Differential Sensitivity of a and C Nerve Fibres to Long-Acting Amide Local Anaesthetics

Rosenberg, P. H.; Heinonen, Erkki

doi:10.1093/bja/55.2.163

Cited by 123 publications

(32 citation statements)

References 9 publications

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“…In addition, in most institutions, a test dose of local anesthetic is used before the definitive dose is injected and the local anesthetics are used with opioids, thus making it difficult to choose the anesthetic concentration of a particular agent by the measured MLAC value alone. In the study by Gautier et al 1 2 the patients given bupivacaine 0.1% with sufentanil rated their analgesia to be unsatisfactory and this concentration of bupivacaine is higher than its recently reported 8 MLAC. On the contrary, our study evaluated the sensory and motor effects of local anesthetic infusions administered during the course of first stage in primiparous women and, therefore, more likely represents the clinical efficacy of the agents studied.…”

Section: Discussionmentioning

confidence: 90%

Comparison of ropivacaine 0.1%-fentanyl and bupivacaine 0.125% — fentanyl infusions for epidural labour analgesia

Finegold

Mandell

Ramanathan

2000

Can J Anesth/J Can Anesth

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Purpose: To compare analgesic efficacies of ropivacaine-fentanyl and bupivacaine-fentanyl infusions for labour epidural analgesia. Methods:In this double-blind, randomized study 100, term, nulliparous women were enrolled. Lumbar epidural analgesia (LEA) was started at cervical dilatation < 5 cm using either bupivacaine 0.25% followed by bupivacaine 0.125% + 2 µg·ml -1 fentanyl infusion (n=50) or ropivacaine 0.2% followed by ropivacaine 0 .1% + 2 µg·ml -1 fentanyl infusion (n=50). Every hour maternal vital signs, visual analog scale (VAS) pain score, sensory levels, and motor block (Bromage score) were assessed. Data were expressed as mean ± 1 SD and analyzed using Chi -Squared and Mann-Whitney U tests at < 0.05. Results:The onset times were 10.62 ± 4.9 and 11.3 ± 4.7 min for the bupivacaine and ropivacaine groups respectively (P = NS). The median VAS scores were not different between the groups at any of the evaluation periods. However, at least 80% of patients in the ropivacaine group had no demonstrable motor block after the first hour compared with only 55% of patients given bupivacaine (P =0.01).Conclusions: Both bupivacaine and ropivacaine produce satisfactory labour analgesia. However, ropivacaine infusion is associated with less motor block throughout the first stage of labour and at 10 cm dilatation.Objectif : Comparer l'efficacité analgésique des perfusions de ropivacaïne-fentanyl et de bupivacaïne-fentanyl pour l'analgésie péridurale pendant le travail obstétrical.Méthode : Cent femmes nullipares et à terme ont été recrutées pour participer à une étude randomisée et à double insu. L'analgésie péridurale lombaire (APL) a été amorcée quand la dilatation cervicale était < 5 cm en utilisant soit de la bupivacaïne à 0,25 % suivie de bupivacaïne à 0,125 % + une perfusion à 2 µg·ml-1 de fentanyl (n=50), soit de la ropivacaïne à 0,2 % suivie de ropivacaïne à 0,1 % + une perfusion à 2 µg·ml-1 de fentanyl (n=50). On a noté à toutes les heures : les signes vitaux de la mère, les scores de douleur à l'échelle visuelle analogique (EVA), les niveaux sensitifs et le bloc moteur (score de Bromage). Les données ont été exprimées en termes de moyenne ± un écart type et analysées d'après le test Chi 2 et le test U de Mann-Whitney à <0,05.Résultats : Les délais d'installation ont été de 10,62 ± 4,9 et de 11,3 ± 4,7 min pour la bupivacaïne et la ropivacaïne respectivement (P = NS). Les scores moyens de l'EVA n'ont pas affiché de différence intergroupe. Cependant, au moins 80 % des patientes qui ont reçu de la ropivacaïne n'avait pas de bloc moteur vérifiable après la première heure contrairement à 55 % seulement des patientes à qui on a donné de la bupivacaïne (P =0,01).Conclusion : La bupivacaïne et la ropivacaïne produisent une analgésie satisfaisante pendant le travail obstétrical. La perfusion de ropivacaïne est toutefois associée à un bloc moteur moins intense pendant la première phase du travail et à 10 cm de dilatation.

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Section: Discussionmentioning

confidence: 90%

Comparison of ropivacaine 0.1%-fentanyl and bupivacaine 0.125% — fentanyl infusions for epidural labour analgesia

Finegold

Mandell

Ramanathan

2000

Can J Anesth/J Can Anesth

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“…13 Several studies have found that sensory blockade is obtained with lower concentrations. 14,15 Lower concentrations of ropivacaine may also have a selective analgesic effect because clinically they block thin A␦ and C nerve fibers more readily than large A␤ fibers. 15 Although ropivacaine at low concentrations may be suitable for providing postoperative analgesia, as shown for outpatient hernia surgery performed under spinal anesthesia, 4 higher concentrations are required for effective surgical anesthesia.…”

Section: Discussionmentioning

confidence: 99%

Anesthetic Efficacy of Different Ropivacaine Concentrations for Inferior Alveolar Nerve Block

Elsharrawy

Yagiela

2006

Anesthesia Progress

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This study was conducted on 72 American Society of Anesthesiologists class 1 patients scheduled for extraction of a mandibular third molar after inferior alveolar nerve block. Each patient was randomly administered one of the following ropivacaine concentrations: 0.75%, 0.5%, 0.375%, or 0.25% (18 patients per group). Onset of block (mean Ϯ SD) was rapid for both 0.75% (1.4 Ϯ 0.4 minutes) and 0.5% (1.7 Ϯ 0.5 minutes) ropivacaine but significantly slower for the 0.375% (4.2 Ϯ 2.5 minutes) and 0.25% (10.7 Ϯ 3.0 minutes) concentrations. Tooth extraction was performed successfully with the 0.5% and 0.75% concentrations, and supplemental injections were not required. Second injections, however, were required with 0.375% ropivacaine. Anesthesia was unsuccessful in 13 patients given 0.25% ropivacaine even after 3 injections. The mean durations of soft tissue anesthesia were 3.3 Ϯ 0.3 hours and 3.0 Ϯ 0.3 hours for the 0.75% and 0.5% concentrations, but significantly shorter with more dilute concentrations. The duration of analgesia showed a similar pattern, with the 0.75% and 0.5% concentrations producing prolonged analgesia of 6.0 Ϯ 0.4 hours and 5.6 Ϯ 0.4 hours. These results indicate that 0.5% and 0.75% concentrations were effective for intraoral nerve blockade, with both a rapid onset and prolonged duration of pain control.

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“…In our study with amphibian myelinated nerve, flicker K + channels are more frequently found in thin nerve fibers ( < 5 Ixm) which in general conduct pain. Therefore, a specific blockade of these fibers may lead to a predominant block of pain, a so-called differential nerve block (Rosenberg and Heinonen, 1983;Raymond and Gissen, 1987). In fact, bupivacaine and ropivacaine in low concentrations are clinically used for this purpose.…”

Section: A New Mode Of Nerve Blockmentioning

confidence: 99%

Local anesthetics potently block a potential insensitive potassium channel in myelinated nerve.

Bräu

Nau

Hempelmann

et al. 1995

The Journal of General Physiology

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A B S T R A C T Effects of some local anesthetics were studied in patch clamp experiments on enzymatically demyelinated peripheral amphibian nerve fibers. Micromolar concentrations of external bupivacaine depolarized the excised membrane considerably. The flicker K § channel was found to be the most sensitive ion channel to local anesthetics in this preparation. Half-maximum inhibiting concentrations (IC50) for extracellular application of bupivacaine, ropivacaine, etidocaine, mepivacaine, lidocaine, and QX-314 were 0.21, 4.2, 8.6, 56, 220, and > 10,000 ~M, respectively. The corresponding concentration-effect curves could be fitted under the assumption of a 1:1 reaction. Application from the axoplasmic side resulted in clearly lower potencies with IC5o values of 2.1, 6.6, 16, 300, 1,200, and 1,250 ~M, respectively. The log(IC 50)-values of the local anesthetics linearly depended on the logarithm of their octanol:buffer distribution coefficients with two regression lines for the piperidine derivatives and the standard amino-amides indicating an inherently higher potency of the cyclic piperidine series. Amide-linked local anesthetics did not impair the amplitude of the single-channel current but prolonged the time of the channel to be in the closed state derived as time constants "re from closed-time histograms. With etidocaine and lidocaine ~c was 133 and 7.2 ms, and proved to be independent of concentration. With the most potent bupivacaine time constants of wash in and wash out were 1.8 and 5.2 s for 600 nM bupivacaine. After lowering the extracellular pH from 7.4 to 6.6, externally applied bupivacaine showed a reduced potency, whereas at higher pH of 8.2 the block was slightly enhanced. Intracellular pH of 6.4, 7.2, 8.0 had almost no effect on internal bupivacaine block.It is concluded that local anesthetics block the flicker K + channel by impeding its gating but not its conductance. The slow blocker bupivacaine and the fast blocker lidocaine compete for the same receptor. Lipophilic interactions are of importance for blockade but besides a hydrophobic pathway, there exists also a hydrophilic pathway to the binding site which could only be reached from the cytoplasmic side of the membrane. Under physiological conditions, blockade of the flicker K § channel which is more sensitive to bupivacaine than the Na § channel might lead via

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Differential Sensitivity of a and C Nerve Fibres to Long-Acting Amide Local Anaesthetics

Cited by 123 publications

References 9 publications

Comparison of ropivacaine 0.1%-fentanyl and bupivacaine 0.125% — fentanyl infusions for epidural labour analgesia

Comparison of ropivacaine 0.1%-fentanyl and bupivacaine 0.125% — fentanyl infusions for epidural labour analgesia

Anesthetic Efficacy of Different Ropivacaine Concentrations for Inferior Alveolar Nerve Block

Local anesthetics potently block a potential insensitive potassium channel in myelinated nerve.

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