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.

Locoregional anaesthetic techniques are invaluable for providing multimodal analgesia for painful surgical procedures. This prospective, randomised study describes a nerve stimulator-guided brachial plexus blockade (BPB) in rabbits undergoing orthopaedic surgery in comparison to systemic lidocaine. Premedication was provided with intramuscular (IM) medetomidine, fentanyl, and midazolam. Anaesthesia was induced (propofol IV) and maintained with isoflurane. Nine rabbits received a lidocaine BPB (2%; 0.3 mL kg-1), and eight received a lidocaine constant rate infusion (CRI) (2 mg kg-1 IV, followed by 100 µg kg-1 min-1). Rescue analgesia was provided with fentanyl IV. Carprofen was administered at the end of the surgery. Postoperative pain was determined using the Rabbit Grimace Scale (RGS) and a composite pain scale. Buprenorphine was administered according to the pain score for two hours after extubation. Rabbits were filmed during the first two hours to measure distance travelled and behaviours. Food intake and faeces output were compared. Every rabbit in CRI required intraoperative rescue analgesia compared to none in BPB. However, rabbits in both groups had similar pain scores, and there was no difference in the administration of postoperative analgesia. There were no significant differences in food intake or faeces production over 18 h, and no significant differences in distance travelled or behaviours examined during the first two hours. BPB seems superior for intraoperative analgesia. Postoperatively, both groups were comparable.

The objective of our study was to compare the efficacy of sciatic and saphenous ultrasound nerve blocks with and without US-guided obturator nerve block in dogs undergoing tibial-plateau-levelling-osteotomy (TPLO) surgery. This study was developed in two phases: identification of an ultrasound window in the inguinal region for obturator nerve block and utilization of it in dogs undergoing TPLO. Dogs were assigned randomly to one of two groups: one received the three blocks with 0.5% ropivacaine (ON group) and the second one (NoON group) with NaCl instead of ropivacaine for the obturator block. In phase 1, the obturator nerve was visible between the pectineus and the abductor muscles and was approached using an in-plane technique. It was possible to use the ultrasound window for phase two. The number of dogs that received at least one bolus of intraoperative rescue analgesia in the NoON group (12/15 dogs) was significantly higher (p = 0.003) in comparison with the ON group (4/15). An ultrasound window to block the obturator nerve in the inguinal compartment with an in-plane technique was found. The use of this approach could produce adequate analgesia with less motor function impairment in dogs for TPLO surgery.

To evaluate the sensory and motor effects promoted by a combined sciatic and femoral nerve block in calves using two approaches. Six calves were used, in a crossover study. Ultrasound combined with neurostimulation, was used to perform the following block combinations: the proximal approach (PA), which consisted of the association of the parasacral approach (sciatic nerve block) and ventral to the ilium approach (femoral nerve block); distal approach (DA) consisted of the association of a lateral approach to the pelvic limb approach (sciatic nerve block), and an inguinal approach, underneath the femoral trigone (femoral nerve block). Pressure algometry and motor function of the limb where evaluated. Mechanical nociceptive threshold (MNT) increase, and ataxia duration means were 9.5 ± 0.7 kg and 10.4 ± 3.9 hr for PA and 10.4 ± 3.9 kg and 12.7 ± 1.9 hr for DA, respectively with no significant difference. There was no significant difference between MNT elevation time and the duration of ataxia using the same approach. The DA treatment showed significant MNT elevation in 72% of the tested regions, while the PA treatment showed an elevation in 100% regions tested. Topographic approaches closer to where the spinal nerves emerge produced a larger desensitised area.

BACKGROUND: Dexmedetomidine is a highly selective alpha-2 receptor agonist without any effect on the GABA receptor. It provides an excellent sedative and analgesic profile with few side effects. We report our experience with dexmedetomidine use during orthopaedic surgery under locoregional anaesthesia to ensure adequate sedation and optimal postoperative pain control.
METHODS: In this retrospective analysis, we included 128 patients who underwent orthopaedic surgery between January 2019 and December 2021. All patients received the same local anaesthetic dose of 20 ml of ropivacaine 0.375% + mepivacaine 0.5% for axillary and supraclavicular block and 35 ml of ropivacaine 0.375% + mepivacaine 0.5% for triple nerve block (femoral, obturator and sciatic nerve). The cohort was divided into two groups based on sedation drugs used during surgery (dexmedetomidine, or group D, vs midazolam, or group M). All patients received postoperative 24-h analgesia consisting of 60 mg of ketorolac, 200 mg of tramadol and 4 mg of ondansetron. The primary outcome measured how many patients in the two groups required an analgesic rescue dose of pethidine and the time to first pethidine administration. To reduce confounding, we included patients in two groups with non-statistically different demo-anamnestic parameters and who received the same dose of intraoperative local anaesthetic and postoperative analgesia.
RESULTS: The number of patients in group D who did not require a rescue dose of analgesia was significantly greater than in group M (49 vs 11, p < 0.001). Time-to-first postoperative opioid administration did not show a fundamental difference between the two groups under examination (523.75 ± 131.55 min vs 564 ± 117.84 min). Total opioid consumption was higher in the M group than in the D group (3529.8 ± 30.36 μg vs 1864.8 ± 31.59 μg, p 0.075), with a mean opioid consumption significantly higher in the M group than in the D group (26.26 ± 42.8 μg vs 69.21 ± 46.1 μg, p < 0.001): D group received 62.06% less opioid than M group.
CONCLUSIONS: The continuous infusion of dexmedetomidine during orthopaedic surgery performed under locoregional anaesthesia has been shown to increase the analgesic effect of local anaesthetics and reduce the consumption of major opioids in the postoperative period. Dexmedetomidine offers a unique ability to supply sedation and analgesia without respiratory depression, having a wide safety margin and an excellent sedative capacity. It does not increase the rate of postoperative complications.

This randomised, prospective, masked clinical trial evaluated the postoperative analgesic efficacy of an ultrasound-guided transversus abdominis plane block (TAPB) with bupivacaine in cats undergoing ovariohysterectomy.
Thirty-two healthy adult female cats undergoing elective ovariohysterectomy were randomised to undergo TAPB with bupivacaine (treatment group [TG], n = 16) vs placebo (control group [CG], n = 16) in addition to preoperative analgesia with buprenorphine (0.02 mg/kg IM). All patients received a general anaesthetic and, before surgical incision, a bilateral two-point (subcostal and lateral-longitudinal) TAPB was performed using 1 ml/kg bupivacaine 0.25% (0.25 ml/kg/point) or saline. Each cat was assessed by a blinded investigator before premedication (0 h) and at 1, 2, 3, 4, 8, 10 and 24 h postoperatively using the UNESP-Botucatu Feline Pain Scale - short form. Buprenorphine (0.02 mg/kg IV) and meloxicam (0.2 mg/kg SC) were administered when pain scores were ⩾4/12. Ten hours postoperatively, meloxicam was administered to cats that did not receive rescue analgesia. Statistical analysis included Student\'s t-tests, Wilcoxon tests and χ2 tests, and a linear mixed model with Bonferroni corrections (P <0.05).
Of the 32 cats enrolled, three in the CG were excluded from the analysis. The prevalence of rescue analgesia was significantly higher in the CG (n = 13/13) than in the TG (n = 3/16; P <0.001). Only one cat in the CG required rescue analgesia twice. Pain scores were significantly higher in the CG compared with the TG at 2, 4 and 8 h postoperatively. Mean ± SD pain scores were significantly higher in the CG, but not in the TG, at 2 (2.1 ± 1.9), 3 (1.9 ± 1.6), 4 (3.0 ± 1.4) and 8 h postoperatively (4.7 ± 0.6) than at 0 h (0.1 ± 0.3).
A bilateral ultrasound-guided two-point TAPB with bupivacaine in combination with systemic buprenorphine provided superior postoperative analgesia than buprenorphine alone in cats undergoing ovariohysterectomy.

UNASSIGNED: The erector spinae plane (ESP) block consists of an interfascial injection of local anaesthetic between the erector spinae muscle group and the transverse processes of the thoracic vertebrae. This block targets the dorsal rami of the thoracic spinal nerves to desensitise the cutaneous area near the dorsal midline, the paraspinal muscles, the dorsal vertebral laminae and the facet joints. The purpose of this case series is to describe the perioperative analgesic effect and complications of ultrasound-guided ESP block with bupivacaine in three cats undergoing spinal surgery. Only one cardiovascular response was recorded in this case series. Just one cat received intraoperative rescue analgesia. Cats 1 and 2 recorded just one high pain score in the first 24 h postoperatively, and cat 3 recorded three high pain scores. The total amount of methadone given in the 24 h postoperatively was 0.6 mg/kg in cat 1, 0.9 mg/kg in cat 2 and 0.8 mg/kg in cat 3. All three cats suffered mild and transient intraoperative complications, which were easily addressed. There were no postoperative complications.
UNASSIGNED: This case series documents a novel locoregional anaesthesia technique as an alternative to traditional systemic analgesia. The technique is part of a multimodal analgesia approach for spinal surgery in cats. Perioperative analgesic effect and complications presented in this case series are evaluated and discussed.

OBJECTIVE: To retrospectively compare the efficacy and duration of effect of three commonly used locoregional blocks in dogs undergoing pelvic limb orthopaedic surgery.
METHODS: Retrospective clinical study.
METHODS: A total of 236 dogs that underwent pelvic limb surgery and were administered a locoregional technique.
METHODS: A total of 236 hospital records were reviewed and 230 included in statistical analysis. Dogs were grouped as following: electrostimulation-guided pre-iliac femoral and sciatic nerve block (group PFS, n = 70); ultrasound-guided saphenous and sciatic nerve block (group SS, n = 76); or lumbosacral epidural (group EPI, n = 84). In group EPI, bupivacaine 0.5% or ropivacaine 0.75% was used with morphine. Dogs were pain scored (short form of the Glasgow Composite Measure Pain Scale) hourly following recovery from anaesthesia. Analysed data included: time to first postoperative dose of methadone, pain score at that time, intraoperative rescue analgesia, intraoperative hypotension and ability to walk and urinate overnight. Separate analyses were performed including all pelvic limb surgeries and including only elective stifle surgeries. Kruskal-Wallis and Mann-Whitney tests were performed. A p value < 0.05 was considered significant. The median (range) is reported.
RESULTS: For all pelvic limb surgeries, the time to first postoperative methadone was 530 (110-1337), 440 (140-1030) and 466 (135-1094) minutes in groups EPI, PFS and SS, respectively, and was not significantly different. Postoperatively, 10/84, 15/70 and 12/76 dogs in groups EPI, PFS and SS, respectively, did not require methadone (nonsignificant). Significantly fewer dogs in group EPI (18%) required intraoperative rescue analgesia compared with group SS (38%), but not compared with PFS (30%). Significantly more dogs in group EPI had hypotension intraoperatively (30%) and urinary retention postoperatively (62%).
CONCLUSIONS: Intraoperative analgesia may be superior with EPI than SS for some surgeries of the pelvic limb, but not for stifle surgeries. All three techniques provided similar requirement for postoperative analgesia, but EPI caused higher incidence of intraoperative hypotension and postopertive urinary retention.

OBJECTIVE: To develop an ultrasound-guided dorsal approach to the brachial plexus and to investigate the nerve distribution and staining of a dyed injectate in common kestrel (Falco tinnunculus) cadavers.
METHODS: Prospective, cadaver study.
METHODS: A group of three common kestrel cadavers (six wings).
METHODS: All cadavers were fresh-frozen at -20 °C and thawed for 10 hours at room temperature before the study. The cadavers were placed in sternal recumbency and their wings were abducted. A 8-13 MHz linear-array transducer was placed over the scapulohumeral joint, at the centre of a triangle formed by the scapula and the humerus. The brachial plexus was identified between the scapulohumeralis muscle and the pectoralis major muscle, as hypoechoic structures lying just cranially to the axillary vessels. After ultrasound-guided brachial plexus identification, a 22 gauge, 50 mm insulated needle was advanced in-plane using ultrasound visualization. A volume of 0.5 mL kg-1 of a 3:1 (2% lidocaine:methylene blue) solution was injected. Following cadaver dissection, the pattern of the spread was assessed, and the extent of nerve staining was measured with a calliper and deemed adequate if more than 0.6 cm of the nerve staining was achieved.
RESULTS: The brachial plexus was clearly identified in all wings with the dorsal approach. After dye injection, all the branches of the brachial plexus defined as nerves 1-5 (N1, N2, N3, N4 and N5) were completely stained in five (83%) and partially stained in one (17%) of the six wings.
CONCLUSIONS: The ultrasound-guided dorsal approach allows a clear visualization of the brachial plexus structure. The injection of 0.5 mL kg-1of a lidocaine/dye solution produced complete nerve staining in most cases. Further in vivo studies are mandatory to confirm the clinical efficacy of this locoregional anaesthesia technique in common kestrels (Falco tinnunculus).

This study aimed to describe the prominent landmarks for an in-plane ultrasound-guided lateral approach to an axillary RUMM block in cats and document the anatomical distribution of injected solution in cadavers.
Eleven mixed breed, frozen-thawed cat cadavers were used. The ultrasound probe was placed on the lateral aspect of the forelimb. A spinal needle was used to inject either methylene blue 5 mg/ml or permanent tissue dye 1:10 within the focal clustering point of the radial (R), ulna (U), median (M) and musculocutaneous (Mc) nerves. The block was approached from either a cranial or caudal direction. Specimens were immediately dissected. A successful block was defined as ⩾20 mm of continuous stain on all nerves (R, U, M and Mc), a partial block as one or more nerves stained ⩾20 mm continuously and a negative block failed to stain any nerve ⩾20 mm.
The cranial approach stained the R 8/9, U 6/9, M 6/9 and Mc 8/9 nerves successfully, while the caudal approach stained the R 7/9, U 8/9, M 7/9 and Mc 5/9 nerves successfully. There were no statistical differences on staining rates between approaches or limbs used.
The lateral approach to an axillary RUMM block is feasible in cats and may be a useful alternative to current approaches used for brachial and antebrachial desensitisation. Both cranial and caudal approaches produced similar results; however, further research in live animals will determine the clinical applicability.