Intercostal Nerve Block: Governed by Two Hazards

The intercostal nerve block is one of the oldest techniques in regional practice and one of the simplest to describe: the nerve runs in the subcostal groove with its artery and vein, and depositing local anaesthetic there anaesthetises a band of chest wall. Its difficulty is not anatomical. It is that the pleura is immediately deep to the target, and that the chest wall absorbs local anaesthetic faster than almost anywhere else in the body.

Those two facts govern everything about how the block is used, and they are the reason newer fascial plane techniques have taken over much of its territory. This reference sets out the anatomy, the honest evidence position in acute and chronic pain, and the two safety issues that define it. It sits under our clinical reference to nerve blocks in outpatient pain practice.

The neurovascular bundle, and why the order matters

Each intercostal nerve runs in the costal groove on the undersurface of its rib, accompanied by the intercostal vein and artery. The conventional mnemonic for the arrangement from superior to inferior — vein, artery, nerve — is the reason the block is placed at the inferior border of the rib, and the reason the artery is the structure most likely to be encountered on the way.

The nerve gives off a lateral cutaneous branch well before the anterior axillary line. A block placed too far anteriorly therefore misses the lateral chest wall entirely, which is a common cause of an apparently failed block that was in fact correctly performed in the wrong place.

Because each nerve supplies a single narrow band, and because adjacent dermatomes overlap, useful coverage generally requires blocking several levels — which multiplies both the number of needle passes and the total dose.

Where it sits against the newer blocks

The most directly relevant recent evidence is a 2026 meta-analysis comparing the erector spinae plane block against intercostal nerve block in thoracic surgery and chest wall trauma.

The erector spinae plane block produced significantly lower pain scores at one hour, twenty-four hours and forty-eight hours. But it produced no significant difference in opioid consumption at twenty-four or forty-eight hours, no difference in hospital stay, and no difference in time spent under analgesia. The authors concluded that both techniques manage thoracic pain effectively, with the erector spinae plane block offering enhanced analgesic effect.

That is a fair summary, and it is worth reading carefully rather than as a verdict. A technique that lowers pain scores without reducing opioid use has produced a statistically robust effect whose clinical meaning is uncertain. What the comparison does establish is that intercostal block is no longer the default for chest wall analgesia when a fascial plane alternative is available and the operator is competent in it — largely because a single fascial plane injection covers multiple levels without approaching the pleura repeatedly.

For chronic chest wall pain, the pillar reference records intercostal block as modest for acute trauma with an evidence gap for chronic pain. Nothing in the recent literature closes that gap.

Local anaesthetic systemic toxicity

This is the block’s defining pharmacological hazard, and it is not a theoretical one.

The intercostal space produces among the highest peak plasma local anaesthetic concentrations of any regional technique for a given dose, because the space is highly vascular and the injectate sits adjacent to the intercostal artery. Multiply that by the several levels needed for useful coverage and the total dose climbs quickly toward the maximum.

The practical rules follow directly: calculate the total dose in milligrams per kilogram before starting rather than per level as you go, treat the multi-level block as a single cumulative exposure, and have lipid emulsion immediately available. The recognition and management of local anaesthetic systemic toxicity is set out in the nerve blocks reference.

Pneumothorax

The parietal pleura lies immediately deep to the intercostal groove, and pneumothorax is the complication every account of this block leads with. Reported rates vary widely with operator experience, technique and whether imaging was used, which is itself a reason to be sceptical of any single quoted figure.

Ultrasound changed this block more than most, because the pleura is one of the easiest structures to identify on a scan and its movement is unmistakable. Seeing the pleural line, rather than inferring its depth from the rib, is the difference the technology makes here. What guidance does and does not improve generally is covered in musculoskeletal ultrasound for pain practice.

Patients should be told what a post-procedural pneumothorax feels like and what to do about it, because the presentation can be delayed past the point at which they have gone home.

For clinicians

This is a block where the margin between the correct plane and the pleural space is measured in millimetres, and where dose arithmetic across multiple levels matters as much as needle control. It is learned under supervision on live anatomy. This reference carries no needle depths or trajectories for that reason.

Empire teaches the intercostal nerve block under ultrasound guidance within Advanced Musculoskeletal Ultrasound Guided Injections, alongside the other peripheral and paravertebral techniques in the pain management academy.