Low and high frequency stimulation tests to characterize the effects of edrophonium on vecuronium-induced neuromuscular block

Abstract

We recorded adductor pollicis mechanical activity in response to low (0.1 and 2 Hz) and high (50 and 100 Hz) frequency stimulation 15 min after edrophonium 250, 500 and 1000 micrograms kg-1, given to antagonize vecuronium-induced block at 10, 25 and 50% pre-reversal twitch height. We studied 54 ASA class I and II anaesthetized (methohexitone, fentanyl, nitrous oxide) young adult patients allocated randomly to nine groups of six patients each. The greater sensitivity of train-of four (TOF) ratio and residual force after 100-Hz, 5-s tetanic stimulation (RF100) to residual deficit allowed discrimination more readily between the effects of edrophonium dose and pre-reversal twitch height (P < 0.001, two-way analysis of variance). The highest reversal scores (approximately 0.9 TOF ratio and 0.6 RF100) were obtained when edrophonium 500-1000 mg kg-1 was given at 50% twitch height (P < 0.05, Duncan's test).

Is recovery of neuromuscular transmission complete after the use of neostigmine to antagonize block produced by rocuronium, vecuronium, atracurium and pancuronium?

“…Our results have confirmed previous data indicating that rocuronium, in common with vecuronium and atracurium, can be antagonized easily to an endpoint of a TOF ratio of 0.7 when neostigmine 40 g kg 91 is given at 25% recovery of control twitch height [9][10][11][12] . But the "gold standard" of these authors (a TOF ratio of 0.7) does not imply complete recovery of neuromuscular transmission.…”

“…Mean values in patients who received rocuronium were as high (about 0.8) as in patients who received vecuronium and atracurium. In contrast with patients who received neuromuscular blockers of intermediate duration of action, the mean value for RF 100 Hz in patients in group Pan was only approximately 0.3, confirming the previously reported very high sensitivity of measured RF 100 Hz [8][9][10][11][12] . The use of RF 100 Hz is important also because a small, but statistically significant and clinically important 0.15 TOF ratio difference is amplified by a factor of 3-4 for the compound investigated in this study.…”

“…In normal patients receiving medium duration neuromuscular blocking agents (rocuronium [3][4][5][6][7] , vecuronium, atracurium) a TOF ratio of 0.7 is currently obtained after administration of neostigmine given at a twitch height of 10-25%, but even for vecuronium, data related to a TOF ratio of 0.9 are still scarce [8][9][10][11][12] .…”

“…In addition to the 2 Hz TOF stimulation pattern, the use of high stimulation rates, especially 100 Hz tetanic stimulation, to quantify recovery of neuromuscular transmission may be desirable because of the TOF ratio limitations for detection of residual neuromuscular block in many clinical situations [8][9][10][11][12] . In normal awake patients also, firing rates of approximately 100 Hz are often observed in different muscle types 13 .…”