## 4 Discussion
Additionally, postoperative opiate consumption was low in both groups without any significant statistical difference, with a mean morphine consumption of 1 mg overall. This result could be correlated to the long and complex type of surgery and the timing of the block execution. In fact, we observed a mean surgical time between 3 and 4 h; moreover, a phase of recovery from anaesthesia and weaning from mechanical ventilation in ICU before weaking up was always needed. Therefore, extubation often happened several hours after the critical phase of acute postoperative pain, which is particularly intense in the immediate period after the end of the surgery, as shown in the study of [PERSON] et al. [2]. Moreover, considering the timing of the block execution, patients were often extubated several hours after the execution of the parasternal block when the analgesic effect is not at the apex anymore, which is in accordance with the studies demonstrating that the analgesic effect of the block usually last between 5 and 12 h [26; 27]. Nevertheless, the small difference in pain detected at patients awakening could have had a role in the prolonged extubation time observed in  
Figure 2: **Postoperative Pain. **_Legend:_ Maximum postoperative (numeric rating scale) pain scores in both study groups reported during four postoperative intervals. Values are median (horizontal bars), IQR (box) and range (whiskers). Denotes statistical significance (\(p<0.05\)). the Control group. Performing the block during the postoperatively probably impacted more on pain, but some difficulties may rise, such as the oedema of the nearby tissues and the sterile medication applied on the wound itself, which both may be complicating factors for ultrasound visualization. Moreover, and most important, performing the block before the surgery has an important impact on diminishing intraoperative opiates consumption, as demonstrated by [PERSON] et al. [28]. Another interesting result regards intraoperative fentanyl consumption: intraoperative administration in the Control group was twice the dose used in the Parasternal group. This result is in line with a recent study conducted in 2020 [16], which compared two groups of cardiac surgery patients who underwent parasternal block before and after the intervention. Authors found a significant reduction in intraoperative opioid administration in the preoperative Parasternal group, suggesting an important pre-emptive and intraoperative effect of the block. Limiting the intraoperative dosage of opiates could lead to rapid weaning from mechanical ventilation, early extubation and lucid weaking up, which improves patient outcomes. Moreover, considering the low NRS scores and the successful postoperative pain control in both groups, the analgesic intraoperative regimen adopted probably had an important influence on the postoperative period. Multimodal pre-emptive analgesia with opiates, FANS, regional anaesthesia, corticosteroids, and paracetamol plays a fundamental role in preventing the development of surgical pain [29]. Notably, time to extubation could be affected by several other factors, such as preoperative conditions, i.e., pre-existing pulmonary and neurologic disorders; surgical factors, such as intraoperative and postoperative bleeding; and postoperative conditions, such as arrhythmia or bleeding. Nevertheless, we did not register significant differences in patients' characteristics and perioperative conditions that could have affected or delayed time to extubation. It must be said that other parameters, such as intraoperative heart rate and pressure values, use of vasopressor drugs, conscious state at awakening and respiratory complications, have not been evaluated in our study. Pulmonary performance is another interesting result to underline. Postoperative chest pain is usually evaluated with the patient in a supine position in the absence of movement. Respiratory evaluation could be a way to evaluate parasternal block efficacy when the thorax is moving.