Increased body mass index and ASA physical status IV are risk factors for block failure in ambulatory surgery - an analysis of 9,342 blocks.

Purpose: Regional anesthesia can be the technique of choice for selected ambulatory surgery procedures, but in spite of its benefits, it has an inherent failure rate even in experienced hands. We examine the efficacy and factors associated with failure of ambulatory regional anesthesia techniques.

Methods: This study included 9,342 blocks performed on 7,160 patients at the Duke University Ambulatory Surgery Center.