Effect of EEG-guided General Anesthesia on Cumulative Dose of Norepinephrine

EEG-guided General Anesthesia vs. Routine Care and Cumulative Dose of Norepinephrine in Patients Having Vascular Surgery: a Pilot Randomized Trial

Intraoperative hypotension is common in patients having non-cardiac surgery under general anesthesia and is associated with major postoperative complications including myocardial injury, AKI, and death.

Intraoperative hypotension is also common in patients having vascular surgery. To treat intraoperative hypotension, vasopressors - such as norepinephrine - and fluids are used. However, high-dose vasopressor and excessive fluid therapy are also associated with postoperative complications.

The depth of general anesthesia may be a modifiable cause of intraoperative hypotension. Deep levels of general anesthesia may cause cardiovascular depression with intraoperative hypotension and higher vasopressor requirements. Optimal depth of general anesthesia is defined as a state in which the patient is at low risk of recall of intraoperative events while maintaining blood pressure stability with minimal intervention.

Depth of anesthesia can be confirmed using clinical signs, the concentration of inhaled or intravenous anesthetics, or neuromonitoring such as processed electroencephalography (pEEG). pEEG presents an opportunity to monitor changes in human brain electrical activity and to help estimating the patients' level of (un)consciousness and the optimal depth of anesthesia. EEG-guided general anesthesia may thus decrease norepinephrine doses needed to treat intraoperative hypotension in patients having surgery.

We will include consenting patients ≥45 years scheduled for elective vascular surgery under general anesthesia if:

• surgery is expected to last at least 60 min AND
• the estimated blood loss during surgery is less than 1000 mL AND
• intraarterial blood pressure monitoring (arterial catheter) is planned during surgery

We will not include patients with previous transplantation of kidney, liver, heart, or lung and those who are septic (according to current Sepsis-3 definition). And we will not include patients with American Society of Anesthesiologists' physical status V and VI, or pregnancy.

We will exclude patients after randomization if they were treated with vasopressors others than norepinephrine during surgery.

Written informed consent will be obtained from all patients prior to study inclusion.