The prevalence of hip replacement surgery is increasing nowadays. Patients are usually older age and suffer from comorbidities may be an anesthetic and analgesic challenge. Erector spinae plane block (ESPB) is a newly described technique that is has been demonstrated in previous studies for chronic and acute pain treatment. The exact volume and concentration of local anesthetic (LA) to be used in ESPB is not well established.

Aim of the work is to compare the analgesic effects of three different concentrations of the same volume of local anesthetics; 30 ml of 0.50% vs 0.375% vs 0.25% bupivacaine in patients undergoing hip surgeries.

Prospective randomized double blinded study that will be conducted in at Kasr El-Ainy hospital orthopedic surgical theater.

patients, undergoing hip surgeries will be randomly allocated into three equal groups, each (n=44), using computerized generated random tables

1. Group F: 44 patients will receive single shot erector spinae block at the level of L4 with 30 ml 0.50% bupivacaine.
2. Group M: 44 patients will receive single shot erector spinae block at the level of L4 with 30 ml 0.375% bupivacaine.
3. Group H: 44 patients will receive single shot of erector spinae block at the level of L4with 30ml 0.25% bupivacaine .

Inclusion Criteria:

• Both genders (Males and females).
• Type of surgery; unilateral elective hip surgeries
• Physical status ASA I, II.
• Age ≥ 18 and ≤ 65 Years.
• Body mass index (BMI): > 20 kg/m2 and < 35 kg/m2.

Exclusion Criteria:

• Patients with known sensitivity or contraindication to drug used in the study (local anesthetics, opioids).
• History of psychological disorders and/or chronic pain.
• Contraindication to regional anesthesia e.g. local sepsis, pre- existing peripheral neuropathies and coagulopathy.
• Infection of the skin at the site of needle puncture area.
• Patient refusal.
• Severe respiratory or cardiac disorders.
• Advanced liver or kidney disease.
• Pregnancy.
• Patient with surgery duration more than two hours.