Anesth Analg 2008; 107:1082-1083
© 2008 International Anesthesia Research Society
doi: 10.1213/ane.0b013e3181800aae
LETTER TO THE EDITOR
Section Editor:
Lawrence Saidman
Editor's note: Due to a publisher's error, the following response by Amar et al. to the Letter to the Editor by Lohser and Brodsky published in the July 2008 issue (Anesth Analg 2008;107:342) was left out of the July issue. The publisher apologizes for the error.
Frequency-Dependent Block in Humans?
Markus F. Stevens, MD, DEAA, DESRA
Department of Anesthesiology; Academic Medical Center; University of Amsterdam; Amsterdam, Netherlands, m.f.stevens{at}amc.uva.nl
To the Editor:
Langen et al. were not able to demonstrate that repetitive motor activity speeded the onset of interscalene block1 in contrast to Okasha et al. who showed that muscular exercise decreased latency of onset of supraclavicular block.2 A similar difference in results has been shown when, in an experimental setting, we demonstrated that nonpainful electrical stimulation with high frequencies (10, 50 Hz) could enhance ulnar nerve block in volunteers,3 whereas studies using transcutaneous electrical nerve stimulation (TENS) did not speed or facilitate local anesthetic action in patients.4,5 Thus, what can be concluded from these five investigations assessing the frequency-dependent action of local anesthetics to enhance conduction block in humans—two showing an advantage and three showing no advantage?
The frequency-dependent action of local anesthetics has been shown in experimental studies from single channel patch-clamp investigations to mammalian isolated nerve preparations.6,7 In all of these studies, the enhancement of local anesthetic action by high-frequency stimulation vanishes within seconds. The fact some authors2,3 found effects lasting longer than the stimulation or exercise may not be directly linked to the frequency-dependent action of local anesthetics.
REFERENCES
- Langen KE, Candido KD, King M, Marra G, Winnie AP. The effect of motor activity on the onset and progression of brachial plexus block with bupivacaine: a randomized prospective study in patients undergoing arthroscopic shoulder surgery. Anesth Analg 2008;106:659–63[Abstract/Free Full Text]
- Okasha AS, el Attar AM, Soliman HL. Enhanced brachial plexus blockade. Effect of pain and muscular exercises on the efficiency of brachial plexus blockade. Anaesthesia 1988;43:327–9[Web of Science][Medline]
- Stevens MF, Klement W, Lipfert P. Conduction block in man is stimulation frequency dependent. Anaesthesist 1996;45:533–7[Web of Science][Medline]
- Stevens MF, Linstedt U, Neruda B, Lipfert P, Wulf H. Effect of transcutaneous electrical nerve stimulation on onset of axillary plexus block. Anaesthesia 1996;51:916–9[Web of Science][Medline]
- Tsen LC, Thomas J, Segal S, Datta S, Bader AM. Transcutaneous electrical nerve stimulation does not augment combined spinal epidural labour analgesia. Can J Anaesth 2000;47:38–42[Web of Science][Medline]
- Nau C, Wang GK. Interactions of local anesthetics with voltage-gated Na+ channels. J Membr Biol 2004;201:1–8[Web of Science][Medline]
- Gokin AP, Philip B, Strichartz GR. Preferential block of small myelinated sensory and motor fibers by lidocaine: in vivo electrophysiology in the rat sciatic nerve. Anesthesiology 2001;95:1441–54[Web of Science][Medline]
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