Determinants for the duration of a single-shot interscalene brachial plexus block: concentration vs. volume of local anesthetics

摘要

Interscalene brachial plexus block (ISB) has been widely used to control postoperative pain in patients undergoing shoulder and arm surgeries. Continuous ISB with catheter insertion has been shown to be more effective than single-shot ISB for postoperative pain control. However, catheter-related complications, such as dislodgement and infection, should be considered when using continuous ISB with a catheter. When single-shot ISB is chosen for the fear or prevention of catheter-related complications, the duration of ISB is critical to achieve effective postoperative pain control. There are various determinants for the duration of nerve block. Local anesthetics, itself, have two determinants for the duration of nerve block, the concentration and volume, regardless of the characteristics of the local anesthetic used. Pippa et al. [1] reported that low concentration and high volume of local anesthetics for ISB covered more block areas and avoided complications, compared with high concentration and low volume of local anesthetics at the same dose. However, Zhai et al. [2] reported that ropivacaine 50 mg with 0.25, 0.5, or 0.75% with different volumes for ISB had similar block results, although 0.75% showed a faster onset.