what was the last value of an chloride lab test in patient 84346 until 51 months ago?
select labevents.valuenum from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 84346 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'chloride' ) and datetime(labevents.charttime) <= datetime(current_time,'-51 month') order by labevents.charttime desc limit 1