The ultrasound-guided erector spinae plane (ESP) block is a locoregional anaesthesia technique primarily used to provide analgesia to anatomical structures innervated by the dorsal branches (DB) of the spinal nerves. However, several clinical studies in humans have demonstrated its analgesic efficacy in areas innervated by the ventral branches (VB) of the spinal nerves, such as thoracic and abdominal surgeries. In veterinary medicine, the ESP block has been extensively studied in dogs at the thoracic, thoracolumbar, and lumbar regions. In contrast, only one cadaveric study, focused on the lumbar area, has been published in cats. The objective of this research was to evaluate the feasibility of an ultrasound-guided longitudinal approach to the thoracic ESP block in feline cadavers. A total of 15 feline cadavers were used for this purpose: 3 for the anatomical study, and 12 for the ultrasound-guided approach (24 sides). The needle tip was ultrasound-guided to the transverse process of the seventh thoracic vertebra (T7), and a mixture of methylene blue (0.5%), lidocaine, and iopromide (0.4 mL kg⁻¹) was administered. A computed tomography (CT) scan was subsequently performed to assess the distribution of the contrast medium, followed by anatomical dissection to evaluate the distribution of dye. Contrast medium was observed within the erector spinae musculature, between T1 and T13 (24 out of 24 sides), with a distribution spanning 8 (4–11) vertebral bodies. Anatomical dissection showed staining of two (0–9) DB, mainly T6, T7, and T8, and 0.5 (0–1) VB, with T7 the only one stained. Additionally, staining of the sympathetic trunk was observed in 7 out of 24 sides. Based on these findings, this technique may be indicated in surgeries involving the epaxial region. However, further studies are needed to confirm its effectiveness in providing analgesia to structures associated with the VB of the spinal nerves and the sympathetic trunk.

The serratus plane block is an ultrasound-guided anaesthetic technique that aims to provide analgesia to the lateral thoracic wall cranial to the 8th rib. This block can be performed in a superficial (between the latissimus dorsi and the serratus ventralis thoracis (SVT) muscles) or deep plane (between the intercostales externi and the SVT muscles). This study aimed to assess the distribution and nerve staining of a mixture of 0.4 mL kg⁻¹ of methylene blue and iopromide 50:50 performing a deep serratus plane (DSP) block at the level of the 5th rib. We hypothesise that this technique would be feasible and could stain the rami cutanei laterales (RCL) of the intercostales nerves cranial to the 8th rib in cat cadavers. This study was divided into two phases. Phase 1 consisted of an anatomical study of the thoracic wall (2 cadavers). Phase 2 consisted of the ultrasound-guided injection of the aforementioned mixture and the assessment of its distribution by computed tomography and anatomical dissection (12 cadavers). Contrast media spread a median of 5.5 (2.5–7.5) intercostal spaces. The dye stained a median of 3 (0–5) RCL, affecting RCL 2 (17.39%), RCL 3 (57.17%), RCL 4 (78.26%), RCL 5 (91.30%), RCL 6 (78.26%), and RCL 7 (8.70%) within the DSP. Occasionally, the rami dorsales laterales and the thoracicus longus nerve were stained. Based on these findings, the DSP block performed with a volume of 0.4 mL kg⁻¹ of an anaesthetic could provide analgesia in the area innervated from T4 to T6.

The rectus sheath block is an ultrasound-guided anaesthetic technique which aims to provide analgesia to the abdominal midline. This study aimed to assess the distribution of 0.4 mL kg⁻¹ of a mixture of methylene blue and iopromide injected into each hemiabdomen in the internal rectus sheath in cat cadavers. We hypothesise that this technique would be feasible and would cover the rami ventrales of the last thoracic and the first lumbar spinal nerves. The study was divided into two phases. Phase 1 aimed to study the anatomical structures of the ventral abdominal wall (four cats were dissected). Phase 2 (ten cadavers) consisted of an ultrasound-guided injection of the mixture mentioned above and the assessment of its distribution by computed tomography and anatomical dissection. The results showed the staining of the cranioventral abdominal wall with a craniocaudal spread of four (three to eight) vertebral bodies. Methylene blue stained three (one to four) rami ventrales, affecting T10 (60%), T11 (100%), T12 (90%), T13 (50%) and L1 (5%). Based on these results, it could be stated that this technique could supply anaesthesia to the midline of the abdominal midline cranial to the umbilicus in clinical patients, but it may not be able to provide anaesthesia to the middle and caudal midline abdominal region.

The ultrasound-guided erector spinae plane (ESP) block is a locoregional anesthesia technique primarily aimed at providing analgesia to structures innervated by the dorsal branches of the spinal nerves (DBSN). While this block has been widely studied in dogs, evidence in cats is limited, and only a few cadaveric studies have addressed the lumbar region. The aim of this study was to compare the injectate distribution and staining of the DBSN following ultrasound-guided lumbar ESP blocks performed using either a longitudinal or transverse approach in feline cadavers. A total of 15 feline cadavers were included, with 3 used for anatomical dissection and 12 for ultrasound-guided injections (24 sides). Injections were performed at the level of the third lumbar vertebra (L3) using a mixture of methylene blue, lidocaine, and iopromide (0.4 mL kg⁻¹ per side). Needle placement and injectate spread were guided and confirmed by ultrasonography, followed by computed tomography (CT) and anatomical dissection to evaluate contrast and dye distribution. CT images revealed longitudinal spread of the contrast in all injections, with the transverse approach producing exclusively longitudinal distribution and the longitudinal approach showing occasional ventral spread beneath the transverse processes (25% of sides). Dissections demonstrated staining of a median of 2 DBSN per side for both approaches, predominantly L2–L3, with rare partial staining of ventral branches (VBSN) observed only with the longitudinal approach. The sympathetic trunk was not stained in any injection. No statistically significant differences were observed between approaches, except for L1 DBSN staining, which was identified significantly more frequently with the transverse approach (p = 0.033). These findings indicate that ultrasound-guided lumbar ESP block is anatomically feasible in feline cadavers and that both longitudinal and transverse approaches can result in injectate distribution to the DBSN.