Comparison of local anesthetics for digital nerve blocks: a systematic review

Purpose To evaluate the time to onset of anesthesia, duration of anesthesia, and pain on injection of local anesthetics. Methods A systematic search of the English literature was performed of the Medline, Cochrane Central Register of Controlled Trials, The Allied and Complementary Medicine Database (AMED), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases. The study selection process was adapted from the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement, and 6 articles were complied with the study inclusion criteria. Results Six studies (335 nerve blocks) were included in our final analysis measuring 6 local anesthetic preparations (lidocaine, lidocaine with epinephrine, bupivacaine, bupivacaine with epinephrine, lidocaine with bupivacaine, and ropivacaine). Lidocaine demonstrated the shortest mean onset of anesthesia (3.1 min) and bupivacaine the longest (7.6 min). Lidocaine also demonstrated the shortest mean duration of anesthesia (1.8 h) and ropivacaine the longest mean duration (21.5 h). Lidocaine with epinephrine demonstrated the least mean pain on injection (26 mm on a visual analog scale) and bupivacaine with epinephrine the most mean pain (53 mm). Conclusions Lidocaine with epinephrine provides a good short-term anesthesia and may reduce the risk of injury or complication while the finger in still anesthetized. Bupivacaine with lidocaine provides good long-term anesthesia and may reduce the need for postprocedural anesthesia. Ropivacaine likely provides the longest duration of anesthesia but the absence of epinephrine means a tourniquet must be used to create a bloodless field and thus is contraindicated in some procedures such as flexor tendon repairs where active testing may be required. Clinical relevance Lidocaine with epinephrine, bupivacaine with epinephrine, and ropivacaine all provide benefits in digital nerve blocks. The surgeon may choose the most appropriate local anesthetic or combination of local anesthetics based on the procedure to be undertaken and the postoperative requirements.