*2.2.1 Intraoperative monitoring technique*

Intraoperative monitoring technique includes all routine basic physiological monitors also known as "Standard American Society of Anesthesiologists (ASA) monitors" such as Non-invasive blood pressure devices, Electrocardiography, Pulse oximetry for Oxygen saturation, capnography, and temperature monitoring. Additionally, an invasive intra-arterial catheter is inserted for continuous blood pressure monitoring preferably before induction to monitor and maintain the hemodynamics, central venous access, and Foley's catheter for urine output. Also, advanced cardiac output monitoring is usually considered in patients with significant cardiovascular and renal disease and to help in optimization of fluid status. However, there is limited data available on the usefulness of these cardiac output monitoring in intracranial bypass surgery. Likewise, cerebral function monitoring such as electroencephalogram (EEG) and somatosensory evoked potential (SSEP) have been used intraoperatively but less evidence available in the literature regarding their benefits [28–30]. Lastly, the role of other monitoring technique for global cerebral function such as transcranial Doppler, cerebral oximetry, and jugular bulb oxygen saturation have been reported; however, there is paucity of evidence available in the literature that their use help in early detection of cerebral ischemia or favorably impact the outcome [31–33].
