ were mostly related to higher scores in modified Rankin scale (mRS) after 90 days. There were 60.6% cases with mRS ≥ 4 and 70.6% with mRS ≥ 3 in the hyperoxia group, compared to 43.0% and 56.1% in the paO₂ ≤ 120 group, p < 0.01, respectively. Mortality was higher in the hyperoxia group, 28.6% vs 18.7%, p = 0.04. After regression adjustment by confounding factors, poor functional outcome was still significantly higher in the hyperoxia group, for both mRS ≥ 4 and mRS ≥ 3: OR 2.2.7, IC 95%, 1.22-4.23, p = 0.01 and OR 2.07, IC 95%, 1.05-4.029, p = 0.04, respectively. Both the National Institute of Health Stroke Scale Score (NIHSS) values at 24 h after the IAMT and the days of ICU stay were significantly higher in the hyperoxia group.

Conclusions: In patients with ischemic stroke in the anterior cerebral circulation treated with IAMT, we found an association between admission PaO2 > 120 mmHg and worse functional outcome 90 days after ischemic stroke, but this association needs further confirmation by other studies.

Keywords: Cerebral blood flow; Hyperoxia; Ischemic; Mortality; Oxygen; Stroke.

Fig. 1

Flowchart of patients included in the study

Fig. 2

Distribution of scores in the modified Rankin scale at 90 days after IAMT for each group. Score distribution in both groups was unequal, in a significant way: 60.6% of cases with mRS ≥ 4 and 70.6% with mRS ≥ 3 were observed in the hyperoxia group, in comparison with 43.0% and 56.1%, respectively, observed in paO2 < 120 group, p < 0.01. Mortality was higher in the hyperoxia group, 28.6% vs 18.7%, p = 0.04

Fig. 3

Discriminative capacity of the model. ROC curve