what is the daily maximum value of patient 59473's base excess since 6 years ago?
select max(labevents.valuenum) from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 59473 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'base excess' ) and datetime(labevents.charttime) >= datetime(current_time,'-6 year') group by strftime('%y-%m-%d',labevents.charttime)