The use and effectiveness of ultrasound guidance for peripheral nerve block procedures. A systematic review

 

Nº de DOI: 10.34896/RSI.2026.58.31.001

 

 

AUTHORS

1. Luis Roberto Ordeñana Robles. General Practitioner. Attached to Private Clinics of Ecuador. Graduate of the State University of Guayaquil. (Guayaquil-Ecuador). https://orcid.org/0009-0004-9359-8386
2. Luis Gabriel Jimbo Lupercio. General Practitioner. Attached to Private Clinics of Ecuador. Graduate of the University of Cuenca. (Cuenca-Ecuador). https://orcid.org/0009-0006-1081-3189
3. José Jesús Cabello Alcivar. General Practitioner and Master’s Degree in Occupational Health. Attached to Private Clinics of Ecuador. Graduate of the University of Guayaquil. (Guayaquil-Ecuador). https://orcid.org/0009-0003-9060-7171
4. Lisseth Carolina Moya Cantos. General Practitioner. Attached to Dr. Rafael Rodríguez Zambrano Hospital. Graduate of the Technical University of Manabí. (Portoviejo-Ecuador). https://orcid.org/0009-0002-7991-7569
5. Felix Fernando Pacheco Vasconez. General Practitioner. Attached to Private Clinics of Ecuador. Graduate of the University of Guayaquil. (Daule, Ecuador). https://orcid.org/0009-0002-9010-5051

 

ABSTRACT

This review will conclude with a discussion of individualized ultrasound guided intervention in the improvement of perioperative outcomes and support of enhanced recovery protocols.

KEY WORDS

Ultrasound-guided regional anesthesia, peripheral nerve block, fascial plane block, clinical efficacy and safety outcomes.

RESUMEN

Esta revisión concluirá con una discusión sobre la intervención individualizada guiada por ultrasonido en la mejora de los resultados perioperatorios y el apoyo a protocolos de recuperación mejorada.

PALABRAS CLAVE

Anestesia regional guiada por ultrasonido, bloqueo de nervios periféricos, bloqueo de plano fascial, eficacia clínica y resultados de seguridad.

INTRODUCTION

The practice of regional anesthesia has undergone a fundamental shift over the past three decades, moving away from an emphasis on surface anatomy and physiological responses to visualization of anatomy. Ultrasound guided regional anesthesia (UGRA), has become the new standard of care, as it affords real-time visualization of anatomy which aids in appropriate needle placement and local anesthetic deposition. This systematic review will review the procedural and clinical effectiveness and safety of ultrasound guidance for peripheral nerve blocks (PNBs). The review will include clinical trials and meta-analyses from the years 2015 to 2025 to provide a synthesis of findings on the relationship between ultrasound guidance to block success rates, onset times, and decreased local anesthetic volume. The literature suggests that real-time visualization increases the accuracy of a needle nerve interaction in comparison to LM techniques which improves pain control and therefore reduces opioid use¹. The review will also demonstrate how regional anesthesia techniques have evolved into fascial plane blocks, such as the erector spinae plane and quadratus lumborum blocks, which have expanded the mechanism of postoperative analgesia for truncal and abdominal surgery². There is evidence to suggest UGRA is more effective at reducing vascular punctures and local anesthetic systemic toxicity, however prevention of long-term neurological injury or numbness is ongoing³. In addition, there is merit in integrating advanced technologies, such artificial intelligence (AI), or 3D imaging to further standardize regional anesthetic procedures and reduce human error.

OBJECTIVE

The goal of the systematic review is to answer the following research questions related to the current state of UGRA:

1. How does UGRA compare to conventional methods regarding block success, time to onset, and total volume of local anesthetic required?
2. What are the specific technical considerations for applying ultrasound to upper extremity, lower extremity and truncal blocks?
3. To what extent does real-time visualization decrease the incidence of procedural complications (e.g. vascular puncture, nerve injury)?
4. What is the role of newer technologies (e.g. AI and robotics) in increasing precision and accessibility of regional anesthesia?

 

METHODOLOGY

Search Strategy and Information Sources:

A systematic search of the literature was conducted to identify relevant studies published between January 2015 and October 2025. This time frame was chosen to capture the most updated information on innovations related to ultrasound technology and the development of new fascial plane blocks. This search included six major databases (including PubMed, Google Scholar, and specialized anesthesia registries). The search strategy utilized a combination of Medical Subject Headings (MeSH) and keywords including «ultrasound-guided regional anesthesia,» «peripheral nerve block,» «fascial plane block,» «clinical efficacy,» and «safety outcomes».

Inclusion and Exclusion Criteria:

Studies were included if they met the following inclusion criteria: (1) original research employing human subjects, including randomized controlled trials (RCTs), cohort studies, meta-analyses, (2) focused on ultrasound-guided peripheral nerve or truncal blocks, and (3) reporting on clinical outcomes such as pain scores, opioid consumption, block duration, or complication rates. Studies were excluded if they solely included neuraxial anesthesia (spinal/epidural), exclusively used animal models, and published papers using ultrasound merely for vascular access instead of nerve localization. Case reports and editorials were included only if they provided distinctive technical information on recently described blocks.

Data Extraction and Management:

Data extraction was done via a standardized template to enhance consistency across the review. Information was collected for the included studies regarding the relevant patient population (pediatric specifics included), the type of nerve block, the ultrasound technique (e.g., in-plane vs. out-of-plane), local anesthetic regimen, and primary and secondary outcomes. In instances of meta-analysis, pooled effect sizes and confidence intervals were recorded so that high-level synthesis could be performed.

RESULTS

The Role of Peripheral Nerve Blocks in Contemporary Anesthesia:

Peripheral nerve blocks (PNBs) remain a mainstay of multimodal analgesia – they provide targeted pain relief while minimizing systemic side effects on the cardiovascular system with general anesthesia and opioid utilization. In the modern perioperative environment, the treatment of acute postoperative pain is now recognized as a critical element of recovery, impacting the physiological state of a patient and their psychological status throughout the perioperative period⁴. Effective analgesia is correlated with rapid mobilization of a patient, reduced respiratory and cardiovascular complications, as well as reduced length of stay in the hospital. PNBs have important clinical use in a variety of surgical divisions, including orthopedic, vascular and general oncology, where a successful nerve blockade is vital for successful management of complex pain syndromes⁵.

Moving from Landmark and Nerve Stimulation to Ultrasound Guidance:

The procedures of regional anesthetic delivery have gone through designated eras of technology. Prior to ultrasound guidance, clinicians utilized either the landmark (LM) technique, which utilized surface anatomy and tactile sensation (e.g., “fascial clicks”) to estimate the needles distance from the target nerve. The variability in human anatomy and anatomy, particularly in patients with high body mass index or muscle atrophy, in conjunction with LM techniques correlated with increased failure of nerve blocks, and increased incidence of vascular and pleural puncture.
Following this, peripheral nerve stimulation (PNS) was developed, which provided a more objective physiological marker by delivering a motor response to an electrical current. Though this advancement resulted in improved reliability of nerve localisation, it remained indirect because if one does not elicit a motor response during PNS, it does not necessarily guarantee that the clinician is «safe distance» (advancing and potentially causing damage) from the nerve. Similarly, eliciting a motor response does not automatically indicate that the drug will achieve effective anesthesia if the local anesthetic does not appropriately diffuse.

The real «game changer» came with ultrasound³. In regional anesthesia, the idea of an indirect application of ultrasound was first described in 1978 when sonar (Doppler) ultrasound was used to map the subclavian artery to establish a landmark for supraclavicular blocks³. The first true «game-changer» came in 1994 by Kapral and colleagues when they described performing a supraclavicular brachial plexus block under direct ultrasound guidance³. Moving from «blind» or physiologically estimating to direct anatomical visualization, the clinician was now able to visualize the nerve, the needle, and the spread of local anesthetic, all in real time, significantly changing the safety and efficacy profile of regional anesthesia.

Problem statement and rationale for the review:

Although UGRA has quickly gained acceptance, the rapid introduction of new techniques and ongoing emergence of clinical evidence necessitates a synthesis of our current evidence. New fascial plane blocks are being introduced at a rate that exceeds the publication of evidence from large-scale randomized controlled trials². While ultrasound has been associated with higher technical success, there are questions related to clinical significance in certain circumstances. For example, some data regarding the erector spinae plane block for breast surgery suggest that differences in analgesic benefit based on ultrasound guidance, while statistically significant, may not be clinically significant⁶. Furthermore, we need to examine how ultrasound guidance fits in with newer pharmacological adjuncts and advancements in artificial intelligence (AI)-assisted identification (which ultimately aim to decrease and/or standardize user-dependent operational variance) ¹.

Technical Applications of Ultrasound in Nerve Blocks:

Upper Extremity Block Techniques:

The brachial plexus is the primary target for upper extremity regional anesthesia, and ultrasound has transformed the approaches to this structure. The supraclavicular approach is frequently referred to as the «spinal of the arm» due to the brachial plexus being most compact at this level, located lateral and superior to the subclavian artery³. Real-time imaging allowed the clinician to avoid the pleura, which is very nearby, significantly reducing the risk of pneumothorax as compared to landmark-based techniques.

In the interscalene area, ultrasound allows for the identification of the C5-C7 nerve roots, located between the anterior and middle scalene muscles. This is especially important for shoulder surgery, where visualization of the phrenic nerve on the anterior scalene surface allows for «phrenic sparing» techniques, such as injecting the local anesthetic slightly more lateral or using lower volumes¹.

When considering blocks for the forearm and hand, the infraclavicular and axillary block techniques are commonly used. The infraclavicular block under ultrasound guidance is visualized using a single injection technique with the three cords (lateral, medial, posterior) in relation to the axillary artery. In the axillary approach, ultrasound utilizes the individual terminal nerves (median, ulnar, radial, and musculocutaneous), which can be separated by fascial planes, or sometimes the axillary veins, under ultrasound, the ability to visualize and confirm that the respective nerve receives adequate exposure to the anesthetic provides assurance that each nerve is properly blocked³.

Lower Extremity Block Techniques:

Ultrasound has helped address some of the issues that are inherent to lower extremity blocks which often deal with deeper structures and more complex fascial anatomy. The femoral nerve block is commonly used for hip and knee surgery and is performed by identifying the femoral nerve, which is located lateral to the femoral artery and deep to the fascia iliaca. By placing the ultrasound transducer in this area, the clinician will see the injectate traveling beneath the fascia, which is a better indication of a successful block compared to simple needle placement near the artery.

The sciatic nerve is also the largest nerve of the body and can be visualized at several areas along the length of the nerve including the subgluteal space towards the popliteal fossa. The popliteal approach is when ultrasound identifies the bifurcation of the sciatic nerve into the tibial and common peroneal nerves. Studies suggest that injecting at the site of bifurcation will result in a faster onset sensory/motor blockade compared to injecting more proximal to the bifurcation.

The adductor canal block is gaining popularity as a motor-sparing block to the femoral nerve block for total knee arthroplasties. The ultrasound is useful in identifying the saphenous nerve and nerve to the vastus medialis muscle within the adductor canal, deep to the sartorius muscle. The visualization of the femoral artery while in the canal is an important landmarks to ensure that the local anesthetic deposition within the correct fascial plane to achieve analgesia while minimizing the risk of hindering the patients participate in an early physical therapy process².

Truncal and Abdominal Wall Block Applications:

The «renaissance» of regional anesthesia is seen largely in the development of truncal and abdominal wall blocks². These techniques focus mainly on the fascial planes that the nerves run through, instead of targeting the nerves directly. The Transversus Abdominis Plane (TAP) block is one of the first blocks to be adopted as an ultrasound block for accurate deposition of the local anesthetic agent between the internal oblique and transversus abdominis⁴.

The Quadratus Lumborum (QL) block is another development that can extend analgesia in abdominal laparoscopic procedures⁸. By injecting local anesthetic surrounding the QL muscle, visceral and somatic analgesia can be achieved which results in less inflammatory response to surgical trauma, and quicker return to baseline physiological functions⁸. There are multiple variations of the QL block (lateral, posterior, and anterior), which all require high-resolution ultrasound to visualize the muscle layers and retroperitoneal structures beneath it.

The Erector Spinae Plane (ESP) block has surfaced a flexible approach for thoracic and abdominal pain. In this technique, the needle is placed in the plane deep to the erector spinae muscle, directed toward the transverse process of the vertebrae with a local anesthetic². While the ESP block is technically easier than paravertebral blocks, its clinical success is still developing. For example, a meta-analysis of breast cancer surgery conducted trials evaluating the efficacy of the ESP block, which discovered that while the block reduced morphine consumption significantly at 24 hours, the mean difference was roughly 17.6 mg, which some researchers argue fall below the clinical threshold of importance in all patient populations⁶.

In the pediatric population, ultrasound-guided interfascial plane blocks have become vital for the provision of long-acting analgesia complications⁷. The accuracy of ultrasound is particularly useful in children due to their smaller anatomical dimensions and physiological differences related to local anesthetics, which demand high levels of individualization⁷.

Additionally, the expansion of UGRA into chronic pain management, and the use of 3D ultrasound and real-time imaging are allowing more accurate assessments of challenging patient anatomies³. The most recent advancement is the integration of AI-assisted ultrasound platforms that use machine-learning algorithms which assist in identifying nervous structures and the guiding of needles into those structures, with a goal of minimizing human error and standardizing care regardless of provider experience^1,3.

Analysis of Clinical Effectiveness:

Block Success Rates and Quality of Anesthesia:

The shift to ultrasound (US) guidance has completely changed the definition of success in regional anesthesia, as the intent is no longer a probabilistic functional endpoint, but a deterministic anatomical one. It is now widely accepted that ultrasound guidance is the gold standard for nerve localization, especially in lower extremity procedures, which often cannot achieve satisfactory anatomical depth and complexity by the traditional landmark technique⁹. Systematic reviews of block success rates show that while ultrasound improves the reliability of the block, the degree of improvement will be site specific.

In the upper extremity, the approach (e.g., axillary, supraclavicular, infraclavicular) does demonstrate some subtle differences in surgical anesthesia success. When comparing ultrasound-guided axillary brachial plexus blocks to infraclavicular approaches, metaanalysis shows, while there is some statistical significance for achieving adequate surgical anesthesia with either technique (RR: 0.92), the differences between axillary and supraclavicular approaches are less clear-cut¹⁰. Anesthesia quality can also be improved by ultrasound, as the local anesthetic can completely surround the nerve target, allowing all fascicles to benefit from the local anesthetic (the circumferential spread). It can also eliminate «patchy block» when using nerve stimulation, where, in some cases, the plexus is in proximity but the needle is only stimulating a subcomponent.

Onset Time and Duration of Sensory and Motor Blockade:

One of the most significant advancements clinically, with ultrasound guidance is the improvement in on set time. Ultrasound allows for the localization of the local anesthetic to the area of distribution of the nerve – often the paraneural or sub-epineural space, which allows for more rapid diffusion across the neural sheath- compared to the approximation of the needle position with nerve stimulation or landmark techniques. Studies of lower extremity blocks consistently show a small but consistently improved onset time and overall block quality with ultrasound⁹.

The onset is quicker and the duration of the block can be more accurately predicted. The visualization of the «donut sign»- the nerve is completely encircled- ensures that the block is robust and can lead to consistent duration of the local anesthetic even beyond blocks that have asymmetric spread. In some applications, e.g., thoracic paravertebral block (TPVB), effectiveness is even more enhanced with multilevel blocks that have been shown to lead to better acute analgesia and possibly reduced chronic postsurgical pain at the 6 month follow-up¹¹.

Procedure Efficiency and Number of Needle Redirections:

Procedure efficiency is a complex metric, in compassing preparation time, needling time, and number of needle redirections. While the ultrasound equipment must be set up and the pre-scan is added to the total time, «needle-to-nerve» time is often decreased. For example, ultrasound-guided selective nerve root blocks (SNRB) of the cervical spine have been shown to be of shorter duration compared to both fluoroscopy-guided interlaminar blocks or epidural transforaminal blocks yet provide similar pain relief¹².

Nonetheless, the efficiency of ultrasound-guided peripheral nerve blocks is also highly dependent on the specific approach utilized. One study indicated that ultrasound-guided infraclavicular blocks were performed faster than ultrasound-guided axillary blocks. This suggests that anatomical access and the number of required injections (i.e. single or multiple) can play a big part in the pace of the procedure¹⁰. Reducing the redirections with the needle can also lead to increased efficiency by minimizing tissue trauma, discomfort and improve the entire perioperative experience.

Volume Reduction of Local Anesthetics:

Possibly the most significant impact pharmacological transformation with the use of ultrasound guidance is the ability to perform a successful block with significant reductions in the total volume of local anesthetic used, or Minimal Effective Volume (MEV). Visualization allows the clinician to employ a targeted strike, where the medication is deposited precisely where it is needed versus a high volume carpet bomb to overcome some uncertainty regarding localization.

The reduction in volume has important implications not only on safety but also on the quality of recovery. Using lesser volumes can enable the clinician to perform motor-sparing blocks which are important components of modern Enhanced Recovery After Surgery (ERAS) protocols. For example, a reduction in volume with an interscalene block can limit the spread to the phrenic nerve and decrease the chance of hemidiaphragmatic paresis while still enabling effective analgesia for shoulder surgery¹³.

Safety Profiles and Complication Rates:

Incidence of Vascular Puncture and Hematoma Development:

One of the key safety drivers for using ultrasound guidance is the ability to visualize vascular structures in real time. Identifying veins and arteries, as well as anatomical variance, can help improve the clinician’s ability to redirect the needle to avoid unintentional punctures. In patients receiving cervical spine interventional procedures, it was found that ultrasound-guided SNRB had a significantly lower rate of intravascular injection in comparison to fluoroscopic guidance¹². Likewise, the literature regarding central venous access illustrates how much ultrasound guidance has effectively become a tool to avoid mechanical complications, such as unintended arterial puncture and cannulation¹⁴.

Prevention of Local Anesthetic Systemic Toxicity:

Local Anesthetic Systemic Toxicity (LAST) remains one of the most dreaded complications in regional anesthesia. Top-level evidence from leading societies like the American Society of Regional Anesthesia and Pain Medicine (ASRA) provides clear evidence that ultrasound significantly mitigates the risk of LAST¹³. The mitigation of LAST risk is attributed to two factors: direct visualization of the injection to confirm it is not intravascular, and the overall reduction in the total dose of local anesthetic necessary to achieve a successful block. The guidelines as established by the Italian Society of Anesthesia (SIAARTI) are clear that ultrasound is a powerful adjunct to enhance safety, but must be part of a structured approach that combines aspiration tests with incremental dosing¹⁵.

Frequency of Post Operative Neurological Symptoms:

Despite the improvements in visualization, the impact of ultrasound on the frequency of Post Operative Neurological Symptoms (PONS), is less definitive. Evidence-based assessment finds that ultrasound guidance does not have a meaningful effect on rate of PONS compared to conventional approaches¹³. This most-likely signifies that nerve injury as an event is multifactorial: mechanical trauma from the needle, chemical toxicity from the anesthetic, and even surgical factors such as positioning, or tourniquet use. ASRA practice advisories have expressly stated that although ultrasound may assist in determining the needle-nerve relationship, the use of ultrasound does not remove the inherent risks of nerve injury as a result of aggressive needle maneuvers or the inability of the operator recognizing intraneural placement of the needle within the nerve¹⁶.

Safety Outcome Comparison to Conventional Approaches:

When comparing ultrasound to landmark and nerve stimulation approaches, and consider only immediate mechanical complications, the safety of ultrasound is generally better. For example, ultrasound significantly reduces the incidence and severity of hemidiaphragmatic paresis after a brachial plexus block, a relevant safety outcome for patients who may have compromised respiratory function¹³. Additionally, the early application of regional anesthesia due to the increased safety afforded by use of ultrasound, and overall ease of use in settings such as the Emergency Department (ED), provides an effective alternative to systemic management of pain while avoiding the risks of systemic overdose with high opioid use¹⁷.

DISCUSSION

The synthesis of existing studies support evidence that ultrasound guidance provides a moderate, but clinically significant, speed and quality of block performance for a variety of anatomical locations. For the upper limb the choice of axillary, supra- or infra-clavicular approaches should be individualized to the surgical procedure as well as patient-specific parameters. For example, the infraclavicular approach has been described as having improved success rates and faster completion time in some studies when compared to axillary approach. More importantly, axillary approach may be preferred in cases where subjective patient adverse effects are prioritized. In truncal and abdominal approaches, ultrasound has allowed a practical application to fascial plane blocks when previously these blocks were impractical, providing a wider practice of regional anesthesia in modern practice.

The clinical indication for ultrasound-guided nerve blocks extends beyond the immediate setting defined as perioperative. The use of ultrasound for effective multimodal analgesia plays a critical role in reducing opioid utilization, along with some of the complex risks of opioid use, e.g. respiratory depression or nausea. In pediatric populations, for example, maintaining homeostasis with adequate analgesia or nerve conduction blocks is critical to prevent acute pain from transitioning to moderate to severe pain in as much as 70% of hospitalized pediatric patients. Additionally, early interventions with regional anesthesia in the emergency department population has been shown to logically reduce transitions from acute to chronic pain.

Ultrasound guidance, while advantageous, has limitations. The use of ultrasound is very operator-dependent and establishes a sophisticated level of hand-eye coordination and visuospatial processing. The «learning curve» for an operator is a real limitation, specifically, a novice practitioner may actually be less safe with ultrasound than an expert practitioner using traditional tactile-based landmark techniques. Perhaps relatedly, the «illusion of safety» from visualization may lead to overconfidence and more complex blocks attempted without training. Further, the capital cost of high-quality ultrasound machines continues to be a limiting factor to universal uptake of ultrasound-guided techniques in resource-limited settings.

The evidence supports using ultrasound guidance into routine practice, particularly for higher-risk procedures, and/or patients with challenging anatomy. To that end, ultrasound-guided SNRBs may be a faster and potentially safer technique for chronic pain management compared to traditional fluoroscopy. Clinicians must also consider the benefits of ultrasound guidance while understanding various patient and procedural considerations to ensure the complete safety triad, which includes nerve stimulation and pressure monitoring. Finally, as transition from tactile based approaches to ultrasound guided techniques will necessitate a large reallocation of formal resources toward training and overall equipment maintenance to ensure the theoretical safety benefits realized in practice.

A large limitation of the literature is the heterogeneity of study designs, with the absence of sufficiently powered randomized controlled trials for certain lower extremity blocks. The majority of studies address the issue of technical success (e.g., «time to perform block»), as opposed to long-term clinical outcomes (e.g., «quality of recovery» or «development of chronic pain»). Additionally, the rapidly evolving technology surrounding ultrasound may prevent older studies from capturing the capabilities of modern day, high-resolution ultrasound. Robust research is needed to address these knowledge gaps, particularly in regards to the efficacy of newer fascial plane blocks, and to assess the impact of ultrasound on patient-reported outcome measures.

 

CONCLUSIONS

1. This systematic review highlights the revolutionary advancement of ultrasound guidance in peripheral nerve block procedures. By replacing indirect physiological markers with direct anatomical visualization, ultrasound has maximized block success rates, minimized block onset times, and allowed for dramatic reductions in local anesthetic volumes. The safety aspect of regional anesthesia is now exemplified by a significant decrease in vascular puncture incidence and local anesthetic systemic toxicity, nevertheless, postoperative neurological symptoms remain a concern and are best prevented with a multimodal safety approach.
2. The clinical application of ultrasound-guided blocks is now a fundamental component of contemporary perioperative care and multimodal analgesia, leading to improved patient recovery and minimized opioid consumption. While limitations corroborated by technology, and human operator exist, the overarching body of evidence supports the use of ultrasound guidance as the new gold standard for most regional anesthesia applications. Future research should focus on standardized training for ultrasound-guided block applications, long-term efficacy of the newer block techniques, and the use of artificial intelligence to further improve accuracy and safety in nerve localization. Ultimately, regardless of the benefits of ultrasound application in regional anesthesia, the selection of a regional anesthesia technique is an individualized decision, taking into consideration clinical evidence, patient-specific elements, and operator expertise (10).

 

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