Ultrasound-guided retromammillary injections in dogs: a feasibility, descriptive and anatomical study.

OBJECTIVE: To evaluate the feasibility of an ultrasound-guided technique targeting the medial branches of the dorsal ramus of the spinal nerves (DRSN) by injecting a dye solution at the caudal aspect of the base of lumbar mammillary processes [i.e. the retromammillary (RM) space]. STUDY DESIGN: Feasibility, descriptive, anatomical study. ANIMALS: Eleven canine cadavers. METHODS: Using anatomical dissections, the relationship between the mammillary processes and the branches of the DRSN of the thoracolumbar and lumbar spine was studied in two cadavers. Subsequently, ultrasound-guided RM injections were administered in nine cadavers, randomly assigned to low volume (LV; 0.01 mL kg-1) of a dye solution at multiple points from L3 to L6 on one side, and high volume (HV; 0.4 mL kg-1) at a single L4 point on the contralateral side. Gross anatomical dissections were immediately performed after the injections. The RM injections were feasible if ultrasonographic landmarks were identifiable in at least 80% of cases, and 80% of LV injections showed medial branch staining. A one-sample binomial test was used for testing feasibility. RESULTS: The medial branches emerged shortly after the DRSN exited the intervertebral foramen and traveled towards the caudal aspect of the base of the mammillary process, which served as the target injection point. With LV, 36 out of 36 (100%) injected medial branches were stained, meeting the criteria of feasibility (p < 0.001). The median (range) number of stained medial branches per cadaver were 4 (4-4) and 2 (1-3), with LV and HV, respectively. Although no lateral branches were stained with LV, 1 (0-2) was stained with HV. Neither ventral branch staining nor epidural spread was noted in any cadaver. CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasound-guided RM injections are feasible and allow for selective staining of the medial branch of the DRSN in canine cadavers at the lumbar spine.

Greater ischiatic notch plane versus parasacral block in dogs undergoing pelvic limb surgery: a retrospective noninferiority cohort study on perioperative opioid consumption.

OBJECTIVE: To compare perioperative opioid consumption in dogs undergoing pelvic limb surgeries and receiving a lumbosacral plexus block by combining a lumbar [lateral pre-iliac (LPI)] block with a lumbosacral trunk [i.e. parasacral (PS group) or greater ischiatic notch plane (GIN group)] block. Study design Retrospective, descriptive, exploratory, noninferiority cohort study. METHODS: Medical records of 37 client-owned dogs were analyzed. Intraoperative (primary outcome) and postoperative (24 hours) opioid use, 24 hour cumulative pain scores and prevalence of complications were compared between the two groups. Opioid use was quantified in morphine equivalents (ME, mg kg-1 ). The noninferiority limit for intraoperative opioid consumption was set at 0.05 ME kg-1 hour-1. Demographic data, procedure duration, surgery type and perioperative dexmedetomidine and ketamine use were also collected. A t-test or Wilcoxon rank-sum test, a Fisher's exact test and multivariable linear regression were used. Significance was set at p < 0.05. RESULTS: The GIN and PS groups comprised 17 and 20 dogs, respectively. Total intraoperative ME consumption was 0.17 (0.11-0.21) and 0.22 (0.16-0.30) mg kg-1 hour-1 for the GIN and PS groups, respectively (p = 0.077). The noninferiority analysis adjusted by surgery type and body mass revealed that the mean difference between the groups (GIN - PS) was -0.039 (95% CI -0.11-0.03, p = 0.247) ME mg kg-1 hour-1, indicating that the GIN group was not inferior to the PS group regarding intraoperative ME consumption. Dexmedetomidine and ketamine use, postoperative ME consumption and pain scores were similar between groups. CONCLUSIONS AND CLINICAL RELEVANCE: This retrospective study and preliminary observations support the clinical use of the GIN plane block, demonstrating its noninferiority to the PS block when combined with the LPI block for multimodal perioperative analgesia in dogs undergoing pelvic limb surgeries.

Retrospective comparison between low-volume high-concentration and high-volume low-concentration levobupivacaine for bilateral erector spinae plane block in dogs undergoing hemilaminectomy.

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. STUDY DESIGN: Retrospective observational equivalence trial. ANIMALS: 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. CONCLUSIONSAND CLINICAL RELEVANCE: 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.

Effect of intravenous fentanyl on cough reflex and quality of endotracheal intubation in cats.

OBJECTIVE: To assess the effects of intravenous (IV) fentanyl on cough reflex and quality of endotracheal intubation (ETI) in cats. STUDY DESIGN: Randomized, blinded, negative controlled clinical trial. ANIMALS: A total of 30 client-owned cats undergoing general anaesthesia for diagnostic or surgical procedures. METHODS: Cats were sedated with dexmedetomidine (2 µg kg-1 IV), and 5 minutes later either fentanyl (3 µg kg-1, group F) or saline (group C) was administered IV. After alfaxalone (1.5 mg kg-1 IV) administration and 2% lidocaine application to the larynx, ETI was attempted. If unsuccessful, alfaxalone (1 mg kg-1 IV) was administered and ETI re-attempted. This process was repeated until successful ETI. Sedation scores, total number of ETI attempts, cough reflex, laryngeal response and quality of ETI were scored. Postinduction apnoea was recorded. Heart rate (HR) was continuously recorded and oscillometric arterial blood pressure (ABP) was measured every minute. Changes (Δ) in HR and ABP between pre-intubation and intubation were calculated. Groups were compared using univariate analysis. Statistical significance was set as p < 0.05. RESULTS: The median and 95% confidence interval of alfaxalone dose was 1.5 (1.5-1.5) and 2.5 (1.5-2.5) mg kg-1 in groups F and C, respectively (p = 0.001). The cough reflex was 2.10 (1.10-4.41) times more likely to occur in group C. The overall quality of ETI was superior in group F (p = 0.001), with lower laryngeal response to ETI (p < 0.0001) and ETI attempts (p = 0.045). No differences in HR, ABP and postinduction apnoea were found. CONCLUSIONS AND CLINICAL RELEVANCE: In cats sedated with dexmedetomidine, fentanyl could be considered to reduce the alfaxalone induction dose, cough reflex and laryngeal response to ETI and to improve the overall quality of ETI.

Analgesic efficacy of a bilateral erector spinae plane block versus a fentanyl constant rate infusion in dogs undergoing hemilaminectomy: a retrospective cohort study.

BACKGROUND: Erector spinae plane block (ESPB) is an ultrasound-guided interfascial plane block used to provide analgesia in dogs undergoing hemilaminectomy. The aim of this study is to compare the analgesic efficacy of a bilateral ESPB with a fentanyl constant rate infusion (CRI) in dogs undergoing hemilaminectomy. METHODS: This is a retrospective cohort study. Anaesthetic records of client-owned dogs undergoing hemilaminectomy (June 2019-August 2020), and in which a bilateral ESPB was performed (group ESPB), were retrieved and compared to a cohort of 39 dogs that underwent hemilaminectomy (September 2014 - June 2017) and in which a fentanyl CRI (2 µg/kg bolus followed by 5 µg/kg/hour) was used as a primary intraoperative analgesia (group CRI). The prevalence of dogs in which intraoperative rescue fentanyl boluses were administered, the total dose of rescue fentanyl boluses administered, the postoperative methadone requirement and anaesthetic complications during the first 24 postoperative hours were evaluated. Univariate statistical analysis was used. RESULTS: Group ESPB comprised of 93 dogs. The bilateral ESPB was performed using a median (range) levobupivacaine volume of 1 (0.5-1.7) mL/kg per side, at a concentration of 0.125% (0.12-0.25). At least one rescue fentanyl bolus was administered in 54.8% and in 56.4% of dogs in group ESPB and CRI, respectively (p > 0.99). The number of rescue fentanyl boluses was higher in group CRI (p = 0.006), especially during lumbar hemilaminectomy. Rescue fentanyl boluses were more frequently administered from skin incision to end of vertebral lamina drilling in group CRI (p = 0.001), and from end of vertebral lamina drilling to end of surgery in group ESPB (p = 0.0002). During the first 6 (p = 0.0035) and 6-12 (p = 0.0005) postoperative hours, the number of dogs that required at least one dose of methadone was higher in group CRI. In group ESPB, dogs were more likely to become hypothermic (p = 0.04). One dog, not included in the study, developed sinus arrest after performing a caudal thoracic ESPB. CONCLUSIONS: Under the conditions of this study, a bilateral ESPB was associated with a lower number of rescue fentanyl boluses administered in dogs undergoing hemilaminectomy, especially between skin incision to end of vertebral lamina drilling. Despite ESPB being associated with a reduced opioid consumption during the first 12 hours postoperatively, differences in the postoperative management precluded any firm conclusion regarding its postoperative effect.

Extradural anaesthesia-analgesia in dogs undergoing cholecystectomy: A single centre retrospective study.

Objectives: To assess the effects of extradural anaesthesia-analgesia (EAA) in dogs undergoing cholecystectomy. Materials and methods: Medical records of dogs undergoing cholecystectomy between 2011 and 2019 were retrieved and allocated to two groups depending if analgesia was provided systemically (group SA) or extradurally (EAA). Preoperative data, intraoperative antinociceptive medications, postoperative analgesia, perioperative complications, and food intake were compared. Results: Overall 41 medical records were included in the study: 19 and 22 dogs were allocated to groups SA and EAA, respectively. In group EAA, an extradural catheter was placed preoperatively in 8 dogs; in the remaining, it was placed postoperatively but an extradural injection was performed preoperatively. The extradural catheter tip was between the 4th lumbar and the 10th thoracic vertebrae. Intraoperatively, nociception was more likely to occur in group SA [OR 55.42 (2.97-1,035.06)]. During the first 24 and 48 h postoperatively, more dogs in group SA required methadone [OR 24 (2.81-268.4) and OR 11.56 (2.37-45.06), respectively] and additional analgesic drugs [OR 25 (3.47-281.9) and OR 35.29 (1.86-668.2), respectively] compared to group EAA. Voluntary postoperative food intake was also significantly higher in group EAA. Clinical significance: Compared to systemic analgesia, the use of extradural anaesthesia-analgesia reduced perioperative analgesic requirement and promoted postoperative food intake in dogs undergoing cholecystectomy.

Ultrasound-guided bilateral erector spinae plane block in dogs undergoing sternotomies anaesthetised with propofol-dexmedetomidine continuous infusion.

BACKGROUND: To describe the use of a bilateral thoracic (T5 - T9) ultrasound-guided erector spinae plane block (UG-ESPB) in dogs undergoing sternotomy anaesthetised with propofol and dexmedetomidine continuous infusions. METHODS: Demographic information, perioperative anaesthetic and analgesic drugs, the prevalence of hypotension and nociceptive events, and their treatment, were recorded and analysed. Local anaesthetic injection point, volume and concentration were reported for each dog. In attempt to differentiate somatic nociception from visceral nociception, the surgery was divided into three timeframes: from the skin incision to the thoracic cavity opening; from the latter to the beginning of its closure; from thoracic cavity closure to the end of surgery. RESULTS: Overall, 10 dogs were included and four experienced nociception: somatic nociception was recorded in one dog, whereas visceral nociception was recorded in four dogs. The overall fentanyl consumption to control nociception was 0.3 µg/kg/h. No adverse events associated with the UG-ESPB were reported. CONCLUSION: The bilateral UG-ESPB could be used as a part of a multimodal analgesic technique in dogs undergoing sternotomies. However, more clinical studies are warranted to assess its safety and effects.

Retrospective Preliminary Assessment of Routine Follow-Up Low-Field Magnetic Resonance Imaging in Dogs Presumptively Diagnosed With Discospondylitis.

Background: The usefulness of routine follow-up Magnetic Resonance Imaging (MRI-2) in asymptomatic dogs treated for discospondylitis is unknown. Methods: This cross-sectional retrospective study investigated the features of MRI-2 in a heterogeneous group of dogs treated for discospondylitis, and if these were associated with the presence or absence of clinical signs. After comparing initial MRI (MRI-1) and MRI-2, an observer, blinded to the dog's clinical signs, described the MRI-2 findings. The study population was then divided into symptomatic or asymptomatic at the time of MRI-2. Two separate observers subjectively classified the discospondylitis as active or inactive. Repeatability and interobserver agreement were evaluated. Results: A total of 25 dogs were included. At the time of MRI-2 16 (64%) dogs were asymptomatic and 9 (36%) were symptomatic. Based on MRI-2, 20 (80%) and 18 (72%) out of 25 dogs were considered to have active discospondylitis by the first and second observers, respectively. Interobserver agreement was moderate. No MRI-2 features were associated with the clinical status. The subjective classification of inactive discospondylitis was significantly associated with asymptomatic clinical status, but the classification of active discospondylitis was evenly distributed between groups. Conclusion: This study did not identify a meaningful association between the clinical status of dogs treated for presumptive discospondylitis and MRI-2 results. There were no specific MRI-2 features which were associated with the clinical status.

Evaluation of bilateral maxillary nerve block in dogs undergoing surgery for brachycephalic obstructive airway syndrome.

This retrospective study assessed the effect of an intraoral bilateral maxillary nerve block in dogs undergoing surgery for brachycephalic obstructive airway syndrome (BOAS). Records of dogs that underwent BOAS surgery were retrieved. Cases were assigned to Group B or C if a preoperative bilateral maxillary nerve block was performed or not. Type and dose of local anesthetic, inhalant anesthetic minimum alveolar concentration multiples, intraoperative fentanyl and injectable anesthetic use, prevalence of intraoperative hypotension or bradycardia, and postoperative opioids administration, were compared between groups. Sixty-seven cases met the inclusion criteria: 33 were assigned to Group B and 34 to Group C. In Group C, 18 dogs required intraoperative fentanyl (P = 0.005), and 12 needed injectable anesthetic top-ups (P = 0.006). Hypotension, or bradycardia, were not different between groups. Bilateral maxillary nerve block reduces intraoperative fentanyl and injectable anesthetic requirement in dogs undergoing BOAS surgery.

Évaluation du bloc nerveux maxillaire bilatéral chez les chiens brachycéphales opérés pour un syndrome obstructif des voies respiratoires. Cette étude rétrospective a évalué l'effet d'un bloc nerveux maxillaire intra-oral bilatéral chez des chiens brachycéphales subissant une intervention chirurgicale pour le syndrome obstructif des voies respiratoires (BOAS). Les dossiers des chiens qui ont subi une chirurgie BOAS ont été récupérés. Les cas ont été classés dans le groupe B ou C si un bloc du nerf maxillaire bilatéral préopératoire était réalisé ou non. Le type et la dose d'anesthésique local, les multiples de concentration alvéolaire minimale d'anesthésique par inhalation, l'utilisation peropératoire de fentanyl et d'anesthésiques injectables, la prévalence de l'hypotension ou de la bradycardie peropératoire et l'administration postopératoire d'opioïdes ont été comparés entre les groupes. Soixante-sept cas répondaient aux critères d'inclusion : 33 ont été affectés au groupe B et 34 au groupe C. Dans le groupe C, 18 chiens ont eu besoin de fentanyl peropératoire (P = 0,005) et 12 ont eu besoin de compléments anesthésiques injectables (P = 0,006). L'hypotension ou la bradycardie n'étaient pas différentes entre les groupes. Le bloc nerveux maxillaire bilatéral réduit les besoins peropératoires en fentanyl et en anesthésique injectable chez les chiens subissant une chirurgie BOAS.(Traduit par Dr Serge Messier).

Success Rate and Perioperative Complications of Lumbosacral Extradural Anaesthesia in Dogs Undergoing Total Hip Replacement: A Double-Centre Retrospective Study.

OBJECTIVE: The aim of this study was to retrospectively evaluate the success rate and perioperative complications of lumbosacral extradural anaesthesia in dogs undergoing total hip replacement. STUDY DESIGN: Records of dogs undergoing total hip replacement in which lumbosacral extradural anaesthesia with 0.5% levo- or bupivacaine combined with either morphine or buprenorphine were retrieved. Success rate was defined as intraoperative fentanyl consumption <1 µg/kg/h with no intravenous infusion of other analgesic drugs and no additional morphine/methadone within the first 3 hours from premedication. Prevalence of intraoperative anaesthetic and postoperative surgical complications was calculated. RESULTS: Overall, 206 dogs were included in the study. Success rate was 88.7%. Hypercapnia (75.2%), hypotension (46.1%), hypothermia (27.7%) and regurgitation (6.3%) were recorded during anaesthesia. Within 24 hours post-surgery, urinary retention (17.8%), vomiting/regurgitation/diarrhea (8.2%) and sciatic neurapraxia of the operated limb (5.8%) were recorded. Luxation of the operated hip occurred at 48 and 72 hours after surgery in two dogs and one dog respectively. One dog had cardiopulmonary arrest at 52 hours after surgery. CONCLUSION: While hypercapnia, hypotension and hypothermia might develop intraoperatively, the high success rate and the relatively low prevalence of postoperative surgical complications directly associated with lumbosacral extradural anaesthesia justify its use in dogs undergoing total hip replacement.

Serum C-reactive protein in dogs with paraplegia secondary to acute intervertebral disc extrusion.

BACKGROUND: Apart from the absence of nociception, there is no readily available prognostic test for dogs presenting with paraplegia secondary to acute intervertebral disc extrusion (IVDE). OBJECTIVE: To assess if serum C-reactive protein (CRP) can predict the postoperative outcome in paraplegic dogs undergoing surgery for IVDE and to assess the association between serum CRP and presence/absence of nociception on admission, and serum CRP and presence/absence of intramedullary changes seen on magnetic resonance imaging (MRI). ANIMALS: One hundred dogs that underwent surgery at our hospital between 2018 and 2020 because of acute paraplegia secondary to IVDE and in which serum CRP was measured. METHODS: Retrospective observational cohort study. Dogs were classified as 4 or 5 according to the modified Frankel score (MFS) depending on presence/absence of nociception, respectively. MRI images were reviewed and the T2-weighted hyperintensity: L2 vertebral body length was measured. Postoperative outcome was defined as positive if nociception, ambulation or both returned after decompressive surgery. RESULTS: The median (95% CI) serum CRP was 4 (4-5) and 6 (4-7) mg/L in MSF4 and MSF5, respectively (P = .03). A weak linear relationship (R2  = 0.049, P = .03) was found between CRP and the T2-weighted hyperintensity: L2 vertebral length. Outcome data was available for 85 dogs: CRP was 4 (4-5) and 5 (4-10) mg/L in positive and negative outcome dogs, respectively (P = .32). CONCLUSION AND CLINICAL IMPORTANCE: Serum CRP did not predict outcome after surgery in dogs with paraplegia secondary to IVDE.

Comparison between intravenous lidocaine and fentanyl on cough reflex and sympathetic response during endotracheal intubation in dogs.

OBJECTIVE: To compare the effects of intravenous (IV) lidocaine and fentanyl on the cough reflex and autonomic response during endotracheal intubation in dogs. STUDY DESIGN: Randomized, blinded, superiority clinical trial. ANIMALS: A total of 46 client-owned dogs undergoing magnetic resonance imaging. METHODS: After intramuscular methadone (0.2 mg kg-1), dogs were randomized to be administered either IV lidocaine (2 mg kg-1; group L) or fentanyl (7 µg kg-1; group F). After 5 minutes, alfaxalone was administered until endotracheal intubation was possible (1 mg kg-1 IV over 40 seconds followed by 0.4 mg kg-1 increments to effect). Total dose of alfaxalone was recorded and cough reflex at endotracheal intubation was scored. Heart rate (HR) was continuously recorded, Doppler systolic arterial blood pressure (SAP) was measured every 20 seconds. Vasovagal tonus index (VVTI) and changes (Δ) in HR, SAP and VVTI between pre-intubation and intubation were calculated. Groups were compared using univariate and multivariate analysis. Statistical significance was set as p < 0.05. RESULTS: Group F included 22 dogs and group L 24 dogs. The mean (± standard deviation) alfaxalone dose was 1.1 (± 0.2) and 1.35 (± 0.3) mg kg-1 in groups F and L, respectively (p = 0.0008). At intubation, cough was more likely in group L (odds ratio = 11.3; 95% confidence intervals, 2.1 - 94.2; p = 0.01) and HR increased in 87.5% and 54.5% of groups L and F, respectively (p = 0.02). The median (range) ΔHR between pre-intubation and intubation was higher (13.1%; - 4.3 to + 55.1) in group L (p = 0.0021). Between groups, SAP and VVTI were similar. CONCLUSION AND CLINICAL RELEVANCE: At the stated doses, whilst reducing the alfaxalone dose, fentanyl is superior to lidocaine in suppressing the cough reflex and blunting the increase in HR at endotracheal intubation in dogs premedicated with methadone.

Sevoflurane with opioid or dexmedetomidine infusions in dogs undergoing intracranial surgery: a retrospective observational study.

This study reports the clinical use of two sevoflurane-based anesthetic techniques in dogs undergoing craniectomy. Twenty-one animals undergoing elective rostrotentorial or transfrontal craniectomy for brain tumor excision, anesthetized with sevoflurane, were enrolled in this retrospective, observational study. Anesthetic records were allocated to two groups: Sevo-Op (sevoflurane and short acting opioid infusion): 8 dogs and Sevo-Dex (sevoflurane and dexmedetomidine infusion): 13 dogs. Average mean arterial pressure (MAP), heart rate, end-tidal carbon dioxide, end-tidal sevoflurane and intraoperative infusion rates during surgery were calculated. Presence of intra-operative and post-operative bradycardia, tachycardia, hypotension, hypertension, hypothermia, hyperthermia was recorded. Time to endotracheal extubation, intraoperative occurrence of atrioventricular block, postoperative presence of agitation, seizures, use of labetalol and dexmedetomidine infusion were also recorded. Data from the two groups were compared with Fisher's exact test and unpaired t tests with Welch's correction. Odds ratio (OR) and 95% confidence interval (CI) were calculated for categorical variables. Intra-operatively, MAP was lower in Sevo-Op [85 (± 6.54) vs. 97.69 (± 7.8) mmHg, p = 0.0009]. Time to extubation was longer in Sevo-Dex [37.69 (10-70) vs. 19.63 (10-25), p = 0.0033]. No differences were found for the other intra-operative and post-operative variables investigated. Post-operative hypertension and agitation were the most common complications (11 and 12 out of 21 animals, respectively). These results suggest that the infusion of dexmedetomidine provides similar intra-operative conditions and post-operative course to a short acting opioid infusion during sevoflurane anesthesia in dogs undergoing elective rostrotentorial or transfrontal intracranial surgery.

Peripheral nerve block versus systemic analgesia in dogs undergoing tibial plateau levelling osteotomy: Analgesic efficacy and pharmacoeconomics comparison.

OBJECTIVE: To compare the perioperative effects and pharmacoeconomics of peripheral nerve blocks (PNBs) versus fentanyl target-controlled infusion (fTCI) in dogs undergoing tibial plateau levelling osteotomy (TPLO). STUDY DESIGN: Randomized clinical study. ANIMALS: A total of 39 dogs undergoing unilateral TPLO. METHODS: After acepromazine and methadone, anaesthesia was induced with propofol and maintained with isoflurane. Dogs were allocated to group fTCI [target plasma concentration (TPC) 1 ng mL-1] or group PNB (nerve stimulator-guided femoral-sciatic block using 0.2 and 0.1 mL kg-1 of levobupivacaine 0.5%, respectively). If nociceptive response occurred, isoflurane was increased by 0.1%, and TPC was increased by 0.5 ng mL-1 in group fTCI; a fentanyl bolus (1 µg kg-1) was administered in group PNB. During the first 24 postoperative hours, methadone (0.2 mg kg-1) was administered intramuscularly according to the Short Form Glasgow Composite Pain Scale, or if pain was equal to 5/24 or 4/20 for two consecutive assessments, or if the dog was non-weight bearing. The area under the curve (AUC) of pain scores, cumulative postoperative methadone requirement, food intake and pharmacoeconomic implications were calculated. RESULTS: Incidence of bradycardia (p = 0.025), nociceptive response to surgery (p = 0.041) and AUC of pain scores (p < 0.0001) were greater in group fTCI. Postoperatively, 16/19 (84.2%) and eight/20 (40%) dogs in groups fTCI and PNB, respectively, were given at least one dose of methadone (p = 0.0079). Food intake was greater in group PNB (p = 0.049). Although total cost was not different (p = 0.083), PNB was more cost-effective in dogs weighing >15 kg. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with group fTCI, incidence of bradycardia, nociceptive response to surgery, postoperative pain scores, cumulative methadone requirement were lower, and food intake was greater in group PNB, with an economic advantage in dogs weighing >15 kg.