how many hours has elapsed since patient 15447 stayed in careunit tsicu for the first time in the on their current hospital visit?
select 24 * ( strftime('%j',current_time) - strftime('%j',transfers.intime) ) from transfers where transfers.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 15447 and admissions.dischtime is null ) and transfers.careunit = 'tsicu' order by transfers.intime asc limit 1