The use of volatile anesthetics for the maintenance of anesthesia can enhance the action and prolong the duration of non-depolarizing muscle relaxants. The objective of this study was to establish the relation between the post tetanic count (PTC) and the time to reappearance of the first response (T1) by train-of-four (TOF) nerve stimulation following rocuronium 0.6 mg/kg (ED95 X 2) during sevoflurane versus propofol anesthesia.

Fifty adult patients were randomized to one of two groups, which had anesthesia maintained with sevoflurane or propofol. During sevoflurane or propofol anesthesia, neuromuscular block was monitored by mechanography using TOF stimulation every 12 s. At 6 min intervals, a tetanic stimulation (50 Hz) was applied for 5 s, which was preceded and followed by a 15 s period of 1 Hz single stimulation until the reappearance of T1.

First responses to PTS appeared earlier in the propofol group (12.5 ± 5.2 min) than in the sevoflurane group (16.6 ± 7.4 min), and first responses to TOF stimulation also occurred significantly sooner in the propofol group (24.8 ± 5.1 min) than in the sevoflurane group (32.6 ± 8.9 min). The interval between the appearance of PTC and T1 was shorter in the propofol than in the sevoflurane group.

We conclude that sevoflurane prolonged recovery from deep neuromuscular block by rocuronium as compared to propofol. The PTC method can be used to predict the time to first response to TOF nerve stimulation during intense rocuronium induced neuromuscular blockade.