Low dose axillary block by targeted injections of the terminal nerves

Purpose: To compare anesthetic time, success rate and adverse effects of axillary block by single or multiple injections of local anesthetic. Methods: Two groups of patients were studied. In group T (targeted injections, n = 53) the four terminal nerves were located by electrical stimulation, and anesthetized with 5 ml mepivacaine 1% with epinephrine 5 mu g.ml(-1) (MEPE). In group S (single injection, n = 53) 80 mL MEPE 1% were injected into the neurovascular sheath, transarterially or after eliciting paresthesia. Patchy blocks were supplemented after 30 min. The patient was ready for surgery when analgesia was present in all areas distal to the elbow. Results: The block was complete at 11 min (6-15) in Group T and 7 min (5-13) in group S, P < 0.01. Supplementation was required in 46% in group S compared with 13% in group T: P < 0.001: anesthesia time was 32 min (19-52) in group T, and 39 min (16-58) in group S, P=0.02. The average doses 6MEPE were 3.5 mg.kg(-1) (2.4-5.6) in T group and 12.0 mg.kg(-1) (8.9-16.4) in S group. However, 22% of patients in group T and 4% in group S reported tourniquet pain, P=0.02. Paresthesia was elicited in 42% of patients in group S and 89% in group T, P < 0.001. Conclusions: Small targeted injections of MEPE reduce total anesthetic time, give better spread of analgesia in the hand and forearm, and may be safer thana single large injection.