Recent studies have shown different results concerning the effects of
smoking on neuromuscular blocking agents. Some reports indicate that s
mokers need higher doses of vecuronium, but are more sensitive to atra
curium. The aim of this study was to evaluate the effects of smoking o
n onset and recovery time after a single 0.6 mg/kg intubating dose of
rocuronium an analog of vecuronium. Methods: Following institutional a
pproval and informed consent, 20 smokers (>10 cigarettes/day) and 20 n
onsmokers were included in the study. Following oxazepam premedication
and induction with fentanyl and thiopental, single-twitch stimulation
of the ulnar nerve was performed every 10 s. Following stabilisation
of control responses, patients received rocuronium 0.6 mg/kg for intub
ation. Anaesthesia was maintained with enflurane less than or equal to
0.8 vol.% (end-tidal) and 65% nitrous oxide in oxygen. Onset time and
recovery to 25% and 75% of the twitch control values were recorded. R
esults: Onset and recovery times were not different between smokers an
d nonsmokers. Conclusions: The results of the present study suggest th
at chronic nicotine exposure does not change onset time or duration of
rocuronium neuromuscular blockade. A previous study found a greater n
eed for vecuronium in smokers and discussed stimulation of the neuromu
scular junction and enhanced biotransformation due to the enzyme-induc
ing properties of nicotine. The differences in our results could be pa
rtly due to a longer period of refraining from smoking in our patients
, leading to very low nicotine blood concentrations without the propos
ed receptor-stimulating effect. Another cause for different behaviour
of the two analogs could be different elimination pathways. Recent inv
estigations suggest that rocuronium may not be eliminated principally
by the liver. Therefore, enhanced nicotine-induced biotransformation,
as suggested for vecuronium, would not occur with rocuronium.