Across broad surgical populations, cerebral hypoperfusion is associated with increased mortality, stroke, brain cellular injury, and poor functional outcomes. Based on available evidence, The Brain Trauma Foundation recommends that cerebral perfusion pressure (CPP) be maintained greater than 60 mmHg in high-risk settings to minimize risk of cerebral ischemia. Though several lines of investigation have focused on optimal cerebrovascular management in the intensive care unit and cardiac surgery settings, much less focus has been placed on cerebrovascular management during non-cardiac surgery.

Preliminary data indicate that intraoperative CPP routinely falls below 60 mmHg in neurosurgical and trauma surgery settings, though the relationship between reduced intraoperative CPP and outcomes remains unclear. Furthermore, effective methods by which low intraoperative CPP could be prevented have not been thoroughly investigated, which represents the first required step prior to studying the relationship between intraoperative CPP and clinical outcomes. Thus, the aim of this study is to evaluate the efficacy of an automated algorithm that alerts clinicians to a decrease in CPP below 60 mmHg. This study tests the hypothesis that an automated pager alert system (triggered by CPP falling below 60 mmHg) will increase intraoperative CPP compared to standard of care.

This will be a single-center study taking place at the University of Michigan Health System, Ann Arbor, MI. The study has been approved by the University of Michigan Medical School Institutional Review Board (IRBMED).

Automated pager alert protocols have been previously published from the investigators' department, and this alerting system is used for operational purposes on a daily basis. Surgical patients will be automatically screened using a designed script from the anesthesia information management system (Centricity, Wishahaka, WI).

The script will screen for active surgical patients with intracranial pressure (ICP) data recording in our hospital's non-cardiac operating rooms. When these data are captured, an automated enrollment process will occur if the following electronic charting criteria are met:

• Age ≥ 18 years old
• Case identified as a general anesthetic
• Non-intracranial aneurysm surgery
• Non-pregnant patient

After "anesthetic induction end" time is documented within the case, the alerting system will turn on after a 10-minute grace period. The alerting system will then retroactively measure median CPP values over 5-minute epochs, and if median CPP is < 60 mmHg, the following alphanumeric pager alert will be delivered:

"Patient: LAST NAME, FIRST NAME, OR(N), has a cerebral perfusion pressure < 60 mmHg. Disregard alert for intracranial aneurysm cases or if patient is pregnant."

This alert will be delivered twice total (if criteria are met). The aim of the pager alerts will be to relay information regarding cerebral ischemia risk between when CPP decreases below 60 mmHg. Final clinical decision-making, however, will be left to the anesthesia team. The pager alerts will not otherwise compel action, and no other recommendations will be made.

Inclusion Criteria:

• Adult (≥18 years old) surgical patients
• Intracranial pathology requiring intracranial pressure (ICP) monitoring

Exclusion Criteria:

• Intracranial aneurysm surgery
• Cases with pressures monitored from a lumbar drain
• Cardiac surgery cases
• Enrolled in conflicting study
• Pregnancy