what number of hours has it been since patient 27172 received his first prescription of furosemide during their current hospital visit?
select 24 * ( strftime('%j',current_time) - strftime('%j',prescriptions.startdate) ) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 27172 and admissions.dischtime is null ) and prescriptions.drug = 'furosemide' order by prescriptions.startdate asc limit 1