Double burst stimulation(2,3): A new stimulating pattern for residual neuromuscular block

Purpose: We present a new stimulating pattern: double burst stimulation(2,3) (DBS2,3) for evaluating residual neuromuscular block. Methods: Forty adult patients were studied. For DBS2,3 two burst stimuli were applied every 750 msec. The first consisted of two tetanic stimuli of 0.2 msec duration and the second of three tetanic stimuli of 0.2 msec duration. At varying degrees of neuromuscular block induced by vecuronium, the presence or absence of fade, or the presence or absence of waxing (i.e., the feeling that the muscular contraction in response to the second burst was stronger than that to the first) was determined by an observer blinded to the depth of neuromuscular block. In addition, the relationship between the train-of-four (TOF) ratio and DBS2,3 ratio was established at varying depths of neuromuscular block (TOF ratio 004-1.00). Results: The probabilities of tactile detection of fade in response to DBS2,3 were 100, 76, 15, 9, 3, 0, and 0% at a TOF ratio of 0-0.40, 0.41-0.50, 0.51-0.60, 0.61-0.70, 0.71-0.80 0.81-0.90, and 0.91-1.00, respectively. Waxing in response to the DBS2,3 was identified in 0, 6, 32, 84, and 98% of cases when the TOF ratios were 0.00-0.60, 0.61-0.70, 0.71-0.80, 0.81-0.90, and 0.91-1.00, respectively. A close linear relationship existed between the TOF ratio and DBS2,3 ratio (r = 0.96, P < 0.000001). Conclusion: DBS2,3, is of clinical use because when residual neuromuscular block is clinically important, fade can be identified but once neuromuscular function returns to a sufficient level, waring can be detected.