Francisco Medina-Bautista

Ultrasound-guided transversus abdominis plane blocks may provide somatic analgesia for equine abdominal procedures, but evidence in adult horses remains limited. This prospective, blinded, randomized, paired study evaluated the feasibility, sensory effects, and motor effects of a two-point transversus abdominis plane block in eight healthy, standing, unsedated mares. Each horse received lidocaine 2% (2 mg/kg in 0.1 mL/kg per injection site) on one side and saline on the contralateral side. Responses to standardized mechanical stimulation were assessed at 21 sensory evaluation points per side for 300 min. The block was completed successfully in all horses without visible discomfort or procedural complications. No desensitization occurred on saline-treated sides. Following lidocaine administration, sensory blockade began at a median of 10 min, peaked at 30 min, and lasted a median of 258 (233–260) minutes. Desensitization was significantly greater at the stifle and intermediate horizontal levels than at the coxal tuberosity level. Transient motor impairment occurred in seven of eight horses and was severe in two. The technique produced multi-metameric desensitization, predominantly in the ventrocaudal flank, but limited dorsal coverage and frequent motor impairment may restrict its clinical application. Further dose optimization and clinical safety and efficacy studies are warranted.

Background: Despite its frequent use in equine clinical practice, scientific data on the use of acetaminophen in horses remain limited. Objective: To map and critically appraise the available evidence on the analgesic use, safety and pharmacokinetics of acetaminophen in horses. Study Design: Structured scoping review. Methods: A comprehensive search was performed in accordance with the PRISMA Extension for Scoping Reviews using the terms ‘(paracetamol OR acetaminophen) AND (pain OR safety OR toxicosis OR pharmacokinetics) AND (horse OR pony OR donkey OR mule)’ across Web of Science, Scopus, and PubMed from database inception to 27 July 2025. Experimental and clinical studies, reviews and case reports evaluating acetaminophen in equids were eligible. Publications without acetaminophen information about analgesia, safety or pharmacokinetics in horses were excluded. Each article was screened and charted according to study design, level of evidence (LoE) (methodological robustness) and thematic domain by two evaluators. Results: Of the initial 45 articles, 27 met eligibility criteria. Ten studies were classified as LoE 1, six as LoE 2, seven as LoE 3, and four as LoE 5. Based on study design and thematic domain, the included publications comprised four categorised as ‘case reports’, seven as ‘narrative reviews’, one as ‘prospective comparative studies’, 11 as ‘pharmacokinetics’, and four as ‘pharmacokinetics and concentration–effect relationship’. Main Limitations: Limited number of clinical studies and heterogeneity of available evidence. Conclusions and Clinical Relevance: This review highlights the growing but still limited evidence on acetaminophen use in horses. While pharmacokinetic data are robust, clinical trials remain scarce and underpowered. Acetaminophen appears promising as part of multimodal analgesia, yet its efficacy as a sole agent and long‐term safety require further investigation before widespread clinical adoption.

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 2O) 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.

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.

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.

An 11‐year‐old, 500 kg, healthy mare was admitted for tenovaginoscopy. A jugular venous catheter was inserted to administer detomidine for diagnostic imaging and for anaesthesia‐related drug administration. The horse was premedicated with intramuscular acepromazine and intravenous flunixin. For sedation, 7.5 mL of a solution, presumed to be xylazine 2%, was drawn up in a syringe and labelled with a sticker. Two minutes after injection of 7.5 mL from xylazine‐labelled syringe, the horse showed severe ataxia and fell. Nystagmus and catatonia appeared while one person sat on its neck, to prevent it from rising. After 8 minutes, the horse could not be kept down and took several uncoordinated attempts to stand, still showing nystagmus and ataxia for several minutes. The xylazine‐labelled syringes were analysed. They contained pure ketamine. This case report should raise awareness about clinical errors, a healthy error culture and use of Morbidity and Mortality Rounds to improve patient and personnel care.