Early observations and pilot data that first suggested a new direction
Regional anaesthesia was traditionally performed using landmark-based techniques — palpating anatomical structures and inserting needles toward presumed nerve locations — followed by the nerve stimulator era beginning in the 1980s, which added electrolocation to improve accuracy. Both approaches were 'blind' to the actual tissue planes, requiring high volumes of local anaesthetic and accepting relatively high failure rates (15-25% for some blocks). La Grange and colleagues first described ultrasound-guided vascular access in 1978, but it was Kapral's 1994 publication demonstrating ultrasound-guided supraclavicular brachial plexus block that signalled the potential for real-time visualisation of nerves, surrounding structures, and needle trajectory to transform regional anaesthesia practice.
Landmark RCTs and pivotal trials that established the evidence base
A series of RCTs through the 2000s and 2010s established the superiority of ultrasound guidance over nerve stimulation for peripheral nerve blocks. Abrahams and colleagues published an influential meta-analysis (2009) of 13 RCTs demonstrating that ultrasound guidance improved block success rates, reduced procedure time, and decreased the incidence of vascular puncture compared to nerve stimulation. The key advantage was not just accuracy but safety — the ability to see the needle, nerve, and surrounding vasculature in real-time reduced complications and allowed lower volumes of local anaesthetic. For the supraclavicular block specifically — previously considered high-risk due to pneumothorax — ultrasound made it one of the safest and most reliable upper extremity blocks. Multiple subsequent Cochrane reviews confirmed these benefits across different block types.
Follow-up studies, subgroup analyses, and real-world validation
Ultrasound visualisation catalysed an explosion of novel fascial plane and truncal blocks that would have been impossible with landmark or nerve stimulation techniques. The transversus abdominis plane (TAP) block, described by Rafi in 2001 and refined with ultrasound guidance by Hebbard, became the prototype for interfascial plane blocks. The erector spinae plane (ESP) block (Forero 2016) emerged as a simpler alternative to paravertebral blocks for thoracic and abdominal analgesia. The PROSPECT collaboration (Procedure-Specific Postoperative Pain Management) systematically evaluated regional techniques within ERAS pathways, producing evidence-based recommendations for optimal block selection by surgical procedure. The field evolved from simply 'seeing the nerve' to understanding fascial anatomy and designing blocks targeting specific tissue planes for spread of local anaesthetic.
Integration into clinical practice guidelines and recommendations
The ASRA/ESRA 2023 joint practice advisory recommends ultrasound guidance as the preferred technique for peripheral nerve blocks when available. The European Society of Regional Anaesthesia (ESRA) strongly recommends ultrasound guidance for all peripheral nerve blocks, citing improved success rates, faster onset, and reduced complications. The PROSPECT guidelines provide procedure-specific recommendations integrating regional anaesthesia into multimodal analgesia pathways. The AAGBI and NICE guidelines recommend ultrasound for vascular access and nerve blocks. The overall guideline consensus is that ultrasound is the standard of care for regional anaesthesia in institutions where it is available.
ASRA/ESRA Joint Practice Advisory 2023
Ultrasound guidance recommended as the preferred technique for peripheral nerve blocks when available
PROSPECT Guidelines (Procedure-Specific)
Procedure-specific recommendations for regional anaesthesia technique selection within multimodal analgesia pathways
Now
Current standard of care and ongoing research directions
Ultrasound-guided regional anaesthesia is the standard of care in high-income countries, with point-of-care ultrasound considered an essential anaesthesia skill. The landscape has evolved dramatically: over 30 distinct ultrasound-guided blocks are now described, interfascial plane blocks (TAP, ESP, quadratus lumborum, pectoralis, serratus anterior plane) have expanded the analgesic toolkit beyond traditional nerve blocks, and continuous catheter techniques allow prolonged analgesia. Current frontiers include AI-assisted nerve identification and real-time block guidance, liposomal bupivacaine for prolonged single-injection analgesia, and the integration of regional anaesthesia into ambulatory surgery pathways to eliminate opioid prescriptions entirely. The PROSPECT collaboration continues to refine procedure-specific recommendations, and the evidence base for newer fascial plane blocks (particularly ESP) is maturing through ongoing RCTs. Training has been transformed by simulation and the standardisation of competency assessment.
Is nerve stimulation still needed with ultrasound?+
Nerve stimulation is no longer required as a primary technique when ultrasound is available. However, it retains value as a confirmatory tool — if a motor response is elicited at low current (0.3-0.5 mA) while the needle tip appears perineural on ultrasound, this provides dual confirmation of needle position. Some practitioners use combined ultrasound-nerve stimulation for deep blocks (e.g., infraclavicular) where visualisation is challenging. Pure nerve stimulation remains a backup when ultrasound is unavailable.
What are interfascial plane blocks and how do they differ from traditional nerve blocks?+
Traditional nerve blocks target specific named nerves (e.g., femoral, sciatic). Interfascial plane blocks inject local anaesthetic between fascial layers, relying on spread through tissue planes to reach sensory nerves traversing those planes. Examples include TAP (transversus abdominis plane), ESP (erector spinae plane), and quadratus lumborum blocks. They are technically simpler (targeting a plane rather than a specific nerve), have a larger margin of safety, and often provide broader coverage, but their block quality is less predictable than targeted nerve blocks.
How has ultrasound changed local anaesthetic volumes?+
Ultrasound guidance has enabled significant volume reduction. When performing landmark-based blocks, high volumes (30-40 mL) were needed to increase the probability of drug reaching the target nerve. With real-time visualisation of circumferential nerve spread, effective blocks can be achieved with 50-70% less volume — for example, 5-15 mL for most peripheral nerve blocks. This reduces the risk of local anaesthetic systemic toxicity and enables multiple blocks in the same patient within safe dose limits.
What is the evidence for erector spinae plane (ESP) blocks?+
The ESP block was described in 2016 and rapidly adopted due to its technical simplicity and presumed safety profile. However, the evidence base is still maturing. Multiple RCTs demonstrate analgesic benefit after thoracic and abdominal surgery, but the mechanism of action (paravertebral spread vs intercostal spread) remains debated, and the block is inconsistent in its dermatomal coverage. PROSPECT currently recommends it as a consideration for thoracic surgery when paravertebral blocks or epidurals are not feasible, but notes the evidence is of moderate quality.
