Failure of recruitment

In this study, the primary objective was to estimate the minimum effective volume of bupivacaine 0.5% resulting in successful block in 90% of patients (MEV90) for ultrasound-guided retroclavicular approach to infraclavicular brachial plexus block.

A "biased coin up-and-down sequential design" will be applied to assess the minimum effective volume in 90% of patients for the retroclavicular brachial plexus block. The first subject received 25 ml 0.5% bupivacaine . Each subsequent patient received a dose that depended on the response of the previous one. If the previous block is successful, the block will be performed either by a reduction of the volume by 2.5 ml with a probability ß = 0.11 or by a same dose of the previous one with a probability 1-ß = 0.89 in the next patient.

Inclusion Criteria:

• patients who received infraclavicular brachial plexus block for elective elbow, forearm, wrist, or hand surgery
• American Society of Anesthesiologists class I, II or III

Exclusion Criteria:

• patients <18 years old
• >65 years old
• body mass index (BMI) <20 or >35 kg/m2
• inability to provide written informed consent
• refusal of regional anesthesia
• pregnancy
• contraindication for regional anesthesia

Adults between 18 and 65 years of age with infraclavicular brachial lexus block for elective elbow, forearm, wrist, or hand surgery , were selected in the study.