DOUBLE BURST MONITORING DURING RECOVERY FROM ATRACURIUM-INDUCED NEUROMUSCULAR BLOCKADE - A COMPARISON WITH TRAIN-OF-4

Background. Double burst stimulation (DBS) was originally introduced f or improved manual detection of residual neuromuscular blockade. Previ ous studies demonstrated a high correlation between mechanomyographica l responses to DBS and train-of-four (TOF) stimulation during recovery from neuromuscular blockade. However, repeatability and bias analyses that are recommended when new monitoring devices are introduced into clinical practise [11] have not yet been performed. Object. The object of the present study was to evaluate if DBS3,350/50 (3 stimuli at 50 Hz followed 0.750 sec later by 3 stimulations at 50 Hz) and TOF measur ements are in so close agreement that they can be used interchangeably during spontaneous recovery from atracurium blockade. Methods. The st udy comprised 20 women undergoing gynaecological laparotomy and anaest hetised with fentanyl, thiopentone, halothane, and nitrous oxide. The neuromuscular blockade was induced and maintained with atracurium. The ulnar nerve was stimulated using DBS or TOF stimulation. Neuromuscula r transmission was monitored mechanomyographically. Alternating sequen ces of 4 DBS and 6 TOF stimulations were applied during the phase of s pontaneous recovery. Repeatability, bias (accuracy) and limits of agre ement were calculated as proposed by Bland and Altman [11]. Results. T he repeatability coefficients before any neuromuscular blocking agent was given were 3.4 and 7.7% for T1 and D1, respectively (P <0.05), and 3.8 and 3.5% for TOF ratio and DBS ratio, respectively (P >0.05). The mean difference between duplicated DBS and TOF measurements during re covery (repeatability) differed from zero due to the ongoing recovery process. It was therefore not possible to calculate the repeatability coefficients. The DBS ratio bias decreased from 6.69 to 3.51% (P <0.05 ) during recovery. The limits of agreement between the DBS and TOF rat ios increased from -2.07 to 15.45%, to -11.93 to 18.95% during recover y, while the limits of agreement between the DBS and TOF twitch height s increased from -5.02 to 10.68%, to -21.02 to 25.26%. Conclusion. The limits of agreement between DBS and TOF responses were so wide that D BS and TOF can not be used interchangeably.