Indication
- Regional anesthesia for spinal surgery
- Acute pain relief in acute back pain
Technique
- Targets the plane between the erector spinae muscle group and the transverse processes of the vertebrae.
- A needle is inserted under ultrasound guidance to identify the correct anatomical landmarks.
- Under ultrasound guidance, the needle is advanced between the erector spinae muscle group and transverse process; after contact with the bone, the local anesthetic can be injected.
- Local anesthetic is injected into the fascial plane, allowing the solution to spread along the thoracic or lumbar spine.
Mechanism of action
Local Anesthetic Spread:
- The injected local anesthetic spreads within the fascial plane between the erector spinae muscle and the transverse process.
- It diffuses ventrally to reach the intervertebral foramen, affecting both the dorsal and ventral rami of the spinal nerves.
- This provides somatosensory blockade of the paravertebral region, including the thoracic and lumbar dermatomes.
- Can cause some muscle relaxant effects
Paravertebral Space Involvement:
- The anesthetic may extend into the paravertebral space, mimicking the effects of a traditional paravertebral block.
- This can result in unilateral segmental analgesia, covering both somatic and visceral pain pathways.
Sympathetic Chain Modulation:
- Potentially contributing to relief in neuropathic or sympathetically maintained pain.
Central and Neuroplastic Effects:
- There is emerging evidence that repeated ESP blocks may induce central desensitization or reduce central sensitization in chronic pain states.
- This could explain its effectiveness in conditions like post-thoracotomy pain syndrome, fibromyalgia, or neuropathic pain.
Anti-Inflammatory and Systemic Effects:
- Some researchers propose that the anesthetic may modulate local inflammatory mediators, though this is still under investigation
Complications
Common / Mild Complications
- Transient Hypotension: Due to sympathetic blockade (though less common than with neuraxial blocks).
- Local Anesthetic Systemic Toxicity (LAST): Rare, but possible if a large dose is injected intravascularly or accidentally.
- Injection Site Pain or Bruising: Mild discomfort or hematoma at the needle insertion site.
- Infection: As with any needle procedure, there is a small risk of local infection or abscess formation.
Rare / Serious Complications
- Pneumothorax: While the ESP block is performed more laterally and superficially than the paravertebral block, there is a theoretical risk of lung puncture, especially at higher thoracic levels.
- Vascular Injury: Accidental puncture of the intercostal or segmental vessels.
- Nerve Injury: Direct trauma to the spinal nerve roots or dorsal rami, potentially causing neuropraxia or paresthesia.
- Inadvertent Intrathecal/ Epidural Injection: If the needle penetrates too deeply, the anesthetic could enter the epidural or subarachnoid space, leading to a high spinal or systemic effects.
- Local Anesthetic Toxicity: Symptoms include tinnitus, metallic taste, seizures, or cardiac arrhythmias if significant amounts are absorbed rapidly.