Stimulation of ulnar nerve and measurement of adductor pollicis response have been used for many years in clinical practice and research, but different muscles respond differently to relaxants, both in terms of onset and duration of blockade.
The onset time of neuromuscular blockade at the vocal cords and at the orbicularis oculi muscle(OO) was similar, and was shorter than at the adductor pollicis muscle(AP).
The purpose of this study was to examine which will be the best stimulus among double burst stimulation(DBS), train of four(TOF) and single twitch stimulation(STS) on OO or AP for an indicator of the optimal time for tracheal intubation.
Two hundreds and thirty six healthy patients were randomly allocated to six groups in which DBS(n=34), TOF(n=36) and STS(n=37) group in OO group, and DBS(n=43), TOF(n=43) and STS(n=43) group in group. Anesthesia was induced with thiopental sodium
3~5mg/kg and maintained with 1% enflurane until intubation.
Neuromuscular block was induced by intravenous vecuronium 0.1mg/kg and applied facial nerve or ulnar nerve stimuli immediately by DBS, TOF and STS using LNNERVATOR(Fisher & paykel Co.) continuously.
The complete relaxation time of OO group was closely observed with author's naked eyes, but the time of AP group were measured by tactile response of thumb.
Tracheal intubation was tried immediately by the author after complete disappearance of the muscle contraction. The intubation time from intravenous injection of vecuronium was recorded, and the intubating conditions were evaluated by vocal cord
opening, coughing reflex and response to laryngoscopy attempts.
@ES The results were as follows:
@EN 1) The intubation time of OO group was 195.97(12.82 sec. In DBS group, 182(8.46 sec. In TOF group and 167.73(6.24 sec. In STS group, respectively and there were no significance among groups.
2) The intubation time of AP group was 290.56(12.1 sec. In DBS group, 276.79(10.32 sec. In TOF group and 230.16(0.88 sec. In STS group, respectively and there were no significance among groups. But the intubation time of AP group was
significantly
prolonged more than that of OO group, as much as 95 sec. of DBS group, 94 sec. of TO F group and 63 sec. of STS group, respectively(P<0.05).
3) There were no significance of vocal cords opening and response to laryngoscopy attempts in three groups, but DBS group(6%) was statistically less cough reflex than TOF(37%) and STS group(33%) in OO group(P<0.05). There were no significance of
the
intubation responses among three groups in AP group.
4) Coughing reflex ratio(positive cough cases/total cases(100)of OO group(36%) was significantly more than that of AP group(12%) in TOF group, and coughing reflex ratio of OO group(32%) was significantly more than that of AP group(12%) in STS
group,
but there were no significance of coughing reflex ratio between OO and AP group in DBS group.
With the above results the authors concluded that DBS on facial nerve observed orbicularis oculi muscle was most reliable index to determine the optimal time for tracheal intubation, and facial nerve stimuli was more sensitive than ulnar nerve
stimuli
due to reduce 95 sec. of intubation time The optimal intubation time was about 196 sec. after vecuronium(0.1mg/kg).
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