Continuous Non-invasive Blood Pressure Monitoring to Increase Hemodynamic Stability During Sitting Position Orthopedic Surgery: Prospective Randomized Study

Intraoperative hypotension (MAP <65 mmHg) in patients undergoing general anesthesia is a notable risk factor for the development of post-operative complications including acute kidney injury (AKI), myocardial injury, stroke and delirium, and is strongly associated with increased mortality. Moreover, the mean and systolic blood pressure values tend to undergo significant fluctuations with different positions assumed by the patient during surgery, decreasing in the transition from the supine position to the sitting position (beach chair position) typically used during surgery that involves the anatomical district of the shoulder or proximal humerus. Since severe hypotensive phenomena are connected with cerebral hypoperfusion and are associated with negative outcomes, close monitoring of blood pressure is necessary. The investigators have introduced in clinical practice the use of non-invasive ClearSight sensor (Edwards Lifesciences Corp, Irvine CA, USA), which uses the volume-clamp and Physiocal technologies to obtain continuously calibrated blood pressure values and hemodynamic parameters. The primary endpoint of this study is to evaluate the number of hypotensive episodes, their quality and their duration in patients monitored with the oscillometric intermittent noninvasive blood pressure method compared to patients with continuous noninvasive monitoring using ClearSight during orthopedic surgery in seated position performed under general anesthesia and with interscalene block. The measure of hypotension will be expressed with the TWA-MAP value (time-weighted average intraoperative MAP) to define the severity and duration of the hypotensive episode. For a subgroup of patients, brain oximetry will be monitored using the ForeSight system to record episodes of cerebral desaturation. Secondary endpoints include: the incidence of brain oxygen desaturation measured using the ForeSight system, number of severe hypotensive episodes (MAP <60 mmHg or <50 mmHg) recorded; time to event: how long does it take for the medical staff to correct the hypotensive episode (treated according to the planned protocol); quantity of vasopressors and/or fluids used to correct the hypotensive event; incidence of perioperative adverse cardiac events and acute kidney injury.

The primary hypothesis is that continuous non-invasive monitoring using ClearSight reduces the incidence of intraoperative hypotensive events (defined by mean arterial pressure below a value of 65 mmHg for more than 1 minute) and the duration of the events themselves, leading to an improvement in patients' outcomes.