Ultrasound-guided serratus plane block as an effective adjunct to systemic analgesia in four dogs undergoing thoracotomy.

Background: Ultrasound-guided serratus plane block (UGSPB) is a loco-regional anesthesia technique designed to desensitize the thoracic wall. It is a compartmental block, where local anesthetic is delivered to the fascial, inter-muscular plane. Since its original description in humans, two cadaveric veterinary studies, redefining the technique, have been performed. Taking into account the successful use of the UGSPB in human medicine, we employed the veterinary description to perform this block in four dogs undergoing thoracotomy. The case series described below aims to share our experience of the clinical application of this new loco-regional anesthesia technique in dogs. Case Description: Four dogs, with different underlying medical conditions underwent cranial lateral thoracotomy. The analgesia protocol consisted of intravenous methadone and UGSPB performed half an hour before the beginning of the procedure. The cardiovascular system was closely monitored for any signs of nociception. Fentanyl, although available as rescue analgesia, was not required in any of these cases as no signs of nociception were present. Conclusion: To the authors' knowledge, this is the first veterinary clinical report using the UGSPB as a part of a multimodal analgesia protocol in dogs undergoing thoracotomy. Based on this observation, UGSPB has the potential to prevent nociception and reduce the intraoperative opioid requirements in dogs undergoing thoracotomy. A prospective randomized clinical trial is required to confirm these promising results.

Comparison of sedation in dogs: methadone or butorphanol in combination with dexmedetomidine intravenously.

OBJECTIVE: Opioids can be combined with alpha-2-adrenoreceptor agonists to sedate dogs for radiography. The study investigated the sedative effects of methadone or butorphanol in combination with dexmedetomidine in dogs undergoing stifle radiography. STUDY DESIGN: Prospective, blinded, randomized, clinical trial. ANIMALS: A total of 52 healthy dogs requiring sedation for stifle radiography were enrolled. METHODS: Dogs were assessed for body condition [body condition score (BCS)], temperament and pain using the short-form composite measure pain scale (CMPS-SF). Dogs were randomized to be administered methadone 0.2 mg kg-1 (group M) or butorphanol 0.2 mg kg-1 (group B) in combination with dexmedetomidine 2 µg kg-1 intravenously (IV). Sedation was assessed using a numerical descriptive score, from 0 (no sedation) to 11 (greatest sedation), before administration and at 5, 10, 15 and 20 minutes by one blinded assessor. Onset signs of sedation, pulse rate and respiratory rates were recorded. Positioning for radiography was attempted at 5 minutes. If positioning was not possible at 10 minutes, dexmedetomidine 2 µg kg-1 was administered IV, with the dog recorded as failed sedation and withdrawn from further analysis. Following normality testing, data were assessed using Student t test, Mann-Whitney test, two-way analysis of variance and Fisher's exact test for failed sedations. Results are reported as mean ± standard deviation. Statistical significance was set at p < 0.05. RESULTS: Groups were similar for sex, age, weight, BCS, temperament and CMPS-SF. The onset of sedation was faster in group B than in group M (p = 0.048). Sedation scores were higher in group B at 10 minutes compared to group M (p = 0.003). Failed sedation occurred in 12 dogs in group M and two in group B (p = 0.002). Pulse rates were lower in group B at 5 and 10 minutes (p = 0.002). CONCLUSION AND CLINICAL RELEVANCE: IV butorphanol provides more effective sedation at 10 minutes than methadone, in combination with dexmedetomidine.

Comparison of intramuscular butorphanol and buprenorphine combined with dexmedetomidine for sedation in cats.

Objectives The objective of this study was to compare the sedative effect of butorphanol-dexmedetomidine with buprenorphine-dexmedetomidine following intramuscular (IM) administration in cats. Methods Using a prospective, randomised, blinded design, 40 client-owned adult cats were assigned to receive IM dexmedetomidine (10 µg/kg) combined with either butorphanol (0.4 mg/kg) ('BUT' group) or buprenorphine (20 µg/kg) ('BUP' group). Sedation was scored using a previously published multidimensional composite scale before administration (T0) and 5, 10, 15 and 20 mins afterwards (T5, T10, T15 and T20, respectively). Alfaxalone (1.5 mg/kg) was administered IM at T20 if the cat was not deemed adequately sedated to place an intravenous catheter. Adverse events were recorded. Friedman two-way ANOVA analysed sedation scores within groups. Mann-Whitney Rank Sum test compared sedation scores between groups; Fisher's exact test analysed the frequency of alfaxalone administration and adverse events. P <0.05 was considered statistically significant. Results Sedation scores between groups were similar at baseline, but at T5, T10, T15 and T20 scores were higher in the BUT group ( P <0.01). Within both groups, sedation scores changed over time and the highest sedation scores were reached at T10. Requirement for additional sedation was similar between groups: two cats in the BUT group and five cats in the BUP group. One cat and 11 cats vomited ( P = 0.002) in the BUT and BUP groups, respectively. No other adverse events were recorded. Conclusions and relevance At these doses, IM buprenorphine-dexmedetomidine provides inferior sedation and a higher incidence of vomiting than butorphanol-dexmedetomidine in cats. Butorphanol-dexmedetomidine may be preferred for feline sedation, especially where vomiting is contraindicated.