The costoclavicular brachial plexus block (CCB) is a recently introduced infraclavicular approach that targets three cords located lateral to the axillary artery in the costoclavicular space . Cords in this space are located more superficially than with the classical approach at the lateral infraclavicular fossa and are clustered, while maintaining a consistent anatomical relationship with each other

Brachial plexus blockade (BPB) thorough the costoclavicular space block is  widely used anaesthesia technique nowadays in the upper limb surgery . Previously peripheral never block was given with Perineural injections guided by surface anatomy or electrical nerve stimulation but recently the ultrasound guided are more successful than injections guided by surface anatomy or electrical neurostimulation.The classical approaches to BPB include interscalene, supraclavicular, infraclavicular, and axillary approaches.

Recently, with the advances in technology ultrasonography guidance has got more attention and has been used to give the BPB through the costoclavicular space (CCS) and considered  as an alternative access pathway to BPB. The CCS is located between the clavicle and the first rib, deep behind the middle of the clavicle.The CCS was introduced as a feasible pathway for BPB by Dahlstrom and Olinger in 2012 in their study of thoracic outlet syndrome,which was later confirmed in a 2016 autopsy study by Sala–Blanch et al.Subsequent studies using the ultrasound-guided CCS approach to BPB, found that the compact anatomy of the CCS had little interindividual variability and allowed for simple performance with few complications and a high success rate, all of which increases the feasibility for continuous nerve blockade through this approach.In recent years, few studies have applied this approach to special groups of individuals, such as pediatric and obese patients, and reported satisfactory results. 

In most of these studies, 0.5% ropivacaine was used but the recent research has shown effective ultrasound-guided supraclavicular BPB using lower local anesthetic concentrationsof ropivacaine and the  data  obtained from few articles provided an information that 0.375% ropivacaine may be effective when given in the CCS. As the risk of systemic (LAST) and direct neurotoxicity increases with higher concentrationsof the drug chances of inadvertentvascukar and pleural injuries may be associated with the block, so we felt it is very  important to understand if a lower concentration of ropivacaine can be used for BPB in the CCS under the ultrasound guidance. Hence, the purpose of this study is to compare the efficacy of 0.375% ropivacaine with 0.5% ropivacaine in ultrasound-guided BPB through the CCS. Our hypothesis is that 0.375% ropivacaine would be noninferior to 0.5% ropivacaine in producing successful BPB when given in the CCS under the ultrasound guidance.