what was the first value of the sodium, whole blood lab test for patient 85895 in a month before?
select labevents.valuenum from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 85895 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'sodium, whole blood' ) and datetime(labevents.charttime,'start of month') = datetime(current_time,'start of month','-1 month') order by labevents.charttime asc limit 1