In 1911, Kulenkampf introduced the concept of locating a nerve with a paresthesia and blocking its conduction with local anesthetic. Paresthesia ruled as the technique of choice for another 50 years. Although the concept of neurostimulation was also introduced around 1910, it took several decades for this technique to be recognized and used. Until recently, neurostimulation has been the primary technique to perform peripheral nerve blocks.

In the past 15 years, an increasing number of investigators have demonstrated the usefulness of ultrasound-guided techniques to perform regional anesthesia. In adults and children, the studies demonstrating the usefulness of ultrasound-guided techniques were initially conducted in patients undergoing upper extremity and superficial peripheral blocks. The use of ultrasound in the pediatric population has gained rapid recognition because of the quality of the images that can be generated in this patient population. The use of ultrasound was eventually extended to deeper peripheral blocks, especially sciatic and lumbar plexus blocks when more powerful portable sonography platforms were developed. The basis defining the use of ultrasound for the performance of neuraxial blocks and for blocks traditionally used for the treatment of chronic pain was also developed in this time frame.

In the past few years, studies have attempted to compare neurostimulation to ultrasoundguided techniques. A systematic review in 2010 examined block onset time, quality, and duration in 16 randomized controlled trials (RCTs) comparing ultrasound guidance with nerve stimulation. Although one RCT found a slower onset time (2 minutes) with ultrasound guidance in upper extremity blocks, all of the other RCTs reviewed found that ultrasound guidance was not different or improved in terms of block onset time (60%), quality (25%), and duration (17%). Although duration was not prolonged in lower extremity blocks, RCTs reviewed showed ultrasound guidance was equivalent or superior for block onset time (71%) and quality (63%). Multiple studies have also demonstrated that ultrasound guidance decreases time to perform peripheral nerve blocks. This results in fewer needle manipulations and improves patient comfort and satisfaction with regional anesthesia.

Utilization of ultrasound was hoped to decrease rare adverse events associated with regional anesthesia. Whether or not ultrasound can reduce the frequency of nerve injury associated with the performance of regional anesthesia is an imporTant but very complex question.