Ultrasound-Guided Axillary Brachial Plexus Block: Influence of Obesity
Condition: Obesity; Morbid Obesity
MeSH terms: Obesity; Obesity, Morbid
Study type: Observational

Summary: 
      Axillary brachial plexus block (freezing the nerves in armpit) is commonly performed as a
      primary anesthetic technique for the elbow/ forearm or hand surgery. These nerves are
      identified using ultrasound and nerve stimulator (by stimulating the nerves using a small
      current through the needle). Axillary brachial plexus block has been shown to result in
      better pain relief, less nausea, vomiting and early discharge from hospital. The use of these
      nerve blocks have also shown to decrease the duration of hospital stay, decreased side
      effects of opioids painkillers and better satisfaction scores over the conventional use of
      intravenous and oral pain medications. These beneficial effects are particularly useful for
      patients who are overweight or obese. A study by Hauouz et al published in Anesthesia and
      Analgesia in July 2010 suggests that the success rate of brachial plexus block is lower for
      obese and overweight patients. However, ultrasound guidance was not used for performing
      axillary brachial plexus block in this study. We propose that with usage of ultrasound
      guidance the success rate of brachial plexus block will be similar in obese and non-obese
      patients.

      In this study, we want to compare the success rate of axillary brachial plexus block for
      obese and non-obese patient groups. We would also like to look at performance time,
      complications and patient satisfaction for our study population.
    

Detailed description: 
      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.
    

Intervention name(s): Brachial plexus block
Intervention type(s): Procedure
Intervention description(s): Ultrasound guided axillary brachial plexus block
Other intervention name(s): Axillary block
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients undergoing surgical procedures on upper limb (elbow, forearm and hand) scheduled
        to receive ultrasound-guided axillary brachial plexus block as their primary anesthetic
        modality at SJHC
      
Keywords: Ultrasound-guided Axillary Brachial Plexus Block; Obesity; Performance time; Failure rate; Acute complications