Erector Spinae Plane Block (ESPB)

a powerful single-injection trunk block that provides extensive hemithorax and hemiabdominal analgesia

• A truncal inter-fascial plane block with improved safety versus traditional epidural, paravertebral and intercostal blocks; and improved posterior anesthesia versus serratus anterior block.

QUICK SUMMARY:

This block uses a single injection in the erector spinae plane (ESP) to anesthetize multiple vertebral levels of spinal nerves where they branch into dorsal and ventral rami.

• An ultrasound probe is placed on the back in cephalocaudal orientation approximately 3cm from midline at the desired vertebral level and the thoracic vertebral transverse process (TP) is identified on ultrasound.

• A block needle directed via in-plane ultrasound guidance to the posterior surface of the TP.

• This places the needle tip in the cephalocaudal-oriented ESP which lies between the erector spinae muscles (superficial) and the TPs (deep).

• After test aspirations and test injections, approximately 30 mL of LA is slowly injected in the ESP, distending the ESP and lifting the erector spinae muscles off the transverse processes as in the clip below.

The ESP acts as a “leaky gutter” when injected with LA.

• LA initially flows cephalocaudal in the ESP “gutter” posterior to the TPs spreading LA to multiple vertebral levels from the injection point and anesthetizing the dorsal rami. (Fig 1A)

• LA then “leaks” anteriorly, anesthetizing the intercostal nerves at their ventral rami origin. (Fig 1B)

What we love about the Erector:

• extensive, reliable hemi-truncal analgesia - ~3 vertebral levels above and 4 levels below injection point (Fig 2)
• safety - needle path is in chest wall, outside thoracic cage, and away from pleura, spinal cord, and deep vessels. The needletip is visible throughout procedure. The broad transverse processes shield deeper structures.
• the TPs provide large targets for sonographic identification and needle guidance
• patient can be positioned prone, lateral ducubitus, or seated; depending on patient and operator preference
• rapid performance - needling time typically less than 5 minutes

Erector is GREAT for hemithorax/hemiabdominal anagesia:

• extensive chest wall trauma
• posterior rib fractures
• thoracic or abdomnial acute herpes zoster or post herpetic neuralgia
• vertebral compression fracture
• acute appendicitis! (after CT confirmation and surgery consult)

Erector is NOT great for:

• surgical-grade anesthesia of lateral or anterior thorax/abominal wall (i.e. using as sole anethetic for painful chest/abd wall procedures such as abscess drainage). It provides analgesia in this region, but unlikely surgical grade anesthesia.

How it's done:

Positioning

Expose the posterior thorax by placing the patient prone, in lateral decubitus, or leaning forward in a seated position. For the prone position, stand at the head of the bed with the ultrasound system on either side of the bed at the level of the patient's thighs. For the lateral decubitus position (with patient lying on their unaffected side), sit at the side of the bed facing the patient's back with the ultrasound system on the opposite side of the bed (anterior to the patient). For the seated position, seat the patient on the edge of the bed leaning forward onto a side table in a position similar to the seated lumbar puncture position. Stand behind the patient with the ultrasound system located on the opposite side of the bed anterior to the patient. For all positions, elevate the bed to a level where the needle, probe, and ultrasound screen can all be viewed in direct line-of-site with minimal head movement.

Identifying the optimal location for block placement

The substantial LA spread associated with this block allows for flexibility in block placement location. For rib fractures, target the TP that approximately coincides with the area the patient finds most painful. For acute herpes zoster, target the TP just above the rash so the needle does not pass through skin compromised by blisters.

Survey scan

Key bony structures (spinous process, TP, and rib) can be differentiated by their shapes and relative depths as the transducer is moved laterally from midline. At the targeted vertebral level, place a high-frequency linear transducer or lower frequency curvilinear probe in cephalocaudal orientation over the midline of the back to identify the vertebral spinous process. (Figure 3A, Figure 3B). Keeping the probe oriented cephalocaudal, slide the probe approximately 3cm laterally towards the side to be blocked, identifying the TP injection target (Figure 3C). To confirm TP identification, slide the probe beyond the target laterally, passing the probe over the costotransverse junction to the rib. The posterior rib adjacent to the costotransverse junction is both lateral and deep to the TP (Figure 3D). By sliding back and forth over the costotransverse junction, the differentiation between the TP and rib will be clear. The TP will be more superficial, blunter, and wider; the rib will be deeper, rounder, and thinner.

An alternative approach that we have been favoring since publication: start the survey scan far laterally on the posterior rib (near the posterior axillary line) then slowly scan medially until the TP appears. Scanning this direction (from far lateral towards the midline) allows for clear identification of rib while moving medially, making the abrupt appearance of the TP very distinct on the ultrasound image. "Scan Direction" arrow below shows this survery scan direction

Injection

With the transducer fixed over the targeted TP, identify a block needle insertion site aligned with the long axis of the ultrasound beam and approximately 1-2 cm away from the probe. (Figure 4A) The insertion site can be cephalad or caudad to the probe, as the TP can be approached from either direction. After sterile prep, place a LA skin wheal at the insertion site using a 25-27g needle. Then insert a block needle (for this block a standard 20g 3.5 in [90 mm] Quincke tip LP needle works well) through the skin wheal and advance the needle at a 30-45 degree angle towards the ultrasound beam. The transducer needs to be held firmly in a fixed position over the target and the operators focus should be on carefully aligning the needle with the transducer (focus on the hands) during the first 1-2 cm of insertion. After initial insertion of 1-2 cm stop further needle advance and make slight transducer and needle adjustments (keeping the TP in view) until the needle tip is visible on ultrasound (focus switchs to the ultrasound screen). Keeping the needle tip in view, continue advancing with in-plane ultrasound guidance to the posterior surface of the targeted TP. The operator will feel firm resistance upon contacting the TP (land gently -- the periosteum is sensitive). Once the needle tip is in the ESP below the erector spinae muscle, we recommend alternating aspiration (to confirm lack of inadvertent vascular puncture) with injection of small aliquots of LA or NS. Anechoic fluid should be seen separating the erector spinae muscle from the TP, confirming spread within the ESP. As with other plane blocks, using up to 10 mls of NS to gently hydrodissect open the ESP space and confirm location prior to switching to LA can be useful. Once satisfied with the needle position, gradually inject LA until a total of 30 mLs is deposited within the plane (Figure 4B). In our experience, total needling time is usually less than 5 minutes and trunk/abdominal anesthesia develops within 30 minutes