instruction: hey what was patient 6215's average phenytoin, free value during the first hospital visit?
response: SELECT AVG(labevents.valuenum) FROM labevents WHERE labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 6215 AND NOT admissions.dischtime IS NULL ORDER BY admissions.admittime LIMIT 1) AND labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'phenytoin, free')