Blind versus ultrasound-guided maxillary nerve block in donkeys

Ultrasound-guided and 'blind' sciatic nerve injection techniques: Comparison in rat cadavers

OBJECTIVE

To compare the success rate and extent of sciatic nerve staining with a bupivacaine-dye solution using two injection techniques: 'blind' or ultrasound-guided approach.

STUDY DESIGN

Prospective, experimental, randomized, cadaveric study.

ANIMALS

Adult female Wistar rat cadavers [n = 24, mass 352 g (323-374)].

METHODS

Each sciatic nerve was randomly allocated to one of two groups: 'blind' (group B) or ultrasound-guided approach (group US) to injection. Following injection of bupivacaine-dye solution (0.1 mL), gross anatomical dissection was performed to visualize nerve staining, categorizing it as either positive or negative. The length of nerve staining was then measured and visual inspection conducted to identify potential nerve damage. Fisher's exact test was used to compare positive or negative nerve staining, and the Wilcoxon signed rank test used to compare the length of nerve staining between groups.

RESULTS

In group B, the bupivacaine-dye solution stained 16/24 sciatic nerves (67% success). In group US, staining was successfully observed in all 24 nerves (100% success, p < 0.004). The length of nerve staining [median (interquartile range)] was 2 (2-3) mm in group B and 5 (4-6) mm in group US (p < 0.001). One sciatic nerve in group B had injectate distributed over 16 mm, suggestive of an intraneural injection. No signs of laceration or nerve damage were visible under 6× magnification in either group.

CONCLUSIONS AND CLINICAL RELEVANCE

The ultrasound-guided approach for sciatic nerve injection demonstrated a higher success rate with superior injectate distribution when compared with the 'blind' approach. Ultrasound guidance is recommended over a 'blind' approach for sciatic nerve block in rats when possible.

Ultrasound-guided sciatic nerve block in Wistar rat cadavers: Relevant anatomy and injection distribution

OBJECTIVE

To investigate the feasibility of an ultrasound-guided sciatic nerve block by describing the sonoanatomy and comparing the distribution of two volumes of bupivacaine dye solution for nerve staining.

STUDY DESIGN

Randomized, experimental, assessor-blinded cadaveric study.

ANIMALS

A total of 40 adult female Wistar rat cadavers.

METHODS

After studying the sonoanatomy of the sciatic nerve and adjacent structures using a high-resolution linear transducer (19-5 MHz), rat cadavers were randomly divided into two groups that were administered either 0.1 mL (group 0.1) or 0.2 mL (group 0.2) of bupivacaine dye solution per nerve, delivered via an in-plane technique. The extent of nerve staining was subsequently evaluated following dissection. Statistical analysis consisted of assessing data distribution using the Shapiro-Wilk test, followed by paired t-tests for continuous data, Mann-Whitney U test and McNemar's test for categorical data. Statistical significance was defined as p < 0.05.

RESULTS

The sciatic nerve was identified bilaterally as a double ellipsoid-shaped image, surrounded by a hyperechoic fascia separating the biceps femoris from the adductor muscle. The hypoechoic structure formed by the bupivacaine dye solution around the nerve was effectively visualized using ultrasound imaging. Sciatic nerve staining was successfully achieved in all pelvic limbs, with dye spread of 4.82 ± 1.55 mm and 5.47 ± 2.18 mm in groups 0.1 and 0.2, respectively (p = 0.128).

CONCLUSIONS AND CLINICAL RELEVANCE

This study achieved a detailed understanding of the sonoanatomy of the sciatic nerve and its adjacent structures, highlighting the feasibility of the ultrasound-guided technique for injection in Wistar rats. Furthermore, the results show a comparable distribution of dye solution in both groups. Use of the ultrasound-guided sciatic nerve block technique in rats not only exhibits substantial potential for regional anesthesia but also opens avenues for translational studies.

Blind Versus Ultrasound-Guided Low-Volume Perineural Injection of Tibial and Fibular Nerves in Equine Cadaver Limbs

Techniques for local anesthesia of the tibial (TN) and superficial and deep fibular nerves (FNs) in horses are well established. Ultrasound-guided perineural blocks can identify the nerve location, reduce the anesthetic volume needed and avoid needle misplacement. The aim of this research was to compare the success of blind perineural injection technique (BLIND) to ultrasound-guided technique (USG). Fifteen equine cadaver hindlimbs were divided into two groups. Perineural injection of the TN and FNs was performed using a mixed solution of radiopaque contrast, saline and food dye. BLIND (n = 8) used 15 mL for the TN and 10 mL for each fibular nerve. USG (n = 7) used 3 mL for the TN and 1.5 mL for each fibular nerve. The limbs were radiographed immediately after injections and sectioned transversally to evaluate the diffusion and presence of the injectate adjacent to the TN and FNs. The presence of dye immediately adjacent to the nerves was considered a successful perineural injection. No statistically significant difference was observed between groups for success. Distal diffusion of injectate following perineural injection of the TN was significantly less for USG compared to BLIND. Proximal, distal and medial diffusion of injectate following perineural injection of FNs was significantly less for USG compared to BLIND. Low-volume USG results in less diffusion but similar success compared to BLIND leaving it up to veterinarian preference when selecting a technique.

Efficacy of greater auricular and auriculotemporal nerve blocks performed in rabbits

OBJECTIVE

To evaluate the efficacy, duration and safety of greater auricular and auriculotemporal nerve blocks in rabbits.

STUDY DESIGN

Prospective, randomized, crossover, experimental study.

ANIMALS

A total of 11 healthy adult Dutch-belted rabbits.

METHODS

The rabbits underwent general anesthesia and injections of the greater auricular and auriculotemporal nerves using either bupivacaine (0.3 mL kg^-1, 0.5%) or the same volume of saline. After anesthesia, the efficacy and duration of nerve blocks were assessed using analgesiometry forceps on the pinna and cotton-tipped applicators within the vertical ear canal. Rabbits were monitored for abnormal carriage of the ear and auriculopalpebral nerve block of the ipsilateral eye. Body weight, food intake, fecal output and fecal pellet diameter were measured daily for 6 days after the nerve blocks were performed and compared with baseline to assess short-term effects.

RESULTS

The greater auricular nerve was successfully blocked in 12/16 (75%) ears for mean ± standard deviation duration of 88 ± 52 minutes. In successfully blocked ears, altered ear position was noted in five/16 (31%) cases. The auriculotemporal nerve was blocked in one/16 ears for 120 minutes. The auriculopalpebral nerve was inadvertently blocked in three/16 ears. Food intake and fecal output decreased significantly during the treatment day but returned to pretreatment values after 24 hours. There was no change in body weight or fecal pellet diameter for either treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

The results suggest that duration of the greater auricular nerve block with 0.5% bupivacaine was short-lived in the live rabbit. Auriculotemporal nerve block was only achieved in one ear; therefore, further studies are warranted to evaluate the contribution of these blocks in the pain management of rabbits undergoing auricular surgery.

Anesthesia, Sedation, and Pain Management of Donkeys and Mules

The number of donkeys in the world may not be increasing but awareness of their use and concern for welfare and pain recognition and treatment are receiving increasing veterinary interest. Therefore, accurate information about anesthesia and analgesia in donkeys and mules is important to more equine practitioners. This review highlights the current knowledge on various anesthetic and analgesic approaches in donkey and mules. The authors emphasize that there is still much information that is not available about donkeys and mules; in many circumstances, the clinician must use available equine information to treat the patient, while monitoring for differences in response.