*2.2.4 Oxygenation and ventilation strategies*

Cerebral oxygenation depends on the content of oxygen in the arterial blood, cerebral blood flow, and metabolic activity of brain tissue. All of these elements can be altered in patients with chronic cerebral ischemia. Intraoperative goals of oxygenation and ventilation should be maintaining normo-oxygenation and normocarbia [18, 19, 45]. Carbon dioxide is a potent modulator of cerebrovascular tone and influences the cerebral blood flow with changes in ventilation and can be a potential factor in determining neurologic complications perioperatively. In one systematic review, cerebrovascular reactivity to PaCO2 is maintained under both propofol and inhalational agents provided anesthetic concentration within the range used in clinical anesthesia [46]. Sumikawa et al., intraoperative hypocapnia (PaCo2 30-35 mm Hg) is linked to delayed recovery of consciousness and postoperative neurologic deficits [47]. Therefore, one should aim at maintaining normocarbia with PaCO2 between 35 to 40 mm Hg.

## *2.2.5 Hemodynamic management*

Effective and prompt hemodynamic control is crucial during the perioperative period. Both hypotension and hypertension have a detrimental effect on postoperative outcomes. Hypotension is poorly tolerated by patients with MMD and leads to cerebral ischemia and thrombosis of the bypass graft postoperatively. Likewise, hypertension results in intracranial hemorrhage especially at the site of anastomosis either during or after the surgery. The incidence and extent of postoperative cerebral ischemia can be decreased by adopting individualized perioperative blood pressure management [48]. The optimal blood pressure target during surgery is not well described but the general recommendation is to keep the blood pressure within 10% to 20% of the preoperative baseline blood pressure for all patients [18, 19, 45]. Careful titration of anesthetic during induction and maintenance of anesthesia is critical in regulating the blood pressure. Any episode of hypotension (systolic less than 100 mm Hg) should be treated promptly with vasoactive drugs. Similarly, persistent perioperative hypertension should be controlled with drugs such as hydralazine, esmolol, or labetalol.
