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Division of Sleep Medicine, Sleep Disorders Program, Brigham and Womens Hospital and Harvard Medical School, Boston, MA, meikermann{at}rics.bwh.harvard.edu
To the Editor:
In a study of 32 patients undergoing elective surgery, Capron et al. (1) compared the sensitivity different tests in detecting residual paralysis. Using the 100 Hz-tetanus test, the authors reported a fade of muscular contraction at a mechanomyographic train-of-four (TOF) ratio of
0.87 in 21 of the 32 patients (1). This is significant, as the adductor pollicis muscle does not fade during 100 Hz stimulation in the absence of neuromuscular blockade (2). The observation fade at 100 Hz tetanic stimulus at a TOF ratio of approximately 0.9 is consistent with other reports (3,4), and suggests that 100 Hz tetanic stimulation is a very sensitive method for detection of minimal neuromuscular blockade. It is also in agreement with our recent report (5) that the force of adductor pollicis muscle contraction can be decreased postoperatively with high frequency nerve stimulation, even with recovery of the TOF-ratio to 0.91. Detection of a minimal neuromuscular blockade is clinically important, because it can cause misdirected swallowing (6), and partial upper airway obstruction (7).
However, the authors conclude that the 100-Hz tetanus test is "unreliable," because a fade during 100-Hz tetanic stimulation was not always present, even at very low TOF-ratios of 0.14. (1) There might be some evidence (3,5) suggesting that assessment of a fade after high frequency nerve stimulation (i.e., between 50 and 100 Hz) provides a higher negative predictive value to exclude a residual paralysis compared with other available clinical tests such as double burst or TOF fade.
REFERENCES
This article has been cited by other articles:
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F. Donati Does Fade with 100-Hz Tetanic Stimulation Reliably Detect Residual Neuromuscular Blockade? Anesth. Analg., January 1, 2007; 104(1): 215 - 216. [Full Text] [PDF] |
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