SEE Question

You are called to provide anesthesia for a cerebral endovascular thrombectomy on a patient experiencing an acute ischemic stroke. Based on the results of a recent study, how will the patient’s in-hospital mortality risk MOST likely be affected if you administer general anesthesia (GA) versus monitored anesthesia care (MAC)?

• □ (A) Increased
• □ (B) Decreased
• □ (C) Unchanged

For patients with acute ischemic stroke, timely restoration of cerebral blood flow is the most effective maneuver for salvaging ischemic brain tissue. Endovascular thrombectomy is commonly employed for patients with large vessel occlusion. This procedure may be performed using either GA or MAC. However, a growing body of evidence suggests that patients who undergo this procedure with GA have higher odds of respiratory complications and death, as well as worse functional outcomes, compared to those who receive MAC.

Hyperoxia during reperfusion has been shown to cause vasoconstriction and decreased perfusion in the coronary, cerebral, renal, and peripheral vasculature. Hyperoxia is more likely to occur under GA; thus, it is possible that hyperoxia is the mechanism underlying the association between worse outcomes and the use of GA for thrombectomy. The authors of a recent study aimed to test this hypothesis.

In this retrospective cohort study, 358 adult patients received intra-arterial therapy for acute ischemic stroke. Of these patients, 104 (29%) received GA and 254 (71%) received MAC. Time-weighted averages were calculated for intraoperative data, including oxygen saturation (SpO₂). Time-weighted average SpO₂ values were divided into tertiles. The authors used propensity score adjustment for potential confounding factors, including ASA Physical Status, National Institutes of Health Stroke Scale, anesthesia duration, and comorbidities.

Patients in the GA group had higher SpO₂ values compared with patients in the MAC group. However, no difference in the rate of in-hospital mortality was found between patients who underwent cerebral endovascular thrombectomy with GA versus MAC; this was true both before and after adjusting for SpO₂ tertile. With respect to SpO₂ values and mortality rate, the results exhibited a U-shaped effect. SpO₂ values were divided into tertiles to account for this nonlinear relationship. Patients in the highest SpO₂ tertile (time-weighted average SpO₂, 98.18-99.98) had 3.8 times higher odds of mortality than those in the middle tertile (time-weighted average SpO₂, 96.95-98.17). Patients in the lowest tertile (time-weighted average SpO₂, 91.64-96.94) did not have significantly higher odds of mortality compared to the middle tertile.

The exposure-mediator and mediator-outcome relationships exhibited in this study suggest that SpO₂ may be a mediator of the relationship between anesthetic method and mortality rate. However, the results demonstrate that SpO₂ has, at most, a modest mediator role in the variable effect of GA versus MAC on the in-hospital mortality rate in the setting of endovascular treatment for ischemic stroke.

In summary, GA was associated with higher SpO₂ values compared to MAC among patients treated with endovascular thrombectomy for acute ischemic stroke. SpO₂ values that were higher than the middle tertile were associated with higher odds of mortality. However, GA itself was not associated with higher odds of death. The results support the general practice of avoiding oxygen supplementation in patients who are not hypoxic.