[Utility of double burst stimulation in the detection of residual neuromuscular blockade]

To assess the usefulness of double burst stimulation (DBS) for detecting neuromuscular blockade caused by atracurium and vecuronium.

One hundred nineteen adult patients were randomly assigned to receive atracurium (n = 62) or vecuronium (n = 57), with electromyographic monitoring of the number of responses to train of four (TOF) stimuli, TOF-ratio (TR) and the amplitude of the first TOF response (T1) in the pollicis adductor and the response to neurostimulator DBS in the contralateral forearm. During recovery from neuromuscular blockade an independent anesthesiologist manually assessed two responses to DBS every minute as being clearly differentiated, doubtful or undifferentiated. The results were later compared to T1 and TR.

Significant differences (p < 0.05) between groups were observed for TR in doubtful (0.27 +/- 0.18 and 0.34 +/- 0.17 for atracurium and vecuronium, respectively) and undifferentiated (0.34 +/- 0.22 and 0.43 +/- 0.18, respectively) responses to DBS, and for T1 with three TOF responses (26.0 +/- 13.6 and 33.1 +/- 14.2, respectively) or four responses (30.9 +/- 14.1 and 38.7 +/- 18.4, respectively). T1 values when TR was 0.75 (extubation criterion) were 68.1 +/- 23.8% and 60.5 +/- 17.4% for the atracurium and vecuronium groups, respectively (NS).

Assuming that DBS reduces the risk of residual curarization and that a TOF-ratio greater than 0.75 indicates adequate recovery from neuromuscular blockade, manual assessment of DBS response as obtained in this study indicates curarization and equal responses do not guarantee its absence. The most reliable index of recovery from neuromuscular blockade is the TR obtained by electromyographic monitoring.