Oxygen Saturation and Postoperative Mortality in Patients With Acute Ischemic Stroke Treated by Endovascular Thrombectomy

Abstract

BACKGROUND: Monitored anesthesia care (MAC) and general anesthesia (GA) with endotracheal intubation are the 2 most used techniques for patients with acute ischemic stroke (AIS) undergoing endovascular thrombectomy. We aimed to test the hypothesis that increased arterial oxygen concentration during reperfusion period is a mechanism underlying the association between use of GA (versus MAC) and increased risk of in-hospital mortality. METHODS: In this retrospective cohort study, data were collected at the Cleveland Clinic between 2013 and 2018. To assess the potential mediation effect of time-weighted average oxygen saturation (Spo 2 ) in first postoperative 48 hours between the association between GA versus MAC and in-hospital mortality, we assessed the association between anesthesia type and post-operative Spo 2 tertiles (exposure-mediator relationship) through a cumulative logistic regression model and assessed the association between Spo 2 and in-hospital mortality (mediator-outcome relationship) using logistic regression models. Confounding factors were adjusted for using propensity score methods. Both significant exposure-mediator and significant mediator-outcome relationships are needed to suggest potential mediation effect. RESULTS: Among 358 patients included in the study, 104 (29%) patients received GA and 254 (71%) received MAC, with respective hospital mortality rate of 19% and 5% (unadjusted P value <.001). GA patients were 1.6 (1.2, 2.1) (P < .001) times more likely to have a higher Spo 2 tertile as compared to MAC patients. Patients with higher Spo 2 tertile had 3.8 (2.1, 6.9) times higher odds of mortality than patients with middle Spo 2 tertile, while patients in the lower Spo 2 tertile did not have significant higher odds compared to the middle tertile odds ratio (OR) (1.8 [0.9, 3.4]; overall P < .001). The significant exposure-mediator and mediator-outcome relationships suggest that Spo 2 may be a mediator of the relationship between anesthetic method and mortality. However, the estimated direct effect of GA versus MAC on mortality (ie, after adjusting for Spo 2 ; OR [95% confidence interval {CI}] of 2.1 [0.9-4.9]) was close to the estimated association ignoring Spo 2 (OR [95% CI] of 2.2 [1.0-5.1]), neither statistically significant, suggesting that Spo 2 had at most a modest mediator role. CONCLUSIONS: GA was associated with a higher Spo 2 compared to MAC among those treated by endovascular thrombectomy for AIS. Spo 2 values that were higher than the middle tertile were associated with higher odds of mortality. However, GA was not significantly associated with higher odds of death. Spo 2 at most constituted a modest mediator role in explaining the relationship between GA versus MAC and mortality.

Oxygen saturation before and after mechanical thrombectomy and functional outcome in patients with acute ischemic stroke

“…Furthermore, in recent clinical studies, higher oxygen saturation after recanalization was found to be associated with higher odds of mortality (6,7). In addition, arterial hyperoxia was independently associated with inhospital death as compared with either normoxia or hypoxia in ventilated stroke patients admitted to the ICU (7). These studies, however, did not explore the influence of postoperative oxygen saturation on a 3-month poor outcome.…”

“…In previous studies, prophylactic low-dose oxygen supplementation was not found to reduce death or disability in patients with AIS and receiving room air during the first 24 h after stroke was associated with better outcome after 7 months compared to supplemental oxygen therapy with 100% oxygen (18,19). Furthermore, in recent clinical studies, higher oxygen saturation after recanalization was found to be associated with higher odds of mortality (6,7). In addition, arterial hyperoxia was independently associated with inhospital death as compared with either normoxia or hypoxia in ventilated stroke patients admitted to the ICU (7).…”

“…Theoretically, there is sufficient blood flow and oxygen after reperfusion, and excessive oxygen may potentiate brain injury by triggering the production of free radicals and facilitating vasoconstriction-induced hypoperfusion ( 4 , 5 ). Recent studies have also demonstrated that higher oxygen saturation after recanalization is associated with higher odds of mortality ( 6 , 7 ).…”

Stroke thrombectomy perioperative anesthetic and hemodynamic management

“…Rapid sequence induction and video laryngoscopy for intubation can be helpful in patients with a potentially difficult airway, reducing the incidence of hypoxia and hemodynamic instability. Extubation of GA patients after the procedure should be encouraged as early as safely possible, as is avoiding unnecessary oxygen supplementation unless the patient is hypoxic 18 42. It should also be kept in mind that the conversion between different anesthesia types during the procedure may be associated with an increased incidence of morbidity and mortality 43…”

“…In another recent study, an important U shaped, non-linear relationship was demonstrated between mortality and SpO 2 in the postoperative period after EVT. High SpO 2 values found in AIS patients who received GA during EVT could explain the association between GA and increased mortality 42…”