Ultrasound and its evolution in perioperative regional anesthesia and analgesia.

Perioperative regional anesthetic and analgesic techniques have evolved considerably over the past four decades. Perhaps, the most impressive development in recent years has been the rapid adoption and widespread utilization of ultrasound (US) guidance to perform targeted delivery of local anesthetics and catheters in a consistent manner for postoperative pain control. This article briefly reviews the history of US in regional anesthesia and perioperative analgesia, the evidence basis for this practice, the clinical application of novel techniques and imaging modalities, and possible future technology and research directions.