Effect of body mass index on angle of needle insertion during ultrasound-guided lateral sagittal infraclavicular brachial plexus block.

STUDY OBJECTIVES: The aim of our study was to establish the angle of needle insertion from the anterior chest wall during ultrasound-guided infraclavicular brachial plexus block and to examine for any correlation between body mass index (BMI) and insertion angle.

DESIGN: This is a prospective observational study.

SETTING: The setting is at an operating room, university-affiliated teaching hospital.

PATIENTS: The patients are 23 American Society of Anesthesiologists physical status 1-3 patients scheduled to undergo elbow, forearm, or hand surgery under regional anesthesia with or without general anesthesia.

INTERVENTIONS: The intervention is infraclavicular brachial plexus block with or without perineural catheter insertion.

MEASUREMENTS: The measurement is the angle of needle insertion in relation to the anterior chest wall, BMI, and needle visibility as graded by the anesthesiologist.

MAIN RESULTS: Twenty-three patients were studied. The mean (SD) BMI was 28.5 (5.4). The median (range) of angle of needle insertion was 50 (33-60). The Pearson correlation coefficient for BMI and angle of needle insertion was 0.357. There were no reported complications.

CONCLUSIONS: The median (range) angle of needle insertion in relation to chest for our study patients was 50° (33°-60°). The needle visibility was rated difficult, requiring hydrolocation or "heeling-in," in 39% of cases. There was a moderate correlation between BMI and angle of insertion. Despite difficulties with needle visualization, the ultrasound-guided infraclavicular brachial plexus block provided reliable analgesia.