when was the last time that patient 81461 had the chloride minimum value since 12/2105?
select labevents.charttime from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 81461 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'chloride' ) and strftime('%y-%m',labevents.charttime) >= '2105-12' order by labevents.valuenum asc, labevents.charttime desc limit 1