Version May 2024
INTRODUCTION — The erector spinae plane (ESP) block is a paraspinal fascial plane block that involves injection of local anesthetic (LA) between the tip of the transverse process of the thoracic or lumbar vertebra and the anterior fascia of the erector spinae muscles [1]. The block targets the dorsal and ventral rami of the thoracic and abdominal spinal nerves to provide analgesia for multiple types of surgical procedures and painful conditions. This topic will discuss the anatomy, ultrasound imaging, and injection techniques for performing thoracic and lumbar ESP block.
General considerations common to all peripheral blocks, including patient preparation and monitoring, use of aseptic techniques, drug choices, contraindications, and complications, are discussed separately. (See "Overview of peripheral nerve blocks".)
ANATOMY — The erector spinae plane lies between the fascia covering the anterior aspect of the erector spinae muscles and the posterior surface of the transverse processes of the vertebrae.
●Muscles, fascia and planes – The erector spinae muscle complex consists of three muscles - the iliocostalis, longissimus, and spinalis muscles (figure 1). They run on either side of the spinous processes of the vertebral column from the base of the skull to the pelvis. Their caudal insertions are on the sacrum, iliac crest and lumbar spinous processes. Cranial insertions are at transverse and spinous processes of the thoracic and cervical vertebrae up to C2, as well as attachments to ribs [2,3].
In the thoracic region, the erector spinae muscle group is overlaid by the trapezius and rhomboid major muscles. The rhomboid major muscle tapers at approximately T5, so may not be visualized during blocks performed at or below this level. In the lumbar region, they are overlaid by the serratus posterior inferior and latissimus dorsi muscles.
The erector spinae plane (ESP) is a fascial plane between the anterior aspect of the erector spinae muscles and the posterior surfaces of the vertebral transverse processes. In the thoracic region, the plane is open to intercostal spaces laterally and is bounded by laminae and interspinous ligaments medially.
●Communications – The erector spinae plane communicates with the thoracic paravertebral and epidural spaces through the intertransverse connective tissue [4]. The superior costotransverse ligament that forms most of the dorsal border of the thoracic paravertebral space has fenestrations which may allow spread of local anesthetic (LA) into the paravertebral space from more superficial injection within the ESP (figure 2) [5-7]. The ESP also communicates with intercostal spaces laterally [8] (figure 3).
●Nerves – In the thoracic spine, spinal nerves exit the vertebral canal and continue as ventral and dorsal rami within the ESP (figure 4). In the lumbar region, the ventral rami of L1 to L4 form the lumbar plexus, and the dorsal rami split into medial, intermediate, and lateral branches (figure 5) [9].
CLINICAL ANATOMIC CORRELATIONS
●Uses – The role of erector spinae plane (ESP) blocks in anesthesia and analgesia is evolving. The ESP block has primarily been used to provide analgesia for thoraco-abdominal procedures as a potentially safer alternative to epidural, or paravertebral techniques. It has also been used for analgesia for breast, shoulder and upper extremity, spine, hip and lower extremity procedures, cesarean delivery, for multiple rib fractures, and chronic pain syndromes [1].
The literature supporting the use of ESP blocks for many of these indications is inconsistent, and much of the literature consists of case reports or case series. Some randomized trials have found reduced pain scores and postoperative opioid consumption with ESP blocks for analgesia after thoracic and breast surgery [10-13]. Utility of lumbar ESP block for hip surgery and cesarean delivery has been reported only in case reports and small randomized trials [14,15].
●Mechanism of action – The mechanism of action of ESP blocks is unclear.
•Thoracic ESP block – In addition to blocking the dorsal and ventral rami with local anesthetic (LA) within the ESP, postulated mechanisms include spread to the paravertebral, epidural, and intercostal spaces, and diffusion posteriorly into the erector spinae muscles. The best available evidence suggests that the primary mechanism for the effect of ESP block involves spread of LA and diffusion within the ESP, to the intercostal spaces and paravertebral spaces [16], and to adjacent neural structures (eg, spinal nerve roots, dorsal and ventral rami) [17]. Cadaver and live human studies using dye or radiocontrast have found that epidural spread is possible, but does not consistently occur at the time of the block, though diffusion to these spaces may subsequently occur [18-20]. Posterior spread into the erector spinae muscle itself is common, and may be a mechanism for block of dorsal rami (figure 3).
Spread to the epidural or paravertebral spaces, which would block sympathetic fibers, provides a mechanism by which the ESP block could provide visceral analgesia.
•Lumbar ESP block – The mechanism of action of lumbar ESP block has been far less studied than the mechanism of thoracic ESP block. Whereas some reported clinical effects support block of the dorsal ramus of spinal nerves by distribution of local anesthetic through the erector spinae muscles, others suggest a mechanism similar to thoracic ESP block, with infiltration of local anesthetic to the anterior rami at multiple levels.
●Site of injection – The selected level for the block should be as close to the location for the dermatome for the incision or injury as possible. Blocks at multiple sites may be required for extensive dermatomal coverage (eg, for multiple rib fractures).
Examples of block placement for various conditions and surgeries include the following:
•Upper thoracic – T2 to T3
•Lower thoracic – T5 to T7
•Abdominal surgery – T10
•Hip, femur, or lumbar spine surgery – L2 to L3
Cadaver studies have found that with an ESP injection, the LA spreads along the fascial plane in a cranio-caudal fashion. In one study, a 20 mL ESP injection spread 3 to 4 levels cranially and 3 to 4 levels caudally from the site of injection, as well as spread into the intercostal spaces [8]. A median volume of 3.4 mL of LA can cover a single dermatome [21].
There are case reports of coverage from T2 to T8 after a block performed at T5 [22], and from T7 to T11 after a block performed at T7 [23]. In the author’s experience, ESP block performed with 20 mL of local anesthetic produces two-segment anesthesia anteriorly and four-segment anesthesia posteriorly, and sensory analgesia in an additional two segments anteriorly and two to four segments posteriorly.
SINGLE INJECTION ESP BLOCK — For erector spinae plane (ESP) block we suggest using ultrasound guidance [1], which we describe here.
Thoracic block
Ultrasound equipment — For most patients we use a high frequency (10 to 15 MHz) linear array transducer, with the depth set to 3 to 5 cm. For patients with obesity, we use a low frequency (2 to 5 MHz) curvilinear transducer, and adjust the depth as necessary. (See "Ultrasound for peripheral nerve blocks", section on 'Transducers'.)
Patient positioning — Thoracic ESP block is commonly performed in the sitting position (picture 1). Lateral and prone positions may be used, particularly if the block is performed after induction of anesthesia.
Performing thoracic block — ESP block is most commonly performed with the ultrasound transducer in a parasagittal orientation, which has routinely been used in trials involving this block, and which we describe here. Transverse orientation has been described in case reports.
●Identify the correct block level – To identify the target transverse process (TP), either count ribs or count spinous processes.
•Count ribs – We count ribs with ultrasound rather than surface landmarks to more accurately identify the desired TP level, particularly when spinous processes (SPs) are not clearly palpable.
-Place the transducer in sagittal orientation approximately 6 cm from midline. Start cranially to identify the first rib, or caudally to identify the 12th rib.
-Slide the transducer cranially or caudally parallel to the spine, counting the ribs until the desired level is reached. Center the rib on the ultrasound screen.
-Slide the transducer medially to visualize the tip of the TP, typically approximately 3 cm lateral to the midline.
•Count spinous processes – Palpate the spinous prominens (C7) and counting caudally to the desired level. At the levels T4 to T8, the spinous process of the vertebral body above correlates with the TP of the vertebral body one below. Place the transducer over the target spinous process and slide laterally along the lamina to find the TP.
●Identify the TP – Scan from lateral to medial, looking for the transition from rib to TP (image 1). Ribs appear round, thin, and surrounded by visible pleura. In contrast, TPs appear as flat, with squared off acoustic shadows and with less visible surrounding pleura. At the point of transition from rib to TP (the costo-transverse angle), the TP is more superficial than the rib.
Mark the desired TP and center it on the ultrasound screen.
●Insert the block needle in plane to the transducer at either end and advance the needle to contact the tip of the transverse process, visualizing the needle tip throughout (image 2 and figure 4 and movie 1 and figure 6).
●After negative aspiration, inject 1 to 3 mL of saline, visualizing elevation of the fascia of the erector spinae muscle off the TP (image 3 and movie 2). Adjust the tip of the needle as necessary to clearly visualize separation of the erector spinae muscle (ESM) from the TP.
●After negative aspiration, inject 20 mL of local anesthetic in 5 mL increments, with gentle aspiration between injections, while visualizing the hypoechoic pocket of local anesthetic (LA) lifting the ESM.
●Scan cranially and caudally to visualize spread of LA within the ESP.
Lumbar block — Lumbar ESP block is technically more challenging than thoracic block as the muscle layers are deeper and thicker than in the thoracic region, and the tips of the TPs are deeper and more lateral [24].
Ultrasound equipment — For lumbar ESP block we use a low frequency (2 to 5 MHz) curvilinear transducer, with the depth set to 4 cm, adjusted as necessary.
Patient positioning — Lumbar ESP block is usually performed in the prone position. It can also be performed in the lateral position, which can be useful if the block is placed in an anesthetized patient.
Performing lumbar block
●Identify the correct block level – Identify the target TP by counting them either caudal to cranial from the sacrum or cranial to caudal from T12. Note that the T12 TP is shorter than other thoracic and lumbar TPs. The author scans cranially from the sacrum.
●Identify the tip of the TP – Obtain a parasagittal oblique interlaminar view to identify laminae. At the desired level, slide the transducer laterally to visualize the TPs, which cause acoustic shadows separated by psoas muscle. Move the transducer laterally beyond the tip of the TP (until the acoustic shadows disappear) and then move it slowly back until the shadows reappear. This is the tip of the TP, which is the needle target.
●Visualize the erector spinae muscle overlying the TP.
●Insert the block needle in plane to the transducer at either end and advance the needle to contact the tip of the transverse process, visualizing the needle tip throughout (figure 5).
●After negative aspiration, inject 1 to 3 mL of saline, visualizing elevation of the fascia of the erector spinae muscle off the TP. Adjust the tip of the needle as necessary to clearly visualize separation of the ESM from the TP.
●After negative aspiration, inject 30 to 40 mL of local anesthetic in 5 mL increments, with gentle aspiration between injections, while visualizing the hypoechoic pocket of LA lifting the ESM. Cranial-caudal spread of LA is not as apparent in the lumbar level as it is during thoracic ESP block.
Local anesthetic choice and dose
●Choice of LA – We base the choice of LA on the total volume that will be used, aiming to maximize efficacy while minimizing the risk of local anesthetic systemic toxicity (LAST) with this high-volume block. We add epinephrine 1:200,000 to the block solution to reduce systemic uptake (table 1). (See 'Side effects and complications' below.)
•Single injection unilateral thoracic block – 0.5% ropivacaine, bupivacaine, or levobupivacaine with epinephrine 1:200,000
•Single injection lumbar or bilateral block – 0.2% ropivacaine, 0.25% bupivacaine or levobupivacaine with epinephrine 1:200,000
●Volume of LA solution – In most studies 20 to 30 mL of local anesthetic have been used for unilateral ESP block aiming for spread over multiple interspaces.
•For thoracic block, the author uses 20 mL of the LA solution for average size adults. For taller patients or when extensive spread is required, the volume can be increased to 30 mL, with a slightly lower concentration of LA.
•For lumbar ESP we use larger volumes, usually 30 to 40 mL of LA solution. In a review of studies of spread of injectate during ESP block, a median of 5 mL of injectate was needed to cover one vertebral level in the lumbar region, whereas only 3.3 to 3.5 mL was needed for one level in the thoracic region [25]. We use lower concentration LA for even single injection lumbar blocks because larger volumes are used, compared with thoracic block.
LAs for peripheral nerve blocks and the use of adjuvant drugs are discussed in more detail separately. (See "Overview of peripheral nerve blocks", section on 'Drugs'.)
CONTINUOUS ESP BLOCK — Continuous erector spinae plane (ESP) block with a perineural catheter is indicated for prolonged analgesia as in acute postoperative pain, rib fractures and certain chronic pain syndromes.
Catheter placement technique — Strict sterile technique must be used (including a sterile ultrasound transducer cover, full operating room table cover) for continuous block. The technique for continuous block is similar to a single-injection block. Continuous block can be performed with a catheter-through the needle technique using a Touhy needle instead of a block needle, or with a catheter-over needle kit [26,27]. Here we describe the more commonly used catheter-through the needle technique.
Technique for using a catheter-over-the needle is similar, except that if a catheter-over the needle technique is used, insert the needle farther from the edge of the transducer and at a shallower angle than would be used for a single shot block, to make it easier to advance the device. The needle/catheter must be inserted further into the ESP, as most such devices do not allow advancing the catheter beyond the tip of the needle.
●Locate the desired block level as described above, mark the skin, and visualize the transverse process (TP).
●With the transducer in a parasagittal orientation, insert an 18 gauge Touhy needle in plane from either end of the transducer at a 45 degree angle to the skin, with the needle bevel facing up (away from the surface of the TP).
●Place the needle tip at the caudal edge of the tip of the TP.
●After negative aspiration, inject 1 to 3 mL of saline to lift the fascia of the erector spinae muscle off the TP.
●Insert the catheter and advance 2 to 5 cm into the ESP, while visualizing the tip of the catheter (image 4).
●Inject 1 to 3 mL of saline through the catheter to confirm correct placement of the catheter tip (movie 3). Use color Doppler if necessary to confirm spread. Adjust catheter position as necessary.
●Remove the needle over the catheter and secure the catheter to the skin.
Infusion drug dose — After injecting a bolus of local anesthetic (LA) as described above for single-injection block, we use 0.2% ropivacaine for continuous block. Optimal dosing regimens have not been determined. The author uses one of the following regimens:
●Ropivacaine 0.2% 8 to 12 mL per hour with or without a patient demand dose of 10 mL, lockout interval 60 minutes
Or
●Ropivacaine 0.2% by programmed intermittent bolus 20 mL every 3 hours, with or without a patient demand bolus of 10 mL, lockout interval 60 minutes [26,27].
SIDE EFFECTS AND COMPLICATIONS — The incidence of complications specific to erector spinae plane (ESP) blocks is unknown, but they are likely rare. In a review of 45 randomized trials involving thoracic ESP blocks (1904 blocks in 1386 patients), no complications were reported [28]. In a single institution retrospective cohort study of 342 patients who underwent bilateral ESP blocks for spine surgery, there was one unilateral pneumothorax after a T12 ESP block, thought to be unrelated to the block, and no other complications reported [29].
Importantly, local anesthetic systemic toxicity (LAST) is possible, particularly because of the high vascularity of the erector spinae muscle, close proximity of the block to the intercostal spaces in the thoracic region, the large area of tissue contact with local anesthetic (LA), and the high volumes used for the block. Thus, the author adds epinephrine to the block solution to reduce systemic absorption. There are case reports of LAST from low thoracic and lumbar ESP blocks [30,31]. LAST is discussed in detail separately. (See "Local anesthetic systemic toxicity".)
There are isolated reports of pneumothorax from mid-thoracic blocks and of motor block after low thoracic and lumbar blocks [32-34]. There are also reports of sympathectomy presumably due to paravertebral spread. In one case, a patient developed transient Harlequin syndrome (hemifacial erythema) with upper extremity diaphoresis and concomitant hypotension after a T3 level ESP block [35]. There is also a report of priapism after a lumbar ESP block, thought to be the result of bilateral paravertebral spread.
Complications common to all peripheral nerve blocks (eg, nerve injury, bleeding, LAST, infection) are discussed in detail separately. (See "Overview of peripheral nerve blocks", section on 'Complications'.)
CONTRAINDICATIONS — As the site of injection is distant from major vascular structures, spinal cord, and pleura, there are few contraindications to erector spinae plane (ESP) blocks. The risks of performing this block in patients with coagulopathy or who are receiving anticoagulants or antiplatelet therapy are not established. There are case reports and small series of ESP block in patients with thrombocytopenia, coagulopathy, or receiving antithrombotic therapy, without bleeding complications [36-41], however, there are too few cases to establish safety. The decision to perform an ESP block in a patient with altered hemostasis should be individualized.
Other contraindications are similar to those applicable for any regional analgesia technique (eg, known allergy to local anesthetic (LA), patient refusal, infection at the block site). (See "Overview of peripheral nerve blocks" and "Overview of peripheral nerve blocks", section on 'Contraindications'.)
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".)
SUMMARY AND RECOMMENDATIONS
●Anatomy – The erector spinae plane (ESP) block involves injection of local anesthetic (LA) between the fascia covering the anterior aspect of the erector spinae muscles (ESMs) and the posterior surface of the transverse processes (TPs) of the vertebrae. The ESP block has primarily been used to provide analgesia for thoraco-abdominal procedures as a potentially safer alternative to epidural, or paravertebral techniques, though there are other indications. (See 'Anatomy' above and 'Clinical anatomic correlations' above.)
The best available evidence suggests that the primary mechanism for the effect of ESP block involves spread of LA within the ESP, to the intercostal spaces and paravertebral spaces, to adjacent spinal nerve roots, and dorsal and ventral rami (figure 3). (See 'Clinical anatomic correlations' above.)
●Single injection thoracic block – ESP block is performed with ultrasound guidance as follows, with further explanation above. (See 'Thoracic block' above.)
•For most patients, use a high frequency (10 to 15 MHz) linear array transducer, with the depth set to 3 to 5 cm, placed in a parasagittal orientation.
•Identify the desired block level by counting ribs or TPs. (See 'Performing thoracic block' above.)
•Place the needle tip on the surface of the TP (image 2 and image 5 and movie 1 and figure 6).
•Hydrodissect with 1 to 3 mL of saline, visualizing separation between the anterior fascia of the ESM and the TP (image 3 and figure 4).
•After negative aspiration, inject 20 mL of LA in 5 mL increments, with gentle aspiration between injections, visualizing spread of LA.
●Single injection lumbar block – ESP block is performed with ultrasound guidance as follows, with further explanation above. (See 'Lumbar block' above.)
•For most patients, use a low frequency (2 to 5 MHz) curvilinear transducer, with the depth set to 4 cm, adjusted as necessary.
•Identify the desired block level by counting TPs caudally from T12 or cranially from the sacrum.
•Insert the block needle on the tip of the TP.
•Hydrodissect with 1 to 3 mL of saline, visualizing separation between the anterior fascia of the ESM and the TP (figure 5).
•After negative aspiration, inject 30 to 40 mL of LA in 5 mL increments, with gentle aspiration between injections, visualizing spread of LA.
●Continuous ESP block technique – Continuous block is performed as described for single-injection block, using a Touhy needle with a 19 or 20 gauge catheter inserted through it, or a catheter-over-the needle kit (image 4). (See 'Continuous ESP block' above.)
●Drug choice – We base the choice of LA on the total volume that will be used, aiming to maximize efficacy while minimizing the risk of local anesthetic systemic toxicity. (See 'Local anesthetic choice and dose' above.)
•Single injection unilateral block – 0.5% ropivacaine, bupivacaine, or levobupivacaine with epinephrine 1:200,000.
•Single injection bilateral block – 0.2% ropivacaine, 0.25% bupivacaine or levobupivacaine with epinephrine 1:200,000.
•Continuous block – After injecting a bolus of LA similar to single-injection block, infusion of 0.2% ropivacaine along with patient-controlled demand doses and/or programmed intermittent bolus.
●Side effects and complications – The incidence of complications specific to ESP blocks is unknown, but they are likely rare. The most significant concern is for LA systemic toxicity due to the vascularity of the erector spinae muscle and adjacent spaces, and high volume of LA used for the block. (See 'Side effects and complications' above.)
●Contraindications – There are few contraindications to ESP blocks. The risks of performing this block in patients with coagulopathy or who are receiving anticoagulants or antiplatelet therapy are not established; the decision to perform the block in such patients should be individualized. (See 'Contraindications' above.)
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