Objective: Delirium is an important and frequently occurring complication in intensive care patients. However, screening and treatment of delirium is not in accordance with current national and international guidelines. The first objective of this prospective study is to describe the barriers and facilitators for guideline adherence. Second, investigators will develop a tailored implementation strategy. Finally, investigators will describe the effects of the tailored implementation on the adherence of the guideline in a pilot study. Design: Current practices, attitudes and deviations from a national (Dutch) delirium guideline will be assessed in a prospective before-measurement. Barriers and facilitators will be identified with surveys and focus group interviews. Adherence to the guideline will be studied in a before-after study in 7 ICUs in the Southwest of the Netherlands. Further, the effect of a multifaceted implementation strategy-guided implementation will be assessed with regard to important clinical outcomes, such as mortality and delirium incidence. Population: Professionals (Physicians/intensivists, nurses' and psychiatrists) and ICU patients. Intervention: The delirium guideline of the Netherlands Society of Intensive Care (NVIC) is implemented in this study. Implementation strategies: Barriers and facilitators will be determined in focus group interviews (n=7) with health care professionals resulting in a tailored guideline implementation strategy. In the development of the strategies specific attention will be paid to sustaining the guideline adherence. Main outcome: 1. Current practices; 2. Barriers and facilitators for guideline adherence; 3. Tailored implementation strategy; 4. Percentage of adherence to the guideline (early screening, prevention and treatment of delirium); 5. Effects of implementation on outcomes (economic, mortality, delirium incidence). Data analysis / power: The main effects, guideline adherence, will be evaluated by comparing the before and after measurements. Calculating from 90% power,2-sided alpha=0.01, 231 patients per periods will be sufficient to test the proposed adherence of 85%. Economic evaluation: The economic analysis will be performed from a health care perspective. Investigator will calculate and compare the direct medical costs of usual care (before) and care after implementation of the guideline. Additionally, the cost of the tailored guideline implementation process will be calculated. The economic analysis will be a cost-minimalization analysis.

Inclusion Criteria:

• Screening delirium by all patients
• Measuring of guide line adherence for all professionals working on the ICU
• Implementation guideline: all professionals

Exclusion Criteria:

• no

ICU patients and professionals