Minimum Effective Volume for Selective Trunk Block

Minimum Effective Local Anaesthetic Volume of a 1:1 Mixture of 2% Lidocaine With 5ug/ml of Epinephrine and 0.5% Levobupivacaine Required for Ultrasound Guided Selective Trunk Block: A Dose Finding Study

The objective of this study is to identify the minimum effective dosage of a mixture of two local anaesthetic drugs called 'levobupivacaine' and 'lignocaine with epinephrine" used to produce an effective ultrasound guided selective trunk block for surgical anaesthesia of the upper limb.

Ultrasound is widely used for brachial plexus block (BPB) and current evidence indicates that it is feasible to accurately identify majority of the main components of the brachial plexus above the clavicle, including the three trunks. Since majority of the innervation to the upper extremity, including the shoulder, arises from the three trunks (superior, middle and inferior) of the brachial plexus, so targeted injections of the individual trunks of the brachial plexus under ultrasound guidance will produce surgical anaesthesia of the entire upper extremity (C5-T1). Principal Investigator refers to this novel technique "selective trunk block" (SeTB) and the preliminary experience with SeTB for surgical anaesthesia of the entire upper extremity has been very encouraging. Currently there are no data describing an optimal dose or volume of local anaesthetic for SeTB. The aim of this study is to identify the minimum dosage of 1:1 mixture of 'levobupivacaine' and "lignocaine with epinephrine" required to produce effective surgical anaesthesia in at least 90% of patients presented for upper limb surgery.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) physical status I-III scheduled to undergo elective upper extremity surgery involving the proximal humerus to distal hand or surgery involving any combination of these regions.

Exclusion Criteria:

• Patient refusal
• pregnancy
• skin infection at the site of block placement
• history of allergy to local anaesthetic drugs
• history of bleeding tendency or with evidence of coagulopathy
• pre-existing neurological deficit
• pre-existing neuromuscular disease.