What’s in a Name? ASRA and ESRA Settle the Debate on Regional Anesthesia Nomenclature

A landmark international Delphi consensus standardizes names and anatomical descriptions for upper and lower limb nerve blocks and the results matter for every clinician, educator, and researcher in the field. This blog is based on El-Boghdadly K, et al.  |  Reg Anesth Pain Med. 2024;49:782–800.

Open-access publication  doi:10.1136/rapm-2023-104884

The Problem with Names

If you’ve ever argued with a colleague about whether you’re doing a “femoral triangle block” or an “adductor canal block” — or whether an “axillary brachial plexus block” is really what someone means when they write “axillary block” — you already understand the problem that a landmark international Delphi study set out to fix.

Regional anesthesia has expanded dramatically with the rise of ultrasound guidance. Each refinement or novel approach tends to earn a new label, often coined by its originator and applied inconsistently across institutions, journals, and continents. The result: a proliferating, confusing, and sometimes contradictory nomenclature that undermines teaching, complicates research synthesis, and may hamper safe adoption of techniques.

A previous ASRA–ESRA collaborative Delphi study successfully standardized nomenclature for abdominal wall, paraspinal, and chest wall blocks. This new study extends that work to upper and lower limb peripheral nerve blocks — the blocks most commonly performed in day-to-day regional anesthesia practice.

Figure 1. (A) Flow chart demonstrating Steering Committee decision-making for names between Delphi rounds to achieve consensus. (B) Flow chart demonstrating Steering Committee decision-making for anatomical descriptions between Delphi rounds to achieve consensus.

How the Study Worked: A Three-Round Delphi Process

The study used a rigorous three-round modified Delphi methodology, the same approach validated in the prior abdominal/chest wall nomenclature study.

●      Round 1: A long list of 104 regional anesthetic techniques (44 upper limb, 60 lower limb) was distributed electronically to 94 international expert collaborators, who voted “agree,” “disagree,” or “unsure” on proposed names and anatomical descriptions. Free-text comments were collected anonymously.

●      Round 2: The steering committee revised the list based on Round 1 feedback. A new proposal emerged: a standardized naming template for peripheral nerve blocks that are uncommonly performed, associated with multiple approaches, or failed to reach consensus.

●      Round 3: A virtual round-table discussion using live polling resolved remaining contested items. 65 collaborators participated.

The study was led by six representatives from ASRA Pain Medicine and ESRA (the Executive Committee) with steering committee oversight. A convenience sample of 94 collaborators — larger than most Delphi studies — strengthens the credibility of these findings. The project received IRB exemption from Stanford University and was approved by both ASRA and ESRA boards.

Key Findings: What Was Agreed — and Why It Matters

Upper Limb Blocks

For upper limb nerve blocks, strong consensus was achieved for 38 names and 33 anatomical descriptions across three rounds. The most significant harmonization involved the infraclavicular brachial plexus block, where three distinct approaches were formally named and differentiated by anatomy:

●      Retroclavicular approach — needle inserted cephalad to the clavicle

●      Costoclavicular approach — needle tip adjacent to the brachial plexus cords around the first part of the axillary artery

●      Coracoid approach — needle tip adjacent to the cords around the second part of the axillary artery

This approach-in-parentheses convention, e.g., infraclavicular brachial plexus block (retroclavicular approach) was agreed upon as the standard template for all blocks with multiple named approaches.

An important clarifying agreement: blocks targeting a nerve plexus should include the word “plexus” in the name (88% consensus). This eliminates the dangerous ambiguity between, for example, “axillary nerve block” (targeting the axillary nerve) and “axillary brachial plexus block” (targeting the brachial plexus at the axilla).

Figure 2: Three approaches to the infraclavicular brachial plexus block relative to the first, second and third parts (proximal, deep to, and distal to the pectoralis minor muscle, respectively) of the axillary artery. ASRA, American Society of Regional Anesthesia.

Lower Limb Blocks

Lower limb blocks generated the most controversy — and produced some of the most clinically significant agreements.

Adductor Canal Block vs. Femoral Triangle Block: This long-standing debate was settled with strong consensus (name 85%, anatomical description 80% in Round 1). The agreed definitions:

●      Adductor canal block — injection within the compartment containing the femoral vessels, distal to the apex of the femoral triangle and proximal to the adductor hiatus

●      Femoral triangle block — injection in the aponeurotic compartment proximal to the apex of the femoral triangle

The upper limit of the adductor canal is the apex of the femoral triangle (where the medial border of the sartorius crosses the medial border of the adductor longus). The inferior border is the adductor hiatus, identifiable on ultrasound as the point where superficial femoral vessels “dive” deep toward the popliteal fossa.

Figure 3. Lower limb ultrasound anatomy at three levels: mid-femoral triangle (location of femoral triangle block), apex of the femoral triangle, and through the adductor canal (location of adductor canal block). ASRA, American Society of Regional Anesthesia.

Sciatic Nerve Block Approaches were harmonized with anatomical descriptors: transgluteal (needle through gluteal muscle), infragluteal (trajectory inferior to the lower gluteal border), and anterior approaches. The previously common term “subgluteal” was retired in favor of “transgluteal” to eliminate confusion with “infragluteal.”

Genicular Nerve Blocks: Strong consensus on names based on anatomical location — superior medial (81%), superior lateral (80%), inferior medial (78%), inferior lateral (81%). Anatomical descriptions for the inferior blocks achieved only weak consensus (67–69%), reflecting ongoing anatomical debate about whether these represent single nerves or nerve groupings alongside genicular vessels.

A Universal Template for Peripheral Nerve Block Naming

One of the most forward-looking agreements from this study is the formal adoption of a standardized naming template for peripheral nerve blocks:

[NAME OF NERVE] + block at the + [ANATOMICAL LOCATION]

Example: Radial nerve block at the wrist  •  Sural nerve block at the ankle

This template applies to any individual peripheral nerve block that is uncommonly performed, associated with multiple approaches, or did not reach consensus in this study. It eliminates the need to coin arbitrary eponyms and anchors block names directly to anatomy, a principle that should future-proof nomenclature as new techniques continue to emerge.

Figure 4. Template for naming peripheral nerve blocks.

Clarity on Plexus vs. Individual Nerve Blocks

The study confirmed that blocks targeting a nerve plexus should always include “plexus” in the name, a rule that immediately clarifies the following common ambiguities:

Ambiguous / Old Term	Standardized Term
Axillary block	Axillary brachial plexus block
Supraclavicular block	Supraclavicular brachial plexus block
Interscalene block	Interscalene brachial plexus block
Axillary nerve block	Axillary nerve block (individual nerve — no change)

Similarly, blocks targeting an individual nerve should include the word “nerve” in the name (81% consensus). These two rules together create a logical, self-explanatory naming system that communicates anatomical intent immediately.

Figure 5. Schematic representation of the various brachial plexus block approaches along its anatomical course. ASRA, American Society of Regional Anesthesia.

Why This Matters for Your Practice

Nomenclature may seem like an academic exercise, but its practical consequences are real:

🎓 Education Inconsistent block names confuse trainees and impede structured learning. A universal standard allows curricula, simulation programs, and competency frameworks to align.

🔮 Research Meta-analyses and systematic reviews depend on being able to pool studies that describe the same technique. Heterogeneous nomenclature has historically meant comparing studies that aren’t truly comparable.

🏥 Clinical Practice Handoff notes, anesthesia records, and consent documents that use standardized terminology reduce miscommunication and support safer care — particularly as regional anesthesia expands beyond dedicated block rooms into perioperative and acute pain settings.

The authors note that the prior abdominal/chest wall nomenclature consensus has already shown evidence of adoption in published literature, suggesting that community-wide uptake is achievable when the recommendations are clear, evidence-based, and broadly endorsed.

The Bottom Line

This ASRA–ESRA consensus study delivers something the regional anesthesia community has needed for years: a rational, anatomy-anchored framework for naming and describing upper and lower limb nerve blocks. Its key deliverables are: 

•  Strong consensus on 38 names and 33 anatomical descriptions for upper and lower limb blocks

•  Weak consensus (still clinically useful) on 5 additional anatomical descriptions

•  Formal adoption of the parenthetical approach convention: e.g., infraclavicular brachial plexus block (retroclavicular approach)

•  A universal naming template for all peripheral nerve blocks: [Nerve name] + block at the + [Location]

•  Mandatory use of “plexus” for plexus-level blocks and “nerve” for individual nerve blocks

•  Clear anatomical delineation of adductor canal block vs. femoral triangle block

•  Harmonized sciatic nerve block approach terminology

Clinicians, educators, and researchers are encouraged to adopt this standard immediately in publications, teaching materials, and clinical documentation. The full consensus tables (Tables 1 and 2) and supplemental appendices are available open-access in the original publication cited below.

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Full Citation

El-Boghdadly K, Elsharkawy H, Mariano ER, et al. Standardizing nomenclature in regional anesthesia: an ASRA-ESRA Delphi consensus study of upper and lower limb nerve blocks. Reg Anesth Pain Med. 2024;49:782–800. doi:10.1136/rapm-2023-104884

Open access at: https://rapm.bmj.com/content/49/11/782