Description of an Ultrasound-Guided Erector Spinae Plane Block and Comparison to a Blind Proximal Paravertebral Nerve Block in Cows: A Cadaveric Study

Abstract

The proximal paravertebral nerve block is commonly used to provide anaesthesia to the flank during standing surgical procedures in adult cattle. It has been reported that additional anaesthetic infiltration may be necessary to provide complete anaesthesia. In humans as well as animal species, another technique-the ultrasound (US)-guided erector spinae plane block (ESPB)-has been described. The goal of the present study was to develop and investigate an US-guided ESPB in comparison to a blind proximal paravertebral nerve block (PPNB) in cow cadavers. In 10 cadaver specimens, injections of methylene blue-lidocaine (1:1) were performed at the level of T13, L1 and L2 vertebras, on one side doing an ESPB block and, on the other side, a PPNB. Five cadavers were injected with high (40 mL per injection for PPNB and 20 mL for ESPB) and five with low (20 and 15 mL, respectively) volumes of injectate. For the ESPB, the ultrasound probe was oriented craniocaudally, and the ventral-cranial aspect of the articular processes (T13, L1 and L2) was targeted for injection. The dye spreading was evaluated by dissection. The landmarks for US-guided injection were easily visualized; however, injections were accidentally performed at T12, T13 and L1. Nevertheless, L2 was stained in 60% of ESPBs. Epidural spreading was observed with both techniques and all volumes. Viscera puncture was reported in two PPNBs. The ESPB resulted in similar nerve staining compared to the PPNB while using a lower volume of injectate. Even better staining is expected with a T13-L2 instead of a T12-L1 ESPB approach. Further studies are warranted to evaluate the clinical efficacy.

Keywords: cattle; erector spinae plane block; paravertebral anaesthesia; regional anaesthesia; spinal nerves.

Figure 1

Superposed photographs from the left lateral view showing part of the skeleton, the trunk and limbs. The targeted spinal nerves for the proximal paravertebral nerve block are T13, L1 and L2, which are drawn in yellow. The flank is delimited cranially by the 13th rib (A), caudally by the Ala ossis ilii (B) and dorsally by the transverse processes of the lumbar vertebrae (C). Credits to C.A.R.

Figure 2

Cranial view at the intervertebral junction L1–L2: anatomical organisation of the spinal nerve L1 and area of innervation of the different Rami. Credits to C.A.R.

Figure 3

Position of the ultrasound probe parasagittally from dorsal midline (yellow dashed line).

Figure 4

(a) Needle (A) placement cranial to the articular process of the second lumbar (L2) vertebra (B). (b) Ultrasound image showing the needle (A) cranially to the articular process of the vertebra L2 (B).

Figure 5

Dissection left side: the ultrasound-guided erector spinae plane block (ESPB) technique and right side: the proximal paravertebral nerve block (PPNB) blind technique. (a) Dorsal view: spread of the dye along the nerves (arrows). (b) Ventral view: spread of dye along the nerves (arrows).

Figure 6

Staining of the dorsal roots of spinal nerves from T13 to L2 (arrows) on the right side (from blind proximal paravertebral nerve block (PPNB) low-volume (20 mL) group) after displacement of the Medulla spinalis. Note the staining of the Dura mater.