Peripheral Nerve Blocks

A peripheral nerve block produces anesthesia or analgesia in the territory of a specific nerve or plexus by depositing local anesthetic close to it, away from the spinal canal. These blocks range from single named-nerve injections to large plexus blocks of the upper or lower limb and fascial-plane blocks of the trunk, and they may be performed as single injections or through indwelling catheters for prolonged analgesia.

Definition

A peripheral nerve block is a regional anesthetic technique that interrupts conduction in a peripheral nerve or plexus by placing local anesthetic adjacent to it, anesthetizing the region that nerve supplies.

Scope

This entry covers the principle of perineural local anesthetic deposition, the main categories of peripheral and plexus blocks, single-injection versus continuous catheter techniques, and the safety considerations specific to peripheral blockade. It is a reference and educational overview and contains no dosing, procedural, or individualized clinical instructions.

Key concepts

• Perineural local anesthetic deposition
• Named-nerve versus plexus blocks
• Brachial plexus blocks (interscalene, supraclavicular, infraclavicular, axillary)
• Lower-extremity blocks (femoral, sciatic, adductor canal)
• Fascial-plane and abdominal-wall blocks
• Single-injection versus continuous (catheter) techniques
• Multimodal, opioid-sparing analgesia
• Nerve localization (stimulation and ultrasound)

Mechanisms

Local anesthetic placed around a peripheral nerve diffuses across the connective-tissue sheaths to reach axons and block their voltage-gated sodium channels, interrupting impulse conduction in the fibers that pass through the injection site (Miller's Anesthesia; Neal 2009). The territory anesthetized depends on which nerve or plexus is targeted and on the spread of the injected solution. Fascial-plane blocks, such as abdominal-wall blocks, work by spreading local anesthetic within a tissue plane to reach the nerves coursing through it (Chin 2017). Continuous techniques maintain block by infusing local anesthetic through a catheter placed near the nerve (Ilfeld 2017).

Clinical relevance

Peripheral nerve blocks provide surgical anesthesia and postoperative analgesia for limb and trunk procedures and are a key component of multimodal, opioid-sparing pain management (Ilfeld 2017; Chin 2017). This entry describes the techniques and their evidence base as reference knowledge and does not offer procedural guidance or individualized recommendations.

Epidemiology

Serious complications of peripheral nerve blocks, including persistent nerve injury and local anesthetic systemic toxicity, are uncommon; society advisories collate the largely observational evidence on their frequency and risk factors and on measures associated with safer practice (Neal 2015).

Evidence & guidelines

Narrative 'essentials of our current understanding' reviews from ASRA summarize the evidence for upper-extremity and abdominal-wall blocks (Neal 2009; Chin 2017), an evidence update addresses continuous peripheral nerve blocks (Ilfeld 2017), and the ASRA neurologic-complications advisory frames block-related nerve-injury risk (Neal 2015). Together these form the principal reference base for the topic.

History

Peripheral nerve blockade developed alongside the introduction of injectable local anesthetics around 1900, with early brachial plexus and other named-nerve techniques relying on surface landmarks and elicited paresthesias (Miller's Anesthesia). The introduction of peripheral nerve stimulation and, subsequently, real-time ultrasound guidance improved localization and broadened the range of blocks, including the more recent fascial-plane techniques of the trunk (Neal 2009; Chin 2017).

Seminal works

• neal-2009-upperextremity
• ilfeld-2017-cpnb
• chin-2017-abdominalwall

Frequently asked questions

What is the difference between a single-injection and a continuous peripheral nerve block?

A single-injection block deposits one dose of local anesthetic near the nerve, giving analgesia for a limited period, whereas a continuous block places a catheter so that local anesthetic can be infused to prolong the effect.

What is a fascial-plane block?

It is a block in which local anesthetic is spread within a tissue plane, such as the layers of the abdominal wall, to reach the nerves traveling through that plane rather than targeting a single named nerve.