Lumbosacral Epidural Space Research Articles

Evaluation of 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)

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.

Computed Tomography-Derived Occipital-Coccygeal Length and Ilium Wing Distance Correlates with Skin to Epidural and Intrathecal Depths in Dogs.

The current clinical techniques for neuraxial needle placement in dogs are predominantly blind without prior knowledge of the depth required to reach the desired space. This study investigated the correlation and defined the relationship between easily obtainable external landmark variables in the dog; occipital–coccygeal length (OCL) and ilium wings distance (IWD), with the skin to epidural and intrathecal space distances using computed tomography (CT). The CT images of 86 dogs of different breeds were examined in this retrospective observational study. Images of dogs in sternal recumbency were optimized to the sagittal view. The distances between the skin and lumbosacral epidural space (LSE) and skin to sacrococcygeal space (SCE) were measured to the ligamentum flavum surrogate (LFS) line. The distance between the skin and the intrathecal space (ITS) was measured from the skin to the vertebral canal at the interlumbar (L5–L6) space. Measurements of the IWD and OCL were performed on dorsal and scout views, respectively. Linear regression equations and Pearson’s correlation coefficients were calculated between variables. Data were reported as mean (standard deviation). Significance was set as alpha < 0.05. After exclusion of four dogs, 82 CT scans were included. The depths were LSE 45 (15) mm, SCE 23 (10) mm, and ITS 50 (15) mm. There was a moderate correlation between OCL with LSE (=14.2 + OCL * 0.05 (r = 0.59, p < 0.0001)), and a strong correlation with ITS (=11.4 + OCL * 0.07 (r = 0.76, p < 0.0001)), while a very weak correlation was found with SCE (=14.0 + OCL * 0.02 (r = 0.27, p < 0.0584)). Similarly, with IWD, there was a moderate correlation with LSE (=10.8 + IWD * 0.56 (r = 0.61, p < 0.0001)), and strong correlation with ITS (=9.2 + IWD * 0.67 (r = 0.75, p < 0.0001)), while a weak correlation was found with SCE (=11.2 + IWD * 0.2 (r = 0.32, p < 0.0033)). Mathematical formulae derived from the multiple regression showed that the body condition score (BCS) improved the relationship between IWD and OCL and the LSE, SCE and ITS, while the addition of body weight was associated with multicollinearity. Further studies are required to determine the accuracy of the algorithms to demonstrate their ability for prediction in a clinical setting.

Dural sac localization using myelography and its application to the lumbosacral epidural in dogs.

Background:The techniques described for the identification of the lumbosacral (LS) epidural space in dogs do not guarantee the needle position or an accidental subarachnoid puncture, especially in small size dogs.Aim:To determine the relationship between body weight and the location of the dural sac (DS) using myelography in dogs, and to determine the possibility of subarachnoid puncture during LS epidural based on the position of the DS.Methods:Four masked observers evaluated 70 myelographic studies of dogs, annotating the vertebrae where the DS ended, if it was localized before or after the LS space, and if accidental subarachnoid puncture during LS epidural injection was possible (yes/no). Body weight (kg) was categorized into: less than 10 kg, between 10 and 20 kg, and more than 20 kg and was also converted to body surface area (BSA) as a continuous variable.Results:The DS ended at the LS space or caudally in 50% of dogs. There was a statistically significant difference between the position of the DS and the dog’s BSA (p = 0.001). The DS ended caudal to the LS space in 72.7% of dogs weighing <10 kg, in 25% of dogs between 10 and 20 kg and in 15% of dogs in the >20 kg category. The observers considered a possible subarachnoid puncture during LS epidural in 69.7% of patients <10 kg, 16.6% on those between 10 and 20 kg, and in 11.7% of the dogs >20 kg.Conclusion:The DS ended caudal to the LS space in almost 3/4 dogs in the <10 kg category, so accidental subarachnoid puncture during LS epidural is highly possible in this weight range.

DIFFERENT VOLUMES AND CONCENTRATIONS IN FIXED DOSES OF BUPIVACAINE IN LUMBOSACRAL EPIDURAL IN RELATION TO CRANIAL SPREAD IN LIVE DOGS

Objective: The objective of this study was to assess whether the volume or concentration of local anesthetic influences its spread and quality of lumbosacral epidural blockade when the total drug dose is fixed.Methods: A total of 30 healthy bitches, undergoing elective ovariohysterectomy received a lumbosacral epidural block with a fixed dose of 0.5 mg/kg b.w. bupivacaine after general anesthesia induction with propofol. Treatment 1 group (low volume, high concentration [LVHC], n=15) received 0.2 mL/kg b.w. of 0.25% bupivacaine, whereas treatment 2 group (high volume, low concentration [HVLC], n=15) received 0.3 ml/kg b.w. of 0.167% bupivacaine. Both solutions contained radio-opaque dye. Heart rate, blood pressure, respiratory rate, rectal temperature, cranial spread, first analgesic rescue, and motor blockade were determined at predetermined intervals.Results: At 5 min, the dorsal cranial spread levels of bupivacaine confirmed by radiographic examination were T8 (T1–T10) for HVLC treatment and T8 (T6–T10) for LVHC treatment (p=0.957). However, there was a significant difference (p=0.029) in the ventral spread levels between HVLC treatment (T2; C7-T6) and LVHC treatment (T6; T5–T11). The first analgesic rescue was needed after 249±58 min in the LVHC treatment group and after 179±32 min in the HVLC treatment group (p=0.0005).Conclusion: It was concluded, if the total dose is fixed, then administration of an HVLC bupivacaine local anesthetic solution in the lumbosacral epidural space seems to produce effective post-operative analgesia for ovariohysterectomy surgery in bitches.

Clinical comparison of the effects of isoflurane or propofol anaesthesia on mean arterial blood pressure and ventilation in dogs undergoing orthopaedic surgery receiving epidural anaesthesia

The aim of this study was to compare the effects on mean arterial pressure (MAP) and ventilation of propofol total IV anaesthesia (TIVA) and isoflurane as anaesthetic maintenance in healthy dogs undergoing orthopaedic surgery, with epidural anaesthesia. Dogs were premedicated IM with dexmedetomidine (4μg/kg) and methadone (0.3mg/kg), induced with IV propofol (0.65–5mg/kg) and randomly assigned to be maintained with isoflurane (group I) or propofol (group P). Isoflurane end-tidal concentration (EtISO) and propofol infusion rate were adjusted during the surgery to maintain a suitable anaesthetic depth. All dogs received bupivacaine (1mg/kg) and morphine (0.1mg/kg) in the lumbosacral epidural space (total volume 0.2mL/kg). MAP was recorded every 5min during the procedure. Statistical analysis was performed using parametric (Student’s t test) and nonparametric (Mann–Whitney U-test, chi-square) tests, as appropriate.Anaesthetic maintenance in groups I and P was accomplished by providing a mean EtISO of 1.12±0.15% and a mean propofol infusion rate of 15.0±4.7mg/kg/h, respectively. MAP was significantly higher in group P than in group I (92±17mmHg versus 78±10mmHg; P=0.021). Eleven dogs in group P and two dogs in group I reached an EtCO2>7.3kPa, requiring mechanical ventilation (P=0.001). In combination with epidural anaesthesia, propofol TIVA improved MAP and is a suitable alternative to isoflurane in orthopaedic surgery of the hind limb in healthy dogs. Nevertheless, since it was associated with increased respiratory depression, mechanical ventilation should be available.

The effect of epidurally administered dexamethasone with lignocaine for post-operative analgesia in dogs undergoing ovariohysterectomy. A dose-response study.

To evaluate the postoperative analgesic and adverse effects of three doses of dexamethasone, administered epidurally in combination with lignocaine, in dogs undergoing ovariohysterectomy (OVH). Twenty-four female dogs undergoing ovariohysterectomy were pre-medicated with acepromazine and general anaesthesia was induced and maintained with propofol. Animals were randomly allocated into four groups of six. The control group was given lignocaine 2% (LI) and the treatment groups were given lignocaine with either 2 mg dexamethasone (LIDEX2), 4 mg dexamethasone (LIDEX4) or 8 mg dexamethasone (LIDEX8) administered at the lumbosacral epidural space. Duration of postoperative analgesia, first analgesic rescue, motor blockade, heart rate, blood pressure, respiratory rate, and rectal temperature were evaluated. The duration of postoperative analgesia was 19.5 (SD 6) hours for LIDEX8 (p=0.001), 10 (SD 2) hours for LIDEX4 (p=0.002), 4 (SD 2) hours for LIDEX2 (p=0.074) treatments compared with values for the LI control treatment 2.2 (SD 1.6) hours. All treatments had significant cardiovascular and respiratory alterations but they were within acceptable range in these clinically healthy female dogs. Dexamethasone added to epidural lignocaine significantly extends the postoperative analgesia after ovariohysterectomy in female dogs.

Evaluation of epiduroscopy for detection of vertebral canal and spinal cord lesions in dogs.

OBJECTIVE To evaluate the potential usefulness of epiduroscopy for clinical diagnosis and treatment of vertebral canal and spinal cord lesions in dogs. SAMPLE Cadavers of 6 mixed-breed dogs. PROCEDURES Dogs were positioned in sternal recumbency, and an endoscope was introduced into the lumbosacral epidural space. A fiberscope (diameter, 0.9 mm; length, 30 cm) was used for 3 dogs, and a videoscope (diameter, 2.8 mm; length, 70 cm) was used for the other 3 dogs. Visibility and identities of anatomic structures were recorded, and maneuverability of the endoscopes was assessed. Extent of macroscopic tissue damage was evaluated by manual dissection of the vertebral canal at the end of the procedure. RESULTS Intermittent saline (0.9% NaCl) solution infusion, CO2 insufflation, and endoscope navigation improved visualization by separating the epidural fat from the anatomic structures of interest. Images obtained with the fiberscope were small and of poor quality, making identification of specific structures difficult. Maneuverability of the fiberscope was difficult, and target structures could not be reliably reached or identified. Maneuverability and image quality of the videoscope were superior, and spinal nerve roots, spinal dura mater, epidural fat, and blood vessels could be identified. Subsequent manual dissection of the vertebral canal revealed no gross damage in the spinal cord, nerve roots, or blood vessels. CONCLUSIONS AND CLINICAL RELEVANCE A 2.8-mm videoscope was successfully used to perform epiduroscopy through the lumbosacral space in canine cadavers. Additional refinement and evaluation of the technique in live dogs is necessary before its use can be recommended for clinical situations.

Pulse Oximetry During Laparoscopy-Assisted Embryo Transfer Under Lumbosacral Epidural Anaesthesia in Goats

Eighteen adult, clinically healthy, Pashmina and Bakerwal goats undergoing laparoscopy-assisted embryo transfer were randomly divided into three equal groups (I, II, III) and injected lignocaine hydrochloride (@ 4.0mg/kg) or ropivacaine hydrochloride (@1.0mg/kg or 0.5mg/kg) at the lumbosacral epidural space, respectively. Pulse oximeter designed for application on human finger was used to record haemoglobin saturation (SpO2) values. The SpO2 values in 2 2 goats of Gr-I, II and III varied from 77.00±4.80 to 87.00±2.00%, 83.66±5.88 to 90.00±0.92% and 89.40±2.88 to 93.00±0.51%, respectively. Goats of Gr-I showed significantly (P<0.05) lower values than Gr-II and III continuously during initial 45 min following induction. The SpO2 values varied from 81.58±2.47 to 89.08±1.18% in 2 Bakerwal and 85.16±3.54 to 90.50±1.70% in Pashmina goats. It was concluded that the pulse oximetry is a useful, inexpensive and easy technique to quickly detect changes in oxygen saturation

Epiduroscopy of the lumbosacral vertebral canal in the horse: Technique and endoscopic anatomy.

Back pain is a common cause of gait alterations and poor performance in horses, but the available imaging modalities are frequently insufficient to isolate the underlying pathology. In human patients, epidural endoscopy (epiduroscopy) is successfully used to diagnose and treat challenging cases of lower back pain. Endoscopy of the cervical epidural space has previously been reported in anaesthetised horses. To develop a technique for lumbosacral epiduroscopy in standing horses and to describe the endoscopic anatomy of the lumbosacral epidural space. Pilot study to assess the feasibility of lumbosacral epiduroscopy in 5 horse cadavers. The cadavers of 5 horses, weighing 457-694kg (mean, 570kg), were suspended in an upright position. Vascular dilators of increasing size were inserted between the first 2 moveable vertebrae caudal to the sacrum to create a minimally invasive approach into the epidural space. A flexible videoendoscope was introduced and advanced as far cranially as the length of the endoscope permitted. The lumbosacral epidural space underwent gross necropsy examination following the procedure. The endoscope was successfully inserted into the epidural space in all horses. Saline injection through the working channel of the endoscope allowed the following anatomical structures to be seen: dura mater, left and right lumbosacral spinal nerves, cauda equina, epidural fat, connective tissue and blood vessels. Using the 60cm working length of the endoscope, the epidural space could be examined as far cranial as L3-T18, depending on the size of the horse. No gross damage to epidural neurovascular structures was observed on necropsy examination. Lumbosacral epiduroscopy is technically feasible in standing horses and may become a valuable diagnostic tool in horses with caudal back or limb pain of unknown origin. Studies in live horses will be necessary to evaluate the safety of the procedure.

Antinociceptive effects of epidural magnesium sulphate alone and in combination with morphine in dogs

ObjectiveTo compare the antinociceptive effects of magnesium sulphate (MgSO4) when administered epidurally alone and in combination with morphine. Study designExperimental, randomized, ‘blinded’, crossover study. AnimalsSix healthy adult Beagle dogs. MethodsEvaluated treatments were MgSO4 (2.5 mg kg−1) alone (Mg), morphine (0.1 mg kg−1) alone (Mo), MgSO4 in combination with morphine (Mm), and sterile water (0.115 mL kg−1; Co) that were injected in the lumbosacral epidural space using an epidural catheter. Antinociception was measured using the von Frey mechanical threshold device applied to the carpal pads, both sides of the thorax and metatarsi. Measurements were obtained at time points: before treatment (baseline) and 0.5, 1, 2, 4, 6, 12, 18 and 24 hours after the epidural injection. Sedation, behaviour score and presence of motor deficits were assessed. Data were analyzed using a linear mixed model and Bonferroni adjustments, with significance set at p < 0.05. ResultsThere were significant effects of treatment and time in all regions. Overall threshold values in grammes force [median (interquartile range)] when stimulation regions were combined were significantly higher in Mg [164 (135–200)], Mo [156 (129–195)] and Mm [158 (131–192)] compared to Co [145 (120–179)]. Thresholds were significantly higher compared to Co in Mg, Mo and Mm at the thorax and metatarsi, but only in Mg and Mo at the carpal pads. No motor deficits were observed at any time point. Thresholds (combined regions) were increased from baseline at one or more time points with all treatments, including control. Conclusion and clinical relevanceEpidural MgSO4 produced an antinociceptive effect characterised by an increase in the mechanical thresholds of similar magnitude to that produced by epidural morphine, compared with the control group, without causing any motor deficits. No potentiation of morphine antinociception was observed. The onset and offset times of antinociception could not be clearly established. To what extent these results can be extrapolated to clinical cases requires further investigation.

USE OF CONTRAST‐ENHANCED COMPUTED TOMOGRAPHY TO STUDY THE CRANIAL MIGRATION OF A LUMBOSACRAL INJECTATE IN CADAVER DOGS

Volumes used in lumbosacral epidural injections for anesthesia have remained unchanged since the 1960s. The goals of this cross-sectional observational study were to characterize the three-dimensional spread of a lumbosacral epidural injection, as well as confirm that the commonly used volume of 0.2ml/kg injected into the lumbosacral epidural space reaches the thoracolumbar (TL) junction in the majority (≥80%) of dogs. Ten clinically normal, adult, nonpregnant, mixed-breed dogs were obtained within five minutes of euthanasia and 0.2ml/kg of radiopaque contrast medium was injected into the lumbosacral epidural space. A computed tomography scan of the TL spine was performed immediately following the injection. Migration of contrast reached the TL junction in 8 of 10 (80%) dogs. Contrast was well visualized in all epidural planes with contrast travelling predominantly in the dorsal epidural space in 7 of 10 (70%) dogs. There was no significant difference in the weight of dogs where the epidural injectate reached the TL junction and those where it did not (P = 0.16), or in the weight of dogs where the cranial-most point of the contrast column was in the dorsal versus the ventral epidural space (P = 0.32). This preliminary study supports the use of computed tomography to characterize injectate distribution in the canine thoracolumbar epidural space and provides evidence that a 0.2-ml/kg volume is likely to reache the TL junction in most dogs. Further studies are needed in live dogs to determine if variables affecting human epidural injectate doses have similar effects in the dog.

Effectiveness of Pulsed Radiofrequency with Multifunctional Epidural Electrode in Chronic Lumbosacral Radicular Pain with Neuropathic Features

Background: Lumbosacral radicular pain is a common clinical finding with a statistical prevalence ranging from 9.9% to 25% in the general population. Objective: To investigate the effectiveness of dorsal root ganglion pulsed radiofrequency (PRF) in patients with chronic lumbosacral radicular pain and neuropathic features. Study Design: Prospective case series clinical outcome study. Methods: We evaluated 34 patients with lumbosacral neuropathic pain who underwent PRF at the corresponding level of radicular symptoms distribution (ranging from L3 to S1). Each patient suffered a single leg-radiating pain with probable neuropathic features (assessed with clinical grading) lasting for &gt; 6 months and unresponsive to previous treatments. A multifunctional PASHA-electrode® was introduced with trans-sacral access through a hollow needle, placed under fluoroscopic guidance into the lumbosacral epidural space and its active tip moved close to the dorsal root ganglion responsible of the clinical symptoms. After connecting the electrode to a generator, stimulation tests were performed and PRF was started and applied for 240 seconds at a frequency of 2Hz, amplitude of 45 V and a tip temperature between 40 – 42°C. If the pain involved more than a single nerve root, the electrode was placed at a different segment and the procedure repeated. Outcome measures included the pain intensity score on a 0 – 10 numeric rating scale (NRS) and the Italian Pain Questionnaire (QUID) at pre-treatment, one and 6 months post-treatment. P values &lt; 0.05 were considered statistically significant. Results: In comparison with pre-treatment, a significant reduction in pain score was observed in mean NRS either at one and 6 months (P &lt; 0.001). The QUID - Pain Rating Index rank displayed a parallel trend at the first (P &lt; 0.001) and last follow-up (P = 0.01). Moreover, a direct correlation between the 2 scales occurred, showing a parallel score decreasing (P &lt; 0.001). Eighteen (52.9%) and 17 (50%) of 34 patients showed pain reduction in NRS &gt; 2 points and &gt; 30%, at one and 6 months, respectively. Limitations: The non-controlled design of the study, the patients were heterogeneous, the small number of patients, and the duration of follow-up was limited to 6 months. Conclusions: PRF of dorsal root ganglion performed with a multifunctional electrode for &gt; 240 seconds appears to be safe and might be more effective than the classic 120 seconds needlemediated approach. Therefore, it may be considered as a valuable tool for the treatment of lumbosacral radicular pain with neuropathic features. Key words: PRF, radicular pain, neuropathic pain, DRG, NRS, PRIr-T, multifunctional electrode

Sacral Hiatus Study in Dry Human Sacra

Background and objectives: The sacral hiatus is the site for caudal epidural anaesthesia during perineal surgery and also for a painless delivery. It is also used for three dimensional colour visualization of lumbosacral epidural space in orthopaedic practice for diagnosis and treatment. Work on the morphometrical study of the sacral hiatus is limited, especially in south indian population. So this study is carried to examine, measure and record the morphometry of sacral hiatus in order to study the anatomical variations which will be useful for caudal epidural anaesthesia. Material and Methods: The study was conducted in the Department of Anatomy, Prathima Institute of Medical Science, Naganur, Andhra Pradesh. 93 dry sacra with complete sacral hiatus were taken for the study. The shape of the sacral hiatus was noted by naked eye. Level of the apex and base of the sacral hiatus was noted with respect to the sacral vertebra. The length of sacral hiatus was measured from apex to the midpoint of base, the anteroposterior depth of sacral hiatus at the apex was measured with the help of vernier calipers. The transverse width of sacral hiatus at the base was measured between the inner aspects of inferior limit of the sacral cornu with the help of divider and then adjusted, and calculated with vernier caliper. Results: In 47 (50.53 %) sacra the shape was Inverted-U and in 25 (26.9 %) sacra Inverted-V. The irregular shaped of sacral hiatus was observed in 11 (11.8 %) cases. A “Dumbbell” shaped sacral hiatus was observed in 5 (5.4%) cases with a nodular bony growth projecting medially from both margins. The dorsal wall of sacral canal was entirely absence in 4 (4.3%) cases. Absence of sacral hiatus, a rare phenomenon, was observed in 1 (1%) specimens only. Conclusion: In the present study, elongated hiatus and narrowing of the sacral canal at apex of sacral hiatus was found in a significant percentage, which should be kept in mind while giving the caudal anaesthesia in Andhra Pradesh region. DOI: http://dx.doi.org/10.3126/jmcjms.v2i1.11391 Janaki Medical College Journal of Medical Sciences (2014) Vol. 2 (1): 17-22

Comparison Between Lignocaine Hydrochloride and Ropivacaine Hydrochloride as Lumbosacral Epidural Anaesthetic Agents in Goats Undergoing Laparoscopy Assisted Embryo Transfer

Abstract Goats (n=12) undergoing laparoscopy assisted embryo transfer were randomly allotted to two groups (I and II) and injected lignocaine hydrochloride (4mg/kg) or ropivacaine hydrochloride (1mg/kg) at the lumbosacral epidural space. The animals were held with raised hind quarters for the first three minutes following injection. Immediately after induction of regional anaesthesia, they were restrained in dorsal recumbency in the Trendelenburg position in a cradle. Laparoscopy was performed after creating pneumoperitoneum using filtered room air. The mean (± S.E) induction time in animals of group I was significantly shorter (5.33 ± 0.61 min) than those belonging to group II (12.66 ±1.99 min). Complete analgesia developed throughout the hind quarters and abdomen for 30 min and 60 min in group I and II animal’s respectively. Unlike animals of group I, group II goats continued to show moderate analgesia for 180 minutes. The motor activity returned after a lapse of 130.00 ± 12.64 min and 405.00 ± 46.31 min respectively. Occasional vocalization and struggling was noticed in two goats one from each group irrespective of the surgical manipulations during laparoscopy. The rectal temperature and respiration rates showed only non-significant increase, but the heart rate values were significantly higher (P &lt; 0.5) up to 150 min in animals of both the groups when compared to their baseline values. From this study, it was concluded that both anaesthetic agents produced satisfactory regional anaesthesia in goats undergoing laparoscopy. However, considering the very long delay in regaining the hind limb motor activity, the use of ropivacaine may not be recommended for this purpose. Supplementation of sedative/tranquilizer with lumbosacral epidural anaesthesia needs evaluation.

Comparison of Two Doses of Ropivacaine Hydrochloride for Lumbosacral Epidural Anaesthesia in Goats Undergoing Laparoscopy Assisted Embryo Transfer

Goats (n = 12) undergoing laparoscopy assisted embryo transfer were randomly allotted to two groups (I and II) and injected same volume of ropivacaine hydrochloride at 1.0 mg/kg and 0.5 mg/kg body weight, respectively, at the lumbosacral epidural space. The hind quarters of all the animals were lifted up for the first 3.0 minutes following injection. Immediately after induction the animals were restrained in dorsal recumbency in Trendelenburg position in a cradle. Laparoscopy was performed after achieving pneumoperitoneum using filtered room air. Regional analgesia and changes in physiological parameters were recorded. The mean induction time in animals of group I (n = 6) was 12.666 ± 1.994 minutes. In these animals the analgesia extended up to the umbilical region and lasted for 60 minutes. Only two animals in group II were satisfactorily induced in 11.333 ± 2.333 minutes. In animals of group I, the time taken for regaining the full motor power was significantly long (405 ± 46.314 min) when compared to group II goats (95 ± 9.219 min). From this study it was concluded that ropivacaine did not produce adequate analgesia in most of the goats at 0.5 mg/kg. When used at 1.0 mg/kg, it produced satisfactory regional analgesia lasting for one hour but the prolonged motor loss precludes its use. Additional studies using ropivacaine hydrochloride at doses in between the two extremes used here may be undertaken before recommending it for lumbosacral anaesthesia in goats undergoing laparoscopy.

Use of electrical nerve stimulation to monitor lumbosacral epidural needle placement in cats

ObjectiveTo determine the minimal electrical threshold (MET) necessary to elicit muscle contraction of the pelvic limb or tail when an insulated needle is positioned outside (METout) and inside (METin) the lumbosacral epidural space in cats. Study designProspective, blinded study. AnimalsTwelve mixed-breed healthy adult cats, scheduled for a therapeutic procedure where lumbosacral epidural administration was indicated. MethodsUnder general anesthesia, an insulated needle was advanced through tissues of the lumbosacral interspace until its tip was thought to be just dorsal to the interarcuate ligament. An increasing electrical current (0.1 ms, 2 Hz) was applied through the stimulating needle in order to determine the MET necessary to obtain a muscle contraction of the pelvic limb or tail (METout), and then 0.05 mL kg−1 of iohexol was injected. The needle was further advanced until its tip was thought to be in the epidural space. The MET was determined again (METin) and 0.2 mL kg−1 of iohexol was injected. The cats were maintained in sternal position. Contrast medium spread was determined through lateral radiographic projections. ResultsThe radiographic study confirmed the correct needle placement dorsal to the interarcuate ligament in all cats. When the needle was placed ventrally to the interarcuate ligament, iohexol was injected epidurally in ten and intrathecally in two cats. The METout and METin was 1.76 ± 0.34 mA and 0.34 ± 0.07 mA, respectively (p < 0.0001). Conclusion and clinical relevanceNerve stimulation can be employed as a tool to determine penetration of the interarcuate ligament but not the piercing of the dura mater at the lumbosacral space in cats.

Evaluation of electrical nerve stimulation for epidural catheter positioning in the dog

ObjectiveTo evaluate the accuracy of epidural catheter placement at different levels of the spinal cord guided solely by electrical nerve stimulation and resultant segmental muscle contraction. Study designProspective, experiment. AnimalsSix male and two female Beagles, age (1 ± 0.17 years) and weight (12.9 ± 1.1 kg). MethodsAnimals were anesthetized with propofol and maintained with isoflurane. An insulated epidural needle was used to reach the lumbosacral epidural space. A Tsui epidural catheter was inserted and connected to a nerve stimulator (1.0 mA, 0.1 ms, 2 Hz) to assess positioning of the tip at specific spinal cord segments. The catheter was advanced to three different levels of the spinal cord: lumbar (L2–L5), thoracic (T5–T10) and cervical (C4–C6). Subcutaneous needles were previously placed at these spinal levels and the catheter was advanced to match the needle location, guided only by corresponding muscle contractions. Catheter position was verified by fluoroscopy. If catheter tip and needle were at the same vertebral body a score of zero was assigned. When catheter tip was cranial or caudal to the needle, positive or negative numbers, respectively, corresponding to the number of vertebrae between them, were assigned. The mean and standard deviation of the number of vertebrae between catheter tip and needle were calculated to assess accuracy. Results are given as mean ± SD. ResultsThe catheter position in relation to the needle was within 0.3 ± 2.0 vertebral bodies. Positive predictive values (PPV) were 57%, 83% and 71% for lumbar, thoracic and cervical regions respectively. Overall PPV was 70%. No significant difference in PPV among regions was found. Conclusion and clinical relevancePlacement of an epidural catheter at specific spinal levels using electrical nerve stimulation was feasible without radiographic assistance in dogs. Two vertebral bodies difference from the target site may be clinically acceptable when performing segmental epidural regional anesthesia.

Substituição da agulha isolada para eletroneuroestimulação pela agulha metálica de cateter intravenoso, na verificação da punção epidural, em cães

Utilizou-se o eletroneuroestimulador como um meio adequado para confirmação do posicionamento da ponta de agulhas isoladas no espaço epidural lombossal, por meio de pequenas estimulações elétricas que provocam contrações dos músculos inervados, empregando-se agulha de cateter intravenoso em vez de agulha isolada para a eletroneuroestimulação. Foram utilizados 40 cães para procedimentos cirúrgicos ortopédicos, abdominais ou retroumbilicais que necessitassem de bloqueio epidural. Durante a introdução gradativa da agulha no canal vertebral lombossacral, estímulos elétricos de 1,5 a 0,5mA foram aplicados. Diante de contrações musculares em membros pélvicos, cauda e/ou ânus, as quais foram consideradas respostas condizentes com o correto posicionamento da agulha no espaço epidural, estimulando raízes da cauda equina, procedeu-se à administração da associação de lidocaína, bupivacaína e tramadol. Constatou-se a adequada anestesia epidural mediante relaxamento do esfíncter anal, ausência dos reflexos patelares e flexor e a analgesia na área cirúrgica abdominal. Conclui-se que o método foi eficaz para a confirmação do correto posicionamento da agulha no espaço epidural durante a realização dessa anestesia regional em cães.

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.

The Morphology and Clinical Significance of the Dorsal Meningovertebra Ligaments in the Lumbosacral Epidural Space

A dissection-based study of 30 embalmed cadavers. To determine the morphology and morphometry of the dorsal meningovertebral ligaments in the lumbosacral segments and to discuss their clinical significance. Postoperative cerebrospinal fluid leakage is associated with longer hospital stays and significant implications for the patient, the surgeons, and society as a whole. To protect the dural sac during lumbar surgery, knowledge of the surgical anatomy of the dorsal meningovertebral ligaments is crucial. A total of 30 adult embalmed cadavers (52-70 yr of age; mean age of 64 yr) were used. The vertebral canal was divided to expose the dural sac and the spinal nerve roots, and the spinal cord was removed. The morphology, quantity, and attachment of the dorsal meningovertebral ligaments in the lumbosacral region were observed, and the length, width, or diameter and thickness of the ligaments were measured with vernier calipers. The dorsal meningovertebral ligaments in the lumbosacral region connect the dura to the ligamenta flava or the lamina. The number of the attachment points on the ligamenta flava was relatively larger than that on the lamina, and the occurrence rate of dorsal meningovertebral ligaments was 97% at L5-S1. The thickest ligaments were observed at the L5 and S1 vertebrae. The length of the ligaments varied from 5.16 to 40.24 mm, and the ligaments extended caudally from their origin on the dura to their attachment to the lamina or the ligamentum flavum. The morphology of the dorsal meningovertebral ligaments was divided into 5 types: strip type, cord type, "Y"-shaped type, grid type, and thin slice type. The dorsal meningovertebral ligaments may contribute to dura laceration and epidural hemorrhage during flavectomy and laminectomy, and an appreciation of this relationship might help reduce the risk of such complications.