Ban C. H. Tsui

Confirmation of epidural catheter placement using nerve stimulation

PurposeTo examine the reliability of low current electrical epidural stimulation to confirm epidural catheter placement.MethodsForty patients with epidural catheters (19G Arrow Flextip plus) already in place for post-operative pain management were studied. An adapter (Arrow-Johans ECG Adapter) was attached to the connector of the epidural catheter. The epidural catheter and adapter were filled with normal saline. The cathode lead of the nerve stimulator was attached to the metal hub of the adapter. Catheter placement was judged to be correct or incorrect, depending upon the presence or absence of truncal or limb movement to 1 Hz stimulation (1–10 mA). A standard test dose (3 ml lidocaine 1.5% with 1:200,000 epinephrine) was then injected. The efficacy of the epidural morphine was assessed independently.ResultsThe sensitivity and specificity of the test was 100% and 91.6% compared with the standard test dose. The positive and negative predictive value was 96% and 100%. In predicting the clinical effect of epidural morphine, the sensitivity and specificity was 96.1% and 76.9%. The positive and negative predictive value was 89% and 90%. The correlation of unilateral or bilateral motor response from the test and sensory response from the lidocaine test with sensitivity and specificity was 91.6% and 53.0%. The predictive value for unilateral response was 61% and for bilateral was 88%.ConclusionThis study establishes this test as a simple, objective and reliable technique for confirmation of epidural catheter placement.RésuméObjectifDéterminer la fiabilité d’une stimulation péridurale électrique de faible intensité utilisée pour confirmer la mise en place d’un cathéter péridural.MéthodeQuarante patients, à qui on avait déjà installé un cathéter péridural (Arrow Flextip plus 19G) pour traiter la douleur post opératoire, ont participé à l’étude. Un adaptateur (Arrow-Johans EXG Adapter) a été fixé au connecteur du cathéter. Ce cathéter et l’adaptateur ont été remplis de sérum physiologique. L’électrode cathodique du neurostimulateur a été fixée à la garde métallique de l’adaptateur. La mise en place du cathéter était jugée correcte ou incorrecte selon la présence ou l’absence d’un mouvement du tronc ou d’un membre à une stimulation de 1 Hz (1–10 mA). Une dose-test standard (3 ml de lidocaïne à 1,5% avec 1: 200 000 d’épinéphrine) a été injectée par la suite. L’efficacité de la morphine péridurale a été évaluée séparément.RésultatsLa sensibilité et la spécificité du test étaient de 100% et de 91,6% en comparaison avec la dosetest standard. Les valeurs de la prédiction positive et négative étaient de 96% et de 100%. Concernant la prédiction de l’effet clinique de la morphine péridurale, la sensibilité et la spécificité étaient de 96,1% et de 76,9%. Les valeurs de la prédiction positive et négative étaient de 89% et 90%. La corrélation entre une réponse motrice unilatérale ou bilatérale au test et une réponse sensorielle au test de lidocaïne avec sensibilité et spécificité était de 91,6% et 53,0%. La valeur prédictive de la réponse unilatérale était de 61% et celle de la réponse bilatérale, de 88%.ConclusionCette étude reconnaît le test comme une technique simple, objective et fiable permettant la confirmation du placement d’un cathéter dans l’espace péridural.

Ultrasound imaging for regional anesthesia in infants, children, and adolescents: a review of current literature and its application in the practice of extremity and trunk blocks.

Complementary to a previous publication related to pediatric extremity and trunk blockade, the authors present a comprehensive narrative review of the literature pertaining to techniques described and outcomes evaluated for ultrasound imaging in pediatric neuraxial anesthesia. The sonoanatomy related to each block is also described and illustrated to serve as a foundation for better understanding the block techniques described. For neuraxial blockade, ultrasound may fairly reliably predict the depth to loss of resistance and can enable a dynamic view of the needle and catheter after entry into the spinal canal. Particularly, in young infants, direct visualization of the needle and catheter tip may be possible, whereas in older children surrogate markers including the displacement of dura mater by the injection of fluid may be necessary for confirming needle and catheter placement. More outcome-based, prospective, randomized, controlled trials are required to prove the benefits of ultrasound when compared with conventional methods.

Thoracic Epidural Analgesia Via the Caudal Approach in Pediatric Patients Undergoing Fundoplication Using Nerve Stimulation Guidance

IMPLICATIONS Epidural catheter placement using electrical stimulation guidance is an alternative approach for positioning the catheter into the thoracic region via the caudal space. This easily performed clinical assessment provides optimization of catheter tip positioning for achieving effective pain control.

Thoracic and lumbar epidural analgesia via the caudal approach using electrical stimulation guidance in pediatric patients: a review of 289 patients.

BackgroundNerve stimulation guidance (Tsui test) has been reported to be an effective alternative to radiographic imaging for proper catheter placement. The purpose of this study was to examine the success rate and complications of continuous caudal epidural analgesia since the implementation of routine use of the Tsui test at the authors’ institution. MethodsThe authors examined prospectively collected data in their pediatric pain service database from 289 children who had attempted caudal placement of a lumbar or thoracic catheter between 1999 and 2002. ResultsIn five patients (aged 5 months–1.6 yr), the catheter did not thread to the desired level and was abandoned in the operating room (technical success rate, 98.2%). Of the remaining 284 patients, the overall analgesic success rate of all caudal route epidural analgesia procedures was 84.9%. There was no significant difference in adequate pain control (success) in infants (aged 1 day–1 yr) versus older children (aged younger than 1 yr). The most common adverse effects were pruritus (26.1%) and nausea and vomiting (16.9%). Of the patients in our study, 57.7% had urinary catheters in situ; of those who did not have a catheter placed, 20.8% experienced urinary retention. The incidence of respiratory depression was 4.2%, but the administration of naloxone for severe respiratory depression was never necessary. Three percent of catheters were removed because of suspected contamination, but no epidural abscesses or systemic infection were noted. ConclusionsThe results of this study suggest that epidural catheter placement via the caudal approach using the Tsui test is an effective and reasonable alternative to direct lumbar and thoracic epidural analgesia in pediatric patients.

Electrophysiologic effect of injectates on peripheral nerve stimulation

Background and Objectives: A small volume of local anesthetic or normal saline abolishes the muscle twitch induced by a 1ow current (0.5 mA) during electrolocation. This study examines the hypothesis that the mechanism of this phenomenon is primarily the electrophysiologic effect of the injectate on the electrical current density at the needle tip. Methods: Five pigs were studied. An insulated Tuohy needle was inserted in each pig toward the left and right brachial plexuses and the left and right femoral nerves. The needle was advanced until corresponding motor responses were observed at each site, using a current of 0.5 mA. The effect of injecting 1 mL each of normal saline and 5% dextrose in water (NS and D5W) on muscle twitch was investigated at all 20 needle insertion sites. Changes in the conductive area induced by the injectates were also demonstrated using gel electrophoresis. Results: In all cases, the muscle twitches were abolished immediately after the injection of NS and recovered instantaneously after a subsequent injection of D5W. The electrical resistance between the needle and the ground electrodes decreased instantly after the NS injection. The resistance not only recovered but also increased after the injection of D5W. In the gel electrophoresis experiment, the results demonstrated that the expanded conductive area induced by the saline column surrounding the insulated needle was similar to that observed with the uninsulated needle. Conclusion: The injection of a conducting solution (i.e., NS) rendered the current that was previously sufficient to elicit a motor response (0.5 mA) ineffective. The most likely reason for this change is that the conductive area surrounding the stimulating needle expanded after the injection and dispersion of the conducting solution (i.e., NS), thereby reducing the current density at the target nerve. This effect can be reversed by injecting a nonconducting solution (i.e., D5W) via the stimulating needle.

Argatroban as anticoagulant in cardiopulmonary bypass in an infant and attempted reversal with recombinant activated factor VII.

HEPARIN-INDUCED thrombocytopenia (HIT) is an infrequent complication of heparin therapy. 1 A unique problem arises in patients with HIT who need anticoagulation, especially if urgent cardiac surgery is planned. We report a case of HIT in an infant in which Argatroban (GlaxoSmithKline, Middlesex, UK) was used as anticoagulant during cardiopulmonary bypass (CPB) and the unsuccessful use of recombinant activated factor VII (rF-VIIa) to reverse the anticoagulant effects postoperatively.

Thoracic epidural catheter placement via the caudal approach in infants by using electrocardiographic guidance

UNLABELLED We examined the success of inserting epidural catheters via the caudal route in infants by using electrocardiographic guidance. A case series of 20 patients with thoracic epidural analgesia was studied. After the induction of general anesthesia, an 18-gauge IV catheter was inserted into the caudal space to allow threading of a 20-gauge epidural catheter. The electrocardiogram (ECG) tracings via the epidural catheter, as well as the surface ECG at the target spine level, were recorded simultaneously with a modified two-channel five-lead ECG system. The epidural catheter was advanced from the caudal space until the tip reached the target level as demonstrated by a match in the configuration of the epidural ECG tracing to that of the surface ECG tracing at the target level. The catheter tip location was verified by postoperative radiographs. All catheter tips were located within two vertebrae of the target level, and satisfactory intraoperative epidural anesthesia was achieved in all subjects. IMPLICATIONS Epidural electrocardiography may be used to guide the positioning of the thoracic epidural catheter tip via the caudal approach to the appropriate dermatome for optimum analgesia.

Determining epidural catheter location using nerve stimulation with radiological confirmation

BACKGROUND AND OBJECTIVES The use of epidural stimulation to confirm epidural catheter placement has been shown. This case report describes the benefits and problems of using the epidural stimulation test to confirm epidural catheter placement and provides supporting evidence for these observations using radiological imaging. CASE REPORT METHODS A nerve stimulator was connected to the proximal end of an epidural catheter via an adapter. The cathode lead was connected to the adapter. The anode lead was connected to an electrode placed on the upper extremity as a grounding site. Using 1 to 10 mA current, a segmental motor response indicated that the catheter was in the epidural space. The absence of a motor response indicated that it was not. CASES In the first patient, the new test predicted subcutaneous epidural catheter placement, which was subsequently confirmed radiologically. In the second patient, the catheter tip was found to be lying near a nerve root, which was again confirmed radiologically. In the third case, a negative test was initially observed with only local muscle movement over the biceps area (T2). After relocation of the grounding electrode to the lower extremity, segmental intercostal muscle movement (T4-5 level) was observed. The catheter placement was radiologically shown to be in the T4-5 region. CONCLUSION This report illustrates some of the potential benefits and problems of using the nerve stimulation test to confirm epidural catheter placement, with radiological verification.

Determination of epidural catheter placement using nerve stimulation in obstetric patients

BACKGROUND AND OBJECTIVES Peripheral nerve and spinal cord stimulation techniques have been used for many years. However, electrical stimulation methods rarely have been used to confirm epidural catheter placement. This study examines the practicality of this technique to confirm epidural catheter placement in obstetric patients. METHODS Thirty-nine obstetric patients in labor were studied. An electrocardiography (ECG) adapter (Arrow-Johans) was attached to the proximal end of the epidural catheter (19-gauge Arrow Flextip plus). Then, the lowest milliamperage (1-10 mA) necessary to produce a motor response (truncal or limb movement) was applied using this setup. A positive motor response indicated that the catheter was in the epidural space. This test was performed initially after catheter insertion and repeatedly after incremental local anesthetic doses. RESULTS The sensitivity and specificity of the new test was 100% and 100%, respectively, with 38 true positive tests and 1 true negative test. The threshold current required to produce a positive test increased after incremental doses of local anesthetic. A case of intravascular epidural catheter migration was detected using this new test. In this case, the patients increased threshold milliamperage returned to the baseline value within 1 hour, despite having received local anesthetic. Intravascular epidural catheter migration was subsequently confirmed by a positive epinephrine test dose. Thus, this test appears to be a potentially useful method to detect intravascular catheter placement. CONCLUSION This study demonstrates that this test may have a role in improving the success rate of epidural anesthesia.

Detection of subarachnoid and intravascular epidural catheter placement

PurposeTo report the detection of subarachnoid and intravascular catheter placement using nerve stimulation through an epidural catheter.Clinical featuresElectrical stimulation (1–10 mA) was applied through the catheter. A positive motor response (truncal or limb movement) indicated that the catheter was in the epidural space. Absence of a motor response indicated that it was not. A low milliamperage (< 1 mA) with bilateral response indicated subarachnoid placement. Intravascular catheter placement was indicated by a positive response to the test, which remains at or returns to the baseline levels (i.e. prior to any local anesthetic injection), despite the administration of local anesthetics. In the first patient, the test confirmed subarachnoid catheter placement during attempts at continuous spinal anaesthesia even though CSF could not be aspirated. Bilateral motor response in the legs was observed at 0.2 mA. In the second patient, inadvertent subarachnoid placement was detected during attempted lumbar epidural block by observing bilateral motor response in the legs at 0.3 mA. In the third patient, intravascular placement was suspected and confirmed by failure to obliterate the motor response despite repeated local anesthetic injection.ConclusionThe new test provides objective information in managing epidural catheters when their position is uncertain.RésuméObjectifDécrire la détection du positionnement d’un cathéter sous-arachnoïdien et intravasculaire à l’aide de la neurostimulation au moyen d’un cathéter épidural.Éléments cliniquesLa stimulation électrique (1–10 mA) a été appliquée au moyen du cathéter. Une réponse motrice positive (mouvement du tronc ou d’un membre) indiquait que le cathéter était dans l’espace épidural et l’absence de réponse, qu’il n’y était pas. Un faible milliampérage (< 1 mA) et une réponse bilatérale indiquaient un placement sous-arachnoïdien. La position intravasculaire du cathéter était indiquée par une réponse positive au test, laquelle demeurait au niveau de base ou y revenait (c.-à-d., avant toute injection d’anesthésique local), malgré l’administration d’anesthésiques locaux. Chez le premier patient, le test a confirmé le positionnement sous-arachnoïdien du cathéter pendant les essais sous une rachianesthésie continue même si le LCR ne pouvait être aspiré. Une réponse motrice bilatérale a été observée à 0,2 mA. Chez le second patient, un placement sous-arachnoïdien involontaire a été détecté, pendant qu’on tentait un bloc péridural lombaire, en notant une réponse motrice bilatérale aux jambes sous 0,3 mA. Chez le troisième patient, le placement intravasculaire a été soupçonné et confirmé par l’échec à bloquer la réponse motrice malgré l’injection répétée d’anesthésique local.ConclusionLe nouveau test fournit une information objective sur la mise en place des cathéters quand leur position est incertaine.