The aim of this study is to determine the minimum effective volume of lidocaine in 90% of patients (ED90) required for single-injection US-guided costoclavicular infraclavicular.

The aim of this study is to determine the minimum effective volume of lidocaine in 90% of patients (ED90) required for single-injection US-guided costoclavicular ICB. Determination of the minimum effective volume of LA is important because it prevents the administration of an unnecessarily large (and potentially toxic) dose. Furthermore, when multiple blocks need to be performed at the same time in the same patient, knowledge of the minimum effective volume allows to the operator to preserve efficacy without sacrificing safety for each block.

Inclusion Criteria:

• age between 18 and 70 years
• American Society of Anesthesiologists classification 1-3
• body mass index between 20 and 30

Exclusion Criteria:

• adults who are unable to give their own consent
• pre-existing neuropathy (assessed by history and physical examination)
• coagulopathy (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. platelets≤ 100, International Normalized Ratio≥ 1.4 or partial prothrombin time ≥ 50)
• renal failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. creatinine≥ 100)
• hepatic failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. transaminases≥ 100)
• allergy to local anesthetics
• pregnancy
• prior surgery in the infraclavicular region
• chronic pain syndromes requiring opioid intake at home