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LETTER TO THE EDITOR

Comparing the Steam Engine With a Horse-Drawn Carriage?

Department of Anaesthesiology and Critical Care Medicine; University Hospital Carl Gustav Carus; D-01307 Dresden; Germany; axel.heller{at}uniklinikum-dresden.de

To the Editor:

For several reasons, we take issue with the study of Liguori et al. (1) who described postoperative neurological symptoms (PONS) in patients receiving interscalene brachial plexus blockade using either mechanical paresthesia or electrical nerve stimulation for nerve localization.

First, a nonsignificant difference between groups in a comparative study may not necessarily mean that two procedures are equal. Absence of evidence is not evidence of absence. A type II error may be present especially when a power analysis is performed using two prior studies with different methodology from different groups, with a time delay of 7 yr, and when each one influenced the case load calculation for one of the two groups of the present trial. One further cause for a missed difference, theoretically, may be found in an inability to differ between electrically or mechanically induced paresthesia produced by electric stimulation cannula.

Second, the percentage of patients with PONS in this study is strikingly high when compared with a recent study of 256 prospective patients receiving interscalene brachial plexus blockade guided by electric stimulation (2). No patient had PONS as opposed to 3% in patients in whom paresthesias had been elicited (3). Among European opinion leaders in regional anesthesia, electric nerve stimulation enjoys broad acceptance regarding its safety in comparison with the mechanical paresthesia technique (4). "When performing nerve blocks paresthesia ... should be avoided in order to reduce nerve lesions" (5).

Third, in the light of most recent publications, high resolution and real-time ultrasound-guided regional anesthesia allows clear visualization of the target as well as adjacent structures and, thus, safe positioning of the needle, as well as observation of local anesthetic spread (6). Since even with neurostimulation peripheral nerve injury may occur, the clear depiction of the nerve and the maintenance of a distance between needle and nerve should reduce the incidence of regional anesthesia-related PONS (7). Furthermore, because observation of local anesthetic spread and, therefore, dosing on demand is now possible, administration of 50–60 mL of local anesthetic, as done in the present study, seems largely outdated and potentially toxic.

In summary, given the acceptance of high resolution ultrasound it must be questioned whether such studies comparing these two techniques (1) are justified especially in light of published closed claim analysis concerning regional anesthesia-related nerve injury (8).

REFERENCES

1. Liguori GA, Zayas VM, YaDeau JT, et al. Nerve localization techniques for interscalene brachial plexus blockade: a prospective, randomized comparison of mechanical paresthesia versus electrical stimulation. Anesth Analg 2006;103: 761–7.[Abstract/Free Full Text]
2. Capdevila X, Pirat P, Bringuier S, et al. Continuous peripheral nerve blocks in hospital wards after orthopedic surgery: a multicenter prospective analysis of the quality of postoperative analgesia and complications in 1,416 patients. Anesthesiology 2005;103:1035–45.[Web of Science][Medline]
3. Choyce A, Chan VW, Middleton WJ, et al. What is the relationship between paresthesia and nerve stimulation for axillary brachial plexus block? Reg Anes Pain Med 2001;26:100–4.
4. Kaiser H, Niesel HC, Hans V. Fundamentals and requirements of peripheral electric nerve stimulation. A contribution to the improvement of safety standards in regional anesthesia. Reg Anaesth 1990;13: 143–7.[Medline]
5. Selander D. Peripheral nerve injury caused by injection needles. Br J Anaesth 1993;71:323–5.[Free Full Text]
6. Litz RJ, Roessel T, Wiessner D, et al. Ultrasound guided interscalene cervical block for carotid surgery. Eur J Anesthesiol 2006;23 (Suppl 37):128.
7. Soeding PE, Sha S, Royse CE, et al. A randomized trial of ultrasound-guided brachial plexus anaesthesia in upper limb surgery. Anaesth Intensive Care 2005;33: 719–25.[Web of Science][Medline]
8. Lee LA, Posner KL, Domino KB, et al. Injuries associated with regional anesthesia in the 1980s and 1990s: a closed claims analysis. Anesthesiology 2004;101:143–52.[Web of Science][Medline]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Heller, A. R. Articles by Litz, R. J. Search for Related Content PubMed PubMed Citation Articles by Heller, A. R. Articles by Litz, R. J.