This article originally appeared in the ASRA News, Volume 14, Issue 4, pp 5-8,22 (November 2014).

Author

Francis V. Salinas, MD
Staff Anesthesiologist
Section Head of Orthopedic Anesthesia
Department of Anesthesiology
Virginia Mason Medical Center
Seattle, WA

Section Editor:  Steven Orebaugh, MD

Schleich first described the use of bilateral rectus sheath blocks (BRSBs) in 1899, with the aim of providing muscle relaxation and analgesia of the abdominial wall by blocking the terminal branches of the thoracolumbar nerves within the substance of the rectus abdominis muscle (RAM).^[1]  It was originally performed as a blind, loss-of-resistance technique.  BRSBs had previously remained underutilized, largely due to concerns over the accuracy of needle-tip placement,^[2] particularly in relation to vascular structures contained within the rectus sheath as well as visceral structures contained within the underlying peritoneal cavity.^[3]  BRSBs are ideally suited for ultrasound guidance because the RAM, layers of the rectus sheath, and important vascular structures are easily identified with ultrasound technology.

Indications

Ultrasound-guided BRSBs provide somatic analgesia over the midline anterior abdominal wall from the xyphoid process superiorly to the symphysis pubis inferiorly.  It is therefore indicated for vertical midline (or paramedian) surgical incisions.  Historically, BSRBs were primarily used as an analgesic adjunct for umbilical hernia repair or laparoscopic gynecologic procedures;^[4-6] however, with the ever-increasing adoption of ultrasound imaging and experience with ultrasound-guided peripheral nerve blockade, more recent indications include analgesia for vertical midline laparotomy incisions for either lower or upper abdominal surgery.^[7-11]  The duration of BRSBs may be extended by placement of catheters within the rectus sheath to allow either continuous and/or intermittent bolus administration of local anesthetics.^[10,11]  Thus, ultrasound-guided BRSBs hold considerable potential as an integral part of a perioperative multimodal analgesic regimen.  

Clinically Relevant Anatomy

Anatomical Course of the Thoracolumbar Nerves

The sensorimotor innervation of the anterior abdominal wall is supplied by the ventral rami of the thoracolumbar spinal (T7-L1) segmental nerves.  The thoracolumbar nerves course along the anterolateral wall within the transversus abdominis plane (TAP), and continue anteromedial within the TAP,  eventually encroaching upon the lateral aspect of the rectus sheath.^[12]  The nerves then enter the lateral aspect of RAM and contribute to the formation of a nerve plexus that runs cranio-caudally within the muscle in close relation to the lateral branch of the deep epigastric artery.^[13]  The thoracolumbar nerves typically pierce the posterior border (89%) and less commonly the lateral border (11%) of the RAM, with the nerves piercing the posterior border within 1.6 to 2.6 cm from the lateral edge of the RAM.  The nerves provide both muscular and cutaneous branches to innervate the muscle fibers and overlying skin.  Notably, the branches of the thoracolumbar nerves do not cross midline.  

Anatomy of the Rectus Sheath

The rectus sheath is formed from the aponeuroses of the fascial sheaths of all three lateral abdominal wall muscles.^[12]  The external oblique (EOM), internal oblique (IOM), and transversus abdominis (TAM) muscles each form a bilaminar aponeurosis at its medial border (Figure 1) converging to form the lateral border of the RAM, termed the linea semilunaris.  The anterior and posterior lamina of the EOM and the anterior lamina of the IOM fuse together and continue further medially over the ventral surface of the RAM to form the anterior portion of the rectus sheath (Figure 2a and Figure 3).  Similarly, the posterior lamina of the IOM and anterior and posterior lamina of the TAM fuse together and continue medially dorsal to the RAM to form the posterior portion of the rectus sheath (Figure 2a and Figure 3).  At the medial border of the RAM, the anterior and posterior portions of the rectus sheath come together, with the fibers coursing further medially toward the medial border of the contralateral RAM forming the midline linea alba.

Figure 1.  Sonoanatomy of the rectus sheath in short-axis above the arcuate line:  RAM=rectus abdominis muscle; EOM=external oblique muscle; IOM=internal oblique muscle; TAM=transversus abdominis muscle.

Figure 2a.  Illustration demonstrating the cross-sectional anatomy of the rectus sheath above the arcuate line:  RA=rectus abdominis muscle.

Figure 2b.  Illustration demonstrating the cross-sectional anatomy of the rectus sheath below the arcuate line:  RA=rectus abdominis muscle.

The anterior portion of the rectus sheath extends along the entire vertical length of the RAM.  In contrast, the posterior portion of the rectus sheath extends only along the upper two-thirds of the RAM.  In the lower one-third, the posterior portion of the rectus sheath stops approximately midway between the umbilicus and symphysis pubis.  At this anatomical transition point, the aponeuroses that had formed the posterior portion of the rectus sheath now also course over the ventral surface of the RAM (Figure 2b).  This transition point is known as the arcuate line.  The transversalis fascia is a thin layer of connective tissue located just deep to posterior portion of the rectus sheath (Figures 2a, 2b, 3).  Located just deep to the transversalis fascia is the parietal peritoneum.  Inferior to the arcuate line, the transversalis fascia is located immediately deep to the posterior border of the RAM.

Figure 3.  Sonoanatomy of the lateral rectus abdominis muscle and rectus sheath in short-axis above the arcuate line also demonstrating the transversalis fascia.

Ultrasound Anatomy and Technique

Short-Axis In-Plane Approach

The transducer (high frequency linear array or low frequency curved array, depending on body habitus) is positioned just lateral to the umbilicus in an axial (transverse) plane (Figure 4).  Identify the layers of the anterior abdominal wall from superficial to deep (Figures 2a, 2b, and 3):

• A layer of subcutaneous tissue and adipose that will vary in depth depending on body habitus.
• Deep to the subcutaneous tissues will be the anterior portion of the of the rectus sheath (a horizontal bright hyperechoic linear structure extending from lateral to medial).  
• Deep to the anterior rectus sheath is the RAM (relatively hypoechoic in relation to the rectus sheath).
• Deep to the RAM will be the posterior portion of the rectus sheath (a horizontal bright hyperechoic structure extending from lateral to medial).
• The deep superior (above the umbilicus) and inferior (below the umbilicus) epigastric arteries may be seen as small, pulsatile, anechoic structures located in the deepest aspect of the RAM.  Color flow Doppler may confirm the presence of blood flow within the arteries.
• Deep to the posterior portion of the rectus sheath will be the transversalis fascia (a hyperechoic linear structure).
• Deep to the rectus sheath and transversalis fascia is the peritoneal cavity, which is identified by the presence of peristaltic movements of the bowel loops.

Figure 4.  External view of an ultrasound-guided rectus sheath block using a short-axis in-plane technique.

Figure 5a. Ultrasound-guided rectus sheath block using a short-axis in-plane technique: (a) initial needle insertion with a small volume of local anesthetic (LA) injected

Figure 5b.  Ultrasound-guided rectus sheath block using a short-axis in-plane technique:   (b) continued advancement of the needle with hydrodissection of the posterior rectus sheath compartment; RA=rectus abdominis muscle.

Single Injection Technique (Video Clip 1)

• Typically, a 21-gauge, 100 mm (or 20-gauge, 150 mm) needle is inserted 3-8cm lateral to the lateral edge of the transducer and guided “in-plane” (Figure 4).
• The needle is advanced in-plane from lateral to medial and superficial to deep.
• The needle should penetrate through the lateral aspect of the linea semilunaris and enter the lateral aspect of the RAM.
• The needle is further advanced until it is positioned deep to the potential space between the deepest (posterior) border of the RAM, but superficial to the posterior aspect of the rectus sheath.  This target site will be referred to as the “posterior rectus sheath compartment.”
• At this point, a small (1-3 ml) volume of local anesthetic (or sterile saline) is injected to confirm correct placement within the posterior rectus sheath compartment, indicated by the appearance of an anechoic fluid collection (Figure 5a).
• Subsequently, 15-20 ml of local anesthetic is incrementally injected while observing for the expanding anechoic fluid collection.  As the local anesthetic is injected, it will often result in clear separation of the deep border of the RAM from the posterior rectus sheath (Figure 5b). Improved local anesthetic spread may be facilitated by advancement of the needle further medially as the anechoic fluid collection visibly expands the posterior rectus sheath compartment in a lateral-to-medial fashion.  
• After local anesthetic injection, the transducer can be translated in a cephalad-to-caudad fashion to visualize cephalad-to-caudad spread within the posterior rectus sheath compartment.
• The same procedure is repeated on the contralateral side.

Continuous Catheter Technique (Video Clip 2)

• If a continuous catheter technique is desired, the same steps above are followed except that a 17-gauge 90-150 mm Tuohy tip needle is used and, after fluid expansion of the posterior rectus sheath compartment, a 19-gauge wire-reinforced catheter is inserted 4-6 cm beyond the needle tip.
• The location of the catheter tip may be confirmed by direct visualization of the catheter or via visualization of local anesthetic spread within the posterior rectus sheath compartment by injecting local anesthetic through the catheter.
• The needle is withdrawn and the catheter is secured to the skin and covered with a sterile clear transparent dressing.

Clinical Pearls and Tips

Although the anterior and posterior rectus sheaths are relatively easy to identify as hyperechoic linear structures that encase the RAM, novices may initially find the technique somewhat more difficult due to the “dynamic nature” of the block.  The anterior abdominal wall may move with respiratory excursions and even small movements may displace the needle out of the imaging plane.  Since this is a compartment block (similar to a TAP block), it is reasonable (and preferred by the author) to perform the block in the operating room after induction of general anesthesia but prior to surgical incision or emergence.

• Local Anesthetic Selection
  • 15-20 ml ropivacaine 0.25% with 1:400,000 epinephrine or bupivacaine 0.25% with 1:400,000 epinephrine per side.  For pediatric patients, the suggested dosing is 0.5 ml/kg (either bupivacaine 0.25% or ropivacaine 0.25% with epinephrine 1:400,000) per side.^[14]
  • This author suggests adding epinephrine to decrease local anesthetic peak plasma concentration (Cmax), as spread of local anesthetic will encompass a relatively large surface area for vascular absorption into the systemic circulation.  Based on initial pharmacokinetic studies, the time to peak plasma concentration (Tmax) is approximately 45 minutes.^[14-16] Thus, the patient should be observed for potential signs or symptoms of local anesthetic systemic toxicity for a minimum of 45 minutes after completion of BRSBs.
  • The expected duration of RSBs is approximately 6-10 hours.  Thus, there should be an analgesic plan for when the analgesic effects of the BRSBs dissipate.
  • For a continuous catheter technique, a small continuous infusion (2-3 ml/hr) is recommended simply to keep to catheter tip patent.  Intermittent bolus injection of 10-20 ml ropivacaine 0.25% per side every 6-10 hours is recommend to maintain postoperative analgesia.^{[11, 12]}

• Current Role of Ultrasound-Guided RSBs in Perioperative Multimodal Analgesia
  • BRSBs may be performed prior to surgical incision to facilitate analgesia immediately after surgery.  If they are performed prior to the surgical incision, they will decrease intraoperative analgesic (opioid) requirements.
  • Alternatively, BRSBs may also be performed in the immediate postoperative setting as a “rescue block technique” (in the event of either unexpected severe postoperative pain after an abdominal surgical procedure or unanticipated failed epidural analgesic technique).
  • BRSBs do not provide complete anesthesia-analgesia for major abdominal surgical procedures, as they do not provide visceral analgesia.  Thus, BRSBs should be used as part of a multimodal analgesic approach that includes NSAIDs or COX-2 inhibitors, acetaminophen, gabapentin, and as-needed systemic opioids.
  • One of the primary indications for BRSBs with or without catheters in our institution is to provide postoperative  abdominal wall analgesia when thoracic epidural analgesia (TEA) is contraindicated.  One potential advantage is the notable lack of sympathectomy (and hypotension) that is commonly associated with TEA.

References

1. Schleich CL.  Schmerzlose operationen.  4th ed.  Berlin:Springer, 1899;240-8.
2. Dolan J, Lucie P, Geary T, et al.  The rectus sheath block-accuracy of local anesthetic placement using loss of resistance or ultrasound guidance.  Reg Anesth Pain Med 2009;34:247-250.
3. Dolan J, Smith M.  Visualization of bowel adherent to the peritoneum before rectus sheath block: another indication for use of ultrasound in regional anesthesia.  Reg Anesth Pain Med 2009;34:280-281.
4. Gurnaney HG, Maxwell LG, Kraemer FW, et al.  Prospective randomized observer-blinded study comparing the analgesic efficacy of ultrasound-guided rectus sheath block and local anaesthetic infiltration for umbilical hernia repair.  Br J Anaesth 2011;107:790-795.
5. Dingeman RS, Barus LM, Chung HK, et al.  Ultrasonographically-guided bilateral rectus sheath block vs. local anesthetic infiltration after pediatric umbilical hernia repair: a prospective randomized clinical trial.  JAMA Surg 2013;148:707-713.
6. Azemati S, Khosravi MB.  An assessment of the value of rectus sheath block for postlaparoscopic pain in gynecological surgery.  J Minim Invasive Gynecol 2005;12:12-15.
7. Shido A, Imamachi N, Doi K, et al.  Continuous local anesthetic infusion through ultrasound-guided rectus sheath catheters.  Can J Anesth 2010;57:1046-1047.
8. Malchow R, Jaeger L, Lam H.  Rectus sheath catheters for continuous analgesia after laparotomy-without postoperative opioid use.  Pain Med 2011;12:1124-1129.
9. Breschan C, Jost R, Stettner H, et al.  Ultrasound-guided rectus sheath block for pyloromyotomy in infants:  a retrospective analysis of a case series.  Paediatr Anaesth 2013;23:1199-1204.
10. Godden AR, Marshall MJ, Grice AS, et al.  Ultrasonography guided rectus sheath catheters versus epidural analgesia for open colorectal cancer surgery in a single centre.  Ann R Coll Engl 2013;95:591-594.
11. Dutton TJ, McGrath JS, Daugherty MO.  Use of rectus sheath catheters for pain relief in patients undergoing major pelvic urological surgery.  BJU Int.  2014;113;246-253.
12. Rozen WM, Tran TMN, Ashton MW, et al.  Refining the course of the thoracolumbar nerves: a new understanding of the innervation of the anterior abdominal wall.  Clin Anat 2008;21:325-333.
13. Rozen WM, Ashton MW, Murray ACA, Taylor GI.  Avoiding denervation of rectus abdominis in the DIEP flap harvest: the importance of medial row perforators.  Plast Reconstr Surg 2008;122:710-716.
14. Flack SH, Martin LD, Walker BJ, et al.  Ultrasound-guided rectus sheath block or wound infiltration in children: a randomized study of analgesia and bupivacaine absorption.  Paediatr Anaesth 2014;24:968-973.
15. Wada M, Kitayama M, Hashimoto H, et al.  Plasma ropivacaine concentrations after ultrasound-guided rectus sheath blocks in patients undergoing lower abdominal surgery. Anesth Analg 2012;114:230-232.
16. Kitayama M, Wada M, Hashimoto H, et al.  Effects of adding epinephrine on the early systemic absorption of local anesthetics in abdominal truncal blocks.  J Anesth 2014;28:631-4.