Serum gastrin and blood glucose levels during halothane-nitrous oxide anaesthesia and strabismus surgery in children. The purpose of this study was to determine whether serum gastrin levels are increased by reflexogenic stimuli applied to the extrinsic muscles of the eye. Serum gastrin and blood glucose concentrations were measured in ten normal children aged between 5 and 12 yr during general anaesthesia with halothane and nitrous oxide and during strabismus surgery. Fasting basal concentrations of gastrin (33.6 +/- 14.8 pg.ml-1) and of glucose (4.43 +/- 0.72 mmol.L-1) were in the normal range of values for children. Intravenous atropine (0.01 mg.kg-1), general anaesthesia with halothane in nitrous oxide and oxygen by mask for three minutes, tracheal intubation, extraocular muscle stimulation and surgical stress did not cause any variation in the mean serum gastrin concentration. On the contrary, tracheal intubation and surgical stress increased blood glucose concentrations (P less than 0.05). There was no difference in the serum gastrin levels after extraocular muscle stimulation between children with positive or negative oculocardiac reflexes (44.5 +/- 16.7 pg.ml-1 vs 38 +/- 14.7 pg.ml-1, respectively). The incidence of vomiting predischarge was 60 per cent. Serum gastrin levels did not differ between children who vomited and children who did not (44.3 +/- 18.5 pg.ml-1 vs 47.1 +/- 16.9 pg.ml-1, respectively). Vomiting after strabismus surgery cannot be attributed to high gastrin serum levels. Consequently, it is unlikely that vomiting after strabismus surgery is linked to an "oculogastric reflex" with the vagus nerve as the efferent pathway. 