Dose effectiveness of transthecal digital block.

PURPOSE: The optimal volume of local anesthetic for transthecal digital block has not yet been identified. The goal of this study was to understand the effect of different volumes of local anesthetic using a modified transthecal digital block.

METHODS: We performed a prospective, randomized, double-blinded, controlled study with normal volunteers. The subjects were randomly divided into 3 groups receiving 1, 2, or 3 mL of 1% lidocaine using a modified transthecal digital block. An investigator blinded to the assignment of subjects and dosages evaluated the onset, progression, and duration of anesthesia. Threshold sensory testing was performed every minute in the first 10-minute period and then at 15-minute intervals up to 85 minutes. Pain was assessed after infiltration using the visual analog scale.

RESULTS: A total of 45 blocks (15 subjects for each dosage) were performed. None of the volunteers who received 1-mL of block had adequate anesthesia. Mean onset of anesthesia with the 2-mL blocks was >6 minutes, whereas those of the 3-mL blocks took only 1.5 minutes. The mean progression and duration of anesthesia were quicker and longer, respectively, in the 3-mL blocks than the 2-mL ones. Pain associated with injection and discomfort after injection in the 2- and 3-mL blocks was not different, but was significantly higher than the 1-mL block.

CONCLUSIONS: The effectiveness of the 3-mL modified transthecal digital block is greater than the 1- and 2-mL blocks in terms of rapidity of onset, completeness, and duration of anesthesia.