Liver resection surgery is a common surgical procedure which is performed on patients with benign, malignant or metastatic hepatic tumor as well as for living liver donor. Liver resection surgery is usually performed through either right subcostal or inversed L-shaped incision; both approaches are associated with a significant postoperative pain which requires intensive analgesic plan to facilitate early mobilization and minimize complications.

There are various lines for pain management in liver resection surgery such as systemic analgesic drugs, neuraxial blocks (e.g., thoracic epidural analgesia) and transversus abdominis plane [TAP] block).

Systemic analgesic drugs are nearly constantly used in liver resection. However, being systemically administered, these drugs have many side effects on many organs and cannot totally eliminate postoperative pain. Thoracic epidural block is commonly associated with hypotension; furthermore, its use has other limitations such as delaying postoperative mobilization and possible hematoma and cord compression in patients with coagulopathy which is expected following liver resection. Therefore, there had been an increased interest in the use of abdominal field blocks to avoid disadvantages of neuraxial blocks and minimize the use of parenteral analgesic drugs.

TAP block is one of the classic field blocks which is extensively used in laparotomies including liver resection. However, the lack of visceral pain control TAP block influences the quality of its analgesic effect in this type of patients. Nevertheless, TAP block, namely the subcostal approach, is still the recommended field block in the latest procedure-specific recommendations for pain management in liver resection as it is the only block which showed good evidence.

In recent years, there has been increased interest in a newer field block, the erector spinae plane block (ESPB), due its easy performance and the possible coverage of visceral pain in addition to the somatic pain. ESPB showed promising results in liver resection surgery. ESBP was superior to TAP block in various abdominal surgeries. However, its analgesic efficacy had not been previously compared in relation to TAP in patients undergoing open liver resection surgery.

An independent research assistant will be responsible for opening the envelope and drug preparation with no further involvement in the study. The local anesthetic solution preparation will be as follow; 2 syringes of 20 ml of 0.25% isobaric bupivacaine.

Upon arrival to the operating room, routine monitors (electrocardiogram, pulse oximetry, and non-invasive blood pressure monitor) will be applied; intravenous line will be secured, and pre-medication drugs will be delivered (metoclopramide 10 mg, and omeprazole 40 mg).

General anesthesia will be induced by 2-3 mg/kg propofol and 1-2 mcg/kg fentanyl. Tracheal intubation by direct laryngoscopy will be facilitated by atracurium 0.5 mg/kg. Anesthesia will be maintained by 2-2.5% sevoflurane and 0.1 mg/kg/20min atracurium.

After induction of anesthesia, patients will receive their assigned intervention.

Intraoperative analgesic management Morphine boluses (titrated 0.05 mg/kg boluses till response) will be given in case of inadequate analgesia (heart rate/mean blood pressure increase by 20% from the baseline) Intraoperative fluid and hemodynamic management will be according to the discretion of the attending anesthetist.

At the end of the surgery, all patients will receive intravenous paracetamol (1 g) and ketorolac (30 mg) before the extubation.

Postoperative care All patients will receive regular intravenous paracetamol 1 g/6hours and ketorolac 30 mg/8hours. Pain assessments using Numerical Rating Scale (NRS) will be performed at rest and during cough at 0.5, 1, 2, 4, 6, 18, 24 hours after leaving the operating room. If NRS score is > 3 intravenous titration of 2 mg morphine is given slowly to be repeated after 30 minutes if pain persisted. If other opioids are given, morphine equivalent dose will be calculated using opioids conversion chart.

Intravenous ondansetron 4 mg will be given to treat nausea or vomiting if occurs.

the following data will be recorded Complications: hematoma, nausea, vomiting, itching, urine retention, constipation, Initial pathology, type and length of skin incision, duration of surgery, blood loss, need for blood transfusion, vasoactive drugs Age, sex, American society of anesthesiologist-physical status (ASA), comorbidity, weight, height and body mass index

Inclusion Criteria:

• adult patients (>18 years),
• ASA-physical status I-III
• undergoing open liver resection surgery for either primary/metastatic hepatic malignancy, biliary tract malignancy, or benign hepatic tumor

Exclusion Criteria:

• history of allergy to any of the study drugs,
• a body mass index (BMI) <18 or ≥ 35 kg/m2,
• coagulopathy (INR >1.5 and/or platelet count <70000/µL),
• local infection,
• history of chronic pain or regular opioid use;
• inability to comprehend the Numeric Rating Scale (NRS),
• liver resection combined with a second surgical procedure, laparoscopic resections,
• pregnant or lactating women.
• Patients with complicated procedures
• those needing postoperative ventilation will be excluded from the study

data can be available from the principle investigator upon reasonable request