To compare the efficacy and duration of action for perineural analgesia with liposomal bupivacaine (LB) versus bupivacaine hydrochloride (BHCl) in a sole-pressure induced model of forelimb lameness in horses.
6 healthy adult research horses.
In 1 randomly assigned forelimb, grade 3/5 lameness was induced by use of a sole-pressure lameness model. Objective lameness (vector sum [VS]) was determined with an inertial sensor system at 0, 1, 6, and 24 hours after lameness induction to evaluate the model. Mechanical nociceptive thresholds (MNTs) and objective lameness (VS and force platform kinetics) were recorded prior to and at 1, 6, 24, 48, and 72 hours after perineural anesthesia of the palmar nerves at the level of the proximal sesamoid bones with LB or BHCl in random order, with a 1-week washout period between crossover treatments. Data analysis was performed with mixed-model ANOVA.
When evaluating the lameness model, there was a decrease in lameness at 24 hours in at least 1 limb of each horse (7/12 limbs); thus, screw length was increased by 1 to 2 mm at each 24-hour interval to maintain lameness. Compared with results at baseline, horses treated with BHCl had significant improvements in median MNT and VS identified at only 1 hour after injection, whereas treatment with LB yielded significantly improved median MNT, VS score, and peak vertical force for up to 24 hours.
In this experimental model of forelimb lameness, LB provided longer analgesia when compared with BHCl and should be further investigated for treatment of pain in horses.
To determine whether palmar digital nerve (PDN) blockade in horses with a combination of dexmedetomidine and mepivacaine would block the response to mechanical force applied to the digit longer than would anesthetizing these nerves with mepivacaine alone or dexmedetomidine alone.
8 mares with no signs of lameness.
In a randomized, crossover, blinded, experimental study, both PDNs of the same forelimb of each horse were anesthetized by perineural injection with either 30 mg mepivacaine alone, 250 µg of dexmedetomidine alone, or 30 mg mepivacaine combined with 250 µg of dexmedetomidine. Each horse received each treatment, and treatments were administered ≥ 2 weeks apart. The mechanical nociceptive threshold was measured at a region between the heel bulbs with the use of a digital force gauge before (baseline) and at 15-minute intervals after treatment.
The mean duration of sensory blockade of the digit was 2-fold longer when a combination of mepivacaine and dexmedetomidine was administered (371 minutes), compared with when mepivacaine alone was administered (186 minutes). Treatment with dexmedetomidine alone did not change the mechanical nociceptive threshold substantially from baseline and resulted in no clinical signs of sedation.
Results indicated that relief from digital pain provided by perineural treatment with mepivacaine for PDN blockade can be extended by adding dexmedetomidine to the injectate.
To determine the accuracy of tidal volume (VT) delivery among 5 different models of large-animal ventilators when tested at various settings for VT delivery, peak inspiratory flow (PIF) rate, and fresh gas flow (FGF) rate.
4 different models of pneumatically powered ventilators and 1 electrically powered piston-driven ventilator.
After a leak flow check, each ventilator was tested 10 times for each experimental setting combination of 5 levels of preset VT, 3 PIF rates, and 4 FGF rates. A thermal mass flow and volume meter was used as the gold-standard method to measure delivered VT. In addition, circuit systems of rubber versus polyvinyl chloride breathing hoses were evaluated with the piston-driven ventilator. Differences between preset and delivered VT (volume error [δVT]) were calculated as a percentage of preset VT, and ANOVA was used to compare results across devices. Pearson correlation coefficient analyses and the coefficient of determination (r) were used to assess potential associations between the δVT and the preset VT, PIF rate, and FGF rate.
For each combination of experimental settings, ventilators had δVT values that ranged from 1.2% to 22.2%. Mean ± SD δVT was 4.8 ± 2.5% for the piston-driven ventilator, compared with 6.6 ± 3.2%, 10.6 ± 2.9%, 13.8 ± 2.97%, and 15.2 ± 2.6% for the 4 pneumatic ventilators. The δVT increased with higher PIF rates (r = 0.69), decreased with higher FGF rates (r = 0.62), and decreased with higher preset VT (r = 0.58).
CONCLUSIONS AND CLINICAL RELEVANCE
Results indicated that the tested ventilators all had δVT but that the extent of each of δVT varied among ventilators. Close monitoring of delivered VT with external flow and volume meters is warranted, particularly when pneumatic ventilators are used or when very precise VT delivery is required.
To investigate the effects of a priming dose of alfaxalone on the total anesthetic induction dose for and cardiorespiratory function of sedated healthy cats.
8 healthy adult cats.
For this crossover study, cats were sedated with dexmedetomidine and methadone administered IM. Cats next received a priming induction dose of alfaxalone (0.25 mg/kg, IV) or saline (0.9% NaCl) solution (0.025 mL/kg, IV) over 60 seconds and then an induction dose of alfaxalone (0.5 mg/kg/min, IV) until orotracheal intubation was achieved. Cardiorespiratory variables were recorded at baseline (immediately prior to priming agent administration), immediately after priming agent administration, after orotracheal intubation, and every 2 minutes until extubation. The total induction dose of alfaxalone was compared between the 2 priming agents.
Mean ± SD total anesthetic induction dose of alfaxalone was significantly lower when cats received a priming dose of alfaxalone (0.98 ± 0.28 mg/kg), compared with when cats received a priming dose of saline solution (1.41 ± 0.17 mg/kg). Mean arterial blood pressure was significantly higher when alfaxalone was used as the priming dose. No cats became apneic or had a hemoglobin oxygen saturation of < 90%. Expired volume per minute was not significantly different between the 2 priming agents.
CONCLUSIONS AND CLINICAL RELEVANCE
Administration of a priming dose of alfaxalone to healthy sedated cats reduced the total dose of alfaxalone needed to achieve orotracheal intubation, maintained mean arterial blood pressure, and did not adversely impact the measured respiratory variables.
To investigate use of a candidate maxillary nerve block in rabbits.
13 healthy New Zealand White rabbits (Oryctolagus cuniculus).
In phase 1, the maxillary nerve block procedure was performed in 7 sedated rabbits with 2 volumes (0.25 and 0.5 mL) of a saline (0.9% NaCl)-tissue marker dye solution (1 injection/side by random assignment). Rabbits were euthanized and dissected; numeric scales were used to rate injection accuracy and extent of staining. In phase 2, the nerve block was performed with articaine hydrochloride-epinephrine solution (0.5 mL) on a randomly assigned side in 6 sedated rabbits, with the contralateral side used as a control. Sensory function of the relevant dermatome was tested in triplicate with an algesiometer 0, 30, and 90 minutes after recovery from sedation. Statistical methods were used to compare results between injection volumes (phase 1) and between treated and control sides (phase 2).
In phase 1, dye was in contact with the targeted nerve after 13 of 14 injections. Accuracy and extent of staining did not differ significantly between volumes. In phase 2, algesiometer-applied force tolerance differed significantly between treated and control sides 30 minutes after recovery from sedation (56 to 145 minutes after the nerve block procedure). No adverse effects were detected in either study phase.
CONCLUSIONS AND CLINICAL RELEVANCE
The described technique for a maxillary nerve block was accurate and effective for desensitization of the relevant dermatome as assessed by algesiometry in healthy rabbits. Additional studies are needed to assess use of this procedure in rabbits of other breeds and its efficacy for clinical use. (Am J Vet Res 2020;81:843-848)
Objective—To determine analgesic effects of intraneural injection of ethyl alcohol or formaldehyde in the palmar digital nerves of horses.
Procedures—Ethyl alcohol was injected in the medial palmar digital nerve of 1 forelimb, and formaldehyde was injected in the contralateral nerve. The lateral palmar digital nerve in 1 forelimb was surgically exposed, but not injected, and the contralateral lateral palmar digital nerve was not treated. For each heel, severity of lameness in response to experimentally induced heel pain (lameness score and peak vertical force), thermal reaction time, and heel skin sensitivity scores were recorded. Heel pain was experimentally induced by advancing a threaded bolt through a custom-made horseshoe to apply pressure to the palmar horned aspect of the hoof. Horses were followed up for 112 days, when a subset of nerves was sampled for histologic analysis.
Results—Alcohol and formaldehyde significantly reduced all measures of heel pain, and analgesia was evident over the 112 days of the study. Pastern circumference was significantly greater for formaldehyde-treated than for alcohol-treated limbs. Histologic evaluation showed preservation of nerve fiber alignment with an intact epineurium, loss of axons, axon degeneration, fibrosis, and inflammation in alcohol-treated and formaldehyde-treated nerves.
Conclusions and Clinical Relevance—Results suggested that intraneural injection of either ethyl alcohol or formaldehyde in the palmar digital nerves of horses resulted in substantial, but partial, heel analgesia that persisted for at least 112 days. No advantage of formaldehyde over alcohol was found, and formaldehyde resulted in greater soft tissue inflammation.
Objective—To evaluate the extent and duration of analgesic effects of tramadol hydrochloride administered epidurally in standing healthy adult cattle.
Animals—5 mixed-breed adult female cattle.
Procedures—1, 2, or 3 mg of tramadol/kg was injected into the first intercoccygeal space of each cow in random order at 1-week intervals. Analgesia, sedation, and ataxia were scored on scales of 0 (no effect) to 3 (complete analgesia or extreme sedation or ataxia) at 5-minute intervals beginning 5 minutes prior to injection and ending 120 minutes after injection. Analgesia was evaluated on the basis of response to pinprick stimuli over 9 caudal regions. Heart rate, respiratory rate, rectal temperature, and rumen motility were assessed 5 minutes before and at predetermined intervals for 120 minutes after tramadol injection.
Results—Analgesia induced via tramadol administration was dose dependent (eg, mean duration of complete analgesia at the perineum was 18 minutes when cows received the 1 mg/kg dose, 60 minutes when cows received the 2 mg/kg dose, and 92 minutes when cows received the 3 mg/kg dose). Slight to mild sedation and ataxia were observed when cows received 2 or 3 mg of tramadol/kg. No significant tramadol-associated changes in heart rate, respiratory rate, rectal temperature, or rumen motility were detected.
Conclusions and Clinical Relevance—Caudal epidural tramadol administration induced analgesia with slight to mild sedation and ataxia in cows. Analgesia in affected regions after administration of 2 or 3 mg of tramadol/kg was considered sufficient to allow common surgical procedures to be performed in standing cattle.
Objective—To evaluate the efficacy and tolerability of oral administration of robenacoxib for treatment of acute pain and inflammation associated with musculoskeletal disorders in cats.
Animals—155 cats requiring relief of signs of pain and inflammation associated with acute musculoskeletal disorders.
Procedures—The study was a multicenter, prospective, randomized, masked, noninferiority field trial. Cats were allocated randomly to 1 of 3 treatment groups: group 1 (1.0 to 2.4 mg of robenacoxib/kg, q 24 h), group 2 (1.0 to 2.4 mg of robenacoxib/kg, q 12 h [daily dosage, 2.0 to 4.8 mg/kg]), and group 3 (ketoprofen [mean dosage, 1 mg/kg, q 24 h]). All cats were administered tablets PO for 5 or 6 days. The primary efficacy endpoint was the investigator global assessment score, which was the sum of scores of signs of pain, inflammation, and mobility assessed in a masked manner by veterinary investigators at baseline, day 2, and day 4 or 5. Cat owners monitored in a nonmasked manner secondary responses by observation of cats’ activity, behavior, appetite, and interactions. Safety was assessed by monitoring adverse events, clinical signs, and hematologic and plasma biochemical variables (before and after treatment).
Results—No significant differences were detected among the 3 treatment groups for any primary or secondary efficacy endpoints or for tolerability variables. Robenacoxib tablets administered once daily were significantly more palatable than ketoprofen tablets.
Conclusions and Clinical Relevance—Robenacoxib tablets administered once daily had noninferior efficacy and tolerability, and superior palatability, compared with the active control drug, ketoprofen, for the treatment of signs of acute pain and inflammation associated with musculoskeletal disorders in cats.