Erector spinae plane block in dogs undergoing hemilaminectomy: A prospective randomized clinical trial.

OBJECTIVE: To compare the perioperative cumulative opioid consumption and the incidence of cardiovascular complications in dogs undergoing hemilaminectomy in which either an erector spinae plane (ESP) block or systemic opioids were administered. STUDY DESIGN: Prospective randomized clinical trial. ANIMALS: A total of 60 client-owned dogs. METHODS: Dogs were randomized to one of three groups: an ESP block (group ESP), a constant rate infusion of fentanyl (group FNT, positive control) or a single dose of methadone as premedication (group MTD, negative control). Intraoperative nociceptive response was treated with fentanyl [1 µg kg-1, intravenously (IV)] boli. Before closure of the surgical site, morphine (0.1 mg kg-1) was applied to the dura mater. The cumulative dose of opioids was recorded and compared between groups. The incidence of intraoperative bradycardia and/or hypotension and the time to extubation were compared between groups. The short form of the Glasgow Composite Pain Scale (SF-GCPS) was used to score nociception before anaesthetic induction and 1, 2, 6, 12,18 and 24 hours postoperatively. Methadone 0.2 mg kg-1 was administered IV if the SF-GCPS score was ≥ 5. RESULTS: Group MTD required more intraoperative rescue analgesia than groups ESP (p = 0.008) and FNT (p = 0.001). The total cumulative intraoperative dose of fentanyl was higher in groups FNT (p < 0.0001) and MTD (p = 0.002) than in group ESP. The incidence of cardiovascular complications was similar between groups. Extubation time was longer in group MTD (p = 0.03). Postoperatively, the time to first rescue analgesia was longer in group ESP than in group MTD (p = 0.03). The cumulative postoperative opioid consumption and pain scores were similar between groups. CONCLUSIONS AND CLINICAL RELEVANCE: The ESP block resulted in a reduced intraoperative opioid consumption compared with the control positive and negative groups.

Agreement between transthoracic echocardiography and esophageal Doppler on aortic flow variables in anesthetized mechanically ventilated dogs.

The use of transthoracic echocardiography (TTE) and esophageal Doppler (ED) for the measurement of hemodynamic variables in anesthetized dogs was studied. Fourteen mixed-breed dogs, without cardiac disease, undergoing general anesthesia for diagnostic or therapeutic procedures were included in this prospective preliminary study. Dogs were premedicated with dexmedetomidine (3 µg/kg) and methadone (0.3 mg/kg), intramuscularly. General anesthesia was induced with propofol intravenously titrated to effect and maintained with isoflurane in oxygen. Animals were positioned in dorsal recumbency. Transthoracic echocardiography was performed using a 5-2 MHz cardiac ultrasound probe placed in the subcostal window, whereas esophageal Doppler was performed using a CardioQ probe (MP50; Deltex Medical, Chichester, UK). Once an appropriate view of the aortic flow was obtained, the variables peak velocity (PV) and velocity-time integral (VTI) were measured. Agreement between methods was evaluated using the Bland-Altman method with single observation per individual. The bias and the limits of agreement (LOA) between the two methods were determined. Mean (± SD) PV was 99.46 cm/s (± 42.73 cm/s) and 110.29 cm/s (± 35.86 cm/s), and VTI was 13.24 cm (± 4.33 cm) and 13.05 cm (± 4.47 cm), for TTE and ED, respectively. Mean differences and LOA were 10.83 cm/s (range: -20.50 to 42.16 cm/s) and -0.19 cm (range: -3.32 to 2.95 cm) for PV and VTI, respectively. No statistically significant differences were determined in the variables measured between TTE and ED in anesthetized dogs without cardiac disease, positioned in dorsal recumbency. This could be of clinical relevance when an evaluation of the intraoperative hemodynamic status of anesthetized dogs is desired.

Concordance entre l'échocardiographie transthoracique et le Doppler oesophagien sur les variables du débit aortique chez des chiens anesthésiés ventilés mécaniquement. L'utilisation de l'échocardiographie transthoracique (TTE) et du Doppler oesophagien (ED) pour la mesure des variables hémodynamiques chez les chiens anesthésiés a été étudiée. Quatorze chiens de race mixte, sans maladie cardiaque, subissant une anesthésie générale pour des procédures diagnostiques ou thérapeutiques ont été inclus dans cette étude préliminaire prospective. Les chiens ont reçu une prémédication avec de la dexmédétomidine (3 µg/kg) et de la méthadone (0,3 mg/kg), par voie intramusculaire. L'anesthésie générale a été induite avec du propofol intraveineux titré à effet et maintenue avec de l'isoflurane dans de l'oxygène. Les animaux ont été placés en décubitus dorsal. L'échocardiographie transthoracique a été réalisée à l'aide d'une sonde à ultrasons cardiaque 5-2 MHz placée dans la fenêtre sous-costale, tandis que le Doppler oesophagien a été réalisé à l'aide d'une sonde CardioQ (MP50; Deltex Medical, Chichester, Royaume-Uni). Une fois qu'une vue appropriée de l'aorte était obtenue, les variables vitesse maximale (PV) et intégrale vitesse-temps (VTI) étaient mesurées. La concordance entre les méthodes a été évaluée à l'aide de la méthode de Bland-Altman avec une seule observation par individu. Le biais et les limites d'accord (LOA) entre les deux méthodes ont été déterminés. La PV moyenne (± SD) était de 99,46 cm/s (± 42,73 cm/s) et 110,29 cm/s (± 35,86 cm/s), et la VTI était de 13,24 cm (± 4,33 cm) et 13,05 cm (± 4,47 cm), pour TTE et ED, respectivement. Les différences moyennes et la LOA étaient de 10,83 cm/s (intervalle : −20,50 à 42,16 cm/s) et de −0,19 cm (intervalle : −3,32 à 2,95 cm) pour PV et VTI, respectivement. Aucune différence statistiquement significative n'a été déterminée dans les variables mesurées entre TTE et ED chez des chiens anesthésiés sans maladie cardiaque, positionnés en décubitus dorsal. Cela pourrait être cliniquement pertinent lorsqu'une évaluation de l'état hémodynamique peropératoire des chiens anesthésiés est souhaitée.(Traduit par Dr Serge Messier).

Incidence of dural sac puncture during neuraxial anesthesia in cats: an observational, retrospective study.

OBJECTIVES: The aim of this study was to determine the occurrence of dural puncture, indicated by cerebrospinal fluid (CSF) outflow, in cats receiving neuraxial anesthesia through a lumbosacral injection guided by a pop sensation method. METHODS: This was an observational, retrospective study. Cats that were scheduled for lumbosacral neuraxial anesthesia were included. Medical records were analyzed to investigate: (1) demographic data; (2) neuraxial anesthesia performed (epidural/spinal); (3) type of needle used, including gauge and length; (4) presence of CSF (yes/no) and/or blood (yes/no) in the hub of the needle; and (5) flicking of the tail during needle advancement (yes/no). RESULTS: A total of 94 medical records were analyzed. A 22 G 50 mm Tuohy needle was used in all cats scheduled for an epidural injection (n = 60), whereas a 22 G 40 mm Quincke needle was used in all cats scheduled for an intrathecal injection (n = 34). CSF outflow was detected in 55/60 (91.7%) cats in which a Tuohy needle was used, and 34/34 (100%) of the cats in which a Quincke needle was used (P = 0.15). Flicking of the tail was detected in 41/60 (68.3%) and in 24/34 (70.6%) injections with Tuohy and Quincke needles, respectively (P >0.99). Traces of blood, but not active blood outflow, were detected via staining of the first drops of CSF in 2/34 cats in which Quincke needles were used and in none of the cats in which Tuohy needles were used (P = 0.12). CONCLUSIONS AND RELEVANCE: This study shows that the lumbosacral approach for neuraxial anesthesia in cats may result in a dural sac puncture when 22 G Quincke or Tuohy needles are used. The pop sensation method should be deemed effective in predicting intrathecal but not epidural needle placement.

Axillary ultrasound-guided approach for the brachial plexus in pig cadavers: A descriptive study.

Effective multimodal analgesia techniques are required when pigs are used as models in orthopedic human research. Regional anesthesia is a widely used technique to provide perioperative analgesia in animals undergoing orthopedic surgery. The brachial plexus (BP) block is indicated to desensitize the forelimb in many species but has not been yet described in pigs. The main aims of this study were to develop an ultrasound-guided axillary approach for the BP and to evaluate injectate spread and nerve staining in pig cadavers. Eight fresh F1 cross breed German Large White and German Landrace male pig cadavers were enrolled. Two cadavers were used for anatomical dissection of the axillary space and to determine the disposition of the BP. Six cadavers were used to perform a bilateral axillary ultrasound-guided approach for the BP, and after injecting 0.3 ml/kg of a solution of 2% lidocaine and new methylene blue (L-NMB), these were dissected to determine injectate spread and nerve staining. Upon dissection, the BP was observed in all the cases surrounded by the axillary sheath and in close proximity to the axillary artery. Ultrasonographic scanning and guidance for the approach to the BP was feasible in all cadavers and upon dissection, all the nerves forming the BP were stained in all their quadrants and in all the cases. In conclusion, the injection of 0.3 ml/kg of L-NMB through an ultrasound-guided axillary approach to the BP was feasible and adequate to entirely stain the BP in all pig cadavers. Further clinical studies are required to evaluate the effectiveness of this technique in live animals.

Ventilator output splitting interface 'ACRA': Description and evaluation in lung simulators and in an experimental ARDS animal model.

The current COVID-19 pandemic has led the world to an unprecedented global shortage of ventilators, and its sharing has been proposed as an alternative to meet the surge. This study outlines the performance of a preformed novel interface called 'ACRA', designed to split ventilator outflow into two breathing systems. The 'ACRA' interface was built using medical use approved components. It consists of four unidirectional valves, two adjustable flow-restrictor valves placed on the inspiratory limbs of each unit, and one adjustable PEEP valve placed on the expiratory limb of the unit that would require a greater PEEP. The interface was interposed between a ventilator and two lung units (phase I), two breathing simulators (phase II) and two live pigs with heterogeneous lung conditions (phase III). The interface and ventilator adjustments tested the ability to regulate individual pressures and the resulting tidal volumes. Data were analyzed using Friedman and Wilcoxon tests test (p < 0.05). Ventilator outflow splitting, independent pressure adjustments and individual tidal volume monitoring were feasible in all phases. In all experimental measurements, dual ventilation allowed for individual and tight adjustments of the pressure, and thus volume delivered to each paired lung unit without affecting the other unit's ventilation-all the modifications performed on the ventilator equally affected both paired lung units. Although only suggested during a dire crisis, this experiment supports dual ventilation as an alternative worth to be considered.

Evaluation of electrical nerve stimulation to confirm sacrococcygeal epidural needle placement in dogs.

OBJECTIVES: To evaluate the use of 0.7 mA as a fixed electrical current to indicate epidural needle placement and to confirm that 0.7 mA is greater than the upper limit of the minimal electrical threshold (MET) for sacrococcygeal epidural needle placement in dogs. STUDY DESIGN: Prospective clinical study. ANIMALS: A group of 20 client-owned dogs. METHODS: During general anesthesia and with standard monitoring, the presence of the patellar reflex was confirmed in all dogs. An insulated needle was inserted through the sacrococcygeal intervertebral junction, and absence of tail movement was confirmed when a fixed electrical current of 0.7 mA was applied. Then, the needle was further advanced toward the epidural space until the expected motor response was obtained - the nerve stimulation test (NST). The NST was considered positive when a motor response of the muscles of the tail was elicited but not the perineal muscles, whereas it was considered negative when no movement of the tail was evoked. The electrical current was turned to 0 mA and then increased by 0.01 mA increments until tail movement was evoked; this was recorded as the MET. In the positive NST cases, 0.05 mL cm-1 occipitococcygeal length of 2% lidocaine or 0.25-0.5% bupivacaine was administered. Epidural blockade was confirmed by the loss of patellar reflex. Descriptive statistics were used to present data. RESULTS: Sacrococcygeal epidural needle placement, corroborated by loss of the patellar reflex, was correctly predicted in 89.5% (95% confidence interval, 68.6-97.1%) of the cases. The MET was 0.22 mA (0.11-0.36). CONCLUSIONS AND CLINICAL RELEVANCE: A current of 0.7 mA is approximately twice the upper limit of the MET for epidural placement. Therefore, this study demonstrates, with a success rate of 89.5%, the adequacy of using 0.7 mA as the fixed electrical current to detect sacrococcygeal epidural needle placement in dogs.

Transversus abdominis plane block in cat cadavers: anatomical description and comparison of injectate spread using two- and three-point approaches.

OBJECTIVE: To describe the sonoanatomy of the abdominal wall in live cats and to compare the distribution pattern of two versus three ultrasound-guided transversus abdominis plane (TAP) injections using clinically applicable volumes of lidocaine-dye solution in cat cadavers. STUDY DESIGN: Prospective anatomical study. ANIMALS: A total of eight client-owned healthy cats and eight cat cadavers. METHODS: Ultrasound anatomy of the abdominal wall, landmarks and sites for needle access were determined in live cats. Ultrasound-guided TAP injections were performed in eight thawed cat cadavers. Volumes of 0.25 or 0.16 mL kg-1 per point of a lidocaine-dye solution were injected using either two [subcostal and preiliac (SP)] or three [subcostal, retrocostal and preiliac (SRP)] injection points, respectively. Each cadaver was then dissected to determine the injectate distribution and the number of thoracolumbar nerves stained with each approach. The target nerves were defined as the ventromedial branches of the thoracic nerves 10 (T10), T11, T12, T13 and lumbar nerves 1 (L1) and L2. RESULTS: Sonoanatomy was consistent with anatomy upon dissection and the TAP was identified in all cadavers. A total of 16 subcostal, 16 preiliac and nine retrocostal TAP injections were performed. The overall staining success rate of the target nerves was 66.7% and 92.6% for the SP and SPR approaches, respectively (p = 0.02). The ventromedial branches of T10, T11, T12, T13, L1 and L2 were stained in 57.1%, 100.0%, 85.7%, 28.6%, 42.9% and 85.7%, and in 66.7%, 100.0%, 100.0%, 100.0%, 88.9% and 100.0% of the cases with the SP and SRP approaches, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The SRP approach allowed a broader distribution around the target nerves, whereas a staining gap was observed at T13 and L1 with the SP approach. Further studies are necessary to investigate the analgesic effect of these approaches in a clinical setting.

Efficacy of tramadol for postoperative pain management in dogs: systematic review and meta-analysis.

OBJECTIVE: To evaluate the evidence of analgesic efficacy of tramadol for the management of postoperative pain and the presence of associated adverse events in dogs. DATABASES USED: A comprehensive search using PubMed/MEDLINE, LILACS, Google Scholar and CAB databases with no restrictions on language and following a prespecified protocol was performed from June 2019 to July 2020. Included were randomized controlled trials (RCTs) performed in dogs that had undergone general anesthesia for any type of surgery. Two authors independently classified the studies, extracted data and assessed their risk of bias using Cochrane's tool. RevMan and GRADE methods were used to rate the certainty of evidence (CoE). CONCLUSIONS: Overall 26 RCTs involving 848 dogs were included. Tramadol administration probably results in a lower need for rescue analgesia versus no treatment or placebo [moderate CoE; relative risk (RR): 0.47; 95% confidence interval (CI): 0.26-0.85; I2 = 0%], and may result in a lower need for rescue analgesia versus buprenorphine (low CoE; RR: 0.50; 95% CI: 0.20-1.24), codeine (low CoE; RR: 0.75; 95% CI: 0.16-3.41) and nalbuphine (low CoE; RR: 0.05; 95% CI: 0.00-0.72). However, tramadol administration may result in an increased requirement for rescue analgesia versus methadone (low CoE; RR: 3.45; 95% CI: 0.66-18.08; I2 = 43%) and COX inhibitors (low CoE; RR: 2.27; 95% CI: 0.68-7.60; I2 = 45%). Compared with multimodal therapy, tramadol administration may make minimal to no difference in the requirement for rescue analgesia (low CoE; RR: 1.12; 95% CI: 0.48-2.60; I2 = 0%). Adverse events were inconsistently reported and the CoE was very low. The overall CoE of the analgesic efficacy of tramadol for postoperative pain management in dogs was low or very low, and the main reasons for downgrading the evidence were risk of bias and imprecision.

Development of a lateral ultrasound-guided approach for the proximal radial, ulnar, median and musculocutaneous (RUMM) nerve block in cats.

OBJECTIVE: To describe a lateral ultrasound (US)-guided approach to the radial, ulnar, median and musculocutaneous (RUMM) nerves through a single proximal in-plane insertion in cats and to determine whether one or two injection points are required to successfully stain all the target nerves. STUDY DESIGN: Prospective study. ANIMALS: A total of eight client-owned healthy cats and 12 cat cadavers. METHODS: In live cats, the US anatomy of the brachium, the landmarks and the site for needle accesses were determined. Then, 12 thawed feline cadavers were used to assess the spread of dye solution and nerve staining following the US-guided proximal-lateral-humeral RUMM injection using one and two injection points. Each cadaver was injected with 0.15 mL kg-1 of a 0.25% new methylene blue solution in either a single injection aimed for the radial nerve of one limb (G1) or via two sites delivering 0.1 mL kg-1 and 0.05 mL kg-1 aimed for the radial and musculocutaneous nerves of the opposite limb, respectively (G2). Upon dissection, staining of the target nerves around their circumference for length of >1 cm was considered successful. RESULTS: Sonoanatomy was consistent with anatomy upon dissection and target nerves were identified in all cadavers. Staining was 100% successful for the radial, median and ulnar nerves in both groups, and 41.7% and 100% for the musculocutaneous nerve in G1 and G2, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: This novel lateral US-guided approach for the proximal RUMM nerve block allowed a good identification of the nerves and related structures, and it provided a consistent muscular structure through which the needle could be easily guided. An injection performed in two aliquots (within the caudal and cranial compartments of the neurovascular sheath) appeared to be necessary to successfully stain all the target nerves.

Mechanism of action of the erector spinae plane block: distribution of dye in a porcine model.

This study aimed to describe the anatomical distribution of dye injected in the erector spinae plane (ESP) in a porcine living model, which could aid to reveal factors potentially relevant to the unexplained clinical effects of the ESP block. Six pigs received 0.6 mL/kg of 0.25% new methylene blue at the level of the sixth thoracic vertebra through either a cranial-to-caudal or a caudal-to-cranial in-plane ultrasound-guided bilateral ESP injection 20 min before euthanasia.Spread of dye evaluated through transverse cryosections (four injections) extended from T5 to T10 and from T5 to T8 when a cranial-to-caudal direction of injection was used, and from T5 to T9 and from T5 to T8 when the opposite direction of injection was used. A median of 4.5 medial and lateral branches of the dorsal rami was observed stained through anatomical dissection (eight injections), regardless of the direction of injection. No evidence of dye was found in the thoracic paravertebral or epidural spaces, where the dorsal root ganglia, ventral rami and rami communicantes are located. In all the cases, dye solution was found in the prevertebral thoracic lymph nodes.In this study, ESP injection resulted in a median spread over five spinal segments (12 injections), staining the lateral and medial branches of the dorsal rami of the spinal nerves, regardless of the direction of the needle used.

Effect of PEEP on Dead Space in an Experimental Model of ARDS.

BACKGROUND: The difference between Bohr and Enghoff dead space are not well described in ARDS patients. We aimed to analyze the effect of PEEP on the Bohr and Enghoff dead spaces in a model of ARDS. METHODS: 10 pigs submitted to randomized PEEP steps of 0, 5, 10, 15, 20, 25 and 30 cm H2O were evaluated with the use of lung ultrasound images, alveolar-arterial oxygen difference (P(A-a)O2 ), transpulmonary mechanics, and volumetric capnography at each PEEP step. RESULTS: At PEEP ≥ 15 cm H2O, atelectasis and P(A-a)O2 progressively decreased while end-inspiratory transpulmonary pressure (PL), end-expiratory PL, and driving PL increased (all P < .001). Bohr dead space (VDBohr /VT), airway dead space (VDaw /VT), and alveolar dead space (VDalv /VTalv ) reached their highest values at PEEP 30 cm H2O (0.69 ± 0.10, 0.53 ± 0.13 and 0.35 ± 0.06, respectively). At PEEP <15 cm H2O, the increases in atelectasis and P(A-a)O2 were associated with negative end-expiratory PL and highest driving PL. VDBohr /VT and VDaw /VT showed the lowest values at PEEP 0 cm H2O (0.51 ± 0.08 and 0.32 ± 0.08, respectively), whereas VDalv /VTalv increased to 0.27 ± 0.05. Enghoff dead space and its derived VDalv /VTalv showed high values at low PEEPs (0.86 ± 0.02 and 0.79 ± 0.04, respectively) and at high PEEPs (0.84 ± 0.04 and 0.65 ± 0.12), with the lowest values at 15 cm H2O (0.77 ± 0.05 and 0.61 ± 0.11, respectively; all P < .001). CONCLUSIONS: Bohr dead space was associated with lung stress, whereas Enghoff dead space was partially affected by the shunt effect.

Changes in serum cortisol and blood glucose concentrations in anesthetized, pain-free dogs administered fentanyl.

OBJECTIVE: To evaluate whether fentanyl administered at analgesic doses in pain-free anesthetized dogs increases the serum cortisol or blood glucose concentrations and is associated with postanesthetic dysphoria. STUDY DESIGN: Experimental, blinded, randomized crossover. ANIMALS: A group of six adult research dogs. METHODS: Each dog was anesthetized twice and was administered fentanyl or saline with a 15-day wash-out period. Treatment allocation was randomly assigned via a closed envelope technique. Cortisol and glucose concentrations were measured on arrival in the research room (TPRE), induction of general anesthesia (TIND), extubation (TEXT) and 1 hour after extubation (TPOST). Dogs were premedicated with methadone (0.1 mg kg-1) and carprofen (4 mg kg-1) intravenously (IV), anesthesia induced with propofol (4-6 mg kg-1) IV and maintained with isoflurane in oxygen. Standard anesthesia monitoring was performed throughout the experiment. Fentanyl (5 µg kg-1 over 90 seconds followed by 7.5 µg kg-1 hour -1) or an equivalent amount in mL of saline solution were administered IV for 60 minutes. TPRE behavior scores and recovery scores were evaluated using descriptive 4-point scales. Data from serum cortisol and blood glucose concentrations were analyzed with a Split Plot on time test, whereas recovery scores were analyzed using a Wilcox match-pairs signed rank test. Statistical significance was set at p < 0.05. RESULTS: There were no significant increases in serum cortisol and blood glucose concentrations over time, and there were no differences between treatments. None of the dogs developed postanesthetic dysphoria with either treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl, administered at analgesic doses to healthy, pain-free, anesthetized dogs, was not associated with significant changes in serum cortisol or glucose concentrations in the studied population.

Sonographic evaluation of epidural and intrathecal injections in cats.

OBJECTIVES: To describe the ultrasonographic anatomy of the caudal lumbar spine in cats and to detect ultrasound (US) signs associated with epidural or intrathecal injection. STUDY DESIGN: Prospective, clinical study. ANIMALS: Twenty-six client-owned cats. METHODS: Transverse (position 1) and parasagittal (position 2) two-dimensional US scanning was performed over the caudal lumbar spine in all cats. Midline distances between the identified structures were measured. Cats assigned to epidural injection (group E, n = 16) were administered a bupivacaine-morphine combination confirmed by electrical stimulation. Cats assigned to intrathecal injection (group I, n = 10) were administered a morphine-iohexol combination injected at the lumbosacral level and confirmed by lateral radiography. The total volume injected (0.3 mL kg-1 ) was divided into two equal aliquots that were injected without needle repositioning, with the US probe in positions 1 and 2, respectively. The presence or absence of a burst of color [color flow Doppler test (CFDT)], dural sac collapse and epidural space enlargement were registered during and after both injections. RESULTS: US scanning allowed measurement of the distances between the highly visible structures inside the spinal canal. CFDT was positive for all animals in group E. In group I, intrathecal injection was confirmed in only two animals, for which the CFDT was negative; seven cats inadvertently and simultaneously were administered an epidural injection and showed a positive CFDT during the second aliquot injection, and the remaining animal was administered epidural anesthesia and was excluded from the CFDT data analysis. Dural sac collapse and epidural space enlargement were present in all animals in which an epidural injection was confirmed. CONCLUSIONS AND CLINICAL RELEVANCE: US examination allowed an anatomical description of the caudal lumbar spine and real-time confirmation of epidural injection by observation of a positive CFDT, dural sac collapse and epidural space enlargement.

The use of a nerve stimulation test to confirm sacrococcygeal epidural needle placement in cats.

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.

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

OBJECTIVE: To 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 DESIGN: Prospective, blinded study. ANIMALS: Twelve mixed-breed healthy adult cats, scheduled for a therapeutic procedure where lumbosacral epidural administration was indicated. METHODS: Under 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. RESULTS: The 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 RELEVANCE: Nerve 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.

The use of electrical stimulation to guide epidural and intrathecal needle advancement at the L5 -L6 intervertebral space in dogs.

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.