what is the monthly average amount of drain out #1 hemovac that patient 55503 had until 11/2104?
select avg(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 = 55503 ) ) and outputevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'drain out #1 hemovac' and d_items.linksto = 'outputevents' ) and strftime('%y-%m',outputevents.charttime) <= '2104-11' group by strftime('%y-%m',outputevents.charttime)