when was the last time patient 14749 until 04/2104 had a base excess laboratory test?
select 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 = 14749 ) and strftime('%y-%m',labevents.charttime) <= '2104-04' order by labevents.charttime desc limit 1