Onset and duration of action of rocuronium - from tracheal intubation, through intense block to complete recovery

Background: The primary objective of this study was to establish the relati on between the post tetanic count (PTC) and the time to reappearance of the first response (T-1) in train-of-four (TOF) nerve stimulation following ro curonium 0.6 mg/kg, 0.9 mg/kg, and 1.2 mg/kg. The secondary objective was t o evaluate the intubation conditions after 1 min. Methods: One hundred and eight patients were randomised to one of three dos es of rocuronium: 0.6, 0.9 or 1.2 mg/kg. Tracheal intubation was performed at 60 s by a blinded investigator During propofol, fentanyl, midazolam anae sthesia the neuromuscular block was monitored by mechanography using TOF st imulation every 12 s. At 6 min intervals, a tetanic stimulation (50 Hz) was applied for 5 s preceded and followed by a 30 s period of 1 Hz stimulation until the reappearance of T-1. Results: There was a significant difference in recovery following the high dose and the two lower doses. The relation between time (min) to reappearan ce of T-1 (t) and PTC can be expressed as follows: t((0.6 and 0.9 mg/kg)(mi n)) = 18.8-6.46 root PTC and t((1.2 mg/kg)(min)) = 26.1-9.12 root PCT. T-1 was seen at a mean PTC level of 8 or 9 in all three soups. The intubation c onditions were graded as excellent or good in all patients except in two pa tients following the 0.6 mg/kg dose of rocuronium. Conclusion: The PTC method can be used to predict the time to first respons e to TOF nerve stimulation during intense rocuronium induced neuromuscular blockade. The relation between PTC and the time to T-1 was prolonged after 1.2 mg/kg compared with 0.6 mg/kg and 0.9 mg/kg. No further improvement in intubation conditions at 60 s was evident by increasing the rocuronium dose from 0.9 mg/kg to 1.2 mg/kg.