Pulmonary Function Changes and Diaphragmatic Paralysis Following Ultrasound Guided Supraclavicular Brachial Plexus Blockade: The Effects of Decreased Local Anesthetic Volume

The supraclavicular approach to brachial plexus blockade was first described by Kulenkampf in 1911. With classic "blind" techniques, an incidence of pneumothorax has been reported ranging from 0.5-6.0%, limiting its widespread use, despite the belief that the supraclavicular approach is the most consistent, effective technique for anesthetizing the brachial plexus. With the advent of ultrasound guidance and real time visualization this risk has been minimized and a resurgence in utilization of this approach has occurred. Increased block success, diminished performance times, and lower anesthetic volumes have been observed with this technique when compared to nerve stimulator techniques. Despite these advantages, brachial plexus anesthesia above the clavicle is associated with diaphragmatic dysfunction and caution must be demonstrated in patients with respiratory disease. Interscalene brachial plexus blockade has been widely documented to produce a 100% incidence of hemidiaphragmatic paresis and an associated 25% mean reduction in forced vital capacity (FVC) with local anesthetic volumes ranging from 20 - 45mL 8-10, these parameters for supraclavicular brachial plexus blockage are not as well defined. Previous investigations report an incidence of hemidiaphragmatic paresis of 1-75% with supraclavicular brachial plexus blockade. This study will address whether diaphragmatic function and respiratory mechanics can be preserved with lower anesthetic volumes in ultrasound guided supraclavicular brachial plexus blockade.