The definition of block "success" in the contemporary literature: are we speaking the same language?

A successful nerve block is the common goal that shapes modern regional anesthesia practice and research, yet the meaning of block "success" can be open to interpretation. For this Special Article, we reviewed all applicable randomized controlled trials published over the last decade to determine the most commonly used definitions of block success. We also sought to uncover which relevant indicators of block success are routinely reported in the contemporary literature. Twenty-two trials that explicitly designated the term block "success" as their primary outcome measure were identified. The most common definition of block success was the achievement of a surgical block within a designated period, used in half of the trials. Block success was inconsistently defined in the remaining 11 trials. Patient-related indicators of block success including postoperative pain and patient satisfaction were measured in only 4 trials, whereas anesthesiologist-related indicators such as block onset time and complications were reported most frequently. Surgeon- and hospital administrator-related indicators were not collected in any trial. We found that the definition of block success is highly variable in the contemporary regional anesthesia literature. Our findings underscore the clear and present need for a comprehensive definition of block success, whereas future research should endeavor to capture the indicators of block success that are important to all key perioperative stakeholders.