Lower interscalene approach, the novel landmark for more success rate of supraclavicular block: a comparison with the classical approach in fresh cadavers.

ABSTRACT

Objective: To create a novel landmark for supraclavicular block, the lower interscalene approach, to increase its success rate. Methods: A prospective study was performed and carried out at the Department of Forensic Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University. Both the lower interscalene approach and the classical approach were tested by simulating the supraclavicular block in forty fresh cadavers. Each approach was randomly done on each side of the same body. To determine the accuracy of the needle tip encroachment on the epineurium, staining of methylene blue on the nerves was defined as the success of the nerve localization. The localization of methylene blue was observed and the correlation between the success rates of the dye stained on the nerve trunk and the length of the patient’s neck was analyzed. Results: The success rate of three - nerve - trunk localization was 62.5 % by the lower interscalene approach, compared with 40 % by the classical approach (p value = 0.037). The success rates of superior, medial and inferior nerve trunk localization in the lower interscalene group were 70.0 %, 92.5 % and 97.5 %, compared with 67.5 %, 87.5 % and 65.0 % in the classical group, respectively. Their p values were 0.5, 0.355 and 0.001 respectively. There was neither correlation between the succsess rate of nerve localization and the clavicle length nor the neck length, but there was significant correlation between the success rate of three - nerve - trunk localization and the needle insertion depth in the classical group (p value = 0.031). Conclusion: Compared with the classical approach, the lower interscalene approach obtained more spreading of methylene blue on the brachial plexus as well as on the inferior nerve trunk. The authors therefore recommend the lower interscalene approach as the novel landmark for more success of supraclavicular block.