Abstract:

Objective To investigate the effects of different inspired oxygen concentrations on perioperative cerebrovascular function in patients with a history of ischemic stroke. Methods A total of 150 patients scheduled for elective surgery with a history of ischemic stroke were enrolled from Renji Hospital， Shanghai Jiao Tong University School of Medicine， between June 2020 and March 2024. Using a random number table， patients were allocated into two groups： F30 group （intraoperative fraction of inspired oxygen， FiO? = 30%） and F80 group （FiO? = 80%）， with 75 patients in each group. Bilateral middle cerebral artery （MCA） blood flow was continuously monitored using transcranial Doppler （TCD）， including mean flow velocity （Vm）， resistance index （RI）， and pulsatility index （PI）. Cerebral oxygen saturation （rScO?） was measured using a FORE-SIGHT oximeter. Arterial blood gas analysis was performed preoperatively， 1 hour after induction， and before extubation to assess pH， partial pressure of arterial carbon dioxide （PaCO?）， oxygenation index （OI）， base excess （BE）， hematocrit （Hct）， and lactate （Lac）. Peripheral blood samples were collected 24 hours postoperatively to measure thromboxane A? （TXA?） and prostacyclin （PGI?） levels. At 1 month postoperatively， telephone follow-up was conducted to evaluate the risk of recurrent cerebral ischemic events using the ABCD2 score and Essen Stroke Risk Score （ESRS）. Results No significant differences were observed in baseline characteristics between the two groups. Perioperative arterial blood gas parameters did not differ significantly between groups （P > 0.05）. Compared with the F30 group， the F80 group exhibited a smaller reduction in mean flow velocity （Vm） of the affected MCA at the end of surgery （8.18% ± 3.34% vs. 13.57% ± 5.32%， P < 0.05）， while no significant intergroup differences were found in RI or PI. At 1 hour after induction and before extubation， rScO? of the affected hemisphere was significantly increased in the F80 group as compared with the F30 group （P < 0.05）， whereas no significant difference was observed in the contralateral hemisphere. Before extubation and on postoperative day 1， TXA? levels were significantly lower and PGI? levels higher in F80 group compared with F30 group （P < 0.05）. The proportion of patients at high risk of cerebral ischemia by ABCD2 and ESRS at 1 month postoperatively did not differ between groups （P > 0.05）. Conclusion In patients with a history of stroke， intraoperative administration of 80% FiO? under general anesthesia better maintains perioperative cerebral hemodynamic stability and cerebral oxygen saturation， improves cerebrovascular endothelial function， but does not significantly affect the short-term incidence of postoperative cerebrovascular events compared with 30% FiO?.

Key words: stroke, cerebrovascular function, fraction of inspired oxygen, transcranial doppler, cerebral oxygen saturation