Epidural Spread of Erector Spinae Plane (ESP) Block

The erector spinae plane (ESP) block is a recently developed approach in regional anesthesia, targeting a paraspinal fascial plane for the administration of local anesthetic (LA). By infiltrating LA between the tip of the transverse process of either thoracic or lumbar vertebrae and the anterior fascia of the erector spinae muscles, this technique aims to provide analgesia for a wide array of surgical interventions and pain management scenarios. A unique phenomenon associated with ESP block is the possibility of epidural spread of the anesthetic, resulting in additional anesthesia.

Comprising the iliocostalis, longissimus, and spinalis muscles, the erector spinae muscle complex spans the length of the vertebral column from the base of the skull to the pelvis, with insertions at various points along the spine and surrounding structures. Notably, these muscles play a pivotal role in supporting the spinal column and facilitating movement.

In the thoracic region, the erector spinae muscles are partially overlaid by the trapezius and rhomboid major muscles, while in the lumbar region, they lie beneath the serratus posterior inferior and latissimus dorsi muscles.

The erector spinae plane itself is a distinct anatomical entity, situated between the anterior aspect of the erector spinae muscles and the posterior surfaces of the vertebral transverse processes. In the thoracic region, this plane interfaces laterally with the intercostal spaces and is demarcated medially by the laminae and interspinous ligaments.

Facilitating communication with both the thoracic paravertebral and epidural spaces, the erector spinae plane can serve as a conduit for the spread of LA, potentially extending analgesic effects of an ESP block beyond the primary injection site – epidural spread. This phenomenon is facilitated by structures such as the superior costotransverse ligament, which harbors fenestrations permitting LA migration into adjacent spaces.

The clinical utility of ESP blocks continues to expand, with applications ranging from thoraco-abdominal surgeries to procedures involving the breast, shoulder, upper and lower extremities, spine, hip, and cesarean deliveries, as well as in the management of multiple rib fractures and chronic pain syndromes.Spread of LA into nearby spaces, including the paravertebral, epidural, and intercostal regions, as well as diffusion into the erector spinae muscles, may prove useful in certain cases. However, epidural spread may lead to unwanted side effects, making it important for anesthesiologists to understand the potential complications of the ESP block and be prepared to manage them if necessary.

Although specific complications related to ESP blocks remain poorly characterized, existing evidence suggests their rarity. While instances of adverse events such as unilateral pneumothorax have been reported, they appear to be isolated occurrences. However, caution should be exercised, particularly in patients with coagulopathies or receiving anticoagulant therapy, where the safety profile of ESP blocks remains uncertain and warrants individualized assessment.

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