Ovid: Peripheral Nerve Blocks: A Color Atlas

Brachial Plexus Blocks

A. Parascalene Block

Giorgio Ivani

Valeria Mossetti

Patient Position: The patient lies supine, the head slightly to contralateral side, the arm extended comfortably along the body; a roll sheet is placed under both shoulders.

Indications: Anesthesia and postoperative analgesia for surgery of the shoulder and of the proximal upper arm, above the elbow.

Needle Size: A 23- to 24-gauge, 25- to 35-mm, insulated beveled needle.

Volume: Ropivacaine 0.2% for children up to 7 years, levobupivacaine 0.5% for older children, 0.5 mL/kg.

Anatomic Landmarks: The clavicle, the lateral border of the sternocleidomastoid muscle, and the transverse process of C6 (Chassaignac tubercle). The puncture is made at the junction of the upper two-thirds with the lower third of the line joining the C6 transverse process to the midpoint of the clavicle (Fig. 47-1).

Approach and Technique: Find the superficial projection of the Chassaignac tubercle (insertion of the transverse line at the level of the cricoid cartilage and the lateral border of the sternocleidomastoid muscle). The site of introduction of the needle is the junction of the upper two-third and the lower one-third of the line joining the midpoint of the clavicle and the Chassaignac tubercle. Set the nerve stimulator at a frequency of 2 Hz and a current of 2.5 mA. Connect this to the pen dedicated for the transcutaneous technique (instead of the pen it is possible to use the negative electrode of the ENS) and point it perpendicularly to the skin in an anteroposterior direction until a motor response (contraction of biceps and/or brachial muscle) is elicited. Then insert the needle connected to the nerve stimulator set at 1 mA and 2 Hz, exactly at the point evidenced via transcutaneous in an anteroposterior direction until a motor response is again elicited. Adjust the position of the needle to maintain the appropriate muscle response with a current of 0.4 to 0.5 mA. Then, after negative aspiration, slowly inject the local anesthetic solution.

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Figure 47-1. The puncture point for the parascalene block.

Tips

The parascalene approach is the safest supraclavicular approach to the brachial plexus, aiming at penetrating the interscalene space at a distance from the apical pleura, the great vessels and nerve of the neck, the stellate ganglion, and the spinal canal. In children the use of the parascalene block is safer and has lower incidence of complications than the other blocks (interscalene and infraclavicular block).
The brachial plexus is located at a depth of 7 to 20 mm from the skin.
This technique provides excellent analgesia to the upper part of the arm, but in 50% of patients the lower branches of the cervical plexus are also blocked.
Complications include:
- Horner syndrome (ptosis of the eye, miosis, anophthalmos, hyperemia of the conjunctiva, hyperthermia, anhidrosis of the face) for the stellate ganglion block.
- Because of the risk of respiratory failure linked to bilateral phrenic paralisys given by bilateral block, this block is contraindicated in cases of acute or chronic respiratory insufficiency or whenever it is necessary a bilateral block.
- Vessel puncture of the large blood vessel of the neck (carotid artery and internal jugular vein) or of the vertebral artery.
- Pneumothorax.
Epidural and intrathecal injections are avoided by using this technique.
If the position of the needle is too lateral, causing the stimulation of the suprascapular nerve (levator scapulae muscle), retract the needle and advance more ventral; if the position is too ventral, causing the stimulation of the phrenic nerve (unilateral singultus), retract the needle and advance more lateral.

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Suggested Readings

Carre P, Joly A, Cluzel Field B. Axillary block in children: single or multiple injection? Paediatr Anaesth 2000;10(1):35–39.

Dalens B. Regional anaesthesia in infants, children and adoloscents. Baltimore: Williams & Wilkins, 1995:550.

Fisher WJ, Bingham RM, Hall R. Axillary brachial plexus block for perioperative analgesia in 250 children. Paediatr Anaesth 1999;9:435.

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C. Use of Paravertebral Blockade in Children

Per-Arne Lonnqvist

Introduction

In order to map the innervation of the intrathoracic and intraabdominal organs Sellheim and Läwen in the beginning of the nineteenth century were the first to inject local anesthetics in the paravertebral space (PVS) and the technique was later used by Kappis (1919) to provide surgical analgesia for abdominal surgery. Deposition of local anaesthetics in the PVS will lead to strict unilateral anaesthesia of one or more adjacent dermatomes (Fig. 47-3) and the main indications for paravertebral nerve block (PVB) are unilateral thoracic or abdominal surgical procedures (Table 47-1).

History

The use of PVB in children was first described in 1992. Sabanathan reported a method for intraoperative placement of a catheter in the PVS during thoracic surgery and Lönnqvist described a modification of the Eason-Wyatt technique for percutaneous preoperative cannulation of the PVS.

Figure 47-3. Distribution of somatic and sympathetic blockade after thoracic PVB for thoracotomy (right) and renal surgery (left), respectively; blue, somatic blockade, red, sympathetic blockade. Recommended level of injection: thoracotomy, T5 or T6; renal surgery, T9. Recommended volume of local anesthetic, 0.5 mL/kg at all levels.

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Table 47-1. PVB: summary

Indications	Thoracotomy Subcostal abdominal incisions Renal surgery Appendectomy Inguinal hernia repair Orchidopexy Rib fractures
Puncture level	Thoracotomy: Th 5-6 Abdominal surgery: Th 9-10 Inguinal hernia repair and orchidopexy: Low thoracic level (Th 12 to Th 10) + L1
Lateral distance from the spinous proc (mm)	0.12 × kg + 10.2
Depth from skin to PVS (mm)	0.53 × kg + 21.2
Injection volume and infusion rates:
Toddlers and older children	Levobupivacaine 0.25%, bupivacaine 0.25% with adrenaline, or lidocaine 1% with adrenaline
	Bolus: 0.5 mL kg^-1 Continuous infusion: 0.25 mL kg^-1 h^-1
Infants	Bolus: 0.5 mL/kg, bupivacaine 0.25% Infusion: 0.2 mL kg^-1 h^-1, bupivacaine 0.25% Serum concentrations at 24 h: 2.00 (SD 0.63) mg/L
Neonates	Bolus: 0.5 mL kg^-1, bupivacaine 0.25% Infusion: 0.2 mL kg^-1 h^-1, bupivacaine 0.25% Serum concentrations at 24 h: 2.00 (SD 0.63) mg/L
Failure rate	Loss-of-resistance: <10% Nerve stimulator guided: <5%
Complications	Hypotension 5% (only adults) Vascular puncture 4% Inadvertent pleural puncture 1% Pneumothorax 0.5%

Anatomy

The PVS is a triangular wedge-shape area situated in the angle between the lateral border of the vertebral body and the anterior surface of the transverse process. The PVS only exists between Th 1-12. Below Th 12 the space is sealed off by the origin of the psoas muscle from the vertebral body and the transverse process. Cranially the space appears to communicate with fascial planes in the neck since an upper thoracic PVB may cause Horner syndrome. The different thoracic levels of the PVS communicate, which is the foundation for spread of an injection of local anesthetics to multiple segments (Fig. 47-4). The medial boundary of the PVS is the lateral part of the vertebral body and disc, the dorsal limitation is the transverse process/costotransverse ligament, and the anterolateral boundary is the parietal pleura. Significant structures that pass through the PVS are the spinal nerve root/intercostal nerve, the sympathetic chain, and the intercostal vessels. The PVS is not like

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the epidural space, since the pleura is very adhesive to the other structures, but should instead be viewed as a potential space. This fact accounts for the slight difficulty in introducing a percutaneous catheter into the PVS.

At the lumbar level PVB is still possible but at this level each individual level will have to be blocked separately since the lumbar nerves exit through separate pockets within the psoas muscle, which is the reason why there is no communication in-between adjacent lumbar levels. This is in clear contrast to the situation at the thoracic level.

Technique

Currently three different approaches to perform PVB in children have been described.

Loss-of-Resistance Technique

The skin is punctured laterally to the spinous process and the needle is advanced in a perpendicular manner until contact is made with the transverse process. The Tuohy needle (19 to 20 gauge if ≤1 y, 18 gauge if >1 y) is then “walked” below or underneath the transverse process and by means of a loss-of-resistance technique the costotransverse ligament is pierced and the PVS located. Alternatively, the needle can be “walked” above or over the top of the transverse process but by using this approach there is the risk of hitting the neck of the rib before entering the PVS. If so, the needle will have to be re-angled and it can occasionally be virtually impossible to get at a reasonable approach to the PVS. Thus, to go below the transverse process is clearly advocated by the author.

Once in the PVS the bolus dose of local anesthetic can be injected after careful aspiration to exclude the presence of blood or air. If a continuous technique is preferred, a catheter can be introduced approximately 1 to 2 cm into the PVS through the Tuohy needle. The insertion of the catheter frequently needs some manipulation of the Tuohy needle in order to be successful and occasionally one will have to make the injection of the bolus dose in order to “open up” or “create” a space wide enough to allow catheter insertion. One should not insert more than 1 to 2 cm of the catheter into the PVS since further advancement may cause the catheter to go into the spinal canal through the intervertebral foramen (causing an epidural distribution of the block) or to go laterally, following the path of the intercostal nerve (giving a dense block of only one single dermatome).

The optimum distance from the spinous process to the skin puncture site (SP–PVS distance) and an estimate of the distance from the skin to the PVS (S–PVS depth) can be calculated by the following equations:

SP–PVS distance (mm) = 0.12 × kg + 10.2 ⁶

S–PVS depth (mm) = 0.53 × kg + 21.2 ⁷

The level of the puncture depends on the surgical intervention but for a thoracotomy, the puncture should be performed at Th 5-6 and for renal surgery at Th 9-10.

Nerve Stimulator Guided Technique

The intervertebral lines corresponding to the specific dermatomes are determined by manual palpation. The injection site is marked 1 to 2 cm laterally to the midline on the intervertebral line according to patient weight.

A 21-gauge insulated needle of appropriate length, attached to a nerve stimulator (initial stimulating current: 2.5 to 5 mA, 1 Hz), is thereafter introduced perpendicularly to the skin in all planes. A contraction of the paraspinal muscles is initially observed, and the needle is subsequently advanced until the costotransverse ligament is reached. At this point the contraction of the paraspinal muscles will disappear.

After piercing the costotransverse ligament a proper muscular response of the corresponding level is sought and the needle tip is manipulated into a position allowing a muscular response while reducing the stimulating current to 0.4 to 0.6 mA. At this point the local anesthetic is injected at the appropriate dose and volume.

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The manipulation of the needle tip within the paravertebral space is not an in-and-out movement but is rather an angular manipulation and circumferential rotation around the axis of the needle in order to reach an optimal position of the needle tip with regard to the nerve within the paravertebral space.

Surgical Placement

This approach can be used during thoracotomy procedures. By use of a curved haemostat the surgeon creates an extrapleural tunnel from the medial angle of the parietal pleura incision to the PVS. At this point a pocket stretching over 3 to 4 paravertebral segments is made. An epidural catheter is then introduced into the paravertebral pocket with the aid of the haemostat and the catheter is then secured in place by one or two sutures that also will help to close the extrapleural tunnel, so that the local anesthetic will not leak backward into the pleural space. The catheter is then tunneled through the thoracic wall with the use of a Tuohy needle or similar tunneling device.

Ultrasound Aided Approach

With the aid of ultrasound the position of the transverse processes and the depth to the PVS can easily be determined, something that is quite helpful regardless of whether a loss-of-resistance or nerve-stimulator guided technique is used. A more specialized ultrasound guided technique has so far not been described but is currently under development by the author.

Technique for Orchidopexy

A special technique has been described for use of this block in association with orchidopexy. Adequate nerve block including both the inguinal surgical field as well as testicular innervation is accomplished by injection of local anesthetic at two separate paravertebral levels. The injection made at one lower thoracic level (Th10, 11, or 12) will block the testicular innervation as well as parts of the surgical field in the groin. However, to get a complete block of the inguinal region a separate PVB of L1 (below the transverse process of L1) will have to be performed. This will result in two different types of spread as seen in Figure 47-4.

Figure 47-4. Radiograph after injection of a mixture of local anesthetic and radio-opaque dye.

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Both the low thoracic and the L1 block can be performed through just one single skin puncture. In this instance the skin puncture is made lateral to the L1 spinous process and contact with the transverse process of L1 is made. The needle is then walked over the top of the transverse process and 0.375 ml kg^-1 is injected. This injection is thus made in the most caudal part of the thoracic PVS and the local anesthetic will spread cranially to include at least the Th12–10 levels. The needle is then withdrawn and walked below the transverse process and the L1 level is blocked separately by the injection of 0.125 ml kg^-1.

If a nerve stimulator guided technique is used, muscle contractions of the abdominal wall are clearly seen when the thoracic level is approached and movement of the hip is seen when the L1 root is simulated.

Dosage

Following a negative aspiration test and administration of a test dose, 0.5 mL/kg of the local anesthetic (levobupivacaine 0.25%, bupivacaine 0.25% with adrenaline or lidocaine 1% with adrenaline) is injected in toddlers and older children. This dose will usually cover at least five segments. Following the bolus injection, a continuous infusion of the same local anesthetic solution (0.25 mL kg^-1 h^-1) is started and can be used for approximately 48 hours. A typical distribution of the block will be unilateral analgesia of the trunk ranging from Th4 to Th12.

In neonates and infants slightly modified dosage regimens have been recommended (Table 47-1). These dosages have been found to be both effective and associated with acceptable plasma concentrations of bupivacaine.

Indications

Any surgery involving a unilateral thoracoabdominal incision (e.g., thoracotomy, breast surgery, subcostal abdominal incisions, renal surgery, inguinal hernia repair, and appendectomy). The methods can also successfully be used for multiple rib fractures. In children the main indications are thoracotomy, subcostal abdominal incisions, renal surgery, and inguinal hernia repair. Anecdotal use of PVB for postoperative pain relief following ductus ligation in premature children and congenital diaphragmatic hernia repair has also been reported.

PVB can be particularly useful for postoperative analgesia after orchidopexy. The reason for the efficacy of PVB in this context is that it (contrary to, for example, ilioinguinal-iliohypogastric nerve block) is able to block the pain transmission caused by testicular traction/dissection of the testicular vessels. The pain fibers responsible for this type of pain travel together with the testicular vessels to the Th10 level and can thus be blocked by a low thoracic paravertebral injection of local anesthetic.

To use PVB for orchidopexy is also a nice way to start to learn this technique since the risk for serious complications at the Th12/L1 level is minimal.

In adults, bilateral PVBs have been used for abdominal aortic aneurysm repair, laparoscopic cholecystectomy, and ventral hernia repair, but in children this approach has so far only been reported for surgical placement in association with bilateral thoracotomy.

Failure Rate and Complications

The use of a percutaneous loss-of-resistance technique in a mixed adult and pediatric population was found to be associated with an overall failure rate of approximately 10%; the complications experienced were: hypotension 5% (only adults), vascular puncture 4%, inadvertent pleural puncture 1%, and pneumothorax 0.5%.

The risk for block failure is reduced to <5% when a nerve stimulator guided technique is used; this technique also appears to be associated with a reduced risk for complications. Further improvement can be expected when an ultrasound guided technique has been refined.

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Scientific Literature/Evidence Base in Children

Extended case series has found surgically placed PVBs to be of benefit following thoracic surgery in babies and infants. In a retrospective study the use of continuous PVB provided better postoperative analgesia and lower morphine consumption compared with continuous epidural analgesia. Two recent prospective randomized clinical trials have demonstrated that PVB is superior compared with both regular systemic postoperative analgesia as well as ilioinguinal/iliohypogastric nerve blocks following inguinal hernia repair.

Potential Advantages Compared with Epidural Analgesia

Compared with thoracic or lumbar epidural blocks PVB offers the following advantages:

Analgesia is limited to the area of surgery.
More complete afferent blockade.
Limitation of the sympathetic block; however, the block will include the sympathetic chain contrary to epidural blocks.
No risk for lower limb weakness or paralysis and no risk for urinary retention, making routine Foley catheterization unnecessary.
No risk for unintentional damage to the spinal cord compared with thoracic epidurals.
No risk for significant block of the cardio-accelerator fibers.
Hemodynamic stability caused by a combination of points 3 and 6.
Presence of coagulopathy only constitutes a relative contraindication to the technique.

Due to the specific characteristics of PVB this type of block also appears to posses some preemptive analgesic qualities, something that has not been possible to demonstrate for epidural analgesia.

Conclusion

PVB is a safe and effective alternative for intra- and postoperative analgesia in pediatric patients undergoing thoracotomy or abdominal surgery with a unilateral incision. The block is no more difficult to learn compared with other regional techniques and the use of PVB therefore deserves much more widespread use than has been the case previously.