Minimum Effective Local Anesthetic Volume for Ultrasound Guided Superior Trunk Block

The objective of this study is to identify the minimum effective dosage of a commonly used local anaesthetic drug "levobupivacaine" required to produce an effective ultrasound guided (USG) superior trunk block (STB) in at least 90% of patients for shoulder arthroscopic surgeries.

Inclusion Criteria: * American Society of Anesthesiologists (ASA) physical status I-III scheduled to undergo elective upper shoulder arthroscopic rotator cuff repair procedure Exclusion Criteria: * Patient refusal * pregnancy * skin infection at the site of block placement * history of allergy to local anaesthetic drugs * bleeding tendency or with evidence of coagulopathy * pre-existing neurological deficit or neuromuscular disease.