what was the amount of cerebral drain r ventricular drain output patient 8016 had had on last month/22?
select sum(outputevents.value) from outputevents where outputevents.icustay_id in ( select icustays.icustay_id from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 8016 ) ) and outputevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'cerebral drain r ventricular drain' and d_items.linksto = 'outputevents' ) and datetime(outputevents.charttime,'start of month') = datetime(current_time,'start of month','-1 month') and strftime('%d',outputevents.charttime) = '22'