Erector Spinae Plane Block in Uniportal VATS

Patients will be enrolled into three groups: 1. continuous Erector Spinae Plane Block group (c-ESPB group) 2. continuous Serratus Anterior Plane Block group (c-SAPB group) 3. Intercostal Nerve Block group (ICNB group) * In the c-ESPB group an ultrasound-guided ESPB will be performed by the attending anaesthesiologist at the end of surgery, immediately after the last surgical stitch and before extubation. After an initial bolus of 20 ml 0,2% ropivacaine, a catheter will be left into the fascial plane deep to the erector spinae muscle to ensure continuous infusion (5ml/h for 48 hours) of the local anesthetic. * In the c-SAPB group SAPB will be performed by surgeons intraoperatively, immediately after chest wall disclosure, by injection of 20 ml 0,2% ropivacaine into the fascial plane deep to the Serratus Anterior muscle. After the initial bolus, a catheter will be left into the fascial plane deep to the Serratus Anterior muscle to ensure continuous infusion (5ml/h for 48 hours) of the local anesthetic. * In the ICNB-group ICNB will be performed by surgeons intraoperatively, immediately after drain placement, by injection of 20 ml of 0,2% ropivacaine from within the chest under direct visualization of the intercostal spaces. The "one-shot" ICNB will be associated in this group with intravenous administration of tramadol (300 mg/48 h) by elastomeric pump. The enrollment of patients into a specific group will depend on surgical variables (like disruption or not of serratus muscle/intercostal fascial planes), availability of an operator (surgeon/anesthesiologist) skilled in performing peripheral nerve blocks, logistic variables (availability of materials and ultrasound equipment). The above mentioned primary/secondary outcome measures will be evaluated in each group and compared among them.