Perineural Ultrasound-Guided Axillary Brachial Plexus Block: Influence of Obesity on Block Performance Time, Failure Rate and Incidence of Acute Complications

The prevalence of obesity is increasing throughout the world. General Anesthesia for obese patients is associated with increased risk of difficult/failed tracheal intubation and aspiration of gastric contents. These life-threatening complications can be avoided by use of regional anesthesia. Other potential advantages of regional anesthesia include improved pain control, less incidence of nausea and vomiting, early ambulation, decreased pulmonary complications, shorter hospital stay. On the other hand, regional anesthesia in obese patients can be challenging because of loss in anatomical landmarks. However, the availability of high-resolution ultrasound imaging has decreased the reliance on anatomical landmarks as the vascular, nervous and musculoskeletal structures can be directly visualized. Ultrasound imaging also allows real time needle visualization and local anesthetic can be deposited more precisely allowing faster onset anesthesia and reduced incidence of complications. Brachial plexus can be anaesthetized at various levels along its course to provide anesthesia for elbow, forearm and hand surgery. Axillary region is ideal site for targeting brachial plexus in obese patients as the plexus is superficial in this region and the likelihood of causing serious complications (e.g. pleural puncture) is low. Study of 188 patients by Chan et al showed that use of ultrasound increases the success rate of axillary brachial plexus block from 63% to 80% when compared with nerve stimulation technique. A recent study (Hanouz et al) showed that obesity increases the failure rate and immediate complications of axillary brachial plexus block but ultrasound was not used for performing the block. In current era, we consider ultrasound-guidance as a standard of care. We hypothesize that the block performance time, success rate and incidence of acute complications are similar in obese and non-obese patients when ultrasound-guidance is used to perform brachial plexus block in axillary region.