Infraclavicular brachial plexus blocks. Comparison of neonatal and adult anatomy

Abstract

The infraclavicular (IC) block has been designed to effectively block all the cords and branches of the (BP). However, the majority of paediatric research available uses techniques designed employing adult samples. Although the success rates of these procedures are acceptable, a nerve stimulator is used to identify the BP. Even with the aid of nerve stimulators, no regional anaesthetic technique can be considered safe and consistent until the anatomy has been examined. This study aims to describe the anatomy of the paediatric BP, to determine an improved needle insertion site for the IC block using constant bony landmarks and, finally, to compare the data obtained from the paediatric study to that obtained from a similar adult study. A sample of 52 neonatal (52 left and 50 right axillae; mean length: 0.43m±0.08m; mean weight: 1.94kg±1.62kg) and 75 adult (74 left and 70 right axillae; mean length: 1.70m±0.09m; mean weight: 57.57kg±14.95kg) cadavers were used in the study. No significant difference was found when comparing the left and right sides of either sample. The data for the left and right sides of both samples were therefore combined, i.e., a total of 102 neonatal and 144 adult axillae were examined. The distances of the lateral and medial cords of the BP were measured from the coracoid process (CP) on a line between the CP and the xiphisternal joint (XS). The ideal point of needle insertion (a point halfway between the lateral and medial cords of the BP) was also determined for both samples. These measurements were then converted to a percentage of the CP to XS line distance on both sides. Statistical analysis of the data showed that there was a significant difference between the percentages obtained when comparing the neonatal and adult samples. Two distinct regression formulae were therefore developed in order to predict the ideal point of needle insertion (dependant variable) with the CP to XS line distance as the independent variable. It is clear from this study that children are not small adults and caution is advised when performing paediatric blocks that were developed for adult populations.