Spread of local anesthetic after thoracic erector spinae and thoracic paravertebral block in patients with multiple posterolateral rib fractures

Sir,

Several regional anesthesia techniques are used in clinical practice to offer pain relief in patients who sustain multiple posterolateral ribs fractures (MPLRF) as a result of polytrauma. Each technique has its advantages and offers reasonable pain relief, reduces the worsening of acute lung injury as a result of hypoventilation, facilitates chest physiotherapy, and reduces the overall cost of treatment. Continuous thoracic paravertebral block (ThPVB) and thoracic epidural analgesia (TEA) has been used for years successfully in managing such situations.[1,2] TEA is contraindicated in patients with suspected spinal cord injury under evaluation and coagulopathies. ThPVBs do not act in the presence of hemorrhage in thoracic paravertebral space (PVS) secondary to posterior rib fractures. An alternative recently incorporated in pain relief for rib fracture management is ultrasound (US)-guided serratus anterior plane block (SAPB).[3] However, SAPB is restricted for lateral rib fractures. Recently, the thoracic erector spinae plane block (ESPB) has been used successfully in managing pain due to multiple rib fractures.[4] ESPBs act particularly on dorsal rami, and, in the case of MPLRFs, single injection followed by catheter infusion acts at multiple levels. Here, we have described using eight images the pattern of contrast spread of LA during a continuous ThPVB and a continuous ESPB at the thoracic level. Informed consent was obtained from patients prior to administering the block, for contrast-enhanced computed tomography (CT) studies and for using the images in a scientific journal. A waiver was offered for CT contrast studies. Continuous blocks were performed in four patients (two ThPVB and two thoracic ESPB) who sustained MPLRF. There were no major bone fractures, abdominal or head injury, and had a Glasgow Coma Scale of 15/15 on admission to the intensive care unit. The US-guided ThPVB was performed by the intercostal approach[5] and US-guided ESPB was performed deep to erector spinae muscle (ESM). A linear array, a high-frequency US probe (13-6 MHz, Sonosite Inc.) was used for the blocks.

At 12 h after achieving a visual analog scale (VAS) of less than 4, a CT contrast study was performed by injecting 5 mL of radio-opaque contrast diluted with 0.9% 20 mL normal saline (a volume of 25 mL) through an indwelling catheter in the ESP. Through the paravertebral catheter, 5 mL of radio-opaque contrast diluted with 0.9% 20 mL normal saline (a volume of 25 mL) was injected. The images were reported by a consultant radiologist.

On reviewing CT contrast images of thoracic ESPB patients, the axial section revealed the contrast flow from deep to ESM into the PVS at two levels but no contrast in the epidural space in all planes. The contrast did appear in the PVS in the coronal and the sagittal sections [Figure 1].

Figure 1.

(a) Ultrasound (US)-guided continuous erector spinae plane block. Erector spinae muscle (ESM)—brown outline; Tuohy needle—white broad short arrows; Catheter in erector spinae plane (ESP)—yellow broad short arrows. (b) Coronal image at the level costotransverse junctions; contrast spread from T4 to L4. Contrast spread in ESP—light green); cervicothoracic junction (CTJ)—(dark green arrows); fracture ribs—(red arrows). (c) Contrast in flow between the medial and intermediate ESMs. Medial and lateral ESM—purple; contrast spread from ESP to thoracic paravertebral space (TPVS)—light green; TPVS—light yellow. (d) Volume rendering technique (VRT) scan of erector spinae plane block. Contrast spread in ESP—light green; posterolateral rib fractures—red arrows

In the ThPVB, the spread was visualized in the anterior and posterior epidural space in the axial section in the first patient. In the second patient, in the coronal section, the contrast was lateralized in the epidural space. In both patients, the contrast had traveled across the three thoracic intervertebral foramina in the axial and coronal sections [Figure 2].

Figure 2.

(a) US guided thoracic paravertebral block (TPVB). Trapezius muscle (TPZ)—Trapezius and ESM-brown outline; CTJ—pink; LA—dark blue; TP and rib-light blue, (b)case 1: US-guided paravertebral catheter. Epidural spread from TPVS—dark blue; Epidural catheter in TPVS—white arrows. (c)case 1: Contrast spread after thoracic paravertebral block. Epidural (anterior and posterior spread) from TPVS—light blue arrows; contrast spread along with the pre/para/intercostal spread—green arrows. (d)case 2: lateralization of epidural after ThPVB. Epidural (lateral spread) from TPVS; CTJ—green arrows; thoracic intervertebral foramina—yellow arrows, neuraxial space—yellow arrow

The ESPB is a dorsal rami block. Extensive spread and block can occur as a result of LA spread across the ESP. Cadaveric and radiocontrast studies depict a dorsal and a ventral spread into the PVS.[6,7] In our case series, the spread from the ESPB was in the thoracic PVS in both the patients at the level of T5.

To conclude, the pain relief offered by a thoracic ESPB in a patient with MPLRF is due to the paravertebral spread of LA and an occasional epidural spread. Dense blocks from injections into the thoracic PVS results from blockade of motor, sensory and sympathetic nerves in the PVS and a simultaneous spread into the epidural space.

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Conflicts of interest

There are no conflicts of interest.