Dexmedetomidine prolongs the duration of action of mepivacaine on anesthesia of the palmar digital nerves of horses

OBJECTIVE 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. ANIMALS 8 mares with no signs of lameness. PROCEDURES 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. RESULTS 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. CLINICAL RELEVANCE 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.

Comparative Multimodal Palliative efficacy of gabapentin and tramadol By Using Two Pain Scoring Systems in Cats Undergoing Ovariohysterectomy

The analgesic efficacy of the gabapentin-tramadol combination was compared with meloxicam-tramadol and tramadol perioperative analgesic regimens in cats brought to the clinic for ovariohysterectomy. Thirty adult cats belonging to comparable demographics (age, body weight), were enrolled into a randomized, blinded study after due consent from their owners into four treatment groups. A Gabapentin-Tramadol group (GT-group, n = 10), Meloxicam-Tramadol group (MT-group, n = 10), and a Tramadol group (T-group, n = 10) were formed. Gabapentin capsules at 50 mg were administered orally 2 hours before surgery while the rest received a placebo dose. Tramadol (2 mg/kg, IM) and meloxicam at (0.2 mg/kg, SC) were injected immediately prior to anesthetic premedication. Anesthetic protocol involved premedication with ketamine and xylazine, while anesthesia was induced using propofol. Inhalant isoflurane anesthesia was used to maintain a surgical plane. GT group scored lower on IVAS as well as CPS than MT group, and T group for up to 8 hours after surgery. The mechanical nociceptive threshold remained higher (98±0) for up to 12 hours postoperatively a nd serum cortisol concentrations remained significantly lower during the 24hr period. The addition of gabapentin to the tramadol regimen significantly improved analgesia and mechanical nociceptive threshold than when used on its own.

Long-Term Evaluation of Poly(lactic acid) (PLA) Implants in a Horse: An Experimental Pilot Study

In horses, there is an increasing interest in developing long-lasting drug formulations, with biopolymers as viable carrier alternatives in addition to their use as scaffolds, suture threads, screws, pins, and plates for orthopedic surgeries. This communication focuses on the prolonged biocompatibility and biodegradation of PLA, prepared by hot pressing at 180 °C. Six samples were implanted subcutaneously on the lateral surface of the neck of one horse. The polymers remained implanted for 24 to 57 weeks. Physical examination, plasma fibrinogen, and the mechanical nociceptive threshold (MNT) were performed. After 24, 28, 34, 38, and 57 weeks, the materials were removed for histochemical analysis using hematoxylin-eosin and scanning electron microscopy (SEM). There were no essential clinical changes. MNT decreased after the implantation procedure, returning to normal after 48 h. A foreign body response was observed by histopathologic evaluation up to 38 weeks. At 57 weeks, no polymer or fibrotic capsules were identified. SEM showed surface roughness suggesting a biodegradation process, with an increase in the median pore diameter. As in the histopathological evaluation, it was not possible to detect the polymer 57 weeks after implantation. PLA showed biocompatible degradation and these findings may contribute to future research in the biomedical area.

Preclinical Evaluation of Polymeric Nanocomposite Containing Pregabalin for Sustained Release as Potential Therapy for Neuropathic Pain

This study offers a novel oral pregabalin (PG)-loaded drug delivery system based on chitosan and hypromellose phthalate-based polymeric nanocomposite in order to treat neuropathic pain (PG-PN). PG-PN has a particle size of 432 ± 20 nm, a polydispersity index of 0.238 ± 0.001, a zeta potential of +19.0 ± 0.9 mV, a pH of 5.7 ± 0.06, and a spherical shape. Thermal and infrared spectroscopy confirmed nanocomposite generation. PG-PN pharmacokinetics was studied after a single oral dose in male Wistar rats. PG-PN showed greater distribution and clearance than free PG. The antinociceptive effect of PG-PN in neuropathic pain rats was tested by using the chronic constriction injury model. The parameter investigated was the mechanical nociceptive threshold measured by the von Frey filaments test; PG-PN showed a longer antinociceptive effect than free PG. The rota-rod and barbiturate sleep induction procedures were used to determine adverse effects; the criteria included motor deficit and sedative effects. PG-PN and free PG had plenty of motors. PG-PN exhibited a less sedative effect than free PG. By prolonging the antinociceptive effect and decreasing the unfavorable effects, polymeric nanocomposites with pregabalin have shown promise in treating neuropathic pain.

Protective Effects of PACAP in a Rat Model of Diabetic Neuropathy

Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide with a widespread occurrence and diverse effects. PACAP has well-documented neuro- and cytoprotective effects, proven in numerous studies. Among others, PACAP is protective in models of diabetes-associated diseases, such as diabetic nephropathy and retinopathy. As the neuropeptide has strong neurotrophic and neuroprotective actions, we aimed at investigating the effects of PACAP in a rat model of streptozotocin-induced diabetic neuropathy, another common complication of diabetes. Rats were treated with PACAP1-38 every second day for 8 weeks starting simultaneously with the streptozotocin injection. Nerve fiber morphology was examined with electron microscopy, chronic neuronal activation in pain processing centers was studied with FosB immunohistochemistry, and functionality was assessed by determining the mechanical nociceptive threshold. PACAP treatment did not alter body weight or blood glucose levels during the 8-week observation period. However, PACAP attenuated the mechanical hyperalgesia, compared to vehicle-treated diabetic animals, and it markedly reduced the morphological signs characteristic for neuropathy: axon–myelin separation, mitochondrial fission, unmyelinated fiber atrophy, and basement membrane thickening of endoneurial vessels. Furthermore, PACAP attenuated the increase in FosB immunoreactivity in the dorsal spinal horn and periaqueductal grey matter. Our results show that PACAP is a promising therapeutic agent in diabetes-associated complications, including diabetic neuropathy.

Effects of horse housing on musculoskeletal system post-exercise recovery

This study examined the effects of two housing systems (control housing and loose housing) on musculoskeletal condition during recovery from race-like exercise in Standardbred horses. The hypothesis was that a loose housing system provides better conditions for musculoskeletal recovery than the control housing. Eight adult geldings (mean age 11 years) were used in a study with a cross-over design, with the control housing (CH) and loose housing (LH) treatments each run for 21 days. The horses had ad libitum access to forage and performed two similar race-like exercise tests (ET), on day 7 and day 14 in each treatment. Blood samples were collected before ET, at finish line, and at 7, 22, and 44 h of recovery and analysed for the muscle enzyme activities of creatine kinase and amino transferase. Before and three days after ET, hind leg fetlock joint region circumference and diameter, joint range of motion in right hock and carpus, mechanical nociceptive threshold in back muscle, and movement asymmetry were recorded. Overall circumference and overall diameter of hind fetlock joint region were lower in LH horses than CH horses (P=0.045 and P=0.017, respectively), but no other differences were observed. In conclusion, a loose housing system did not alter the recovery of musculoskeletal condition other than preventing a post exercise enlargement of the circumference and diameter of the hind fetlock joint region.

179 A Comparison of Local Anesthetic Effectiveness in Reducing Pain Associated with Dehorning in Dairy Calves

Dehorning is performed on a high percentage of dairies in the United States. Concern for animal welfare has led to investigating pain mitigation during dehorning. The objective was to compare the effectiveness of bupivacaine liposome suspension, lidocaine, or lidocaine + meloxicam administered at dehorning. Fifty male Holstein calves, 10–14 weeks of age were enrolled and randomly assigned to 1 of 5 treatment groups: 1) bupivacaine liposome suspension block, oral placebo, cautery dehorn (BUP); 2) lidocaine block, oral placebo, cautery dehorn (LID); 3) lidocaine block, oral meloxicam, cautery dehorn (LID + MEL); 4) saline block, oral placebo, cautery dehorn (CON); and 5) saline block, oral placebo, sham dehorn (SHAM). Biomarkers were collected from 0 to 120 hours post-dehorning and included infrared thermography (IRT), mechanical nociceptive threshold (MNT), and pressure mat gait analysis. Biomarkers were statistically analyzed using repeat measures with the calf being the repeated measure. There were no significant treatment differences for IRT measures. A treatment effect was observed for the mean difference of the right horn bud minus a control point which were -1.21 kgF, -1.41 kgF, -1.56 kgF, -1.65 kgF, and -1.68 kgF for the SHAM, CON, BUP, LID + MEL, and LID groups, respectively (P = 0.004). The BUP group did not differ from CON (P = 0.78) or SHAM (P = 0.07). A treatment effect was observed for gait distance means which were 182.05 cm, 189.69 cm, 195.77 cm, 199.54 cm, and 200.59 cm for the SHAM, BUP, LID + MEL, LID and CON groups, respectively (P = 0.04). The CON group did not differ from BUP, LID, or LID + MEL (P > 0.05) but did differ from SHAM (P = 0.02). These data show that administration of bupivacaine liposome suspension at the time of dehorning was not different than lidocaine or lidocaine + meloxicam.

Mechanical Nociceptive Threshold, Tissue Alterations and Horn Growth in Calves after Injection of Isoeugenol or Clove Oil under the Horn Bud

Disbudding of calves is a common, painful intervention. Due to cytotoxic and anesthetic properties, the injection of clove oil or its component isoeugenol may be less detrimental to animal welfare. We investigated mechanical nociceptive threshold (MNT), possible tissue alterations and horn growth for up to 12 weeks after injection of 1.5 mL clove oil (CLOV), isoeugenol (ISO) or saline (CON) or after hot-iron disbudding (BURN; with local anesthesia and sedation, n = 10/treatment). MNT was measured using von Frey filaments and a pressure algometer at four locations around the horn bud. There was a treatment*time point interaction (linear mixed model, p < 0.05). MNT decreased most strongly and for the longest time for BURN in most calves at least for 3 weeks. For ISO, the decrease was less distinct and most calves’ values returned to baseline after 1–2 weeks. MNT in CLOV was intermediate, with decreased values up to 3 weeks in some animals. 12 weeks after the treatment, horn growth was prevented in about 50% of the horns in CLOV and ISO. Tissue alterations such as swellings of the eyelids often occurred in CLOV, but less so in ISO. Our results suggest that injection of isoeugenol causes less pain and thus seems to be beneficial compared to hot-iron disbudding, while clove oil was not advantageous. Regarding the effectiveness of isoeugenol to prevent horn growth, more studies are needed.