Letter to the Editor: In Response
We wish to thank Dr. Tammisto et al. for their positive comments regarding our article . As stated in our discussion, thumb displacement is minimized when the thumb is secured in a force transducer ring. Likewise, baseline shift may be restricted by attachment to a spring, thus improving the accuracy of clinical (i.e., subjective) assessment of neuromuscular recovery.
The prevention of baseline shift by providing some degree of preload to the thumb also can be accomplished during tactile clinical assessment. Interestingly, however, the amount of preload (or thumb fixation) achieved during tactile evaluation is apparently not sufficient to improve accuracy: visual and tactile means of assessment have a very similar incidence of false negatives [2,3]. It thus appears that mechanisms other than baseline shift may, at least partially, be responsible for the lack of tactile accuracy. We also agree with Dr. Tammisto and his colleagues that a "spring method" may constitute an effective improvement in clinical assessment, and likewise advocate the use of more objective means of monitoring.
Sorin J. Brull, MD
David G. Silverman, MD
Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06520-8051
1. Brull SJ, Silverman DG. Real time versus slow-motion train-of-four monitoring: a theory to explain the inaccuracy of visual assessment. Anesth Analg 1995;80:548-51.
2. Viby-Mogensen J, Jensen NH, Engbaek J, et al. Tactile and visual evaluation of the response to train-of-four nerve stimulation. Anesthesiology 1985;63:440-3.
3. Brull SJ, Silverman DG. Visual and tactile assessment of neuromuscular fade. Anesth Analg 1993;77:352-5.