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Veterinary care for rabbits has been growing, and, consequently, the anesthetic and analgesic management of this species must be improved. The aim of the present study was to evaluate the technique of localization of the epidural space with the aid of a peripheral nerve stimulator and epidurographic, comparing two techniques for determining the infused volume in rabbits (Oryctolagus Cuniculus). In a prospective, randomized blinded study, six healthy New Zealand rabbits, adults, and weighing from 2.2 kg to 3.8 kg received two treatments, at 1 week intervals: 0.33 mL/kg (treatment I) or 0.05 mL per centimeter of the spine (treatment II) of ioexol epidurally. In both treatments, a peripheral nerve stimulator (2 Hz, 0.25 mA and 0.1 milliseconds) was used to determine the location of the epidural space. Latero-lateral and ventro-dorsal radiographs were taken after five (T5) and twenty-five minutes (T25) of iohexol administration. The epidural space was correctly accessed in 92% of attempts. Treatment I received a smaller volume of contrast than treatment II, 1.0 ± 0.2 mL versus 2.1 ± 0.1 mL (mean ± standard deviation), respectively (p = 0.007). At T5, the cranial progression of the contrast varied between L4 and L5 in treatment I, and L5 and T10 in treatment II. At T25, no contrast was observed in any rabbit. In conclusion, peripheral nerve stimulator aided in accessing the lumbosacral epidural space, and the administration of 0.05 mL per centimeter of the spine resulted in greater cranial progression of contrast.

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O objetivo do estudo foi verificar clinicamente a dispersão da lidocaína no espaço epidural de cães posicionados em diferentes decúbitos. Foram utilizados 16 cães, com peso médio de 17,5 quilogramas. Esses foram tranquilizados com acepromazina, anestesiados com propofol e alocados em dois grupos, conforme o decúbito de posicionamento: decúbito esternal (GE) e decúbito lateral direito (GLD). Ambos os grupos receberam lidocaína a 2%, no volume de 0,25mL/kg, e permaneceram no mesmo decúbito por 20 minutos. Em seguida, avaliou-se o bloqueio dos membros pélvicos e a extensão do bloqueio, a partir da sétima vértebra lombar, por meio de pinçamento interdigital e do panículo paravertebral. Foi, então, realizada cirurgia de orquiectomia. Após tal procedimento, avaliou-se o tempo total de bloqueio dos membros pélvicos. Todos os cães apresentaram bloqueio bilateral, sem diferenças quanto à extensão cranial entre os grupos, sendo a mediana de 7,5 (1-14) vértebras para GE e de 4 (1-14) para GLD. O tempo de bloqueio dos membros direito e esquerdo foi de 123 ± 26 e 130 ± 20 minutos, para GE, e de 120 ± 21 e 121 ± 20 minutos, para GLD, sem diferenças entre os grupos ou entre os membros. Conclui-se que o decúbito não interfere na distribuição da lidocaína administrada por via epidural.(AU)

The aim of this study was to clinically verify the dispersion of lidocaine in the epidural space of dogs placed in different positions. Sixteen dogs with an average weight of 17.5 kilograms were used. These were tranquilized with acepromazine, anesthetized with propofol and allocated to two groups: sternal decubitus (GE) and right lateral decubitus (GLD). Both groups received 2% of lidocaine in the volume of 0.25mL/kg and remained in the same position for 20 minutes. The blocking of the pelvic limbs and the extension of it from the seventh lumbar vertebra were evaluated by means of interdigital and paravertebral panniculus clamping. Orchiectomy surgery was then performed. Afterwards, the total blocking time of the pelvic limbs was evaluated. All dogs presented bilateral blocking, with no differences in cranial extension between groups, with a median of 7.5 (1-14) vertebrae for GE and 4 (1-14) for GLD. The blocking time of the right and left limbs were 123 ± 26 and 130 ± 20 minutes for GE, and 120 ± 21 and 121 ± 20 minutes for GLD with no difference between groups or between limbs. It is concluded that the decubitus does not interfere with the epidural lidocaine distribution.(AU)

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The objective of the study was to compare the effects of caudal epidural bupivacaine and dexmedetomidine (DEX) combination, with bupivacaine or DEX plain for perineal analgesia in mares. Six healthy saddle mares weighing 330-370 kg and aged 10-15 years were used in this study. Each mare was assigned to receive three treatments: 0.04 mg/kg 0.25% bupivacaine (BP), 2 µg/kg DEX (DX), or 0.02 mg/kg bupivacaine and 1 µg/kg DEX (BPDX). The order of treatments was randomized. All drugs were injected into the caudal epidural space (Co1-Co2) through a 16-G Tuohy epidural needle. After the epidural injections, heart rate, respiratory rate, arterial blood pressures (systolic, diastolic, and mean), and rectal temperature were measured at 5, 10, 15, 30, 60, 90, and 120 minutes, and after this time, every 60 minutes until the end of the experiments. A subjective score system was used to assess analgesia, behavioral and motor blockade at the same time points. The BPDX treatment produced analgesic action with twice the duration (200 minutes) of the BP treatment (97 minutes), but with an analgesic duration shorter than the DX treatment (240 minutes) in the regions of the tail, perineum, and upper hind limbs in mares. All treatments showed mild motor blockade. No behavioral changes were observed in any of the animals. There was hemodynamic stability without significant changes in respiratory rate for all treatments. Epidural analgesia using DEX alone or the combination of DEX and bupivacaine may be an option for painful obstetric and gynecological procedures in mares.

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BACKGROUND: The aims of this study were evaluate cardiopulmonary, sedative and antinociceptive effects of dexmedetomidine-lidocaine combination via lumbosacral epidural injection in sheep. METHODS: Six Santa Inês breed sheep, 16±6 months old and weighing 42.2 ± 5.7 kg were used. Sheep were subjected to epidural anaesthesia with three treatments: L, lidocaine (1.2 mg/kg), D, dexmedetomidine (2.5 µg/kg) or DL, dexmedetomidine plus lidocaine (2.5 µg/kg + 1.2 mg/kg). Drugs were injected via pre-placed lumbosacral epidural catheters. Cardiopulmonary, arterial blood gases, electrolytes, degree of sedation and antinociceptive aspects were measured before drug administration (T0) and then at 15, 30, 60 and 120 min after drug injection (T15-T120) in all treatments and at T0 to T240 in DL. RESULTS: There were significantly increases in PaCO2 at times T60 and T120 in D, and at T30-T120 in DL, compared to baseline. The antinociceptive effects were observed up to 240 min in DL and 60 min in L, and were more intense in DL. Treatment D provided analgesia only in the perineal region, and only at T15. CONCLUSION: The combination of DEX with lidocaine produced similar cardiopulmonary changes compared with either drug alone, but with greater and more prolonged antinociceptive effects.

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Recovery of neuromuscular function is a gradual phenomenon whereby function progresses from absent to normal. The speed of spontaneous recovery can be used to predict the time when neuromuscular function is expected to be restored. However, the speed of recovery might be affected by the dose of the neuromuscular blocker administered, and by the dosing regimen of that dose. The effects of both factors on the speed of spontaneous recovery from vecuronium were evaluated. Seven dogs were anesthetized three times and the train-of-four (TOF) ratio was measured with acceleromyography. Vecuronium was administered at 0.1 mg/kg, 0.2 mg/kg, or 0.1 mg/kg followed by two doses of 0.05 mg/kg was administered each time. In the divided-dose treatment group, aliquots were administered on return of the first twitch (T1) of the TOF from the previous dose. The duration of surgical block, from injection to return of T1, was longest for the divided-dose protocol, intermediate for 0.2 mg/kg single bolus, and shortest for 0.1 mg/kg (P < 0.0001). The recovery period, from return of T1 to a TOF ratio ≥0.9, was longer for 0.2 mg/kg administered as a single bolus than for the other two groups (P = 0.007). Doubling the dose of a single bolus of vecuronium extended the time of surgical block and prolonged the duration of the recovery period. However, dividing that dose into smaller aliquots extended the period of surgical block while shortening the recovery period. Hence, the spontaneous reappearance of T1 should not be used in isolation to predict the time to complete recovery of neuromuscular function.

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Ultrasonography of the lumbosacral and sacrococcygeal spine is described in cats to confirm effective distribution of local anesthetics injected in the sacrococcygeal epidural space. Ultrasound was used to identify the structures of the spinal canal, local anesthetic flow, and to measure the distances between skin and ligamentum flavum.

Utilisation de l'échographie pour évaluer les injections épidurales sacrococcygiennes chez les chats. L'échographie de la colonne lombo-sacrée et sacrococcygienne est décrite chez des chats afin de confirmer la distribution efficace des anesthésiques locaux injectés dans l'espace épidural sacrococcygien. L'échographie a été utilisée pour identifier les structures du canal rachidien, l'écoulement local des anesthésiques et mesurer les distances entre la peau et le ligament jaune.(Traduit par Isabelle Vallières).

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OBJECTIVE: To investigate the nociceptive and clinical effects of buffering a lidocaine-epinephrine solution with sodium bicarbonate in caudal epidural block in mares. STUDY DESIGN: Prospective randomized controlled trial. ANIMALS: Six mixed-breed mares weighing 350-440 kg. METHODS: Each animal was administered two caudal epidural injections, 72 hours apart, using different solutions prepared immediately before injection. The control solution was 7 mL 2% lidocaine hydrochloride with epinephrine hemitartrate (1:200,000) added to 3 mL sterile water for injection (pH 2.9). The alkalinized solution was 7 mL of lidocaine-epinephrine solution added to 2.3 mL sterile water for injection and 0.7 mL 8.4% sodium bicarbonate (pH 7.4). Nociception was evaluated by response to skin pinching at 31 sites in the sacral region and around the perimeter of the anogenital area (distances of 10, 15 and 20 cm) before, and 5, 10 and 15 minutes after epidural injection, then every 15 minutes until the return of nociception in all evaluated sites. The onset and duration times, and intensity of ataxia (grades 0 to 3) were recorded. The paired t test was used to compare the onset and duration of anesthesia and ataxia (p<0.05). RESULTS: Alkalization of the solution resulted in significant decreases in the average time of onset of loss of nociception in the sacral region (40%) and around the perimeter of the anogenital area extending up to 5 cm (36%) and from 5 to 10 cm (32%) from the anus and vulva. Alkalization also decreased the average duration of ataxia (33%), without affecting the duration and extent of anesthesia or the degree of ataxia. CONCLUSIONS AND CLINICAL RELEVANCE: Alkalization of lidocaine-epinephrine solution is advantageous in shortening the duration of ataxia and hastening the onset of anesthesia in areas adjacent to the anogenital area, without reducing the duration of epidural anesthesia, in mares.

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Cardiopulmonary and sedative effects of intravenous or epidural methadone were compared. Six beagles were randomly assigned to group MIV (methadone 0.5 mg/kg IV + NaCl 0.9% epidurally) or MEP (methadone 0.5 mg/kg epidurally + NaCl 0.9% IV). Cardiopulmonary, blood gas and sedation were assessed at time (T) 0, 15, 30, 60, 120, 240 and 480 min after drug administration. Compared to T0, heart rate decreased at T15-T120 in MIV (p < .001) and T15-T240 in MEP (p < .05); mean arterial pressure was reduced at T15-T60 in MEP (p < .01); respiratory rate was higher at T15 and T30 in both groups (p < .05); pH was lower at T15-T120 in MIV (p < .01) and T15, T30 and T120 in MEP (p < .05); PaCO2 was higher at T15-T60 in MIV (p < .01) and T15, T30 and T120 in MEP (p < .01); sedation scores were higher at T15 and T30 in MIV and T15-T60 in MEP (p < .05). At T120 and T240, sedation score was higher in group MEP compared with group MIV (p < .01) In conclusion, cardiopulmonary and sedative effects of identical methadone doses are similar when administered IV or epidurally to conscious healthy dogs.

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Objectives The aim of the study was to evaluate the effectiveness of epidural lidocaine in combination with either methadone or morphine for postoperative analgesia in cats undergoing ovariohysterectomy. Methods Under general anesthesia, 24 cats that underwent ovariohysterectomy were randomly allocated into three treatment groups of eight each. Treatment 1 included 2% lidocaine (4.0 mg/kg); treatment 2 included lidocaine and methadone (4.0 mg/kg and 0.3 mg/kg, respectively); and treatment 3 included lidocaine and morphine (4.0 mg/kg and 0.1 mg/kg, respectively). All drugs were injected in a total volume of 0.25 ml/kg via the lumbosacral route in all cats. During the anesthetic and surgical periods, the physiologic variables (respiratory and heart rate, arterial blood pressure and rectal temperature) were measured at intervals of time zero, 10 mins, 20 mins, 30 mins, 60 mins and 120 mins. After cats had recovered from anesthesia, a multidimensional composite pain scale was used to assess postoperative analgesia 2, 4, 8, 12, 18 and 24 h after epidural. Results The time to first rescue analgesic was significantly ( P <0.05) prolonged in cats that received both lidocaine and methadone or lidocaine and morphine treatments compared with those that received lidocaine treatment alone. All cats that received lidocaine treatment alone required rescue analgesic within 2 h of epidural injections. All treatments produced significant cardiovascular and respiratory changes but they were within an acceptable range for healthy animals during the surgical period. Conclusions and relevance The two combinations administered via epidural allowed ovariohysterectomy with sufficient analgesia in cats, and both induced prolonged postoperative analgesia.

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To test the hypothesis that epidural administration of lidocaine, xylazine or xylazine plus hyaluronidase provides reduced pain and stress during electroejaculation in bulls, eight 30-month-old Nellore bulls received saline solution (control), 2% lidocaine, 2% xylazine or 2% xylazine plus hyaluronidase injected into the first intercoccygeal (Co1-Co2) epidural space in randomized order. Heart rate, respiratory rate, mean arterial pressure, analgesia, animal behavior and motor blockade were evaluated before treatment and at predetermined intervals during and after treatment. Pain and stress were scored subjectively, and semen quality was evaluated. The onset of anesthetic action was significantly faster with lidocaine (3.0 ± 1.2 min) than with xylazine or xylazine plus hyaluronidase (8.9 ± 1.5 and 5.5 ± 2.6 min, P=0.021 and P=0.012, respectively), and the onset of anesthesia with xylazine plus hyaluronidase was significantly faster than that with xylazine alone (P=0.032). Treatment with xylazine or xylazine plus hyaluronidase resulted in less discomfort than treatment with lidocaine, as indicated by animal behavior. Changes in heart rate, respiratory rate and arterial pressure were within acceptable limits. Penile protrusion and semen emission occurred in all animals during all four treatments. Our results suggest that xylazine plus hyaluronidase reduced discomfort during electroejaculation more effectively than xylazine or lidocaine alone. Further experiments are necessary to determine whether electroejaculation with xylazine plus hyaluronidase is feasible for obtaining semen from Nellore bulls unaccustomed to being handled or restrained.

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OBJECTIVE: To determine if a nerve stimulation test (NST) could act as a monitoring technique to confirm sacrococcygeal epidural needle placement in cats. STUDY DESIGN: Prospective experimental trial in a clinical setting. ANIMALS: Twenty-four adult cats, scheduled for a therapeutic procedure where epidural anesthesia was indicated. METHODS: Under general anesthesia, an insulated needle was inserted through the S3 -Cd1 intervertebral space guided by the application of a fixed electrical current (0.7 mA) until a motor response was obtained. The NST was considered positive when the epidural nerve stimulation produced a motor response of the muscles of the tail, whereas it was considered negative when no motor response was evoked. In the NST positive cases, 0.3 mL kg(-1) of 0.5% bupivacaine was administrated before needle withdrawal. Ten minutes after injection, epidural blockade was confirmed by the loss of perineal (anal), and pelvic limbs reflexes (patellar and withdrawal). RESULTS: The use of a fixed electrical stimulation current of 0.7 mA resulted in correct prediction of sacrococcygeal epidural injection, corroborated by post bupivacaine loss of perineal and pelvic limb reflexes, in 95.8% of the cases. CONCLUSION AND CLINICAL RELEVANCE: This study demonstrates the feasibility of using, in a clinical setting, an electrical stimulation test as an objective and in real-time method to confirm sacrococcygeal epidural needle placement in cats.

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OBJECTIVE: To determine the minimal electrical threshold (MET) necessary to elicit appropriate muscle contraction when the tip of an insulated needle is positioned epidurally or intrathecally at the L5-6 intervertebral space (phase-I) and to determine whether the application of a fixed electrical current during its advancement could indicate needle entry into the intrathecal space (phase-II) in dogs. STUDY DESIGN: Prospective, blinded study. ANIMALS: Thirteen (phase-I) and seventeen (phase-II) dogs, scheduled for a surgical procedure where L5-6 intrathecal administration was indicated. METHODS: Under general anesthesia, an insulated needle was first inserted into the L5-6 epidural space and secondly into the intrathecal space and the MET necessary to obtain a muscular contraction of the pelvic limb or tail at each site was determined (phase-I). Under similar conditions, in dogs of phase-II an insulated needle was inserted through the L5-6 intervertebral space guided by the use of a fixed electrical current (0.8 mA) until muscular contraction of the pelvic limb or tail was obtained. Intrathecal needle placement was confirmed by either free flow of cerebrospinal fluid (CSF) or myelography. RESULTS: The current required to elicit a motor response was significantly lower (p < 0.0001) when the tip of the needle was in the intrathecal space (0.48 ± 0.10 mA) than when it was located epidurally (2.56 ± 0.57). The use of a fixed electrical stimulation current of 0.8 mA resulted in correct prediction of intrathecal injection, corroborated by either free flow of CSF (n = 12) or iohexol distribution pattern (n = 5), in 100% of the cases. CONCLUSION AND CLINICAL RELEVANCE: Nerve stimulation may be employed as a tool to distinguish epidural from intrathecal insulated needle position at the L5-6 intervertebral space in dogs. This study demonstrates the feasibility of using an electrical stimulation test to confirm intrathecal needle position in dogs.

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OBJECTIVE: To determine the minimal electric threshold of neurostimulation dorsally and ventrally to the interarcuate ligament in the lumbosacral area necessary to cause muscle contraction of the hind limb or tail and determine whether a continuous electrical stimulation applied to an insulated needle during lumbosacral epidural needle placement could be used to distinguish the epidural from the intrathecal space in rabbits. ANIMALS: 24 New Zealand white rabbits. PROCEDURES: Rabbits received iohexol (0.2 mL/kg) either dorsally (group 1) or ventrally to the interarcuate ligament in the lumbosacral area (groups 2 and 3). Correct placement of the needle was determined by use of the loss of resistance to injection technique (group 2) or a continuous electrical stimulation (group 3) and confirmed by examination of the iohexol distribution pattern on radiographs. RESULTS: In all rabbits of group 1, iohexol was injected in the lumbosacral area, outside the epidural space. In groups 2 and 3, iohexol was injected intrathecally. No pure iohexol epidural migration of iohexol was observed. Mean ± SD minimal electric threshold to elicit a motor response was 1.2 ± 0.3 mA, 0.3 ± 0.1 mA, and 0.3 ± 0.1 mA in groups 1, 2, and 3, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Neurostimulation was a useful technique to determine correct intrathecal needle placement in rabbits but failed to detect the lumbosacral epidural space when the common technique, used in dogs and cats for the lumbosacral epidural approach, was used.

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The aim of this study was to evaluate 3 doses of levobupivacaine (LB) epidurally administered in sheep. Six adult male 24-36 month-old sheep received levobupivacaine at 3 doses, LB05 (0.05 mg/kg), LB15 (0.15 mg/kg), and LB25 (0.25mg/kg), and saline solution into the lumbosacral epidural space. Heart rate, arterial blood pressure (systolic, diastolic, and mean), respiratory rate, rectal, and skin temperature, local anesthesia, and ataxia were determined before treatment and at predetermined intervals. The duration of local anesthesia was 30±5 min, 145±27 min, and 290±18 min for LB05, LB15, and LB25, respectively (P<0.05). Ataxia determined for LB05, LB15, or LB25 was similar to the anesthetic times. There was an increase in heart rate and reduction in arterial pressure in LB25 (P<0.05), whereas LB05 or LB15 did not affect these parameters. Lumbosacral epidural levobupivacaine is an appropriate choice for local anesthesia in sheep.

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The effects of epidural and intravenous (IV) methadone (0.5mg/kg) on the minimum alveolar concentration of isoflurane (ISO(MAC)) were compared in dogs. Six dogs (16.5 ± 2.5 kg bodyweight) received three treatments in random order during isoflurane anaesthesia, with a 7 day washout interval between each study. Methadone was injected via a lumbosacral epidural catheter introduced 10 cm cranially into the epidural canal and the electrical stimulation for ISO(MAC) determination was applied either to the thoracic (EP(T) treatment) or to the pelvic limb (EP(P) treatment) during separate study days. In the IV treatment, ISO(MAC) was determined via electrical stimulation of the pelvic limb. Variables were recorded before (baseline), 2.5 and 5h after drug injection. The ISO(MAC) decreased significantly (P<0.05) from baseline at 2.5 and 5h after methadone in all treatments. At 2.5h, the magnitude of ISO(MAC) reduction did not differ between treatments (mean decreases from baseline: 30-33%). The ISO(MAC) reduction lasted longer following epidural methadone in the thoracic limb (decreases from baseline: 30% at 5h in the EP(T) treatment vs. 19% and 16% in the EP(P) and IV treatments, respectively). Although the isoflurane sparing effect provided by epidural methadone was not significantly greater than IV methadone during the initial stage (2.5h), it was more prolonged than the IV route in specific dermatomes (5h in the thoracic limb) with the epidural technique employed. Methadone may therefore provide a greater isoflurane sparing effect when administered epidurally, compared to IV, when noxious stimulation occurs in specific dermatomes.

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OBJECTIVE: To determine the anaesthetic and systemic effects of dorsolumbar epidural anaesthesia using non-stylet multiport catheters via the caudal approach to administer hypertonic 5% lignocaine (HL) or hypertonic 0.5% bupivacaine (HB) to the flank in standing cattle. MATERIALS AND METHODS: Six healthy adult cattle weighing 310-455 kg received 0.2 mg/kg HL or 0.025 mg/kg of HB; control animals received 0.9% saline solution. All drugs were injected into the dorsolumbar epidural space via a caudal approach through a non-stylet multiport catheter. Each animal received each treatment at random. Evaluations of anaesthesia, ataxia, heart rate, arterial pressures, respiratory rate and rectal temperature were obtained at 0 (basal), 5, 10, 15, 30, 45, 60, 75, and 90 min after epidural injection and then at 30-min intervals until loss of anaesthesia. All animals received a standard noxious stimulus and a 4-point scale was used to score the response. A second scale was used to score ataxia. RESULTS: The duration of anaesthesia in the upper and lower flanks in cattle was 68 +/- 12 and 110 +/- 15 min (mean +/- SD) after dorsolumbar epidural HL or HB, respectively. Both hypertonic local anaesthetics produced a mild ataxia. The systemic changes were within acceptable limits in these clinically healthy cattle. CONCLUSION: In standing cattle the dorsolumbar epidural injection of hypertonic lignocaine provided faster onset of anaesthesia and fewer cardiovascular effects, but had a shorter duration of anaesthesia than hypertonic bupivacaine.

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OBJECTIVE: To determine the analgesic and systemic effects of epidural administration of ketamine, lidocaine or a combination of ketamine/lidocaine in standing cattle. STUDY DESIGN: Prospective, randomized, experimental trial. ANIMALS: Six healthy male cattle weighing between 335 and 373 kg. METHODS: The animals received 0.5 mg kg(-1) of ketamine (K), 0.2 mg kg(-1) of 2% lidocaine (L) or 0.25 mg kg(-1) ketamine plus 0.1 mg kg(-1) lidocaine (KL). All the drugs were injected into the dorsolumbar epidural space via a caudal approach through a non-styletted multiple-port catheter. Each animal received each treatment at random. Evaluations of analgesia, sedation, ataxia, heart rate, arterial pressure, respiratory rate, skin temperature and rectal temperature were obtained at 0 (basal), 5, 10, 15, 30, 45, 60, 75, 90 minutes after epidural injection, and then at 30-minute intervals until loss of analgesia occurred. Skin temperature was taken at these intervals up to 60 minutes. All the animals received a standard noxious stimulus; a 4-point scale was used to score the response. A second scale was used to score ataxia and a third for sedation. RESULTS: The duration of analgesia in the upper and lower flanks in cattle was 140 +/- 15, 50 +/- 14 and 80 +/- 22 minutes (mean +/- SD) after dorsolumbar epidural KL, K or L, respectively. The cardiovascular changes were within acceptable limits in these clinically healthy cattle. CONCLUSIONS: Dorsolumbar epidural administration of KL to cattle resulted in longer duration of analgesia of the upper and lower flanks in standing conscious cattle, than the administration of K or L alone. CLINICAL RELEVANCE: Further research is necessary to determine whether this combination using this technique provides sufficient analgesia for flank surgery in standing cattle.

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OBJECTIVE: To compare the cardiorespiratory, anesthetic-sparing effects and quality of anesthetic recovery after epidural and constant rate intravenous (IV) infusion of dexmedetomidine (DEX) in cats given a low dose of epidural lidocaine under propofol-isoflurane anesthesia and submitted to elective ovariohysterectomy. STUDY DESIGN: Randomized, blinded clinical trial. ANIMALS: Twenty-one adult female cats (mean body weight: 3.1 +/- 0.4 kg). METHODS: Cats received DEX (4 microg kg(-1), IM). Fifteen minutes later, anesthesia was induced with propofol and maintained with isoflurane. Cats were divided into three groups. In GI cats received epidural lidocaine (1 mg kg(-1), n = 7), in GII cats were given epidural lidocaine (1 mg kg(-1)) + DEX (4 microg kg(-1), n = 7), and in GIII cats were given epidural lidocaine (1 mg kg(-1)) + IV constant rate infusion (CRI) of DEX (0.25 microg kg(-1) minute(-1), n = 7). Variables evaluated included heart rate (HR), respiratory rate (f(R)), systemic arterial pressures, rectal temperature (RT), end-tidal CO(2), end-tidal isoflurane concentration (e'ISO), arterial blood gases, and muscle tone. Anesthetic recovery was compared among groups by evaluation of times to recovery, HR, f(R), RT, and degree of analgesia. A paired t-test was used to evaluate pre-medication variables and blood gases within groups. anova was used to compare parametric data, whereas Friedman test was used to compare muscle relaxation. RESULTS: Epidural and CRI of DEX reduced HR during anesthesia maintenance. Mean +/- SD e'ISO ranged from 0.86 +/- 0.28% to 1.91 +/- 0.63% in GI, from 0.70 +/- 0.12% to 0.97 +/- 0.20% in GII, and from 0.69 +/- 0.12% to 1.17 +/- 0.25% in GIII. Cats in GII and GIII had longer recovery periods than in GI. CONCLUSIONS AND CLINICAL RELEVANCE: Epidural and CRI of DEX significantly decreased isoflurane consumption and resulted in recovery of better quality and longer duration, despite bradycardia, without changes in systemic blood pressure.

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OBJECTIVE: To evaluate the extent sensory and motor blocks produced by the epidural injection of different volumes of 0.25% bupivacaine (Bu) with methylene blue (MB), in dogs. STUDY DESIGN: Prospective experimental trial. ANIMALS: Twenty healthy adult mongrel dogs, weighing 9.9 +/- 1.9 kg. METHODS: Dogs were randomly allocated into one of four groups that received 0.2, 0.4, 0.6 or 0.8 mL kg(-1) of an epidural solution containing 0.25% Bu and MB. Sensory block was evaluated against time by pinching the tail, hind limb interdigital web, toenail bases and the skin over the vertebral dermatomes. Motor block was assessed by ataxia, hind limb weight-bearing ability and by loss of muscle tone of the tail and pelvic limbs. Data were collected at 2, 5, 10, 15 and 30 minutes after the end of epidural injection. After the final time point, dogs were euthanatized and laminectomies were conducted to expose the extent of the dural dye staining. RESULTS: The volumes 0.2, 0.4, 0.6 and 0.8 mL kg(-1) of 0.25% Bu and MB blocked a mean of 5, 14.2, 20.2 and 21 dermatomes, respectively. The extent of the sensory block increased up to a volume of 0.6 mL kg(-1). Motor block was longer-lasting and more intense than sensory block. Complete dyeing of the spinal cord with MB was achieved in some dogs at 0.4 mL kg(-1) and all dogs at 0.6 mL kg(-1). CONCLUSIONS: The volume of anesthetic injected into the epidural space plays an important role in the quality of the epidural anesthesia. At 0.25%, bupivacaine provided an efficient sensory block at 0.6 mL kg(-1). CLINICAL RELEVANCE: Relatively high volumes (0.6 mL kg(-1)) of 0.25%, BU and MB were needed to produce an effective sensory and motor block caudal to the umbilicus, but all spinal cord segments were reached by MB at this dose.

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