Fig. 30.1
Surface anatomy for rectus sheath block
Umbilicus
Linea semilunaris: the lateral edge of the rectus abdominal muscle
30.1.2.3 Needle Insertion
After marking the external layer of the rectus sheath on both sides of the abdomen, insert a short-bevel needle at the point where the outer border of the rectus sheath intersects a horizontal line at the level of the umbilicus.
Advance the needle 60° to the skin toward the umbilicus until a loss of resistance and a “pop” is felt, indicating puncture of the anterior rectus sheath.
After injection of local anesthetic on one side, repeat the above steps for the other side.
30.1.2.4 Local Anesthetic Application
For children up to 7 years of age, 0.2 mL/kg 0.2 % ropivacaine is adequate.
For older children, 0.2–0.3 mL/kg 0.5 % levobupivacaine should be used.
30.1.3 Ultrasound-Guided Technique
Subcutaneous structures of the rectus sheath at the level of L3–L4 are depicted in the MRI and corresponding ultrasound images in Fig. 30.2.
Fig. 30.2
(a) VHVS and MRI images of the abdominal wall, showing the rectus abdominal muscle and the rectus sheath. (b) Ultrasound image of the abdominal wall, showing the rectus abdominal muscle and the rectus sheath
30.1.3.1 Scanning Technique
Multiple injections are required for a successful rectus sheath block. A typical approach is injection of local anesthetic on either side of the midline at the upper and lower ends of the excision for a total of four needle insertion points.
A linear (6–15 MHz) transducer is placed in a transverse location on the anterior abdominal wall lateral to the proposed incision site.
The required depth for penetration is usually 2–4 cm but varies with the depth of the subcutaneous layer.
30.1.3.2 Ultrasonographic Appearance (Fig. 30.2b)
At the midline, the hyperechoic linea alba is seen between the belly of the rectus muscle on either side. The most superficial layer is subcutaneous fat.
The peritoneum is seen behind the posterior rectus sheath.
The muscles of the lateral abdominal wall (external oblique, internal oblique, and transversus abdominis, from superficial to deep) are seen lateral to the rectus muscle.
The internal oblique muscle is on the same plane as the rectus muscle, and they are separated by the aponeurosis of the internal oblique.
The target nerves are not visible. They course between internal oblique and transversus abdominis before piercing the posterior rectus sheath to traverse the belly of the rectus muscle.
The target for injection is the lateral gutter between the posterior rectus sheath and the rectus muscle.
The inferior epigastric vessels run through the rectus muscle. They may be seen if the Doppler function is utilized (Fig. 30.3). It is important to avoid puncturing or injecting local anesthetic into these vessels.
Fig. 30.3
Doppler ultrasound image showing location of inferior epigastric vessels in the rectus muscle (RM)
30.1.3.3 Needle Insertion
Depending on subcutaneous fat depth, use a 4–10 cm, 22G needle.
An in-plane (IP) approach is used (Fig. 30.4).
Fig. 30.4
In-plane needling technique for ultrasound-guided rectus sheath block. Blue rectangle indicates probe footprint
Intermittent injection with D5W is recommended to confirm needle tip position.
The needle is inserted from lateral to medial. To avoid puncturing the inferior epigastric vessels, a lateral needle insertion point is chosen. The needle is directed through the external and internal oblique muscles into the lateral gutter of the rectus muscle directly superficial to the posterior rectus sheath. Using this approach, the needle does not enter the belly of the rectus muscle and thereby avoids the inferior epigastric vessels.
Needle tip position may be confirmed by injection of 1–2 mL D5W.
30.1.3.4 Local Anesthetic Application
Performing a test dose with D5W is recommended prior to local anesthetic application to visualize the spread and confirm needle tip localization.
Inject 0.2 mL/kg 0.2 % ropivacaine, 0.25 % bupivacaine, or 0.5 % bupivacaine on each side.
The local anesthetic should be seen to spread between the posterior rectus sheath and the rectus muscle.
30.1.4 Current Literature in Ultrasound-Guided Approaches
For rectus sheath block, the probe is placed over the linea semilunaris (at the lateral aspect of the rectus abdominis muscle) at a level beneath the umbilicus, and the lateral edge of the rectus muscle is positioned at the edge of the screen. The posterior wall of the sheath may be poorly defined at locations caudad to the umbilicus (i.e., below the arcuate line) [1]. The peritoneum appears thick with a hyperechoic border beneath the muscles.
Willschke et al. described their approach for ultrasound-guided rectus sheath block in the clinical portion of their two-part study evaluating the sonoanatomy and clinical feasibility of this block [2]. They stated that their injection site was situated at the location where an optimal view of the posterior sheath was obtained. A short-beveled needle (e.g., 22G, 40 mm with facet tip) was inserted using an out-of-plane approach at the inferior edge of a linear hockey stick probe, using an angle most suitable for the depth of the sheath. The needle tip was placed just between the posterior rectus sheath and the posterior aspect of the rectus abdominis muscle. After negative aspiration (for epigastric vessel puncture), local anesthetic solution was injected; expansion of the space between the sheath and posterior aspect of the rectus muscle denoted proper placement of the needle.
The median depth of the posterior sheath in 30 children was 8.0 mm (range 5–13.8); moreover, there was poor correlation between the depth of the posterior rectus sheath and weight, height, or body surface area [3]. With the sheath’s proximity to the peritoneum and without the possibility of reliable estimations or calculations of optimal needle depth, ultrasound imaging during the block is especially useful. It is also important to note that the posterior wall of the sheath is poorly defined below the arcuate line [1]. Placing the needle more lateral, and thus potentially avoiding puncture into the peritoneum, the umbilical nerve block targets the region lateral to the sheath where the nerves exit from their course between the transversus abdominis and internal oblique abdominal muscles.
Two recent studies compared ultrasound-guided rectus sheath block to the traditional method of local anesthetic infiltration for pain control during umbilical hernia repair. Both demonstrated a reduction in consumption of postoperative opioid and non-opioid analgesia in the rectus sheath block group [4, 5]. Gurnaney et al. [5] showed no difference in time to rescue analgesia between the groups, and Dingeman et al. [4] showed that postoperative pain scores were lower with the ultrasound-guided block. These studies’ findings are supported by a case series of ultrasound-guided rectus sheath block for umbilical hernia repair which showed that patients receiving the block consumed less opioid analgesia in the post-op recovery unit [6]. These results also contrast those of a prior study [7] that did not use ultrasound to guide needle placement, suggesting that improved accuracy leads to more successful blocks.
30.1.4.1 Umbilical Nerve Block
For umbilical hernia repair, an umbilical nerve block can be performed. The scanning field of view should be increased to include the medial aspect of the lateral abdominal muscles and the region where their aponeuroses join to form the rectus sheath. Laterally, the lateral abdominal muscles may be delineated with oblique hyperechoic lines separating them. The external oblique abdominal muscle lies outermost, overlying the internal oblique abdominal and transversus abdominis muscles. The thick rectus abdominis muscle can be identified medially, as can the rectus sheath, formed by the aponeurosis of the transversus abdominis muscle and internal and external oblique abdominal muscles. The intercostal nerve(s) will likely not be visualized by ultrasound imaging. The nerves are small and run longitudinally, thus tangential, to the probe [1]. The hyperechoic and linear appearance of the nerves will closely resemble the aponeurosis of the musculature in this region.
De Jose Maria et al. [1] have described their approach to an ultrasound-guided umbilical nerve block. The probe (10 MHz frequency) was placed where a line between the tenth intercostal space and the umbilicus intersects the rectus abdominis muscle. They rotated the probe between transverse and longitudinal planes in order to obtain a good view clearly delineating the musculature and rectus sheath. The longitudinal plane was used during the block, and the ideal position of the probe was that which best captured the formation of the rectus sheath, by the aponeuroses of the transversus abdominis and internal oblique abdominal muscles. The needle was inserted using an in-plane approach to place the tip close to the lateral edge of the rectus muscle and between the aponeurosis of the abdominal muscles. The local anesthetic spread was observed behind the rectus abdominis muscle and under the internal oblique abdominal muscle.
30.1.4.2 Outcome Evaluation for Blocks at the Anterior Trunk
Earlier reports of the rectus sheath block, using “blind” techniques, describe successful blocks as performed in small numbers of patients [8, 9]. Using ultrasound guidance for rectus sheath blocks in 20 children, Willschke et al. reported a 100 % success rate for intra- and postoperative analgesia (until time to discharge at 4 h), using (predetermined volumes in their study) lower doses of local anesthetics (i.e., levobupivacaine 0.25 % 0.1 mL/kg versus bupivacaine 0.5 % 0.2 mL/kg) than previously described when using “blind” technique with the same injection protocol [3, 9]. Similar doses of local anesthetic have been used for the umbilical nerve block as those for the ultrasound-guided rectus sheath block (i.e., bupivacaine 0.25 % 0.1 mL/kg) [1].
30.1.5 Case Study
Rectus Sheath Block (Provided By A. Spencer)
A 4-year-old girl, 16 kg, presented for same-day repair of epigastric hernia. The patient underwent a general anesthetic combined with an ultrasound-guided periumbilical nerve block in line with the umbilicus (correlating with thoracic tenth dermatome level). A 22G 40 mm, B-beveled needle was inserted in-plane, and 3.5 mL ropivacaine 0.25 % with epinephrine was deposited bilaterally below the rectus abdominis muscle and posterior fascia (equivalent to 0.2 mL/kg per side) (Fig. 30.5). An additional 0.5 mL was injected into the aponeurosis adjoining the rectus abdominis muscle to the external and internal oblique and transversus abdominis muscles. Block duration was 6–12 h; time of surgery was 1 h 10 min.
Fig. 30.5
Ultrasound-guided rectus sheath block. EOM external oblique muscle, IOM internal oblique muscle, TAM transversus abdominis muscle, RAM rectus abdominis muscle. See Case Study for details
Acetaminophen 15 mg/kg po liquid was administered preoperatively, and ketorolac 0.3 mg/kg was given perioperatively; no morphine was given during the case. The patient was comfortable in recovery 30 and 60 min post-op. No additional analgesia was required in the recovery room or on the day surgery ward prior to going home.
30.2 Transversus Abdominis Plane (TAP) Block
30.2.1 Clinical Anatomy
The sensory innervation of the abdominal wall is derived from anterior divisions of the thoracolumbar nerves (T6–L1).
T6–T11 begin as intercostal nerves; T12 is the subcostal nerve; L1 is the ilioinguinal and iliohypogastric nerve.
The thoracolumbar nerve roots exit the space that is bordered between the latissimus dorsi posteriorly and the transversus abdominis anteriorly, within the “lumbar triangle of Petit.”
There are often extensive anastomoses involving the segmental nerves that emerge from the costal margin, such that they rapidly lose their segmental origin [10].
The intercostal nerves, subcostal nerves, and the first lumbar nerves run in a neurovascular plane known as the transversus abdominis plane (TAP) (Fig. 13.9).
The TAP is situated between the internal oblique and transversus abdominis muscles; the plane allows adequate spread of local anesthetic.
30.2.2 Landmark-Based Technique
30.2.2.1 Patient Positioning
The patient may be supine or lateral.Related posts:
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