does patient 12568 ever underwent a base excess test?
select count(*)>0 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 = 12568 )