Post-Video-assisted thoracoscopic surgery pain is a challenging clinical problem that may be associated with increased morbidity and mortality. The current study tests two techniques of regional anaesthesia to control post Video-assisted thoracoscopic surgery pain

Video-assisted thoracoscopic surgery (VATS) is increasingly being used to manage primary lung cancer and helps reduce postoperative pain. However, it is a fact that pain following VATS can be severe and long-lasting. According to previous study, 18.8% of patients who undergo VATS present with persistent pain 2 months after surgery .The provision of pain relief is a significant consideration, and thoracic epidural analgesia is often regarded to be the gold standard. However, epidural analgesia is not always ideal, and other practical regional methods of analgesia after VATS have been proposed as Erector Spinae Plane Block (ESPB) or retrolaminar block (RLB) .

The retrolaminar block (RLB) is a modified paravertebral block that administers local anesthetic between the lamina of the thoracic vertebra and the erector spinal muscles, using landmark technique or under ultrasound guidance. Previous clinical study reported that RLB provides a good analgesic effect after VATS but was inferior to para-vertebral block(PVB).

Erector spinae plane block (ESPB) is a relatively new interfascial block procedure first described for thoracic analgesia. Previous clinical studies reported that ESPB provides a good analgesic effect after VATS (comparable with PVB) and decreases morphine consumption after Lateral thoracotomy surgery. Thus, anaesthesiologists now have a greater choice for regional anaesthesia for thoracic analgesia. Although ESPB and RLB have similar puncture sites, Only one clinical study comparing ESPB and RLB in breast surgery has been reported , The mentioned study was also limited only to female patients. both blocks were compared with PVB but There is no clinical study that compares ESPB and RLB directly in VATS. Although the mechanisms of action of both ESPB and RLB have not yet been completely clarified, one cadaveric study indicated that ESPB leads to a broader spread of the local analgesic into a more extensive range of intercostal spaces from a single point of injection than RLB . Another cadaveric study reported that the lateral pathway, which is involved in the blockade of the intercostal nerve or the lateral cutaneous branches of the intercostal nerves, is the primary mechanism of ESPB, in contrast to RLB.

Based on these anatomical studies, we hypothesize that ESPB can be superior to RLB for postoperative analgesia after VATS.

Inclusion Criteria:

• American Society of Anesthesiologists physical status class (ASA) I, II and III
• Patients undergoing VATS.

Exclusion Criteria:

1. Patient refusal
2. Coagulopathy, bleeding disorders,
3. In-ability to postpone anti-coagulation medications.
4. infection at the injection site
5. pregnancy, breastfeeding,
6. severe obesity (body mass index > 35 kg/m2 )
7. allergy to any drug used in the study
8. preoperative daily use of a non-steroidal anti-inflammatory drug (NSAID) or opioids,
9. Previous surgery in the thoracic vertebral region
10. Liver dysfunction.
11. Injury or a lesion at the block site.

Patients will be randomized using a computer-generated list of random numbers, which will be sealed in closed envelopes. Patients will be randomly allocated to one of two groups; Group I (E) will receive a US-guided ESPB, while Group II (R) will receive a US-guided RLB. An anesthesiologist who is not involved in the data collection team will perform all nerve blocks. Intra- and postoperative data will be collected by an anesthesiologist or intensivist who is blinded to the study protocol.