when is the first time that patient 17435 has had the bicarbonate minimum until 54 months ago?
select labevents.charttime from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 17435 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'bicarbonate' ) and datetime(labevents.charttime) <= datetime(current_time,'-54 month') order by labevents.valuenum asc, labevents.charttime asc limit 1