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.

OBJECTIVE: To compare the analgesic effect of a bilateral ultrasound-guided erector spinae plane block (ESPB) in dogs undergoing hemilaminectomy using either a low-volume high-concentration (LV-HC) or a high-volume low-concentration (HV-LC) local anaesthetic solution.
METHODS: Retrospective observational equivalence trial.
METHODS: A total of 391 client-owned dogs undergoing hemilaminectomy.
METHODS: Dogs were assigned to group LV-HC or HV-LC depending on whether 0.2-0.25% levobupivacaine (0.4-0.5 mL kg-1) or 0.125-0.15% levobupivacaine (0.8-1 mL kg-1) was used to perform the ESPB, respectively. The number of dogs in which intraoperative rescue fentanyl boluses were administered, the total dose of fentanyl administered, the overall methadone consumption during the first 24 hours postoperatively and anaesthetic complications were recorded. Univariate and multivariate statistical analyses were performed considering p < 0.05 significant.
RESULTS: A total of 248 and 143 dogs were assigned to groups LV-HC and HV-LC, respectively. In group HV-LC, the number of dogs requiring fentanyl intraoperatively (64.3%) was higher (p = 0.0001) than that in group LV-HC (43.5%). The overall intraoperative fentanyl consumption was higher in group HV-LC between the first skin incision and the end of the lamina drilling (p = 0.028). According to the regression analysis, the group allocation was the best variable to predict the intraoperative fentanyl consumption (p < 0.001). Antimuscarinic drugs were administered more frequently in group LV-HC (p < 0.02). However, the prevalence of hypotension and other pharmacological cardiovascular interventions did not differ between groups. No differences in methadone consumption during the first 24 hours postoperatively were found between the groups.
UNASSIGNED: When performing a bilateral ESPB in dogs undergoing hemilaminectomy, compared with HV-LC, the use of LV-HC local anaesthetic solution reduces the intraoperative fentanyl consumption without affecting the postoperative methadone requirement.

OBJECTIVE: To perform a qualitative evaluation of the analgesic effects of magnesium in domestic animals, including its anaesthetic sparing effects.
METHODS: All database searches were made using PubMed and Google Scholar. Studies published after 1990, evaluating the use of magnesium and reporting information on analgesia, in dogs, cats, horses, cows, goats and sheep were selected (last search in August 2023). A reference check in the selected papers was performed to identify any study which was omitted. The CERQual (Confidence in Evidence from Reviews of Qualitative research) approach was used to assess confidence and analyse the evidence.
RESULTS: A total of 20 studies relevant to the analgesic effects of magnesium in veterinary patients and two reviews were included. All were published after 2006. Of the 20, five studies provided information about analgesia in the postoperative period in dogs with heterogenous results. Magnesium added epidurally increased the duration of the sensory block in several species. Motor block was also observed when added to spinal analgesia. Results regarding volatile agents sparing effect were conflicting. Occasional moderate adverse effects were reported in dogs, such as nausea and vomiting, when administered as a bolus in conscious animals, and hypotension when administered intraperitoneally. Collapse was reported in horses after epidural administration.
CONCLUSIONS: The evidence of an analgesic effect of magnesium in veterinary patients remains scarce considering the paucity and low quality of published data. Further research may be helpful to establish the efficacy and indications of magnesium in multimodal analgesia in animals.

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.

The primary objectives of the study were to analyse the robotic approach and ultrasound-guided paravertebral block compared to thoracoscopic intercostal nerve block after robotic pulmonary lobectomy on postoperative pain and opioids use. The secondary objectives were to analyse and compare patients\' necessity of additional antalgic drugs and patients\' performance during respiratory therapy, following robotic surgery and in the two groups. Consecutively, 52 patients undergoing robotic pulmonary lobectomies were treated either with ropivacaine-based intercostal nerve block or paravertebral block from February 2022 to October 2022. When necessary, morphine was administered at day 1. Acetaminophen was administered as an additional antalgic drug on demand up to 3 g per day. Pain was measured 1 h after the end of the surgical procedure and daily through the pain numeric rating scale (NRS). Morphine administration rate and per day and total additional administrations of acetaminophen were recorded. Pain and opioids administration was measured 1 month after the procedure. Data were analysed in the overall population and in the intercostal nerve block group VS paravertebral block group. Overall, 34.6% of the patients required morphine administration and 51.7% of the patients required at least daily acetaminophen administration up to discharge. At 1 month postoperatively, four patients presented with chronic pain and one still was under opioid medication. At intergroup analysis, the paravertebral block group demonstrated lower NRS at fixed time points (p < 0.0001) and lower morphine consumption (45.7%VS11.8%; p = 0.02). Acetaminophen rescue administration at fixed time points was lower in the paravertebral block group (p < 0.0001) and mobility and dynamic pain resulted in better results (p = 0.03; p = 0.04). At 1 month, no differences were found between study groups. Similarly to other minimally invasive techniques, postoperative pain may arise after robotic pulmonary lobectomy. Paravertebral bloc can help to reduce postoperative pain as well as morphine and antalgic drugs administration and improve early mobilization.

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.

The aim of this randomized, prospective clinical study was to evaluate the efficacy of dexmedetomidine combined with bupivacaine on sciatic and femoral nerve blocks in dogs. Thirty dogs were selected for elective unilateral tibial plateau levelling osteotomy, and each subject was assigned randomly to receive perineural bupivacaine 0.5% (0.1 mL/kg) and intramuscular dexmedetomidine (0.5 μg/kg) in the BDs group, perineural bupivacaine 0.5% (0.1 mL/kg) plus dexmedetomidine (0.5 μg/kg) in the BDloc group, and perineural bupivacaine 0.5% (0.1 mL/kg) plus intramuscular administration of saline solution the in Bupi group. Nerve blocks were guided by electrolocation. The main intraoperative parameters were registered 10 min before the start of surgery (BASE) and during the skin incision (SKIN), the osteotomy (BONE) and the suture (SUTURE). At 2, 4, 6, 8, 10, 15, 20 and 24 h after blocks, the Glasgow Composite Pain scale (GPCs) was used to identify the degree of pain during the postoperative period. Patients with scores ≥5/20 received rescue analgesia and were excluded. Furthermore, heart rate, mean arterial pressure, footstep capacity, reaction to wound touch and femoral and sciatic skin sensitivity were registered. Parametric data were compared at each time point of the study with the one-way ANOVA for repeated measures and Fisher\'s test for yes/no variables analysis (p < 0.05). No subject required intraoperative rescue analgesia. In BDloc group, the GCPs score was <5/20 for all dogs at all times of the study, and 70% of dogs did not need systemic analgesia. In the Bupi and BDs groups, 100% of subjects achieved a score ≥ 5/20 between 8 and 10 h after the blocks, and 100% of subjects showed femoral and sciatic skin sensitivity and required rescue analgesia within 10 h. Our results showed that the addition of dexmedetomidine as an adjuvant to bupivacaine in SF blocks may prolong the sensory block and ensure sufficient analgesia for up to 24 h in dogs undergoing TPLO surgery.