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Objectives: To evaluate changes in immunological parameters following subcutaneous (SC) and intramuscular (IM) administration of meperidine in horses through quantitative analysis of plasma tryptase, histamine, and IgE levels. Methods: Six adult horses were enrolled in a prospective randomized crossover design. Horses were administered one treatment per day, with a seven day washout period: (a) meperidine 1 mg/kg IM, saline 6 mL SC; (b) saline 6 mL IM, meperidine 1 mg/kg SC; (c) saline 6 mL SC, saline 6 mL IM. Blood samples were obtained for plasmatic histamine (baseline, 5, 10, 15, 30, and 60 min) via LC-MS/MS and plasmatic tryptase (baseline, 15, 30, 60, 120, and 240 min) quantification with enzyme-linked immunoabsorbent assays. Serum immunoglobulin E (IgE) concentrations prior to any meperidine treatment and 7-14 days following the first meperidine treatment were evaluated with enzyme-linked immunoabsorbent assays. Histamine and tryptase concentrations were evaluated with a mixed-effect analysis of variance. The levels of IgE at baseline (before the administration of the first dose of meperidine) were compared with the IgE values at 60 min following the second meperidine administration with the Paired t test. Biopsies of localized injection site reactions from subcutaneous meperidine administration were collected from two horses. Results: No statistically significant elevations from baseline in histamine (p = 0.595), tryptase (p = 0.836), or IgE (p = 0.844) were found in any of the horses in this study. There were no differences between treatment groups. Administration of SC meperidine caused a localized vasculitis and thrombosis with regional edema and hemorrhage. Conclusion: No evidence of anaphylactoid or anaphylactic type reactions occurred following IM or SC meperidine administration.

Background: Neuromuscular block (NMB) during general anaesthesia has an implicit risk of inadvertent residual NMB during recovery. Reversal of NMB is commonly encouraged to decrease this risk, and has historically been performed with neostigmine/atropine, two agents with important cardiac and gastrointestinal side effects. Sugammadex is a new selective relaxant binding agent that can reverse rocuronium‐induced NMB efficiently and without these complications. Recommended doses are possibly cost‐prohibitive. Objectives: To measure the recovery time from rocuronium‐NMB after administration of low‐dose sugammadex, compared with spontaneous recovery. Study design: Nonrandomised in vivo experiments. Methods: Fourteen adult horses undergoing different research procedures were anaesthetised with detomidine and isoflurane. All horses received NMB with rocuronium 0.3 mg/kg IV. Neuromuscular function was measured with acceleromyographic train‐of‐four (TOF) ratio. Recovery occurred spontaneously in five horses weighing (median [range]) 548 (413–594) kg and was enhanced with sugammadex 200 mg (total dose) in nine horses (433 [362–515]) kg. Recovery time from moderate NMB to a TOF ratio 1.0, and total duration of NMB were compared between groups. Cases of recurarisation (decrease in the TOF ratio <0.9 after recovery) were identified within 30 min after sugammadex. Results: The dose of sugammadex was 0.46 (0.39–0.55) mg/kg. The recovery period lasted 21 (17–39) minutes for spontaneous and 4 (3–7) minutes for sugammadex. Total duration of NMB was 58 (41–70) minutes for spontaneous and 36 (21–43) for sugammadex (both p ≤ 0.003). There were no instances of recurarisation. Main limitations: Small sample size. Conclusions: A dose of sugammadex of approximately 0.5 mg/kg substantially shortened the recovery period from rocuronium‐induced NMB from a median of 21 to 4 min, when given at a moderate depth of NMB. No recurarisation was observed within the next 30 min. [ABSTRACT FROM AUTHOR]

Introduction: Understanding the pharmacokinetics and pharmacodynamics of fentanyl in horses is crucial for optimizing pain management strategies in veterinary medicine. Methods: Six adult horses were enrolled in a randomized crossover design. Treatments included: placebo, two 100 mcg/h patches (LDF), four 100 mcg/h patches (MDF), and six 100 mcg/h patches (HDF). Patches were in place for 72 h. Blood was obtained for fentanyl plasma concentration determination, thermal threshold, mechanical threshold, heart rate, respiratory rate, and rectal temperature were obtained prior patch placement and at multiple time points following patch placement for the following 96 h. Fentanyl plasma concentration was determined using LC-MS/MS. Data were analyzed using a generalized mixed effects model. Results: Mean (range) maximum plasma concentration (Cmax), time to Cmax, and area under the curve extrapolated to infinity were 1.39 (0.82-1.82), 2.64 (1.21-4.42), 4.11 (2.78-7.12) ng/ml, 12.7 (8.0-16.0), 12.7 (8.0-16.0), 12 (8.0-16.0) h, 42.37 (27.59-55.56), 77.24 (45.62-115.06), 120.34 (100.66-150.55) h ng/ml for LDF, MDF, and HDF, respectively. There was no significant effect of treatment or time on thermal threshold, mechanical threshold, respiratory rate, or temperature (p > 0.063). There was no significant effect of treatment on heart rate (p = 0.364). There was a significant effect of time (p = 0.003) on heart rate with overall heart rates being less than baseline at 64 h. Conclusions: Fentanyl administered via transdermal patch is well absorbed and well tolerated but does not result in an anti-nociceptive effect as measured by thermal and mechanical threshold at the doses studied. [ABSTRACT FROM AUTHOR]

OBJECTIVE To evaluate the effects of rocuronium and sugammadex on the patient state index (PSI) in dogs anesthetized with propofol. ANIMALS 6 intact healthy male Beagles. PROCEDURES Anesthesia was induced with and maintained on a propofol infusion. The estimated plasma propofol concentration (ePC) was recorded. Baseline PSI and train-of-four ratio (TOFR) readings were collected for 2 minutes in stable general anesthesia. Neuromuscular blockade (NMB) was induced with 0.6 mg/kg, IV, rocuronium, and full NMB was confirmed with a TOFR of 0. After 5 minutes, the neuromuscular function was restored with 4 mg/kg sugammadex, IV (reversal), and monitored for 5 minutes. Throughout the data collection, ePC, PSI, and TOFR were recorded every 15 seconds and compared with mixed-effect ANOVA. RESULTS Baseline ePC, PSI, and TOFR were 3.63 ± 0.38, 41 ± 6, and 0.97 ± 0.08 µg/mL, respectively. There was no difference between the baseline of ePC and PSI from NMB or reversal. Compared to the baseline, the TOFR decreased to 0 with NMB (P < .001) and returned to 0.96 ± 0.08 (P = .721) on reversal. After 5 minutes, sugammadex fully reversed 5 out of 6 dogs to TOFR > 0.90 and partially reversed 1 animal to TOFR = 0.80. CLINICAL RELEVANCE There was no evidence that NMB with rocuronium and sugammadex-induced reversal interfered with PSI readings under steady-state total intravenous anesthesia with propofol. Further evaluation of PSI is warranted to assess its utility in a clinical population to detect changes in levels of consciousness during NMB. [ABSTRACT FROM AUTHOR]

Progression of unilateral laryngeal paralysis (LP) was quantified in an asymptomatic 4‐year‐old beagle during spontaneous breathing stimulated with inhaled 10% CO2. Laryngeal evaluation was performed sequentially to track progression of LP over an 18‐month period. Videos of the larynx during CO2‐stimulated breathing were obtained under propofol anaesthesia. Maximal inspiratory normalised glottal gap area (NGGA) was determined on each occasion for left and right hemiglottis. Left NGGA was smaller than the right side throughout the period of follow‐up. After 18 months, LP had progressed to such a degree that the left arytenoid was completely paralysed with no movement during inspiration. This case report demonstrates the possibility of early detection of LP, and quantification of progression. Early detection may allow regenerative surgical strategies for LP to maintain glottic area and reduce postoperative complication rates. [ABSTRACT FROM AUTHOR]

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Objectives The objective of this study was to evaluate the cardiovascular effects of low-dose atipamezole administered intravenously to isoflurane-anesthetized cats receiving dexmedetomidine. We hypothesized that atipamezole would increase heart rate (HR) and reduce arterial blood pressure in isoflurane-anesthetized cats receiving dexmedetomidine. Methods Six healthy adult domestic shorthair cats were anesthetized with isoflurane and instrumented for direct arterial pressures and cardiac output (CO) measurements. The cats received a target-controlled infusion of dexmedetomidine (target plasma concentration 10 ng/ml) for 30 mins before administration of atipamezole. Two sequential doses of atipamezole (15 and 30 μg/kg IV) were administered at least 20 mins apart, during dexmedetomidine administration. The effects of dexmedetomidine and each dose of atipamezole on HR, mean arterial blood pressure (MAP), CO and systemic vascular resistance (SVR) were documented. Results Dexmedetomidine reduced the HR by 22%, increased MAP by 78% (both P ⩽0.01), decreased CO by 48% and increased SVR by 58% (both P ⩽0.0003). Administration of atipamezole 15 and 30 μg/kg intravenously increased HR by 8% (P = 0.006) and 4% (P = 0.1), respectively. MAP decreased by 39% and 47%, respectively (both P ⩽0.004). Atipamezole 30 μg/kg returned CO and SVR to baseline values. Conclusions and relevance Low doses of atipamezole (15 and 30 μg/kg) administered intravenously to anesthetized cats decreased arterial blood pressure with only marginal increases in HR. Atipamezole 30 μg/kg restored CO and SVR to baseline values before dexmedetomidine administration. [ABSTRACT FROM AUTHOR]

Background: Equine pain scoring may be affected by the residual effect of anesthetic drugs., Objectives: To compare pain scores in the hours immediately following anesthetic recovery to baseline pre-anesthetic scores in equine patients undergoing surgical and non-surgical procedures., Study Design: Clinical observational study., Methods: Fifty adult horses undergoing anesthesia for surgical or non-surgical procedures were enrolled. Horses underwent pain scoring using the Composite Pain Score (CPS) and Equine Utrecht University Scale for Facial Assessment of Pain (EQUUS-FAP) prior to anesthesia (T0) and following anesthetic recovery to standing, every hour for 5 h (T1-T5). Data were analyzed using a generalized linear mixed effects model. A post-hoc Dunnett's test for multiple comparisons was performed for variables where an effect was detected., Results: Mean (95% confidence interval) CPS scores for T0-T5 were 1.6 (1.2-2.0), 6.8 (6.0-7.6), 5.1 (4.3-5.9), 4.3 (3.4-5.2), 3.7 (2.8-4.6), and 2.8 (2.0-3.6) and EQUUS-FAP scores were 0.6 (0.3-0.9), 3.0 (2.5-3.5), 1.9 (1.6-2.2), 1.1 (0.8-1.4), 0.6 (0.4-0.8), and 0.7 (0.4-1.0), respectively. For the CPS, scores greater than 5, and for the EQUUS-FAP scores greater than 3, are consistent with minor pain. There was no effect of type of procedure (surgical vs non-surgical) on CPS or EQUUS-FAP scores. There was an effect of time with CPS scores significantly greater than baseline at T1-T5 and EQUUS-FAP scores significantly greater than baseline at T1 and T2., Main Limitations: Discomfort caused by hoisting was not quantified and it was difficult to ascertain if this affected the results., Conclusions: Post-anesthetic pain scores may be influenced by the residual effect of anesthetic agents for as long as 5 h and 2 h for the CPS and EQUUS-FAP, respectively., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Reed, Krikorian, Reynolds, Holmes, Branning, Lemons, Barletta, Quandt, Burns, Dantino and Sakai.)

Epidural anesthesia, often used during cesarean surgery, can exacerbate hypotension from general anesthesia and delay discharge due to motor block. Decreasing the local anesthetic dose might reduce those complications. Cases of dogs undergoing cesarean section that were anesthetized without epidural ( n = 29) (control) and dogs with low-dose epidural bupivacaine with fentanyl or buprenorphine ( n = 37) were reviewed. The incidence of hypotension was equal between groups. Intraoperative opioids were administered more to control (93%) than to treated dogs (18%; P < 0.0001). Epidural bupivacaine 0.0625-0.125% combined with an opioid reduced the use of intraoperative opioids and did not exacerbate arterial hypotension during cesarean section in anesthetized dogs., (Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.)