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Anesth Analg 2006;102:654-655
© 2006 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000190794.07299.97

LETTER TO THE EDITOR

Is TNS Really No Big Deal?

D. Zaric, MD, C. Christiansen, MD, N. L. Pace, MD, Mstat, and Yodying Punjasawadwong, MD

Department of Anesthesiology, Frederiksberg Hospital, University of Copenhagen, Copenhagen, Denmark, dusanka.zaric{at}fh.hosp.dk (Zaric, Christiansen) Department of Anesthesiology, University of Utah, Salt Lake City, UT (Pace) Department of Anesthesiology, Chiang Mai University, Thailand (Punjasawadwong)

In Response:

We appreciate the comments of Dr. Lambert about the implications for patient safety of the transient neurologic symptoms (TNS) that sometimes develop after spinal anesthesia with lidocaine. There is much speculation as to the nature of TNS but nothing has been substantiated. A systematic review is observational research of published randomized controlled trials; in the 14 included studies, all patients recovered from TNS without permanent sequelae. A future confirmation that TNS after intrathecal lidocaine is associated with nerve root inflammation, as noted in a recent case report (1), would be alarming.

We thank Dr. Lambert for noting a misstatement concerning lidocaine dose and TNS. It appears that the risk of TNS does not depend on the concentration of lidocaine (2,3). A subgroup analysis within our meta-analysis can provide consistent evidence for this lack of a concentration effect. The relative risk with 95% confidence interval for studies comparing 2% lidocaine and other local anesthetics is 8.51 (3.11, 23.32); for studies comparing 5% lidocaine to other local anesthetics the relative risk is 6.34 (3.05, 13.17). These relative risks are not different.

It would be unfortunate if a reader misinterpreted our results as stating, "TNS is really no big deal." Compared with other local anesthetics (except mepivacaine), the relative risk for TNS is about sevenfold higher for lidocaine. We restate our conclusion as follows: "This increased risk of TNS must be weighted against the benefit of rapid, short-acting anesthesia..." (4)

References

  1. Avidan A, Gomori M, Davidson E. Nerve root inflammation demonstrated by magnetic resonance imaging in a patient with transient neurologic symptoms after intrathecal injection of lidocaine. Anesthesiology 2002;97:257-8.[Medline]
  2. Hampl KF, Schneider MC, Pargger H, et al. A similar incidence of transient neurologic symptoms after spinal anesthesia with 2% and 5% lidocaine. Anesth Analg 1996;83:1051-4.[Abstract]
  3. Pollock JE, Liu SS, Neal JM, Stephenson CA. Dilution of spinal lidocaine does not alter the incidence of transient neurologic symptoms. Anesthesiology 1999;90:445-50.[ISI][Medline]
  4. Zaric D, Christiansen C, Pace NL, Punjasawadwong Y. Transient neurologic symptoms after spinal anesthesia with lidocaine versus other local anesthetics: a systematic review of randomized, controlled trials. Anesth Analg 2005;100:1811-6.[Abstract/Free Full Text]




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press