Brendan T. Finucane

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.

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.

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.

The public's fears about and perceptions of regional anesthesia

Background and Objectives The public is not well informed about matters relating to regional anesthesia. Previous studies concerning regional anesthesia have involved patients, surgeons, and anesthesiologists. This study is the first in-depth survey of the attitudes of the general public toward a number of commonly perceived fears about regional anesthesia. Methods A province-wide telephone survey was conducted in Alberta, Canada. The sample surveyed was representative of the adult population of the province and included an equal balance of urban and rural participants. General and regional anesthesia were defined, a scenario involving major knee surgery was described, and participants were asked to choose between regional and general anesthesia. Respondents were then questioned so their attitudes toward commonly perceived fears associated with regional anesthesia could be assessed. Results A total of 1,216 people were surveyed. A preference for regional or general anesthesia was not expressed in this scenario. Approximately 27% of respondents were very concerned about permanent paralysis, back injury, perioperative pain, seeing the surgical procedure, and the prospect of a needle in the back. Only 6% of individuals were concerned about headaches. Conclusions The publics fears and conceptions about regional anesthesia are greatly distorted. The anesthesia community has not been successful in keeping the public informed about regional anesthesia. Future anesthesia-related educational programs should address the concerns of the public about anesthesia matters, particularly regional anesthesia.

A double-blind comparison of ropivacaïne 0.5%, 0.75%, 1.0% and bupivacaine 0.5%, injected epidurally, in patients undergoing abdominal hysterectomy

PurposeRopivacaïne is a new long-acting, injectable local anaesthetic currently undergoing clinical investigation world wide. It is structurally very similar to bupivacaine, but with less potential for central nervous system or cardiac toxicity. The purpose of this double-blind study was: to investigate the dose-response relationship of increasing doses of ropivacaïne on the quality of anaesthesia and the duration of both motor and sensory blockade, and to compare these results with an established local anaesthetic, bupivacaine.MethodsOne hundred and twenty five patients were randomly assigned to one of four treatment groups and 116 completed the study. Epidural anaesthesia was established using 25 ml test solution, injected over three minutes following a satisfactory test dose. Sensory onset, spread and duration, using the pin prick method, and motor scores using a modified Bromage scoring system were compared.ResultsA dose/response relationship was observed with increasing doses of ropivacaïne for all variables tested except analgesia and muscle relaxation (P < 0.01). There were differences in: (i) motor onset (Levels 1 and 2), when ropivacaïne 1.0% was compared with ropivacaïne 0.75% and 0.5% (P < 0.05); (ii) in sensory duration at all levels except T6 when ropivacaïne was compared with ropivacaïne 0.5% (P < 0.05); (iii) differences in sensory duration at T12 and S1 when ropivacaïne 1.0% was compared with bupivacaine 0.5% (P < 0.05); (iv) differences in motor duration at all levels when ropivacaïne 1.0% was compared with ropivacaïne 0.5% (P < 0.05). No serious adverse events were reported in this study.ConclusionIncreasing doses of ropivacaïne were associated with an increased clinical effect. The most consistent differences occurred when ropivacaïne 1.0% was compared with 0.5% and the least consistent between ropivacaïne 0.5%, 0.75% and bupivacaine 0.5%. The main difference between ropivacaïne 1.0% and bupivacaine was in sensory duration. No serious adverse events were reported.RésuméObjectifsLa ropivacaïne est un nouvel anesthésique local injectable à longue durée d’action qui subit des essais cliniques partout dans le monde. Sa structure ressemble beaucoup à celle de ta bupivacaïne mais son potentiel de toxicité pour le système nerveux central est moindre. Les objectifs de cette étude en double aveugle étaient de rechercher la relation dose-effet de doses croissantes de ropivacaïne sur la qualité de l’anesthésie et la durée des bloc sensitif et moteur, et de comparer ces résultats avec un aneslhésique local établi, la bupivacaïne.MéthodesCent vingt-cinq patients ont été assignés aléatoirement à un de quatre groupes et 116 ont complété l’étude. L’anesthésie épidurale a été réalisée avec une solution test de 25 ml, injectée en trois minutes après une dose-lest satisfaisante. L’installation sensorielle, la propagation et la durée, mesurés avec la méthode de la piqûre, et les scores de motricité mesurés sur une échelle de Bromage modifiée ont été comparés.RésultatsUne relation dose-effet a été observée avec l’augmentation des doses de ropivacaïne pour toutes le variables lestées excepté l’analgésie et la relaxation musculaire (P < 0,0.1). Les différences suivantes ont été notées pour: (i) l’installation motrice (niveaux 1 et 2), lorsque la ropivacaïne 1,0% était comparée avec la ropivacaïne 0,75% et 0,5% (P < 0,05); (ii) la durée sensorielle à tous les niveaux excepté T6 quand la ropivacaïne 0,5% (P < 0,5); (iii) des différences de durée sensorielle à T12 et S1 quand la ropivacaïne 1,0% était comparée à la bupivacaïne 0,5% (P < 0,05); (iv) des différence de durée pour la motricité à tous les niveau quand la ropivacaïne 1,0% était comparée avec la ropivacaïne 0,5% (P < 0,05). Aucun effet défavorable n’est survenu pendant l’étude.ConclusionsL’augmentation des doses de ropivacaïne a été associée à une augmentation de l’effet clinique. Les différences les plus importantes sont survenus quand la ropivacaïne 1,0% était comparée à 0,5% et les moins importantes entre la ropivacaïne 0,5%, 0,75% et la bupivacaïne 0,5%. La différence principale entre la ropivacaïne 1,0% et la bupivacaïne portait sur la durée sensorielle. Il n’y a pas eu d’effets secondaires graves.

The attitude of the general public towards preoperative assessment and risks associated with general anesthesia.

Purpose: To survey the general public’s attitude towards preoperative assessment and commonly perceived fears about general anesthesia.Methods: A province wide telephone survey was conducted in Alberta. General and regional anesthesia were defined, a scenario involving major knee surgery was described, and participants were asked to choose between regional and general anesthesia. Respondents used a seven-point scale to rate the importance of seeing an anesthesiologist preoperatively and were questioned about the timing of such a visit. Attitudes towards commonly perceived fears associated with anesthesia were also assessed.Results: A total of 1,216 people were surveyed. Over 30% of respondents felt that it was very important to see an anesthesiologist preoperatively, with a total of over 60% attributing a high degree of importance to this. Fifty percent felt that this assessment should occur on the day prior to surgery. A preference for regional or general anesthesia was not expressed in the situation. Approximately 20% of respondents were very concerned about brain damage, waking up intraoperatively and memory loss. Twelve percent were concerned about dying intraoperatively. Nine percent expressed concern about postoperative pain, with 12% reporting being concerned about nausea and vomiting.Conclusions: The general public considers anesthetic assessment on the day prior to surgery an important part of preoperative preparation. Fears of brain damage, death and intraoperative awareness associated with general anesthesia remain prevalent, suggesting that preoperative education of patients should address these concerns. The general population was less concerned about realistic fears such as nausea, vomiting and postoperative discomfort.RésuméObjectif: Étudier l’attitude générale du public à propos de l’évaluation préopératoire et des craintes qui entourent ordinairement l’anesthésie générale.Méthode: Une enquête téléphonique panprovinciale a été menée en Alberta. On a défini l’anesthésie générale et régionale et décrit le scénario comportant une intervention majeure du genou, puis on a demandé aux participants de choisir le type d’anesthésie. Les répondants ont utilisé une échelle en sept points pour estimer l’importance d’une rencontre préopératoire avec l’anesthésiologiste et pour déterminer le meilleur moment d’une telle visite. On a aussi évalué les craintes habituelles engendrées par l’anesthésie.Résultats: L’enquête a porté sur 1 216 personnes. Plus de 30 % ont considéré la visite préopératoire très importante et un total de plus de 60 %, éminemment importante. Cinquante pour cent ont jugé que cette évaluation devait avoir lieu le jour précédent l’intervention. Aucune préférence n’a été exprimée entre l’anesthésie régionale ou générale. Environ 20 % étaient très préoccupés par les lésions cérébrales, la possibilité de se réveiller pendant l’opération et la perte de mémoire. Chez 12 %, on a noté la peur de mourir pendant l’intervention; 9 % appréhendaient les douleurs postopératoires et 12 %, les nausées et les vomissements.Conclusion: L9 grand public considère l’évaluation anesthésique réalisée le jour précédent l’intervention comme une part importante de la préparation préopératoire. Les craintes de lésions cérébrales, de mort et de conscience peropératoires associées à l’anesthésie générale demeurent répandues, ce qui incite à donner des informations préopératoires qui tiennent compte de ces préoccupations. Cependant, des incidents plus réalistes comme les nausées, les vomissements et l’inconfort postopératoire inquiètent mois la population.

The BURP maneuver worsens the glottic view when applied in combination with cricoid pressure

PurposeThe purpose of this study was to determine if the application of a BURP maneuver to the cricoid cartilage would combine the benefits of both the BURP and the Sellick maneuvers, resulting in an improved glottic view and offer the potential of protection against passive gastric regurgitation.MethodsThis was a double-blind, prospective, randomized, crossover trial. Forty-three patients scheduled for elective surgery participated in this study. General anesthesia was induced using fentanyl, propofol and rocuronium. In a random sequence for each case and blinded to the laryngoscopist, one of three maneuvers was carried out. Direct vertical pressure, using 30 newtons, a BURP maneuver with cricoid pressure, or no pressure was applied to the cricoid and the laryngoscopic view was ascertained. A separate laryngoscopy was conducted for each maneuver and the views were graded as good (part of the glottis seen), poor (only the arytenoids were seen) or no view (only the epiglottis was seen). Endotracheal intubation was then performed in each case.ResultsThe results showed that the combination of the BURP maneuver and cricoid pressure worsened the view obtained at laryngoscopy in 30% of cases (P = 0.007). Cricoid pressure alone worsened the view in 12.5% of cases (P = 0.279). No difference was seen in 65% of cases. All patients but one were intubated easily.ConclusionThere is no benefit to routinely applying a modified “BURP” maneuver to the cricoid cartilage during rapid sequence induction of anesthesia.RésuméObjectifDéterminer si l’application de la manœuvre PAHD (pression vers l’arrière, vers le haut et vers la droite) du cartilage cricoïde va combiner ses effets à ceux de la manœuvre de Sellick, améliorant la visibilité de la glotte et offrant la possibilité d’une protection contre les régurgitations gastriques passives.MéthodeNotre étude à double insu était prospective, randomisée et croisée. Quarante-trois patients de chirurgie réglée y ont participé. Lanesthésie générale a été induite avec du fentanyl, du propofol et du rocuronium. Une des trois manœuvres utilisées selon une séquence aléatoire pour chaque cas a été réalisée à l’insu de la personne qui faisait la laryngoscopie. Une pression verticale directe a été appliquée, utilisant 30 newtons, ou une manœuvre PAHD avec compression cricoïdienne ou aucune pression sur le cricoïde, et la vue laryngoscopique a été vérifiée. Une laryngoscopie séparée a été faite pour chaque manœuvre et les vues classées comme bonne (une partie de la glotte est visible), pauvre (seuls les aryténoïdes sont visibles) ou nulle (seulement l’épiglotte est visible). L’intubation endotracheale a été réalisée ensuite dans chaque cas.RésultatsLa combinaison de la manœuvre PAHD et de la compression cricoïdienne dégradait la vue à la laryngoscopie dans 30 % des cas (P = 0,007). La compression cricoïdienne seule détériorait la vue dans 12,5 % des cas (P = 0,279). Aucune différence n’a été notée dans 65 % des cas. Tous les patients, sauf un, ont été facilement intubés.ConclusionII n’y a pas d’avantage à appliquer régulièrement une manœuvre PAHD modifiée sur le cartilage cricoïde pendant l’induction de l’anesthésie à séquence rapide.

Prolonged Epidural Infusions of Ropivacaine (2 mg/ml) After Colonic Surgery: The Impact of Adding Fentanyl

We evaluated the safety and efficacy of a 72-h epidural infusion of ropivacaine and measured the impact of adding fentanyl 2 &mgr;g/mL to the required infusion rate, on the quality of postoperative pain relief and the incidence of side effects, after colonic surgery. One hundred fifty-five patients scheduled for elective colonic surgery were randomized in this trial. Epidural infusions of ropivacaine 2 mg/mL with fentanyl 2 &mgr;g/mL (R + F) and without fentanyl (R) were commenced during surgery and continued for 72 h postoperatively. This was a prospective, randomized, double-blinded, multi-center trial. The median infusion rate required was less in the R + F group (9.3 vs 11.5 mL/h, P < 0.001). Median pain scores at rest and on coughing were lower in the R + F group (P < 0.0001). The incidence of hypotension was more in the R + F group (P = 0.01). Time to readiness for discharge was delayed in the R + F group (median 6.6 vs 5.5 days, P = 0.012). The addition of fentanyl to ropivacaine resulted in decreased infusion rates and enhanced pain control; however, adverse effects were increased and readiness to discharge was delayed.