Thoracic Paravertebral Block

Thoracic Paravertebral Block (PVTB) was first described by Hugo Selheim in 1905, looking for a safer anesthetic strategy as an alternative to neuraxial approaches. In the following years, Arthur Lawen used the technique to map abdominal viscerotomes (1911), and in 1919 Max Kappis improved the technique, allowing the use of anesthesia for abdominal surgery [1, 2]. After some time “forgotten”, in 1979, PVTB reappeared after Eason and Wyatt improved the technique, enabling continuous analgesia through the placement of a catheter in the Thoracic Paravertebral Space (TPVS) [3].

The TPVS approach allows for unilateral somatic and sympathetic blocking of several metamers with a single injection. To obtain the expected result, it is necessary to know the metameric innervation (dermatomes – skin; sclerotomes – bones; myotomes – muscles of the chest and abdominal walls; angiotomes – arterial and venous vascular system; neurotomes – autonomic nervous system; viscerotomes – viscera of the trunk and abdomen), and then, to choose the level(s) of puncture, volume, dose of anesthetic and the placement of the catheter in the TPVS.

The Erector Spinae Plane (ESP) Block

With the use of ultrasound (US), several new procedures have been described. Interfacial blocks are becoming increasingly popular due to their safety and ease of execution.

In this sense, there is the Erector Spinae Plane (ESP) block, described by Mauricio Forero et al. [4], as an alternative to the Paravertebral Block.

Some key points: ESP block.

1. An ESP block is a fascial plane block that is simpler and safer to perform than a paravertebral block, being almost as effective.
   
2. It can be used in multiple indications, from the neck down to the lumbar region.
   
3. It provides analgesia of the territory supplied by the dorsal and ventral rami of spinal nerves.
   
4. It may provide visceral as well as somatic analgesia.
   
5. A catheter can easily be inserted to allow re-dosing, in order to intensify and increase the length of analgesia. Continuous infusion or intermittent boluses can be used.

Anatomy

The TPVS is a wedge-shaped space present on both sides of the spine and on the entire length of the rib cage. This space narrows as it goes around the costotransverse joints, widening again in the adjacent intercostal/intertransverse region (Figure 30.1).

The PVTS contains the emergence of the thoracic spinal nerve and its division into dorsal and ventral branches (intercostal nerve), the intercostal artery and vein, the sympathetic chain, the white and gray communicating branches of each segment, and the greater, minor and least splanchnic nerves (Figure 30.2 ).

The anatomic bounders: The parietal pleura determines the anterolateral limit of the PVTS. The posterior limit is determined by the superior costotransverse ligament that continues as a posterior intercostal membrane or internal intercostal membrane. Part of the vertebral body, the intervertebral disc, and the vertebral foramen, medially limit the PVTS with continuity to the epidural space. Laterally, the PVTS continues with the intercostal space, where the neurovascular bundle runs between the internal intercostal muscles and the innermost intercostal muscles [1, 2, 4] (Figure 30.3).

Although the innermost intercostal muscles interrupt their internal lining of the rib cage a few centimeters laterally to the transverse process, the thin membrane that covers them, called endothoracic fascia, continues until it adheres to the anterior face of the vertebral bodies, dividing the PVTS into two compartments [1, 4]. The subendothoracic compartment with somatic innervation represented by the dorsal and ventral branches (intercostal nerves) of the spinal nerve, and the extra pleural compartment containing the sympathetic chain and splanchnic nerves. These compartments communicate through the path of the communicating branches of the sympathetic ganglia along the endothoracic fascia next to the intercostal arteries and veins corresponding to each segment.

Depending on the site of the injection, the spread of the anesthetic solution in the PVTS is expected to happen in the craniocaudal direction, reaching the subendothoracic space [4, 5]. This random spread also occurs in the intercostal, epidural, and prevertebral spaces. The patient’s decubitus position can influence anesthetic dispersion. It is a cranial-caudal (patient in lateral decubitus) or more caudal than cranial (patient in a sitting position). An average of 20 ml of local anesthetic includes 5 metamers, which may vary according to the patient’s decubitus, the technique used and the final position of the needle tip in relation to the endothoracic fascia [4, 6–8].

In the thoraco-lumbar transition, the endothoracic fascia continues as a transversalis fascia. Despite the constriction that the arched ligaments of the diaphragm exert on the transversalis fascia and on the Psoas Major and Quadratus Lumborum muscles, the abdominal course of this fascia supports anesthetic spread to the posterior abdomen wall and, consequently, the anesthetic reaches the roots of the lumbar plexus [9, 10].

In the thoraco-cervical transition, the thoracic paravertebral space communicates with the brachial plexus and the cervical sympathetic chain (stellate ganglion) by mechanisms that are not yet well established. It is thought that this communication happens through the Kuntz nerve whenever it is present [11]. The endothoracic fascia, when involving the pulmonary dome, unites its fibers, thickening and inserting itself in the transverse process of C-7, thus forming the Sibson’s fascia or suprapleural membrane, and working as an upper diaphragm with the action of the scalene muscles. Thus, the subendothoracic compartment would continue until its insertion in the C-7, where it would merge with the laminations of the prevertebral fascia, allowing the spread of the local anesthetic to the brachial plexus and cervical sympathetic chain through a fascial plane.

Indications for PVT and ESP Block

• Control of acute post-operative chest pain
  
• Chronic post-operative pain
  
• Post-mastectomy pain
  
• Post-herpetic neuralgia
  
• Rib fracture
  
• Oncological pain – thoracic metastases
  
• Myofascial pain
  
• Lower cervical and interscapular myofascial pain.

Contraindications

• Local or systemic infection
  
• Coagulopathy
  
• Hypotension
  
• Anatomic distortion.

Thoracic Paravertebral Block (PVTB) Technique

Ultrasound-guided PVTB

The use of ultrasonography (USG) in pain medicine is growing and becoming more popular among clinicians. To perform a PVTB guided by USG, it is essential to identify the pleura (PL), internal intercostal membrane (IIM), and transverse process (TP). The monitoring of the needle progression and the final positioning of the tip between the superficial limits are essential for this procedure.

The most used US approaches are:

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