Epidural Anesthesia In Dogs Research Articles

The perfusion index as a method of assessing epidural anaesthesia efficacy in healthy dogs

Abstract Introduction Perfusion index (PI) is used as assessment of epidural anaesthesia efficacy in human medicine, but its usefulness in dogs is unknown. The aim of this study was to evaluate the usefulness of PI in determining epidural anaesthesia effectiveness. Material and Methods This is prospective cross-over experimental study. Five healthy adult beagle dogs were anaesthetised and an epidural catheter was inserted in the lumbosacral area and adjusted so that the end of the catheter was placed at the fourth lumbar vertebra. Single-port catheters were used in the control group and multiple-port catheters were used in the treatment group. A PI probe was placed on a hind leg, and the catheter placement was confirmed via computed tomography. The treatment group received a bolus dose of lidocaine, and the control group received saline, via epidural catheter. The PI value was recorded every 5 min until 30 min after lidocaine injection. Results The PIs of the hind limbs were not significantly different over time, nor were they between the control and lidocaine-injected groups at any point in time. Conclusion The PI is not useful in determining the efficacy of epidural anaesthesia in dogs under general anaesthesia. In the future, finding a reliable method to evaluate the success of regional anaesthesia, even in patients under general anaesthesia, will be necessary.

SimuVet: a preliminary study of the innovative development of a simulator for epidural anesthesia training in dogs.

Epidural anesthesia in dogs is a locoregional anesthesia technique used in veterinary medicine, becoming an important integrated application in the anesthetic protocol to provide safer and more effective analgesia to patients. For this, professionals must adhere to rigorous guidelines and possess technical skills. In this context, in veterinary education, the development of practical clinical skills represents a crucial aspect in the training of these professionals. However, traditional teaching methods have proven insufficient to ensure a consistent level of competence among recent graduates. The introduction of non-animal alternatives for educational purposes has contributed to the development of simulation-based teaching, an innovative and accessible field capable of enhancing pre-clinical proficiency in students and reducing the use of live animals and cadavers. Despite its application in various areas of veterinary education, there are no conclusive results regarding the development of accessible simulators capable of effectively enhancing training in epidural anesthesia in dogs. Therefore, this article represents a pioneering study aimed at sharing a method for creating SimuVet, a realistic simulator for training epidural anesthesia in dogs. The simulator was fully developed by veterinary researchers with limited experience in 3D printing and, after preliminary analysis, demonstrated excellent performance and ultrasonographic anatomy. Future work will focus on the formal validation of this simulator with the aim of improving the teaching and learning process for students and experts in performing epidural anesthesia in companion animals.

Evaluation of perfusion index as a noninvasive tool to determine epidural anesthesia effectiveness in dogs

ObjectiveTo evaluate perfusion index (PI) as a noninvasive tool to determine effectiveness and onset of epidural anesthesia in dogs. Study designProspective clinical trial. AnimalsA total of 21 adult dogs, aged 6.5 ± 3 years and weighing 34.9 ± 6.4 kg, undergoing a tibial plateau leveling osteotomy. MethodsDogs were premedicated intramuscularly with acepromazine (0.03 mg kg–1) and hydromorphone (0.1 mg kg–1) and anesthetized with intravenous propofol (to effect) and isoflurane in oxygen. A surface transflectance probe was secured to the tail base to monitor PI and a dorsal pedal artery catheter was placed for invasive blood pressure monitoring. A lumbosacral epidural was performed with the dog in sternal recumbency. Dogs were randomly assigned for inclusion of epidural morphine (0.1 mg kg–1) or morphine (0.1 mg kg–1) and lidocaine (4 mg kg–1). PI was recorded following instrumentation of each dog just prior to the epidural (baseline), at 10 minute intervals for 30 minutes, before and after the surgical skin incision and before and after completion of the osteotomy. Physiological variables and end-tidal isoflurane were recorded at the same time points. ResultsThere was no significant difference in PI between the groups at any time point. There was a significant change in end-tidal isoflurane before and after the skin incision in the epidural morphine and epidural morphine–lidocaine groups (p = 0.04, p = 0.05, respectively) and before and after the osteotomy in each group for heart rate (p = 0.001, p = 0.04), diastolic (p = 0.01, p = 0.01) and mean arterial blood pressure (p = 0.03, p = 0.05). Conclusions and clinical relevancePI did not provide an objective means for determining the onset or effectiveness of epidural anesthesia in anesthetized dogs and alternate methods of noninvasive assessment should be investigated.

Short-term efficacy of epidural pain management in dogs undergoing cystoscopy.

BackgroundThe effects of epidural anesthesia in dogs undergoing cystoscopy are unknown.ObjectiveTo investigate the effect of epidural analgesia on postcystoscopy pain in dogs.AnimalsTwenty‐six dogs undergoing routine cystoscopy for lower urinary tract disease.MethodsProspective, randomized, blinded observational study. Dogs were assigned either to a treatment group that received epidural anesthesia (preservative free morphine sulfate, 0.09 mg/kg; 1% ropivacaine, 0.2 mg/kg; total volume delivered, 1 mL/4.5 kg of body weight to a maximum of 10 mL; n = 9) or to a nonepidural control group (n = 13). Vital signs were monitored for 24 hours, and sedation and pain scores, behavioral assessments, and presence or absence of complications was evaluated for 5 days postprocedure.ResultsAll dogs tolerated the epidural without complications. Four dogs were removed from the study because of status unblinding, lack of patient cooperation, or incomplete follow‐up. No significant differences were noted in postprocedural pain scores in dogs that received epidural analgesia. Significant differences in postprocedural pain scores were noted in the nonepidural control group. No significant differences were noted in vital signs, behavioral assessments, or the proportion of dogs with a 50% increase in pain scores between the epidural and nonepidural groups.Conclusions and Clinical ImportanceEpidural anesthesia was well‐tolerated. Dogs not receiving the epidural had poor postprocedural pain control. A consistent benefit for the epidural vs nonepidural group could not be identified. Additional studies are required to better assess the impact and efficacy of epidural anesthesia for cystoscopic procedures.

Opioid requirements after locoregional anaesthesia in dogs undergoing tibial plateau levelling osteotomy: a pilot study

ObjectiveTo determine the intraoperative and early postoperative opioid requirement after ultrasound-guided sciatic and/or femoral nerve block or epidural anaesthesia in dogs undergoing tibial plateau levelling osteotomy (TPLO). Study designProspective, masked, pilot, randomized, clinical trial. AnimalsA total of 40 client-owned dogs undergoing TPLO. MethodsEach dog was randomly assigned to group SF (combined sciatic and femoral nerve block), group S (sciatic nerve block), group F (femoral nerve block) or group E (epidural anaesthesia). A total of 0.3 mL kg–1 of ropivacaine 0.5% was administered to each nerve or in the epidural space. Intraoperatively, fentanyl (2 μg kg–1) was administered intravenously when heart rate, mean arterial pressure or respiratory rate increased by >30% compared with baseline values. Postoperatively, a visual analogue scale (VAS) and a modified German version of the French pain scale (4AVet) were used to assess pain every 30 minutes for 150 minutes and again once the morning after surgery. Methadone (0.1 mg kg–1) was administered intravenously if the VAS was ≥ 4 cm [maximal value 10 cm; median (interquartile range)] or the composite pain score was ≥5 [maximal value 15; median (interquartile range)]. Significance was defined as p ≤ 0.05. ResultsGroups SF and E required less total intraoperative and early postoperative opioid doses compared with groups S and F (p = 0.031). No dogs in group SF had a block failure or required postoperative methadone. A reduced methadone requirement was found in group SF compared with all the other groups up to 150 minutes after recovery (p = 0.041). Conclusions and clinical relevanceCombined sciatic and femoral nerve block and epidural anaesthesia lead to less cumulative consumption of perioperative opioids than single nerve blockade. Sciatic or femoral nerve block alone might be insufficient to control nociception and early postoperative pain in dogs undergoing TPLO.

Evaluation of lumbo-sacral epidural anaesthesia or analgesia with lidocaine-acepromazine combination in dogs undergoing cystotomy

<p class="abstract"><strong>Background:</strong> Epidural anaesthesia is one of the most frequently used regional anesthetic techniques recommended for surgical procedures caudal to the umbilicus in dogs. However, the use of lignocaine alone for epidural regional analgesia has been discovered to have shorter duration of analgesia and prolong onset of action, hence there is need to explore combinations of agents that will overcome this challenge. This study aimed to evaluate the anaesthetic/analgesic effect of cranial epidural anaesthesia in dogs undergoing cystotomy using Lignocaine in combination with acepromazine at the dose rates of 7 mg/kg and 0.05 mg/kg respectively.</p><p class="abstract"><strong>Methods:</strong> Eight apparently healthy matured, male and female dogs were used for the experiment. The onset and duration of analgesia was determined. The pulse rates, respiratory rates, mean arterial blood pressure, rectal temperature, complete blood count and the oxygen saturation level were determined at baseline, intra operative and post-operative. </p><p class="abstract"><strong>Results:</strong> There were no significant differences in all the parameters measured before and after the epidural administration of the agents. The onset of anaesthesia was rapid and the duration of anaesthesia was sufficient enough for the procedure to be carried out. However, there was significant difference in PCV, Hb and total RBC count between the baseline and other timing intervals. There were no significant differences in leucocytic and cardiopulmonary parameters between the baseline and other timing intervals.</p><p class="abstract"><strong>Conclusions:</strong> The epidural administration of lignocaine and acepromazine combination at the doses indicated can produced sufficient epidural anaesthesia with rapid onset for the purpose of cystotomy in dogs without major systemic influence on hemodynamic and cardiopulmonary changes.</p>

3D anatomical model for teaching canine lumbosacral epidural anesthesia.

Purpose To develop a 3D anatomical model for teaching canine epidural anesthesia (3DMEA) and to assess its efficacy for teaching and learning prior to the use of live animals.Methods The creation of 3DMEA was based on 3D optical scanning and 3D printing of canine bone pieces of the fifth to the seventh lumbar vertebrae, sacrum and pelvis. A total of 20 male dogs were scheduled for castration. 20 veterinary students watched a video showing epidural anesthesia in dogs before the clinical attempt and were assigned to control or 3DMEA groups. Students in the 3DMEA group trained in the model after the video. For the clinical trial, the epidural procedure was performed by students under the veterinary supervision. When observed the absence of response to nociceptive stimuli, the epidural was considered successful. Then, all students answered a questionnaire evaluating the main difficulty founded in the technique and its degree of difficulty.Results The 3DMEA group reported a lower degree of difficulty to perform the epidural anesthesia technique when compared with the control group (p=0.0037). The 3DMEA reproduced the anatomical structures, allowing the perception of the distance of needle in relation to the iliac prominences during epidural anesthesia. Its mobility allowed simulation of the animal in standing position and sternal recumbency.Conclusion The use of 3DMEA demonstrated greater efficacy in the execution of the technique, being effective in the teaching and learning process before the epidural anesthesia in live animals.

Comparative study of epidural anesthesia in dogs by weight or occipito-coccygeal distance

ABSTRACT The effects of volume on lumbosacral epidural block in dogs were evaluated using two different doses of 2% lidocaine. Ten adult dogs, without defined breed, were subjected to two different anesthetic protocols. In the first, the local anesthetic was calculated based on the body weight (GP), wherein 1.0 mL of local anesthetic was used for each 3.5 kg; in the second protocol, the dose was stipulated according to the occipito-coccygeal (DG) distance with 1.5mL of local anesthetic for every 10 cm of distance. The available time, recovery period, extent of block, and rectal temperature were measured. After the analysis of the results, it was possible to verify that there was an increase in the time in GD when compared with GP, due to the greater volume administered in that group. The recovery period remained similar in both groups, despite the use of different doses. Regarding the extent of blockade, there was an increase in GD in relation to GP due to the increase of the local anesthetic dose. On the other hand, the rectal temperature presented a difference between the groups, remaining lower and below the reference values for the species in GD compared with GP at all moments analyzed, possibly due to a sympathetic action triggered by the cranial extension of the epidural block. It could be concluded that when a longer time and a more cranial blockade of epidural anesthesia are desired, the anesthesia volume should be based on the occipito-coccygeal distance, however, observing the rectal temperature.

Comparison of epidural versus intrathecal anaesthesia in dogs undergoing pelvic limb orthopaedic surgery

ObjectiveTo compare the procedural failure rate (PFR), intraoperative rescue analgesia (iRA) probability and postoperative duration of motor block after epidural and intrathecal anaesthesia in dogs undergoing pelvic limb orthopaedic surgery. Study designProspective, randomized clinical trial. AnimalsNinety-two client-owned dogs. MethodsDogs were assigned randomly to receive either lumbosacral epidural anaesthesia (EA) (bupivacaine 0.5% and morphine 1%) or intrathecal anaesthesia with the same drugs in a hyperbaric solution (HIA). Inaccurate positioning of the needle, assessed by radiographic imaging, and lack of cerebral spinal fluid outflow were considered procedural failures (PFs) of EA and HIA, respectively. Fentanyl (1 μg kg−1 IV) was provided for intraoperative rescue analgesia, when either the heart rate or the mean arterial pressure increased by 30% above the pre-stimulation value. Its use was recorded as a sign of intraoperative analgesic failure. The motor block resolution was evaluated postoperatively. Variables were compared using Fisher's exact test, the Mann–Whitney U test and the Kaplan–Meier ‘survival’ analysis as relevant. ResultsThe PFRs in the EA and HIA groups were 15/47 (32%) and 3/45 (7%), respectively (p = 0.003). Differences in iRA were analysed in 26 and 30 subjects in the EA and HIA groups respectively, using Kaplan–Meier survival analysis. The iRA probability within the first 80 minutes of needle injection (NI) was higher in the EA group (p = 0.045). The incidence of dogs walking within 3 hours of NI was significantly higher in the HIA group (8/20, 40%) than in the EA group (0/17) (p = 0.004). Conclusions and clinical relevanceHIA was found to have lower PF, lower intraoperative analgesic failure and faster motor block resolution. In this study HIA was shown to provide some advantages over EA in dogs undergoing commonly performed pelvic limb orthopaedic surgery in a day-hospital regime.

Ketamine and its combination with pentazocine and meperidine for epidural anaesthesia in dogs

Clinically healthy dogs (15) of either sex aged about 1 year were randomly grouped into 3 with 5 dogs each to study the effect of epidural administration of ketamine alone and in combination with pentazocine and meperidine on clinic – anaesthetic profile in dogs. Ketamine hydrochloride @3 mg/kg b.wt and ketamine @3mg/kg b.wt in combination with pentazocine lactate @ 0.3 mg/kg b.wt and ketamine @ 3mg/kg b.wt in combination with meperidine @ 1mg/kg b.wt were administered epidurally in animals of group 1, 2 and 3, respectively. Marked alteration in rectal temperature, heart rate and respiration rate were recorded at initial intervals of observations in all the groups, however, these values returned towards normalcy by the end of 120 min of observation. Quicker onset of analgesia was recorded in group 2 (3.68±0.22 min) followed by group 3 (3.88±0.17 min) and group 1 (4.08±0.33 min). The duration of analgesia, standing time and recovery time were significantly longer in group 2 and 3 as compared to group 1. None of the groups showed significant variation in duration of recumbency. The treated animals manifested minimum, transient and occasional untoward reactions. It is concluded that pentazocine and meperidine can be given epidurally in combination with ketamine for effective analgesia in dogs.

The effect of epidural injection speed on epidural pressure and distribution of solution in anesthetized dogs

ObjectiveTo determine the effect of injection speed on epidural pressure (EP), injection pressure (IP), epidural distribution (ED) of solution, and extent of sensory blockade (SB) during lumbosacral epidural anesthesia in dogs. Study designProspective experimental trial. AnimalsTen healthy adult Beagle dogs weighing 8.7 ± 1.6 kg. MethodsGeneral anesthesia was induced with propofol administered intravenously and maintained with isoflurane. Keeping the dogs in sternal recumbency, two spinal needles connected to electrical pressure transducers were inserted into the L6-L7 and the L7-S1 intervertebral epidural spaces for EP and IP measurements, respectively. Bupivacaine 0.5% diluted in iohexol was administered epidurally to each dog via spinal needle at L7-S1 intervertebral space, at two rates of injection (1 and 2 mL minute−1 groups), with a 1-week washout period. Epidural distribution was verified with computed tomography, and SB was evaluated after arousal by pinching the skin with a mosquito hemostatic forceps over the vertebral dermatomes. The results were analyzed according to each injection speed, using paired t- and Wilcoxon signed-rank tests. ResultsMean ± SD of baseline EP and IP values were 2.1 ± 6.1 and 2.6 ± 7.1 mmHg, respectively. Significant differences were observed between 1 and 2 mL minute−1 groups for peak EP (23.1 ± 8.5 and 35.0 ± 14.5 mmHg, p = 0.047) and peak IP (68.5 ± 10.7 and 144.7 ± 32.6 mmHg, p <0.001). However, the median (range) of the ED, 11.5 (4–22) and 12 (5–21) vertebrae, and SB, 3.5 (0–20) and 1 (0–20) dermatomes, values of the two groups were not related to injection speed. Conclusions and clinical relevanceThe EP profile during injection was measured by separating the injection and pressure monitoring lines. The increase in epidural injection speed increased the EP, but not the ED or the SB in dogs.

Incidence of delayed hair re-growth, pruritus, and urinary retention after epidural anaesthesia in dogs

Delayed hair re-growth, pruritus and urinary retention are known complications after epidural anaesthesia in dogs. The aim of this study was to prospectively evaluate the effect of epidurally administered drugs on the occurrence of these complications in dogs. Ninety dogs were included in this study. Eighty client-owned dogs undergoing surgery were randomly assigned to one of three epidural treatment groups: either morphine and bupivacaine (MB), bupivacaine (B), or saline solution 0.9% (S) was administered epidurally to these patients. Ten dogs were only clipped in the lumbosacral area (C). Follow-up started 4 weeks after clipping and was performed every 4-5 weeks in cases of delayed hair re-growth or pruritus. Hair re-growth in the lumbosacral area was observed and compared to hair re-growth in the surgical field and the fentanyl patch area. Cytological analysis and a trichogram were performed if hair re-growth was delayed after 6 months. Time interval to first urination postoperatively was recorded (n = 80). Hair re-growth was delayed in 11 dogs (12.2%; B: n = 7, S: n = 2, MB: n = 1, C: n = 1) with no differences between groups. Pruritus was evident in two dogs (2.2%; MB: n = 1, S: n = 1). After 6 months, hair had started to re-grow in all but one dog (B). After 10 months the coat of this dog had re-grown. Time to first urination did not differ between groups. No direct correlation between the particular drugs injected epidurally and delayed hair re-growth, pruritus and urinary retention could be shown. Dog owners should be informed that hair re-growth after epidural anaesthesia could be markedly delayed.

Intraoperative antinociception and postoperative analgesia following epidural anesthesia versus femoral and sciatic nerve blockade in dogs undergoing stifle joint surgery

To compare analgesic efficacy of preoperative epidural anesthesia with efficacy of femoral and sciatic nerve blockade in dogs undergoing hind limb orthopedic surgery. Prospective randomized blinded clinical study. 22 dogs requiring stifle joint surgery. Dogs were premedicated with acepromazine and morphine, and anesthesia was induced with diazepam and propofol and maintained with sevoflurane in oxygen. Prior to surgery, a combination of 1.0% lidocaine solution with 0.25% bupivacaine solution was administered either into the lumbosacral epidural space (11 dogs) or perineurally along the femoral and sciatic nerves (11). Intraoperative nociception was assumed if heart rate or systolic blood pressure increased by > 10% from baseline, in which case fentanyl (2 μg/kg [0.9 μg/lb], IV) was administered as rescue analgesia. Following recovery from anesthesia, signs of postoperative pain were assessed every 30 minutes for 360 minutes from the time of local anesthetic administration via the modified Glasgow pain scale. Patients with scores > 5 (scale, 0 to 20) received hydromorphone (0.1 mg/kg [0.05 mg/lb], IV) as rescue analgesia and were then withdrawn from further pain scoring. Treatment groups did not differ significantly in the number fentanyl boluses administered for intraoperative rescue analgesia. Time to administration of first postoperative rescue analgesia was comparable between groups. Furthermore, there was no significant difference between groups in baseline pain scores, nor were there significant differences at any other point during the postoperative period. Femoral and sciatic nerve blocks provided intraoperative antinociception and postoperative analgesia similar to epidural anesthesia in dogs undergoing stifle joint surgery.

Anestesia epidural com lidocaína isolada e associada ao fentanil para realização de ováriossalpingo-histerectomia em cadelas

Investigou-se o efeito da lidocaína isolada ou associada ao fentanil na anestesia epidural, para realização de ováriossalpingo-histerectomia. Dezoito cadelas foram tranqüilizadas com acepromazina, seguindo-se indução anestésica com propofol, para a realização da punção lombossacra. Os animais foram distribuídos em dois grupos: o grupo GL recebeu lidocaína (8,5mg/kg) e o GLF fentanil (5µg/kg) associado à lidocaína (6,5mg/kg). Mensuraram-se as freqüências cardíaca (FC) e respiratória (FR), pressão arterial sistólica (PAS), variáveis hemogasométricas, concentração sérica de cortisol, necessidade de complementação anestésica com propofol durante a cirurgia, temperatura retal (T), período de latência e duração do bloqueio anestésico. Foi observada redução na FC, FR e PAS no GL e GLF, porém esses parâmetros mantiveram-se dentro dos limites fisiológicos. Para ambos os grupos, a concentração sérica de cortisol manteve-se estável após a cirurgia. Complementação anestésica foi necessária em 40% e 75% dos animais do GLF e GL, respectivamente. Conclui-se que ambos os protocolos foram suficientes para inibir a elevação sérica do cortisol, e resultaram em alterações mínimas cardiorrespiratórias, e que a complementação anestésica foi necessária.

Increased apoptosis of peripheral blood mononuclear cells (PBMC) during general and epidural anaesthesia in dogs

The objective of the study was to investigate the hypothesis that perioperative lymphocytopenia was due to apoptosis of these cells induced by either halothane or epidural anaesthesia in dogs. The relationship between apoptosis induction and plasma concentrations of the stress hormone cortisol and the cytokines TNF-alpha and IL-10 was examined as well. The study was performed on 22 healthy mongrel dogs, equal numbers from both genders, weighing 18.3 +/- 2.9 kg, and aged between 3-5 years. Dogs were divided in three groups. Eight of the animals were anaesthetized with halothane, another eight received epidural anaesthesia using lidocaine, and six served as controls. Venous blood samples were obtained immediately before (0 minute) anaesthesia, during deep anaesthesia (120 minute), and on the next day (24 hour) in order to determine the following parameters: the total lymphocyte counts, the percentage of apoptotic peripheral blood mononuclear cells (PBMC) by flow cytometry, plasma concentrations of the cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) by enzyme-linked immunosorbent assay (ELISA), and plasma cortisol levels by radioimmune assay. Both halothane and epidural anaesthesia in dogs induces apoptosis of PBMC with slight decrease in total lymphocyte counts. These immunomodulatory effects were transient and faded till the 24th hour. Concerning the mechanism of inducing lymphocyte apoptosis by general or epidural anaesthesia, it seemed that neither cortisol, nor the tested cytokines TNF-alpha and IL-10 were implicated in this process. Further investigations are necessary to confirm this assumption.

Anestesia epidural com ropivacaína, lidocaína ou associação de lidocaína e xilazina em cães: efeitos cardiorrespiratório e analgésico

Este estudo investigou o efeito da ropivacaína, da lidocaína e da associação de lidocaína e xilazina na anestesia epidural de cães. Trinta cães foram tranqüilizados com acepromazina intravenosa, distribuídos em três grupos e submetidos à anestesia epidural no espaço lombo-sacro, com lidocaína 2% com vasoconstrictor (GL), ropivacaína 1% (GR) ou com xilazina associada à lidocaína (GXL). Mensuraram-se as freqüências cardíaca (FC) e respiratória (f), a pressão arterial sistólica (PAS), a concentração final expirada de CO2 (EtCO2), o volume minuto (VM) e a temperatura retal (T). Para avaliação da analgesia somática, utilizou-se o teste do panículo e o teste térmico a 55°C. Os protocolos produziram anestesia da região retro-umbilical, sendo que a associação XL produziu bloqueio anestésico mais cranial, porém causou bradicardia moderada. A duração da anestesia foi mais prolongada nos animais dos grupos GXL (240 min) e GR (250 min), quando comparada as do grupo GL (120 min).

Prolongation of epidural anaesthesia in dogs with bupivacaine in a lipid emulsion

An aqueous solution and a lipid emulsion of bupivacaine were administered epidurally in doses of 1.8 mg/kg to six beagle dogs following a randomised two-phase crossover design. The aqueous solution...

Medetomidine, levo-methadone and diazepam as premedication for lumbosacral epidural anaesthesia in dogs

The effect of medetomidine (40 μg/kg) together with levo-methadone (0.5 mg/kg) was evaluated in dogs as a sedative and analgesic premedication followed by a lumbosacral epidural block with mepivacaine 2% or bupi-vacaine 0.5% (0.3–0.5 ml/10cm crown-rump length). When sedation became insufficient in the course of surgery, additional diazepam (0.1–0.2 mg/kg) was administered. Only in 43% of the dogs could surgery be performed without additional sedation. Medetomidine and levo-methadone influenced the cardio-respiratory system markedly. Hypoxaemia as well as hypercarbia were evident. Diazepam had no additional effect on these respiratory changes. After surgery 19 dogs were given atipamezole, 18 received atipamezole and naloxone while 17 received no antagonists. In 10 out of the 19 dogs receiving only atipamezole, fits of excitability were seen, but those receiving atipamezole and naloxone had a quiet recovery.

Chest wall motion during epidural anesthesia in dogs

To determine the relative contribution of rib cage and abdominal muscles to expiratory muscle activity during quiet breathing, we used lumbar epidural anesthesia in six pentobarbital sodium-anesthetized dogs lying supine to paralyze the abdominal muscles while leaving rib cage muscle motor function substantially intact. A high-speed X-ray scanner (Dynamic Spatial Reconstructor) provided three-dimensional images of the thorax. The contribution of expiratory muscle activity to tidal breathing was assessed by a comparison of chest wall configuration during relaxed apnea with that at end expiration. We found that expiratory muscle activity was responsible for approximately half of the changes in thoracic volume during inspiration. Paralysis of the abdominal muscles had little effect on the pattern of breathing, including the contribution of expiratory muscle activity to tidal breathing, in most dogs. We conclude that, although there is consistent phasic expiratory electrical activity in both the rib cage and the abdominal muscles of pentobarbital-anesthetized dogs lying supine, the muscles of the rib cage are mechanically the most important expiratory muscles during quiet breathing.

Cardiovascular effects of dihydroergotamine during epidural anaesthesia in dogs.

The haemodynamic changes during epidural anaesthesia and following the administration of dihydroergotamine (DHE; 10 micrograms/kg i.v.) were studied in 7 dogs (epidural group). Epidural anaesthesia was associated with reductions in mean arterial, mean pulmonary arterial and mean right atrial pressures. Femoral flow was increased by 119.9 +/- 35.0% and femoral resistance fell by 62.7 +/- 7.2%. All these changes were abolished by additional administration of DHE during epidural anaesthesia. In a second group of dogs (control group, n = 8) with intact innervation, i.e. without epidural block, DHE (10 micrograms/kg iv.) also decreased femoral flow and increased femoral resistance which, however, was significantly less pronounced ( p less than 0.01). It is concluded that DHE in epidural anaesthesia constricts arteriolar resistance vessels, mainly within the blocked areas.