Luiz César Pereira Santos

Effects of intraarticular ropivacaine and morphine on lipopolysaccharide-induced synovitis in horses

OBJECTIVE To compare the intraarticular (IA) analgesic effects of ropivacaine and morphine in horses with experimentally induced synovitis. STUDY DESIGN Randomized, blinded cross-over design. ANIMALS Twelve healthy mixed breed horses between 8-15 years old. METHODS Synovitis was induced in the left radio-carpal joint with an injection of lipopolysaccharide (Escherichia coli 055:B5). Six hours later, the horses were treated with an IA injection of 40 mg of ropivacaine (ROPI), 40 mg of morphine (MOR), 20 mg of ropivacaine added to 20 mg of morphine in saline (RM) or 4 mL of saline (SAL), as control. Analgesia was measured subjectively using a numerical rating scale, a simple descriptive scale, pain upon maximal flexion of the carpus and by the range of motion exhibited by the affected joint. Data are reported as mean +/- SD and were analyzed using anova. Blood and synovial data were analyzed by split plots in time with units (treatments: SAL, ROPI, MOR and RM) and subunits (times: T0-24), in a completely randomized design with six replicates. Mean comparisons were made by Tukeys test; differences were considered significant at p < 0.05. RESULTS Ropivacaine had a clinical analgesic effect with a relative short duration ( approximately 2.5 to 3.5 hours). Morphine had a slower onset of action than ROPI, but a stronger analgesic effect of longer duration. The RM showed an earlier onset of action than MOR and had a strong analgesic effect for the 24-hour post-injection period. All treatments caused a significant decrease in total nucleated cells compared with the control, 24 hours after administration. CONCLUSIONS AND CLINICAL RELEVANCE Morphine alone or in combination with ropivacaine produced a strong analgesic effect of prolonged duration, which may offer pain relief for acute synovitis for at least 24 hours.

Sedative and cardiorespiratory effects of dexmedetomidine and buprenorphine administered to cats via oral transmucosal or intramuscular routes

OBJECTIVE To determine if buprenorphine plus dexmedetomidine administered via the oral transmucosal route produces sufficient sedation in cats so that students can insert intravenous catheters. STUDY DESIGN Prospective, randomized, blinded, clinical trial. ANIMALS Eighty-seven shelter-owned female cats aged 4-48 months, weighing 1.1-4.9 kg. METHODS Cats were randomly allocated to two treatment groups based on route of drug administration: oral transmucosal (OTM), or intramuscular (IM). Buprenorphine (20 microg kg(-1)) plus dexmedetomidine (20 microg kg(-1)) were administered as pre-medicants via one of these two routes. Prior to and 20 minutes after drug administration, heart and respiratory rates, systolic arterial pressure, and posture were measured and recorded. Twenty minutes after drug administration the same variables plus each cats response to clipper sound, clipping, and restraint were recorded; higher scores indicated more sedation. RESULTS There were no significant differences between the two groups prior to pre-medication. Within each treatment group heart rate was significantly lower 20 minutes after treatment, but it did not differ significantly between the two groups. Twenty minutes after treatment, respiratory rate was significantly less in the OTM group, but did not differ significantly between the two groups. Systolic arterial pressure did not differ within or between the two groups at either time. Scores for posture increased significantly within both groups, and cats in the IM group had higher scores after treatment. Twenty minutes after treatment, cats in the IM group had higher scores for clipping and restraint than OTM cats. Ketamine (IM) was necessary to facilitate catheterization in 25% and 16% of cats in the OTM and IM groups, respectively, but this was not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE Administration of dexmedetomidine plus buprenorphine by the OTM route is easy to perform, but produces less sedation than the IM route for IV catheterization in cats.

A randomized, blinded, controlled trial of the antiemetic effect of ondansetron on dexmedetomidine-induced emesis in cats

OBJECTIVE To determine the effect of ondansetron on the incidence of vomiting in cats pre-medicated with dexmedetomidine and buprenorphine. STUDY DESIGN Randomized, blinded, controlled trial. ANIMALS Eighty-nine female domestic shorthair cats, aged 3-60 months (median, 12 months) and weighing 1.2-5.1 kg. METHODS Each cat received dexmedetomidine (40 μg kg(-1)) plus buprenorphine (20 μg kg(-1)), intramuscularly as pre-anesthetic medication. Cats were assigned to three treatment groups: ondansetron (0.22 mg kg(-1), intramuscular [IM]), either 30 minutes before the pre-anesthetic medication (ONDA group, n = 31) or with the pre-anesthetic medication (OPM group, n = 30) mixed with the pre-anesthetic medications in the same syringe, or not to receive the antiemetic (control group, n = 28). Emesis was recorded as an all-or-none response. The number of episodes of emesis and the time until onset of the first emetic episode were recorded for each cat. Clinical signs of nausea were recorded whenever they occurred, and a numerical rating scale was used to quantify these signs. Data were analyzed using Kruskal-Wallis and Chi-square test; a Bonferroni correction was made for six comparisons; thus, the two-sided p for significance was 0.05/6 = 0.008. RESULTS There was a significant reduction in the number of cats vomiting, in the episodes of vomiting/cat, the time elapsed between the premedication and the first vomiting and the severity of nausea in the OPM group compared to the ONDA and control groups. CONCLUSIONS AND CLINICAL RELEVANCE In cats, the administration of ondansetron (0.22 mg kg(-1)) ameliorates and reduced the severity of dexmedetomidine-induced nausea and vomiting only when it was administered in association with this drug.

Effects of epidural morphine on gastrointestinal transit in unmedicated horses

OBJECTIVE To evaluate the effect of epidural morphine on gastrointestinal (GI) motility in horses. STUDY DESIGN Randomly ordered crossover design. ANIMALS Six healthy adult horses weighing 585± 48 kg (mean±SD). METHODS Horses were randomly assigned to receive either 0.2 mg kg(-1) morphine or an equal volume (0.04 mL kg(-1)) of saline epidurally (the first inter coccygeal space) with 2 weeks between treatments. The horses were stabled, fed a standardized diet and allowed water ad libitum throughout the duration of the study. Radiopaque spheres were administered by stomach tube. Xylazine 0.2 mg kg(-1) intravenously was administered prior to epidural injection. Heart rate, respiratory rate, GI sounds score and behavior score were recorded before drug administration and after epidural injection at 4, 8, 12, 18, 24 hours and every 12 hours thereafter for 6 days. Feces were weighed, radiographed and the number of spheres counted. Data were analyzed using a mixed effect model. RESULTS At no time did horses exhibit signs of colic or show significant differences between treatments regarding heart rate, respiratory rate, GI sounds score, behavior score, or cumulative number of spheres. The concentration of spheres per kg of feces was significantly lower (p<0.05) for the morphine group at 18 and 24 hours. Using the centroid of the curves (spheres kg(-1) plotted versus time) the average transit time after saline epidural was 38 hours and after morphine it was 43 hours. The weight of feces hour(-1) was significantly lower (p<0.05) at only 4 and 8 hours after morphine. CONCLUSIONS AND CLINICAL RELEVANCE Epidural morphine, at a dose of 0.2 mg kg(-1) , temporarily reduced GI motility but did not cause ileus or colic in this small group of healthy unfasted horses. Care should be taken when extrapolating these data to situations in which other factors may also affect GI motility.

Azaperone e sua associação com xilazina ou dexmedetomidina em suínos

The aim of this study was to evaluate the sedative effects of azaperone and its association with xylazine or dexmedetomidine in swine, as well as verifying the possibility of the butyrophenone agent to counterbalance the effects caused by α2-adreneceptor agonists on the cardiovascular and hemodynamic parameters. For this, eighteen healthy swines of the Dambread X MS 50 lineage aged 50 days-old, weighing around 17.3kg (±1.7) were used. All animals were submitted an isoflurane anesthesia by face mask throughout the period of instrumentation. Basal parameters were measured 30 minutes after recovering from general anesthesia. All swines were randomly assigned into three groups of six animals each: AG (azaperone 2mg kg-1 + sodium chloride 0.5ml - IM), ADG (azaperone 2mg kg-1 + dexmedetomidine 3µg kg-1 - IM) and AXG (azaperone 2mg kg-1 + xylazine 2mg kg-1 - IM). Parameters were again measured at the following times: 15, 30, 45 and 60 minutes after administrating the corresponding drugs to each group. The heart rate had its values reduced in all groups; however this reduction was more significative in AXG. During the study was not observed a biphasic effect over the arterial pressure with an initial increase followed by a gradual decrease. AXG presented reduction of PaO2 and an increase in PaCO2 as well as a better sedative effect. The results allow to conclude that the association of azaperone with xylazine promoted a better tranquilization and muscular relaxation.

Development of a peripheral nerve stimulator-guided technique for equine pudendal nerve blockade.

The aim of this study was to develop and evaluate a procedure for equine pudendal nerve block using a peripheral nerve locator. In the first experiment, six ponies were used to determine the relationship between elicited muscle contractions (anal, perineal or both) and nerves serving the perineal region (pudendal, caudorectal and perineal nerves) when methylene blue dye was injected using the electrolocation technique. This experiment showed that the pudendal nerve was approached effectively when both anal and perineal twitch were elicited during electrolocation. In a second experiment, seven Thoroughbred horses were used to evaluate the appropriate volume of anaesthetic solution for the nerve block. Immediately after euthanasia, lidocaine/methylene blue solution was injected after positive electrolocation. A stained segment of 2 cm or more of the nerve was considered effective and this was evaluated after dissection. Both 10 and 20 mL per injection site resulted in effective nerve staining. Finally, pudendal nerve block was performed and evaluated in 27 horses admitted for selected reproductive surgical procedures including perineoplasty, urethroplasty, clitorectomy in mares and penile examination, phallectomy and urethrostomy in geldings. Surgical time varied from several minutes to 3 h. The choice between lidocaine, mepivacaine or bupivacaine was based on the duration of analgesia required. In mares and males, a volume of 20 mL and 10 mL, respectively, was injected per site. The use of a peripheral nerve stimulator-guided pudendal nerve block is a feasible, safe and reliable alternative for both epidural and general anaesthesia, to provide peri-operative analgesia in clinical equine patients undergoing specific reproductive surgeries.

Nerve stimulation-guided thoracolumbar paravertebral block for flank laparotomy in a horse

A thoracolumbar paravertebral block (TPVB) is commonly performed in ruminants, however, the transverse processes of the thoracolumbar spine are difficult to palpate in some horses. Blind techniques for equine TPVB have been described in the past (Skarda 1991; Moon & Suter 1993). This technique can be quite difficult to perform in a horse with a body condition score greater than 4 (Henneke et al. 1983). In humans, the use of electro-location of the thoracolumbar region has previously been described in detail elsewhere (Naja et al. 2006). This letter reports the use of a nerve stimulator for a thoracolumbar paravertebral block for a standing laparoscopic procedure on a horse. A 5-year-old, 500-kg, thoroughbred mare was presented with a presumptive diagnosis of a granulosa cell tumor on the right ovary. A flank laparoscopy was scheduled in order to perform a right-hand side ovariectomy. The mare was restrained in a standing stock, and the TPVB injection and surgical site were aseptically prepared (Fig. 1). The mare was then sedated with detomidine (10 mg) plus butorphanol (10 mg), intravenously. Immediately after the initial bolus, a detomidine constant rate infusion was initiated to maintain moderate-to-deep sedation. The last thoracic (T18), first and second lumbar (L1 and L2) spinal nerves were then desensitized approximately 5 cm lateral from the dorsal midline using a nerve stimulator (Plexygon Nerve Stimulator; Vygon, Italy). The sites for desensitization were palpated by locating the third lumbar transverse process (L3), which is on a line between the most caudal extension of the last rib and perpendicular to the long axis of the spinal vertebrae (Fig. 1). The distance between the injection sites (from L3 to L2 and L1) was approximately 5 cm. The skin, subcutaneous and superficial musculature of each site (red circles; Fig. 1), was desensitized, using 5 mL of Lignocaine 2% and a 1.5 in (3.8 cm) 21gauge needle. A long beveled 20 gauge – L.150mm-insulated needle (Locoplex; Vygon, France) was then introduced vertically (perpendicular to the skin) until it impinged on the transverse process of L3 (depth 9 cm) when it was then walked off cranially until the intertransverse ligament between L3 and L2 was penetrated. At this time, we aimed to identify an evoked musculature contraction of the flank region using a 1-mA current. Initially, twitching of the lumbar muscles was seen as a result of direct muscle stimulation but as the needle was slowly advanced, an evoked contraction of the muscles composing the flank region (external and internal oblique abdominal muscles and transverse abdominal muscle) could be seen. The proximity with the root of L2 was confirmed when a positive twitch of the most caudal aspect of the flank (closer to tuber coxae) was present when the current was decreased to 0.5 mA. By using a low current intensity, we aimed to avoid unspecific direct muscular stimulation unrelated to the proximity to the paravertebral branches. It is easy to enter the peritoneum, and this is detected by a loss of resistance or aspiration of air. Should this happen, the needle should be withdrawn to a retroperitoneal position before the local anesthetic is deposited. After aspiration to rule out venipuncture, 5 mL of Mepivacaine 2% was infiltrated when at maximum positive stimulation and another 5 mL was infiltrated when retracting the needle 2 cm above this point. The procedure was repeated to desensitize nerves L1 and T18 at the transverse process of L2 and L1, respectively. The proximity with the root of T18 was confirmed by contraction of the most cranial aspect of the flank (closer to the last rib). Adequacy of the block was checked 15 minutes later by sensory loss of the surgical field to pinprick sensation. Lignocaine 2% (10 mL) was used to block the ovarian pedicule using a long needle through the laparoscopic port. The total amount of Mepivacaine and Lignocaine used was 30 and 25 mL, respectively. The block was not only deemed sufficient to desensitize the right flank for the