Ovid: Peripheral Nerve Blocks: A Color Atlas

Single Thoracic Paravertebral Block

A. Thoracic Paravertebral Block

Anna Uskova

Rita Merman

Patient Position: Sitting up across the bed with a stool placed under the feet for stability.

Indications: Anesthesia and immediate postoperative analgesia for inguinal hernia, prostatectomy, and hysterectomy.

Needle size: 22-gauge, 79-mm Tuohy needle.

Volume: 5 mL 0.5% ropivacaine per segment.

Anatomic Landmarks: The paravertebral space is a wedge-shaped space on either side of the vertebral column. Boundaries: anteriorly—parietal pleura; medially—vertebral body, intervertebral discs, and intervertebral foramen; posteriorly—superior costotransverse ligament. The spinous process is the main bony landmark for this block.

Approach and Technique: The spinous processes are palpated and marked with the skin marker. The insertion points are marked 2.5 cm lateral to the superior border of the spinal process and infiltrated with local anesthetic. Then the Tuohy needle is placed perpendicular to the skin with bevel up and advanced up to 3 to 5 cm (Fig. 22-1). When the transverse process is found, the needle is pulled back to the skin and redirected caudally to walk off the inferior aspect or the transverse process, and is then advanced 1.0 cm past the premeasured skin-to-bone distance until a “pop” through the superior costotransverse ligament is appreciated. After the stylet is removed from the needle, the syringe with 0.5% ropivacaine is connected to the needle by extension tubing.

After negative aspiration, 5 ml of local anesthetic is injected at each level to be blocked.

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Figure 22-1. The Tuohy needle is placed perpendicular to the skin with bevel up and advanced up to 3 to 5 cm.

Tips

Inferior angles of the scapulae are used to localize the spinous process of T7 vertebra.
Local anesthesia is performed with two passes of the needle: one perpendicular to the skin (the transverse process can be contacted in thinner patients), then pull the needle back, redirect it caudally, and inject more along the pass to the paravertebral space.
Do not deviate from the parasagittal plane to avoid medial spread and neuroaxial block (postdural puncture headache has been reported after a paravertebral block).
If the needle is redirected caudally and contacts the bone at a shallow distance, reinsert the needle 0.5 cm caudally. (First time was too cephalad and found the rib, instead of the transverse process.)
Too much resistance on injection suggests wrong needle position.
It is not uncommon to see hypotension/bradycardia episodes with this technique in sitting position. Safe practice requires minimal monitoring with noninvasive blood pressure cuff and pulse oxymeter, reliable intravenous access, and supplemental oxygen via nasal cannula. Glycopyrrolate 0.2 mg and ephedrine 50 mg should be always available for treatment. After the episode, extended vital signs monitoring and report to room nurse are recommended.

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Suggested Readings

Karmakar MJ. Thoracic paravertebral block. Anesthesiology 2001;95:771–780.

Klein MK, Steele SM, Greengrass RA. A clinical overview of paravertebral blockade. Internet J Anesthesiol 1999;31.

Liguori Ga, Kahn RL, Gordon J, Gordon MA, Urban MK. The use of metoprolol and glycopyrrolate to prevent hypotensive/bradycardic events during shoulder arthroscopy in the sitting position under interscalene block. Anesth Analg 1998;87:1320–1325.

Lin H, Chelly JE. Suspected postural headache associated with thoracic paravertebral blocks. J Clin Anesth 2006;18:376–378.

Lonnqvist PA, MacKenzie J, Soni AK, Conacher ID. Paravertebral blockade. Failure rate and complications. Anaesthesia 1995;50:813–815.

Merman R, Burman K, Uskova A, Chelly JE. Hypotensive bradycardic events and paravertebral blocks in the sitting position. Anesth & Analg 2006;102:S–134.

Naja MZ, Ziade MF, Lonnqvist PA. General anesthesia combined with bilateral paravertebral blockade (T5-6) vs. general anesthesia for laparoscopic cholecystectomy: a prospective randomized trial. Eur J Anaesthesiol 2004;21:489–495.

Richardson J, Lonnqvist PA. Thoracic paravertebral block. Br J Anaesth 1998;81:230–238.

Saito T, den S, Cheema SPS, et al. A single injection, multisegmental paravertebral block-extension of somatosensory and sympathetic block in volunteers. Acta Anesthesiol Scandi 2001;45:30–33.

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B. Thoracic/Lumbar Paravertebral Nerve Stimulator Guided Block

Patient Position: The patient is sitting and is asked to assume the exaggerated kyphotic position.

Indications: Inguinal hernia surgery.

Needle Size: 22-gauge, 100-mm, b-beveled insulated needle.

Volume: 10 ml per level for inguinal hernia surgery, 5 ml per level for bilateral inguinal hernia surgery.

Anatomic Landmarks: The paravertebral space is triangular in shape and bound medially by the contiguous epidural space via the intervertebral foramen. The posterior wall of the paravertebral space is made up of the anterior costotransverse ligament. The anterior costotransverse ligament extends between the rib and transverse process in the thoracic region. The intercostal nerves and vessels are located in front of the ligament. The anterior and lateral borders of the paravertebral space are defined by the parietal pleura.

Approach and Technique: The superior aspect of the iliac crest is identified and a line is drawn to identify the spinous process of L4. Counting in a cephalad direction from L4, T11 and L2 are identified. The site of introduction of the needle is marked 2.5 cm lateral to the superior aspect of their respective spinous processes. Next, the skin is cleaned with chlorhexidine. This is followed by a local anesthesia with 5 ml lidocaine 1% at T11 and L2. A 22-gauge insulated needle attached to a nerve stimulator (3 to 5 mA, 2 Hz, 1.0 ms) is advanced in a posterior-anterior direction approximately 10° to 20° lateral until it touches the transverse process, or a stimulation of the external and internal oblique muscles, the transverse abdominal muscles, and the rectus abdominis is elicited. If the transverse process is contacted, the needle is “walked off” caudad at T11 and cephalad at L2 and advanced until the proper stimulation is elicited. After correct positioning of the needle the local anesthetic solution is slowly injected after negative aspiration for blood.

Tips

Because the paravertebral space and the epidural space are contiguous, one must specifically avoid the paravertebral block in cases where epidural spread is contraindicated, including aortic stenosis and hemodynamic instability, though it is impossible to predict which block will result in epidural spread. The reason for placing the needle 10° to 20° lateral, rather than perpendicular, is to help avoid the medial structures, including the epidural space, the dural cuff, and the subarachnoid space.
The distance between the posterior aspect of the transverse process and the parietal/visceral pleura on CT scan is approximately 2.6 cm with some variability based on the patient's weight.
Pneumothorax requiring an intervention is a risk associated with thoracic paravertebral block, but is extremely rare. The combination of carefully measuring the depth to the transverse process, using the nerve stimulator initially on supramaximal mode (3–5 mA), and using small needles (22-gauge) provide a margin of safety prior to penetrating the visceral pleura. The visceral pleura will often self-seal following an
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iatrogenic needle puncture. COPD is an independent risk factor that portends an increased risk for pneumothorax despite the use of smaller needles, because the pathologic pleura does not readily self-seal. The supramaximal current assists the anesthesiologist in finding the general location of the desired nerves at T11 and L2, serving as an anatomic GPS. In case of doubt, chest x-rays can help the diagnostic.
Nerve stimulator guided paravertebral blocks are more difficult in thin patients than in average-sized patients.
This block can be used as sole anesthetic. In this case versed and/or propofol can be used for sedation.
Potential complications of paravertebral block include epidural spread, leg weakness, inadvertent intravascular injection, pneumothorax and spinal headache. These complications are rare, occurring in less than 1% of patients, and in most cases resolve with time.
Paravertebral blocks can also be performed for bilateral inguinal hernia repairs.
Inguinal hernia is associated with moderate to severe pain. The use of paravertebral blocks also minimize PONV related to the use of narcotics.