2.3. Outcomes
post-sternotomy
EVENT, SECONDARY
Study groups were compared by the quality of intraoperative nociception control assessed with the NOL index. Accordingly, the NOL index was sampled at five distinct time points: pre-incision, post-incision, pre-sternotomy, post-sternotomy, and pre-CPB (i.e., before CPB initiation). Pre-event values were determined as the average of three NOL index values evenly spaced (i.e., 10 s) and sampled within a 30-s window before the event. Post-event values were determined as the average of three NOL index values evenly spaced (i.e., 10 s) and sampled within a 30-s window starting 60 s after the event. The primary endpoint was the average NOL index over the five sampling time points (NOLav). We considered that NOLav would reflect the nociceptive burden better than comparing groups by single values at each time point. Therefore, the secondary endpoints were the NOL index values and the number of patients with a nociceptive response (i.e., NOL index > 25) at pre-incision, post-incision, pre-sternotomy, post-sternotomy, and pre-CPB.