Brain Function Monitoring During Surgery

While brain function monitoring has been shown to help guide optimal anesthetic dosing and improve recovery in the elderly and young children, its benefits in young adults are not well defined. We hypothesize that brain monitor-guided anesthetic management would decrease post-anesthesia recovery time and improve postoperative experience in this younger group.

This prospective, randomized, single-blinded study at the University of Chicago Medical Center, will enroll adult approximately 100 evaluable patients aged 18-45 years, with ASA physical status I-III, undergoing a scheduled elective surgery, with an anticipated 60-240 minute duration, and receiving general anesthesia. Exclusion criteria includes ASA IV-VI, allergy to anesthetic agents, history of seizures, emergency surgery, procedures precluding SedLine electrode placement, use of gender affirming hormonal therapy, and refusal to participate.

Participants are randomized using gender-stratified block randomization with variable block sizes (4 and 6) generated by an independent biostatistician. Participants and PACU nurses are blinded to group allocation. The anesthesia providers are not blinded due to the nature of the intervention. Postoperative survey interviewers are not blinded.

A member of the research team will use the surgery schedule to identify patients meeting initial study screening criteria. Patients identified as meeting criteria will be approached and study details will be discussed, and after being given time to ask questions, informed consent will be obtained.

The anesthesa care team (i.e., anesthesia providers, etc.) will receive instructions regarding interventional-arms anesthesia administration (i.e., chemical, gas, monitoring, etc.) to use in association with standard of care.

Brain monitoring group: Sedline Density Spectral Array (DSA) between 8-15 or/and Patient State Index (PSI) reading between 25-50 throughout the course of the case in the subjects who are randomly selected in the monitoring group. If the blood pressure (BP) or heart rate (HR) is over 25-30 % baseline, an opioid or other pain medications will be used first, before increasing the dose of inhalational agent or propofol. If BP is low and PSI is on the low end, study team will lower the inhalational agent or propofol first. If the patient moves and BP and PSI are within the ranges, muscle relaxant may be given first unless the use of muscle relaxant is not allowed for the surgical reason. If both opioids and muscle relaxant adjustment fail to achieve the hemodynamic stability and immobility goal, then the study team will adjust the doses of inhalational agent or propofol.

General anesthesia is projected to last 60-240 minutes. The anesthesia care team will treat each sedation component of general anesthesia (i.e., unconsciousness, immobility, nociception and hemodynamic stability) accordingly while the study team understands the 4 components are interlinked.

Non-monitoring group (control or conventional group), the anesthesia providers will administer the anesthetics in the conventional manner, mainly based on the hemodynamic responses and the minimum alveolar concentration (MAC) of inhalational agents during the surgery. The brain activities are not usually monitored in real time by a brain monitor. The anesthesia providers are allowed to use inhalational, intravenous anesthetic agents, opioids and muscle relaxants to produce adequate general anesthesia in both groups. Overall anesthesia care during the surgery will not be compromised.

The anesthesia provider will apply a Sedline Monitor to their forehead during the general anesthesia procedure. The anesthesia provider may use the data from the monitor to affect their anesthetic administration, or may cover the data from the monitor and only use conventional measures to guide anesthetic dosing in these control cases (blood pressure, heart rate, body movement, respiratory rate, MAC of inhalational agent), depending on what group into which the patient has been randomized.

The research team will monitor patient surgical recovery and length of stay (i.e., minutes) in post-operative acute care unit (PACU). The use of validated diagnostic (numeric rating scale (NRS)) to assess post-operative recovery symptoms (i.e., pain, nausea and vomiting) and patient satisfaction with anesthesia received.

Further recovery progress will be assessed at postoperative day-1 (POD1); patients contacted by phone will again rate their satisfaction, pain, nausea and vomiting with the NRS.

Inclusion criteria

• American Society of Anesthesiology Physical Status Classification Grade of 1(normal, healthy patient) to Grade 3 (patient with severe disease)
• Between ages 18-45 years old
• Planned surgery duration between 60-240 minutes General-endotracheal-tube-anesthesia or general anesthesia with laryngeal mask airway
• Subjects capable of giving informed consent or
• Subjects who have an acceptable surrogate capable of giving consent on behalf of the subject
• All contraception methods will be allowable for any subject in this study. Participants may opt-out of a pregnancy test if they would prefer to proceed with surgery without one.

Pregnant women will not be strictly excluded from this study if they meet all other criteria.

Exclusion criteria

• American Society of Anesthesiology Physical Status Classification Grade of 4,5,6 (diseases that are life threatening or no possibility of survival)
• Listed allergies to any commonly used anesthetic agents
• History of seizures, as a seizure while using brain monitoring may influence the anesthesia provider in a way that is not aligned with the purpose of this study
• Any patient undergoing emergency surgery, as can not be ensured that consent will be able to be properly obtained
• Patient refusal to participate in study
• Any patient undergoing surgery that would prevent placement of the Sedline monitor leads (for example - surgery on the patient's forehead/scalp)
• Patients who receive neuraxial anesthesia or a peripheral nerve block as part of their anesthetic
• Patients who are taking gender-affirming hormonal medications, as this can affect the response to anesthetics
• The duration of surgery scheduled <60 minutes