The objective of this study was to evaluate the feasibility and efficacy of the ultrasound-guided thoracolumbar erector spinae plane (TL-ESP) block in standing horses. A total of 24 injections (n = 12) were performed at the L1 level using either 0.1 mL/kg of saline solution (SS group) or 2% lidocaine (LID group). The block feasibility was assessed based on needle visualization and injection time, while efficacy was evaluated through craniocaudal and dorsoventral (DV) spread using the pinprick technique over 270 min. Desensitization was observed at least once in 100% of horses in the LID group and in 75% in the SS group (p = 0.001). However, in the SS group, desensitization was primarily limited to the Th18 metamer at the 2 cm DV position, with a shorter duration compared to the LID group. The block onset occurred at 22.5 (11.25–60) min in the LID group and at 5 (5–30) min in the SS group (p = 0.069). The number of affected metamers was significantly higher in the LID group (2 [1–3]) compared to the SS group (1 [1–2.25], p = 0.014). At the 2 cm DV point, the end of the block effect occurred at 135 (120–210) min in the LID group and at 60 (3.75–60) min in the SS group (p = 0.001). Needle visualization was excellent in 95.8% of cases, and the mean injection time was 2.5 (2–3) min. These findings confirm that the TL-ESP block is a feasible technique in standing horses. However, its effect is predominantly localized to dorsal dermatomes with a limited ventral spread. Future studies evaluating larger volumes and multiple injection sites are warranted to enhance its clinical applicability.

Acetaminophen is increasingly used in multimodal analgesia protocols for dogs, yet its pharmacokinetics (PK) and analgesic efficacy following repeated dosing remain underexplored. This study evaluated the PK, postoperative analgesic effects, pharmacodynamics (PD), and safety of intravenous acetaminophen in dogs undergoing laparoscopic ovariohysterectomy. In a randomized, blinded trial, two doses of acetaminophen (10 and 20 mg/kg IV every 8 h for 24 h) were compared to buprenorphine (20 μg/kg IV every 8 h). The first dose was administered at extubation. Pain was assessed using the Glasgow Composite Measure Pain Scale-Short Form (CMPS-SF) and mechanical nociceptive thresholds during 24 h. A nonlinear mixed-effects model was used to characterize drug disposition, identify plasma analgesic concentration thresholds, and describe pain score evolution over time. Haematological, hepatic, and renal parameters were measured before and 24 h after treatment. Fifty-nine dogs were included. Both acetaminophen doses provided analgesia comparable to buprenorphine. CMPS-SF scores mostly remained between 0 and 2. PK was best described by a two-compartment model, with peak concentrations of 11.49 (7.89 %) and 19.78 (5.18 %) μg/mL and the lower concentrations of 0.11 (71.73 %) and 0.24 (62.06 %) μg/mL for 10 and 20 mg/kg, respectively. The PD model demonstrated sustained analgesia over time. Greyhounds exhibited higher pain scores at several time points, suggesting breed-specific differences in pain sensitivity and drug disposition. No adverse effects were observed. These findings support the use of acetaminophen as a safe and effective analgesic for postoperative pain management in dogs, with the potential need for individualized protocols based on breed-specific responses.

Recovery from general anaesthesia is risky in horses. Alpha₂-agonist administration after anaesthesia enhances the quality of recovery but may prolong this phase. Recovery time and quality were investigated after medetomidine administration at the end of general anaesthesia in a prospective, randomised, masked and clinical study. Horses underwent medetomidine–isoflurane partial intravenous anaesthesia. Medetomidine (0.5 or 1 µg/kg) IV was administered just after isoflurane was discontinued. The duration of different recovery phases and the number of attempts were recorded. A composite scale (from 1—excellent to 6—accident) was used for quality assessment. Mann—Whitney U-test was performed (p < 0.05). Twenty-seven horses per group were included. Results for 0.5 and 1 µg/kg groups were as follows: lateral recumbency time: 35 (24–45) and 43 (35–55) minutes; sternal recumbency time: 6 (3–15) and 5 (2–15) minutes; total recovery time: 47 (40–59) and 49 (42–62) minutes; number of attempts to sternal: 1 (1–1) and 1 (1–2) and to standing: 1 (1–3) and 1 (1–2); and, quality: 2 (1–2) and 2 (1–2), respectively. No significant differences between the groups were found. Medetomidine 0.5 µg/kg dose did not decrease the recovery time but maintained the recovery quality.

Background: Tidal volume (VT) during mechanical ventilation in dogs varies considerably between individuals, but the contributions of airway dead space (VDaw) and alveolar tidal volume (VTalv) to this variability remain unclear. Methods: In this prospective, observational, exploratory study, 95 anesthetized dogs receiving volume-controlled ventilation with VT initially set at 15 mL kg⁻¹ of predicted ideal body weight (IBW) were analyzed. When necessary, TV was titrated within a predetermined quasi-static driving pressure range (i.e., >6 and <10 cmH₂O) to maintain normocapnia. Volumetric capnography was used to measure expired tidal volume (VTe), VDaw, and VTalv. The relative contributions of VDaw and VTalv to VTe variability were assessed across body sizes and breeds, including brachycephalic dogs. In addition, the effects of ideal body weight (IBW) on the variability of VTe, VDaw, and VTalv were evaluated. Results: VTalv accounted for a greater proportion of the observed VTe variability than VDaw, indicating that interindividual differences in VTalv were the primary determinant of VT variability. Brachycephalic dogs exhibited smaller VDaw but similar VTalv compared with non-brachycephalic dogs. Ideal body weight was correlated with proportionally higher VDaw and lower VTalv. Recumbency was not correlated with the observed variability in VT components. Conclusions: VTalv was the main determinant of VT variability among anesthetized dogs, and the brachycephalic breeds studied exhibited smaller VDaw but similar VTalv compared with non-brachycephalic breeds. These findings highlight the importance of considering VTalv and breed-specific airway anatomy when individualizing ventilatory settings.

Standing sedation in horses provides immobilization and analgesia for surgery while avoiding the high risks of general anesthesia. Ketamine at subanesthetic doses may enhance sedation and reduce xylazine requirements, but evidence in clinical settings is limited. In a randomized blinded trial, we evaluated whether adding a low-dose ketamine infusion could reduce the xylazine dose required for effective sedation during standing ventriculocordectomy and laryngoplasty. Fifty-one horses were randomly assigned to sedation with xylazine alone (SX group) or xylazine plus ketamine (KX group) in a continuous rate infusion. The ketamine group received ketamine (0.25 mg/kg intravenous (IV) bolus followed by 0.5 mg/kg/h infusion), while xylazine was administered in both groups via a titrated infusion to effect according to the Ghent Sedation Algorithm. Sedation depth, ataxia, surgical condition scores, and cardiorespiratory parameters were recorded. Data are presented as median (25th–75th percentiles) and estimated effect with 95% confidence intervals (CI). Statistical significance was set at p < 0.05 and at 95% CIs excluding zero. The addition of ketamine did not significantly reduce xylazine requirements (0.9 (0.7–1.3) vs. 0.8 (0.5–1.1) mg/kg/h for SX and KX, respectively; p = 0.139). However, horses receiving ketamine (KX) achieved deeper sedation (Estimate = 2.74; 95% CI: 0.95 to 4.63) with no differences in ataxia or surgical conditions. Cardiorespiratory variables remained stable in both groups, and no adverse events occurred. In conclusion, adding a subanesthetic ketamine infusion improved sedation depth without adverse effects but did not significantly reduce the xylazine requirement.