Thoracic Paravertebral Block 2018-07-24T12:09:38+00:00

Thoracic Paravertebral Block

Thoracic paravertebral block is the technique by which local anaesthetic is injected in wedge shaped paravertebral space alongside of the vertebral body called the thoracic paravertebral space (TPVS). This provides unilateral somatic and sympathetic blockade at selective segmental regions.

Anatomy

TPVS is a wedge shape space where local anaesthetics block the spinal nerves as they emerge from the intervertebral foramen.

Anterolaterally it is bound by the parietal pleura, medially lies vertebral body with intervertebral disc and the intervertebral foramen with its content forming the base of the wedge. Posterior border is formed by superior costotransverse ligament. Superior costotransverse ligament extends from the lower border of transverse process of vertebra above to the upper border of lower vertebra. Between the parietal pleura and superior costotransverse ligament, a fibroelastic structure called as endothoracic fascia is present dividing the space into two spaces, named anterior space as “extrapleural paravertebral space “ and posterior as “ subendothoracic paravertebral” compartment.

Technique

Position: It can be sitting, lateral decubitus or prone position. Prone position is useful in fluoroscopic guided injection for chronic pain relief.

There are 3 approaches to perform a TPVB

  1. LANDMARK Technique: At appropriate level either 20G /22G Tuohy or B bevel block needle can be used for single shot injection. For catheter insertion 18G / 16 G Tuohy needle is used. The needle is introduced 2.5 cm. lateral to the highest level of spine and introduced perpendicularly to hit the transverse process. Then needle is removed and introduced again in cephalad direction until loss of resistance to air is elicited as soon as needle traverses the superior costotransverse ligament. The depth of the space is 1– 2 cm from the transverse process.
  2. ULTRASOUND Assisted technique: This is similar to the landmark technique, but a pre-procedure scan is done to assess the distance of transverse process and TPVS from skin. The ultrasound screening can be performed with either the transverse scan or parasaggital scan.In most patients, a high frequency linear probe (6-13MHz) may be sufficient, in obese patients low frequency USG with 2-5 MHz with lower depth settings may have to be used.

3. ULTRASOUND guided technique

PARASAGGITAL VIEW:

USG probe is placed lateral to the midline. Scanning from lateral to medial round hyperechoic ribs are seen with acoustic shadow. In between the ribs sharp shadow of pleura is visualized. Scanning more medially 2-3 cm from the midline, transverse process is visualized as hyperechoeic and are of more square shape structures deep to the paraspinal muscles casting acousting shadow. Superior costotransverse ligament, pleura and thoracic paravertebral space are clearly seen. For better visualization of pleura USG probe can be tilted slightly obliquely and laterally. Either inplane or out of plane approach can be used for needle insertion. For the inplane technique, keeping the lower transverse process at the edge of the screen where needle is inserted allows for a steep angle of insertion. Needle visualization may be difficult because of oblique position of probe. If this approach is used the needle should be contacted with the transverse process and then it should be withdrawn and readvanced under the transverse process. Any doubt in finding the tip of the needle, hydrodissection should be done with the 2-3 ml of saline. Once the superior costotransverse ligament is penetrated and local anaesthetic injected, the pleura is seen to depress down and the real time spread of local anaesthetic can be seen. Extension of local anaesthetic can also be seen in other paravertebral spaces better with this view.

Parasagittal Inplane Thoracic Paravertebral Block

Parasagittal Out of Plane Thoracic Paravertebral Block

Parasagittal view of Transverse process

Annotated view

TRANSVERSE VIEW:

As USG probe is placed on transversely on spinous process in midline, the spinous process is visualized as a bright hyperechogenic dot with acoustic shadow anteriorly. In thoracic region spinous process is more angulated caudally as compared to lumbar region, hence lamina and transverse process lie above to the spinous process. As probe is placed laterally on transverse process hyperechogenic lamina, transverse process and the rib is identified. After sliding it more caudally only hyperechogenic outline of lamina and transverse process with their acoustic shadow are seen. Lateral to transverse process anteriorly hyperechogenic pleura and lung is visualized. Posteriorly lies the superior costotransverse ligament. There is hypoechogenic paravertebral space visualized between the two. Now sliding the probe slightly caudally hyperechogenic articular process is seen medially with its acoustic shadow, and the superior costotransverse ligament, parietal pleura, lung and apical part of paravertebral space is clearly defined. This view is in between the transverse process. The needle is inserted in either inplane or out of plane approach. Once the transverse process is contacted the needle is withdrawn slightly and directed under the transverse pocess. After confirming negative aspiration for blood and CSF local anaesthetic is injected. The pleura is observed to be depressed and a rim of hypoechogenic fluid is seen around the pleura.

Transverse Inplane Thoracic Paravertebral Block (Sitting Position)

Transverse Out of Plane Thoracic Paravertebral Block (Sitting Position)

Transverse Midline scan- Spinous process

Transverse scan- Transverse process and Rib articulation

Probe walked inferior to lose rib shadow and showing internal intercostal membrane

Transverse Inplane Thoracic Paravertebral Block (Lateral Position)

Operator behind patient

Transverse Inplane Thoracic Paravertebral Block (Lateral Position)

Operator in front of patient

Video of Thoracic Paravertebral Block (Transverse Inplane Lateral to Medial)