instruction: when's the last time that patient 65838 had a excision intervert disc in the last hospital visit?
response: SELECT procedures_icd.charttime FROM procedures_icd WHERE procedures_icd.icd9_code = (SELECT d_icd_procedures.icd9_code FROM d_icd_procedures WHERE d_icd_procedures.short_title = 'excision intervert disc') AND procedures_icd.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 65838 AND NOT admissions.dischtime IS NULL ORDER BY admissions.admittime DESC LIMIT 1) ORDER BY procedures_icd.charttime DESC LIMIT 1