The GUARDIAN Trial - Vasopressor Sub-Study

Participants in the underlying GUARDIAN trial (NCT04884802) will be randomized to: 1) norepinephrine or phenylephrine infusion to maintain intraoperative MAP ≥85 mmHg (tight pressure management); or, 2) routine intraoperative blood pressure management (routine pressure management). Participants in this sub-study will be additionally randomized to norepinephrine or phenylephrine infusion to maintain the designated target intraoperative mean arterial pressure.

Inclusion criteria

• At least 45 years old;
• Scheduled for major noncardiac surgery expected to last at least 2 hours;
• Having general anesthesia, neuraxial anesthesia, or the combination;
• Expected to require at least overnight hospitalization (planned ICU admission is acceptable);
• Are designated ASA physical status 2-4 (ranging from mild systemic disease through severe systemic disease that is a constant threat to life);
• Expected to have direct intraoperative blood pressure monitoring with an arterial catheter;
• Cared for by clinicians willing to follow the GUARDIAN protocol;
• Subject to at least one of the following risk factors:

• Age >65 years;
• History of peripheral arterial disease;
• History of coronary artery disease;
• History of stroke or transient ischemic attack;
• Serum creatinine >175 μmol/L (>2.0 mg/dl) within 6 months;
• Diabetes requiring medication;
• Current smoking or 15 pack-year history of smoking tobacco;
• Scheduled for major vascular surgery;
• Body mass index ≥35 kg/m2;
• Preoperative high-sensitivity troponin T >14 ng/L or troponin I equivalent, defined as ≥15 ng/L (Abbott assay), 19 ng/L (Siemens assay, [Borges, unpublished]), or 25% of the 99% percentile for other assays - all within 6 months;
• B-type natriuretic protein (BNP) >80 ng/L or N-terminal B-type natriuretic protein (NTProBNP) >200 ng/L within six months.

Exclusion criteria

• Are scheduled for carotid artery surgery;
• Are scheduled for intracranial surgery;
• Are scheduled for partial or complete nephrectomy;
• Are scheduled for pheochromocytoma surgery;
• Are scheduled for liver or kidney transplantation;
• Require preoperative intravenous vasoactive medications;
• Have a condition that precludes routine or tight blood pressure management such as surgeon request for relative hypotension;
• Require beach-chair positioning;
• Have a documented history of dementia;
• Have language, vision, or hearing impairments that may compromise cognitive assessments;
• Have contraindications to norepinephrine or phenylephrine per clinician judgement;
• Have previously participated in the GUARDIAN trial.