Rectus sheath block procedure guide

INTRODUCTION — 

Rectus sheath block is a fascial plane block that involves injection of local anesthetic between the rectus abdominis muscle and its posterior sheath. Performed in the subcostal region, it provides analgesia of the ventral abdominal wall in the epigastric region in a T6-T11 dermatomal distribution. This topic will discuss the anatomy, ultrasound imaging, and injection technique for rectus sheath block.

General considerations common to all peripheral nerve blocks, including patient preparation and monitoring, use of aseptic technique, localization techniques, drug choices, contraindications, and complications, are discussed separately. (See "Overview of peripheral nerve blocks" and "Ultrasound for peripheral nerve blocks".)

ANATOMY — 

The target of the rectus sheath block is the potential space between the rectus abdominis (RA) muscle and the posterior rectus sheath deep (dorsal) to the muscle.

Overview of abdominal wall anatomy — The ventral abdominal wall comprises the following, from superficial to deep: skin, subcutaneous fat (Camper’s fascia), investing fascia of the abdominal muscles (Scarpa’s fascia), four different abdominal muscles which partially overlap in different portions of the abdomen, small vessels and nerves, deeper fascia, and the peritoneum. The components relevant for rectus sheath blocks are discussed here.

Rectus abdominis muscles — The RA muscles extend from the xiphoid process and the fifth to seventh costal cartilages to the pubic symphysis (figure 1). In the subcostal epigastric region of the abdomen, directly caudal to the costal margin, the TA muscle typically extends underneath the posterior and lateral border of the RA muscle (image 1) [1].

The medial boundary of the RA muscle is the linea alba, which is the confluence of the posterior and anterior components of the rectus sheath (image 2). The lateral boundary of the RA muscle defines the semilunar line. Lateral to the semilunar line the external oblique, internal oblique, and transversus abdominis muscles comprise the lateral muscular wall of the abdomen.

The superior and inferior epigastric arteries run within the body of the RA muscle and may be injured during needle insertion.

The rectus sheath — The rectus sheath is a fibrous structure that encases the RA muscles bilaterally (image 2). The target of the rectus sheath block is the potential space between the RA muscle body and the posterior rectus sheath.

The components of the posterior rectus sheath change at the level of the arcuate line (also called the semicircular line of Douglas), which is at the level of the anterior superior iliac spines, approximately one third of the distance from the umbilicus to the pubis. Cephalad to the arcuate line, the posterior rectus sheath consists of the aponeuroses of the internal oblique and transversus abdominis muscles and the epimysium of the RA muscle. Caudal to the arcuate line, there is no posterior rectus sheath per se; only the transversalis fascia lies between the posterior epimysium of the RA muscle and the peritoneum. Rectus sheath blocks are not performed caudal to the arcuate line, due to the absence of a rectus sheath below this level. In practice, the authors do not perform rectus sheath blocks below the umbilicus for this reason.

Below the arcuate line, the aponeuroses of the transversus abdominis (TA) and the internal oblique (IO) muscles pass anterior to the RA muscle and join the aponeurosis of the external oblique (EO) muscle to form the anterior rectus sheath.

Nerve anatomy — The nerves blocked by a rectus sheath block originate as ventral rami of thoracic spinal roots at multiple vertebral levels. The ventral rami traverse the paravertebral space, becoming intercostal (T6-T11) and subcostal (T12) nerves while continuing into the transversus abdominis plane (TAP) between the deeper TA and more superficial IO muscles. The rectus sheath block targets only the anterior cutaneous branches of the intercostal nerves. The intercostal nerves enter the posterior rectus sheath at its lateral edge, and then travel between the posterior sheath and the muscle body (figure 2). They pierce the muscle approximately two centimeters medial to its lateral border, though there is significant anatomic variability [2]. The nerves pass through the muscle, penetrate the anterior sheath, and continue on to innervate the skin and subcutaneous tissues of abdominal midline. Motor branches innervate the RA muscle.

CLINICAL IMPLICATIONS OF ANATOMY

Block coverage — The rectus sheath block targets the anterior cutaneous branches of spinal nerves T7-T11. In contrast, the transversus abdominis plane block targets the lateral cutaneous branches as well. This may provide the rationale for combining transversus abdominis plane (TAP) and rectus sheath blocks for effective analgesia for abdominal surgery, as has been demonstrated in multiple studies as described below.

The anterior cutaneous branches of the spinal nerves divide and communicate in an extensive, overlapping plexus within the fascial plane. Thus, complete analgesic coverage requires extensive spread of local anesthetic. The optimal volume of local anesthetic has not been determined using in vivo studies. Midline structures are innervated by nerves from both sides of the body, so bilateral blocks are required for effective midline analgesia [3].

While rectus sheath block can be performed at any point from the xiphoid process to the arcuate line, it is most often described as a bilateral block in the epigastric (eg, subcostal or subxiphoid) region in combination with subcostal TAP blocks. The rectus sheath block can be thought of as a technique that adds anterior cutaneous coverage of the midline in the T6-T10 dermatomes, as opposed to the more lateral and caudal coverage provided by TAP blocks (figure 3).

In the author’s practice, this combination of bilateral rectus sheath and bilateral subcostal TAP blocks is colloquially called a “4-quadrant block.” The combination approach has been well studied, with demonstrated analgesic efficacy for various upper abdominal surgeries [4-11]. (See "Transversus abdominis plane (TAP) blocks procedure guide".)

Motor blockade from a rectus sheath block should produce weakness of the RA muscles and prevent muscle spasm [12], which may reduce postoperative pain, though the clinical impact of this effect is unclear.

Uses — Rectus sheath block does not produce visceral coverage. Alone, it is used for analgesia of the body wall and typically not for surgical anesthesia (figure 3).

The authors use bilateral rectus sheath blocks, usually in combination with subcostal TAP blocks for midline epigastric incisions, laparotomy incisions when there are contraindications to epidural analgesia, and for most laparoscopic abdominal procedures. For umbilical hernia repair, we use bilateral rectus sheath blocks without TAP blocks. For infraumbilical incisions, we refrain from rectus sheath blocks due to the variable location of the arcuate line and the lack of a posterior rectus sheath caudal to the arcuate line.

●Midline laparotomy – Open abdominal surgery requiring midline laparotomy is a common indication for rectus sheath block, either by single injection or continuous block. Ultrasound-guided rectus sheath block has been shown to be superior to wound infiltration [13], whereas studies comparing rectus sheath block to thoracic epidural have been mixed [14-16].

●Laparoscopy – Patients who undergo laparoscopic surgeries that involve supraumbilical port site placement may benefit from rectus sheath block, particularly if a small midline incision is required [17-19]. However, the overall clinical utility of regional anesthesia for totally laparoscopic cases may be limited, particularly in the setting of a comprehensive multimodal pain regimen.

●Infraumbilical incisions – Rectus sheath block has been utilized for Pfannenstiel incision and inguinal hernia repair in both adult and pediatric populations [20,21]; however, studies have suggested lower pain scores and lower postoperative opioid consumption with TAP blocks compared to rectus sheath block for these procedures [22].

●Cardiac surgery – Rectus sheath block has been combined with parasternal and transversus thoracis plane blocks in cardiac surgery involving sternotomy, to provide analgesia for epigastric chest tube sites [23].

Subcostal block placement — In the subcostal region, the transversus abdominis (TA) muscle typically extends underneath the posterior and lateral border of the rectus abdominis (RA) muscle (see 'Rectus abdominis muscles' above). This provides a buffer and separation between the RA muscle and the peritoneum when performing the block at this level, with the transducer contacting the costal margin. Further caudal, the rectus muscle directly overlies the transversalis fascia and peritoneum, without a muscle layer between the posterior rectus sheath and abdominal contents.

BLOCK TIMING — 

Rectus sheath block may be performed preoperatively in a judiciously sedated patient, intraoperatively either before incision or just prior to emergence, or postoperatively in an awake patient. The authors typically place single injection blocks following induction of anesthesia (for patient comfort) but prior to incision. We place continuous blocks after wound closure to avoid having the catheters in the surgical field during the procedure.

Block placement prior to incision avoids any distortion of the anatomy by the surgical procedure, and compared with block placement just prior to emergence, avoids concerns about contamination of the surgical wound or having to avoid the surgical dressing. Post-induction, pre-incision block placement can be performed in parallel with other postinduction tasks (eg, intravenous or urinary catheter placement, positioning).

If the surgeon is concerned about tissue distortion from the block injection, postoperative block placement may be preferred.

SINGLE-INJECTION BLOCK — 

For rectus sheath block, we suggest using ultrasound guidance, which is described here, to minimize the risk of vascular injury or intravascular injection of the block solution, and peritoneal puncture or organ injury.

Patient positioning — Position the patient supine with the proceduralist standing on one side of the patient and the ultrasound machine on the opposite side.

Ultrasound equipment — Select a 5 to 10 MHz linear ultrasound transducer with the depth set appropriately for the patient’s body habitus, typically 3 to 6 cm. For patients with severe obesity, especially with body mass index (BMI) > 50 kg/m², a low frequency curvilinear probe (2 to 5 MHz) may be preferable.

Performing the block — For upper abdominal analgesia, we perform rectus sheath blocks at the costal margin, rather than between the xiphoid and the umbilicus, because of the added margin of safety of having the transversus abdominis muscle between the block target and the peritoneum. (See 'Subcostal block placement' above.)

●For most indications, place the ultrasound transducer midline in the epigastric region in transverse orientation (image 3). For umbilical hernia repair or if only periumbilical incision is planned, place the transducer at the level of the umbilicus.

●From superficial to deep, identify subcutaneous fat (Camper’s fascia), investing fascia of the abdominal muscles (Scarpa’s fascia), the anterior rectus sheath, and underlying rectus abdominis muscles (image 4).

●Identify the bilateral rectus abdominis (RA) muscles that taper to form the connective tissue band of the linea alba in the midline (image 2). In patients with diastasis recti, the RA muscles may be widely spaced with a broad linea alba.

●Deep to the linea alba, identify the trapezoidal or triangular-shaped preperitoneal fat, with the peritoneum and abdominal contents deep to the fat.

●Slide the transducer laterally to the side of the intended block until the lateral edge of the RA muscle (semilunar line) is visible.

•For epigastric block placement, the lateral edge of the probe will encounter the rib edge along the costal margin before the semilunar line is visible. When this occurs, rotate the transducer obliquely and move it laterally and caudally along the rib edge until the edge of the rectus abdominis muscle is visible.

•For periumbilical block placement, leave the transducer in a transverse orientation.

●Identify the posterior rectus sheath, deep to the body of the RA muscle.

•In the subcostal region, the transversus abdominis (TA) muscle is often identifiable deep to the RA muscle and provides a backstop against inserting the needle too far and potentially through the peritoneum (image 1) (see 'Subcostal block placement' above). If the TA muscle is not seen, tilt the transducer slightly cephalad to improve visualization.

•More inferior in the abdomen, visualize the transversalis fascia and peritoneum immediately deep to the posterior rectus sheath (image 4).

●Insert a 21-gauge, 80 to 120 mm, short (B) bevel needle in-plane to the transducer, placing the needle tip deep to the lateral third of the RA muscle to ensure coverage of the target nerves before they pierce the rectus abdominis muscle. (See 'Nerve anatomy' above.)

•The authors insert the needle from medial-to-lateral because we typically perform bilateral blocks and prefer a similar needle approach for both blocks. Medial to lateral insertion for both blocks also eliminates the need to reach as far over the patient for the block on the far side.

•Other clinicians prefer a lateral-to-medial approach to allow a shallower needle trajectory for the approach to the target plane (image 5). For patients with midline abdominal hernias (eg, umbilical hernia), insert the needle from lateral to medial after a thorough scan of the abdomen to assure a needle path free of abdominal contents.

●Advance the needle through the RA muscle to its posterior border. After negative aspiration, inject 2 to 3 mL of local anesthetic or saline to confirm correct placement, visualizing separation of the RA muscle from the posterior rectus sheath (image 6 and image 5).

Note: Injection that expands the RA muscle, appears circular instead of linear, or separates muscle fascicles rather than lifting the muscle may indicate intramuscular needle tip placement. The needle should be advanced further and additional fluid should be injected.

●After correct needle placement is confirmed, inject 10 to 20 mL of LA in 5 mL increments, with gentle aspiration between injections. (See 'Drug choice and dosing' below.)

●Repeat the block on the contralateral side.

DRUG CHOICE AND DOSING

●Local anesthetics – Long-acting local anesthetics (LA; eg, ropivacaine 0.2% or bupivacaine 0.25%) are commonly used for rectus sheath block to maximize duration of analgesia. We use ropivacaine 0.25% (diluted from ropivacaine 0.5%).

The total LA dose injected should be within the maximum allowable dose, including the dose used for the rectus sheath block and any other injections (eg, wound infiltration, other nerve blocks) (table 1). Rectus sheath blocks can result in local anesthetic toxicity (LAST) due to the vascularity of the fascial planes and the high volumes of LA used. (See 'Clinical implications of anatomy' above.)

For adults, the typical volume of local anesthetic for rectus sheath block is 20 mL per side. When performed along with transversus abdominis plane (TAP) block, the rectus sheath block is usually performed with 10 mL per side, and the TAP block with 20 mL per side.

In children, guidelines suggest using doses of 0.25 to 0.75 mg/kg of ropivacaine or bupivacaine for rectus sheath and other fascial plane blocks [24]. A total dose of 0.4 mg/kg 0.25% bupivacaine has been used in some studies [21,25].

Liposomal bupivacaine has been used in a range of regional anesthetic techniques in an effort to prolong the duration of single-shot approaches. However, evidence of a clinically important and cost-effective benefit to using liposomal bupivacaine is not convincing [26-28]. (See "Clinical use of local anesthetics in anesthesia", section on 'Liposomal bupivacaine'.)

●Adjuvants – Adjuvants are commonly added to local anesthetics for peripheral nerve blocks to speed block onset and increase density and duration. We usually administer dexamethasone (8 to 10 mg intravenously, or 4 to 8 mg perineural) to extend the duration of rectus sheath block. Use of adjuvants and various local anesthetics for peripheral nerve blocks is discussed in more detail separately. (See "Overview of peripheral nerve blocks", section on 'Drugs'.)

CONTINUOUS RECTUS SHEATH BLOCK — 

Rectus sheath catheters can provide prolonged analgesia beyond the duration of single-shot techniques.

●Catheter placement technique – The technique for placing the catheter is similar to the technique used for single injection block as described above. A catheter through the needle technique with a Touhy needle, or an over-the-needle technique can be used (see "Overview of peripheral nerve blocks", section on 'Equipment'). Placement is usually performed postoperatively, either before or after emergence from anesthesia, to avoid having a catheter near the surgical field.

•Follow strict sterile technique, with broad sterile skin preparation, sterile gloves, a sterile ultrasound transducer cover, and drape a large sterile field.

•Position the needle tip as described above. (See 'Single-injection block' above.)

•After negative aspiration, inject 1 to 3 mL of saline to verify correct needle tip placement and expand the fascial plane.

•Insert the catheter 2 to 5 cm within the rectus sheath while visualizing the catheter tip. After negative aspiration, inject 1 to 3 mL of saline through the catheter to confirm correct placement of the tip.

•Remove the needle and secure the catheter to the skin, avoiding the surgical field and dressings.

●Infusion drug dose – After injecting a bolus of local anesthetic through the catheter as for single injection block while visualizing spread, we start an infusion of ropivacaine 0.2% or bupivacaine 0.125% at 6 mL/hour with a 4 to 5 mL per hour patient-controlled bolus. A “Y” connector can be used to allow infusion through bilateral catheters with a single pump.

Various infusion regimens have been described. Large volume intermittent bolus is commonly used (eg, total 40 mL 0.2% ropivacaine [29] or 18 mL 0.5% ropivacaine every four hours) [30]. For programmed intermittent bolus, the pump may be programmed to administer between 6 mL per hour and 15 mL every three hours. Comparison studies of the optimal infusion settings for this block have not been reported, so the doses selected are extrapolated from other procedures.

COMPLICATIONS — 

Complications of ultrasound-guided rectus sheath blocks are very rare but can be serious. Vascular injury is possible, since the epigastric vessels run within the rectus muscle, and local anesthetic systemic toxicity (LAST) is a concern given the large volume of LA used for the block and the vascularity of the block plane.

In a single institution retrospective study of over 4000 bilateral rectus sheath blocks performed for analgesia for elective laparoscopic surgery with an umbilical port, complications occurred in approximately 2 percent of blocks [31]. Almost all (88 of 96 complications) involved injection of local anesthetics (LA) posterior (deep) to the rectus sheath. There were eight cases of vascular injury (inferior epigastric or mesenteric arteries), one of which was repaired immediately by the surgeon. There were no cases of LAST or bowel injury. Of note, the median body mass index (BMI) of the patients in this study was 24.1 kg/m² (interquartile range 21.8 to 26.5); results may not be applicable to patients with higher BMI.

The authors treat rectus sheath blocks as low-risk, superficial blocks and do perform them in the presence of antithrombotic drugs or coagulation disorders; these blocks are a viable alternative to thoracic epidural in patients for whom epidural is contraindicated due to coagulopathy. Regional anesthesia anticoagulation guidelines give limited guidance for deciding which blocks should be considered low risk in patients with altered coagulation [32].

Complications common to all peripheral nerve blocks (eg, nerve injury, bleeding, LAST, infection) are discussed separately. (See "Overview of peripheral nerve blocks", section on 'Complications'.)

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Local and regional anesthesia" and "Society guideline links: Acute pain management".)

SUMMARY AND RECOMMENDATIONS

●Anatomy

•The rectus sheath block involves injection of local anesthetic (LA) between the body of the rectus abdominis muscle and its posterior sheath. The block targets anterior cutaneous branches of spinal nerves T7 to T11 that lie in this space (figure 2). (See 'Anatomy' above.)

•Rectus sheath blocks are used for analgesia primarily for midline abdominal incisions, and in combination with other blocks (often transversus abdominis plane blocks) for more lateral incisions (figure 3). (See 'Uses' above.)

●Single injection block – We perform single injection block with ultrasound guidance as follows, with further explanation above. (See 'Single-injection block' above.)

•For most patients use a 5 to 10 MHz linear ultrasound transducer with the depth set to 3 to 6 cm, placed in a transverse orientation (image 4). For subcostal block, slide the transducer laterally and rotate to visualize the relevant structures (image 1).

•Place the needle tip at the posterior border of the rectus abdominis muscle.

•Hydrodissect with 2 to 3 mL of local anesthetic (LA) or saline, visualizing separation of the RA muscle from the fascia (image 6 and image 5).

•After negative aspiration, inject 10 to 20 mL of local anesthetic in 5 mL increments, with gentle aspiration between injections. (See 'Drug choice and dosing' above.)

•Repeat the block on the contralateral side.

●Continuous block technique – Continuous block is performed as described for single-injection block, using a catheter through a Tuohy needle, or a catheter-over-the-needle kit. (See 'Continuous rectus sheath block' above.)

●Drug choice

•Single injection block – Long-acting LAs (eg, ropivacaine 0.2% or bupivacaine 0.25%) are commonly used for rectus sheath block to maximize duration of analgesia. We use dexamethasone as an adjuvant for these blocks (8 to 10 mg intravenously, or 4 to 8 mg perineural) to extend the duration of the block. Other options for adjuvants are possible. (See 'Drug choice and dosing' above and "Overview of peripheral nerve blocks", section on 'Adjuvants'.)

•Continuous block – After injecting a bolus of LA through the catheter as for single injection block, we start an infusion of ropivacaine 0.2% or bupivacaine 0.125% with either continuous infusion or programmed intermittent bolus, with or without patient-controlled demand doses. (See 'Continuous rectus sheath block' above.)

●Complications – Complications of ultrasound-guided rectus sheath blocks are very rare but can be serious, including vascular injury and local anesthetic systemic toxicity. (See 'Complications' above.)

The authors treat rectus sheath blocks as low-risk, superficial blocks and do perform them in the presence of antithrombotic drugs or coagulation disorders.