The aim of this prospective, single blinded, comparative pilot study is to evaluate U/S guided serratus anterior plane catheter block (SAPB) versus patient-controlled analgesia (PCA) on the emergence of post - thoracotomy pain syndrome (PTPS). The investigator's assumed hypothesis is that; SAPB is an effective thoracic analgesic technique that may reduce the development of PTPS.

Lung cancer has the highest incidence of all malignancies worldwide & represents about 13% of all cancer victims. Lung cancer still represents the first cause of cancer deaths and lung resection surgeries could be the main therapeutic procedure. Hence, the number of thoracotomies is progressively increasing with more & more post- thoracotomy pain . Together with amputation, thoracotomy is considered the main etiology of severe & long-term acute and chronic post-surgical pain syndromes (CPSP). The prevalence of post - thoracotomy pain syndrome (PTPS) is variable (30-50%). The international association for the study of pain (IASP) has defined PTPS as "pain that recurs or persists along the thoracotomy scar at least 2 months after the procedure".Besides, PTPS is mostly described with neuropathic manifestations along the thoracotomy scar, mammary & submammary ipsilateral scapular & interscapular areas. Pain is often aching, burning with tingling, numbness, pruritis plus sensory loss and/or hypoesthesia.Preemptive post-thoracotomy analgesia is mostly multimodal & integrates both systemic & regional techniques. Systemic drugs (either given parenterally or through patient controlled - analgesia "PCA") include, NSAIDs, Cox - II inhibitors, paracetamol, opioids, ketamine (as N-methyl-D- aspartate blocker), gabapentins & pregabalin, selective serotonin re-uptake inhibitors and/or duloxetine .Regional analgesic techniques include thoracic epidural analgesia (TEA) which, is considered by many as the gold standard analgesic mode for post-thoracotomy pain .Other regional analgesic techniques are paravertebral analgesia (PVB), intercostal nerve blocks and intrapleural analgesia.Recently SAPB has been practiced more widely as an U/S - guided, simple technique of effective post-thoracotomy analgesia which is comparable with standard techniques such as TEA and PVB.

Inclusion Criteria:

• age > 18y
• American Society of Anesthethiologists (ASA) physical status II or III .
• Patient will undergo thoracotomy for lung resection procedures (metastatectomy, segmentectomy lobectomy, pneumonectomy or pleuropneumonectomy).

Exclusion Criteria:

• Patients with history of drugs (opioids, L.A., NSAIDs) allergy.
• Morbid obese patients (BMI >40) .
• Major cardiorespiratory, hepatic, renal, endocrinal or hematological disorders.
• Patients on chronic analgesic therapy (daily morphine ≥ 30 mg or equivalent dose of other opioids).
• History of drug abuse and neuropsychiatric diseases .
• History of thoracic cancer surgery within the last five years or patients having chest recurrence within 6 months.
• Patients having severe intra or post-operative bleeding or demanding postoperative ventilation will be also excluded from the study.

the final results and conclusion can be shared after finishing and submitting the trial .

the data collector will be blinded to the study groups