how many hours have passed since patient 17667 has received a base excess test for the first time on this hospital encounter?
select 24 * ( strftime('%j',current_time) - strftime('%j',labevents.charttime) ) from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'base excess' ) and labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 17667 and admissions.dischtime is null ) order by labevents.charttime asc limit 1