In case of established delirium within 7-day after initiation of the study intervention, administration of the assigned intervention is stopped since one of the primary endpoints (i.e. incidence) is reached. Unblinding will be performed immediately (24-hours a day, 7 days a week through the local hospital pharmacy at VUmc, procedures and argumentation will be recorded), and the treating physician will further decide on the treatment of the patients' delirium. Nursing staff will perform the DOS score 3-times daily to assess the duration of delirium, according to protocol. In addition, the investigator will assess delirium duration and severity with the DRS-R-98 once-daily. Both the DOS scale and DRS-R-98 are performed until delirium symptoms resolve or if participation in the study is no longer possible due to for example transfer to an other facility, ICU/CCU admission or death.