Anticholinergics improve fibreoptic intubating conditions during general anaesthesia

To determine if anticholinergic agents improve fibreoptic intubating conditions and to compare the efficacy and side effects of glycopyrrolate and hyoscine.

Eighty ASA I adults undergoing elective wisdom tooth extraction were randomly allocated to receive 0.4 mg hyoscine hydrobromide po, 0.4 mg hyoscine hydrobromide im, 0.4 mg glycopyrrolate im or no anticholinergic, one hour pre-operatively. All underwent nasal fibreoptic intubation under general anaesthesia. The time taken to pass the fibreoptic scope was noted and visual analogue scores (VAS) were recorded for clarity of visual field and post-operative sore throat, dry mouth and nausea.

The time to intubation was not different among the four groups (Kruschal-Wallis P = 0.07). The clarity of visual field was improved in all three anticholinergic groups (Kruschal-Wallis P = 0.006), but there was no difference among the three groups (median VAS control 6.4, glycopyrrolate 8.0, oral hyoscine 7.9, im hyoscine 7.7). There was no difference in post-operative side effects among any of the groups at both 30 min and four hours.

The addition of an anticholinergic produced better visual conditions for intubation but had no effect on the incidence of post-operative sore throat, dry mouth and nausea.