NEW EQUIPMENT FOR NEUROMUSCULAR-TRANSMISSION MONITORING - A COMPARISON OF THE TOF-GUARD WITH THE MYOGRAPH-2000

Objective. The present study is to clarify whether the bias and limits of agreement of the TOF-Guard and the mechanomyograph differ from tho se of two mechanomyographs on contra lateral arms. Previous studies of the bias and limits of agreement between acceleromyographical (TOF-Gu ard(R)) and mechanomyographical measurements of neuromuscular transmis sion did not take the error introduced by using contra lateral arms in to consideration. Methods. Fifty-two women undergoing gynecological su rgery were anesthetized with midazolam, fentanyl, thiopental, halothan e and nitrous oxide. Neuromuscular blockade was induced and maintained with atracurium. In 32 patients, neuromuscular monitoring was perform ed with a Myograph 2000(R) on one hand and a TOF-Guard(R) at the other (M/T group). In 20 patients, monitoring was performed with a Myograph 2000(R) at both hands (M/M group). Train-of-four stimulations were ap plied to the ulnar nerve at the wrist in both groups. Bias and limits of agreement between the contra lateral hands in each group were calcu lated as proposed by Bland and Altman. Results. When the TOF ratio was 0.25, TOF ratio bias and limits of agreement in the M/T group were 0. 86 and 17.58 to -15.85, respectively. Corresponding values in the M/M group were -1.75 and 12.3 to -8.8. Bias in the M/T group decreased sig nificantly to -8.1 when TOF ratio increased to 0.70, resulting in limi ts of agreement of 12.1 to -28.4. The corresponding values in the M/M group were bias 2.0 and limits of agreement 10.7 to -6.7. TOF-Guard(R) bias for onset time and time to 5% recovery of T1 (first twitch in TO F) were -19 s and -1.5 min, respectively; both values differed signifi cantly from zero (P < 0.05). Taken together with the changing TOF-rati o bias during recovery in the M/T group, these results indicate differ ent onset and recovery curves for the two monitoring devices. Conclusi ons. Due to wide limits of agreement and different recovery courses, a cceleromyographic and mechanomyographic recordings of neuromuscular tr ansmission cannot be used interchangeably. The substantial variation b etween simultaneous mechanomyographical recordings of neuromuscular tr ansmission obtained in contra lateral arms suggests that this factor s hould be taken into account when studying new neuromuscular monitoring techniques using the two-arm technique.