what was the first value of a bilirubin, total lab test of patient 25493 in the first hospital visit?
select labevents.valuenum from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 25493 and admissions.dischtime is not null order by admissions.admittime asc limit 1 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'bilirubin, total' ) order by labevents.charttime asc limit 1