This study is being conducted to find out if a special device called FloPatch™, which sticks to a persons skin and uses ultrasound to check the blood flow in their neck, can tell if someone going to have low blood pressure after they get put to sleep for surgery. The investigators will be testing this in adults who are having elective non-heart surgery. Basically, the goal is to see if this device can help predict who might have low blood pressure during surgery.

Hypotension is a common side-effect of general anesthesia induction, and is related to adverse outcomes, including significantly increasing risk of one-year mortality. Even short durations of intraoperative hypotension have been associated with acute kidney injury (AKI) and myocardial injury. Myocardial injury after non-cardiac surgery (MINS) is a common postoperative complication associated with adverse cardiovascular outcomes, and intraoperative hypotension is believed to be involved in its development.

In the preoperative setting, a systematic review of 50 studies (2,260 patients) evaluating techniques to assess adult patients with refractory hypotension or signs of organ hypoperfusion found that half of all patients were fluid-responsive, pointing to volume status as a significant risk factor, while also presenting a challenge in distinguishing fluid-responders from non-responders. For surgical patients, preoperative fasting, hypertonic bowel preparations, anesthetic agents, and positive pressure ventilation all contribute to reduced effective circulating blood volume. Optimized fluid therapy remains the cornerstone of treatment of hypovolemia, with excellent effectiveness. Since the liberal use of fluids may result in fluid overload, which is associated with the development of pulmonary edema, wound infection, postoperative ileus, and anastomotic leakage, it is imperative to identify those patients who may benefit from it.

The hypothesis is that the corrected Flow Time (cFT) measured by the FloPatch will help predict hypotension after the induction of general anesthesia.

Inclusion Criteria:

• Adult patients ≥ 18 years
• Undergoing elective noncardiac under general anesthesia

Exclusion Criteria:

• Hypotension, defined as Mean Arterial Pressure (MAP) below 65 mmHg preoperatively on the day of surgery.
• Treated with angiotensin converting enzyme inhibitors (ACE-I) or angiotensin receptor blockers (ARB) on the day of surgery.
• Patients with heart failure with ejection fraction (EF) < 40%.
• A history of any previous neck surgery or trauma.
• Cardiac rhythm other than sinus at the time of common carotid artery corrected Flow Time (cFT) assessment.
• Patients who will receive neuraxial blockade (epidural or spinal) performed before induction of general anesthesia.
• Planned placement of a jugular central venous catheter or surgery to be performed in the area of the FloPatch.
• Patient is pregnant or is undergoing obstetrical surgery.

The study population are adult patients undergoing elective noncardiac surgery at Mount Sinai Hospital in Toronto, Canada.