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Comparison of 3 Intensities of Stimulation Threshold for Brachial Plexus Blocks at the Midhumeral Level: A Prospective, Double-Blind, Randomized Study
  1. Philippe Cuvillon, MD, MSc*,
  2. Nicolas Dion, MD,
  3. Michel Deleuze, MD*,
  4. Emmanuel Nouvellon, MD, MSc*,
  5. Aba Mahamat, MD,
  6. Joel L'Hermite, MD*,
  7. Christophe Boisson, MD*,
  8. Nathalie Vialles, MD*,
  9. Jacques Ripart, MD, PhD* and
  10. Jean Emmanuel de La Coussaye, MD, PhD*
  1. From the *Division of the Department of Anesthesiology and Pain Management, University Groupe Caremeau Hospital, Nîmes, and University of Montpellier 1, Montpellier;
  2. CHA, Centre Hospitalier Affilié de Québec, Québec, Canada; and
  3. Laboratoire d'épidémiologie et de Biostatistiques, Institut Universitaire de Recherche Clinique, Montpellier, and Département Informatique Médicale, CHU Nîmes, France.
  1. Address correspondence to: Cuvillon Philippe, MD, MSc, Département Anesthésie Douleur, Hôpital Caremeau, Place professeur Debré, 30029 Nîmes, France (e-mail: philippe.cuvillon{at}


Background: We conducted this prospective randomized study to compare the success rate and the onset time between 3 intensities of stimulation threshold (<0.5, 0.5-0.64, and 0.65-0.8 mA) when using a peripheral nerve stimulation at the midhumeral level.

Methods: Sixty-nine adult patients undergoing elective hand surgery were studied. Blocks were performed using conventional nerve stimulation technique. Needle advance began at 2 mA (1 Hz, 0.1 millisecond). When motor response (MR) occurred at less than 0.5 mA, needle position was fixed for "group <0.5 mA." For "group 0.5-0.64 mA," the needle was withdrawn until MR occurred at greater than 0.5 mA and disappeared at less than 0.5 mA. For "group >0.65 mA," the needle was withdrawn until MR occurred at greater than 0.65 mA and disappeared at less than 0.65 mA. For each group, patients received 8 mL of ropivacaine 7.5 mg/mL on the 4 nerves (radial, median, ulnar, and musculocutaneous). Primary end point was the number of failed radial nerve sensory blocks at 30 mins.

Results: The time to perform the block was not different between the 3 groups (17 mins [SD, 7 mins] vs 13 mins [SD, 8 mins] and 13 mins [SD, 4 mins], respectively). The time required to obtain a complete sensory block was shorter for the 4 nerves in group <0.5 mA, with a statistical significance for radial and musculocutaneous nerves in group <0.5 mA versus group 0.5-0.64 mA and group >0.65 mA. Patients in group <0.5 mA had a greater success rate for complete sensory radial nerve compared with those of group 0.5-0.64 mA and group >0.65 mA at any interval times between 5 and 30 mins (P = 0.0001). Supplemental local anesthesia was provided for the 3 groups more frequently for the median nerve, with no difference between groups. Group >0.65 mA required 5 general anesthesias (20%) as compared with 1 (4%) in group <0.5 mA (P < 0.05). No adverse event (dysesthesia) occurred after 48 hrs and 45 days.

Conclusion: We conclude that intensity of stimulation influenced onset time and success rate.

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  • This study was supported by Protocole Hospitalier de Recherche Clinique, Nîmes, France.