Fig. 2

a Illustrates the Numeric Rating Scale (NRS) values in both groups during their stay in the PACU while at rest. Pain evaluation was done upon arrival to the PACU and every 15 min during the first 2 h post-operatively, as well as after 4 h. Patients evaluating their pain as > 3/10 on the NRS received a morphine bolus (2 mg every 5 min as needed). Values are Means ± SD. 2 way-ANOVA for repeated measures. P value for difference between both groups: 0.358; P value for difference between times: < 0.001; P value for interaction: < 0.001. b Illustrates the Numeric Rating Scale (NRS) values in both groups during their stay in the PACU during a light head flexion. Upon arrival and every 15 min during the first 2 h post-operatively, as well as after 4 h, patients were asked to do a light head flexion. During this moment, NRS values were recorded. Values are Means ± SD. 2 way-ANOVA for repeated measures. P value for difference between both groups: 0.418; P value for difference between times: < 0.001; P value for interaction: < 0.001