In this chapter, we examine and summarize the evidence for observation care based on age, for example, the pediatric and geriatric population, as the previous chapter did for adults with a given condition or diagnosis, such as chest pain or asthma. The critical questions addressed in this chapter are:

1. 1. Can infants and children (e.g., pediatric patients) be successfully and safely treated in an observation unit setting?

2. 2. Can geriatric patients be successfully and safely treated in an observation unit setting?

This chapter deals with critical issues in observation medicine for adult patients based on a given diagnosis or clinical condition, such as chest pain or asthma. A separate chapter deals with critical issues in observation medicine based on age, for example, observation medicine for pediatric and geriatric patients. The critical questions addressed in this chapter are:

1. 1: In adult patients, when compared with inpatient treatment does the provision of observation services, specifically in a dedicated, protocol-driven observation unit (OU), improve patient outcomes, decrease length of stay (LOS), reduce costs, increase patient satisfaction, and have other benefits, including (but not limited to) decreased readmissions?

2. 2: In adult patients, does the use of OU clinical and administrative methodology (by aggressive early diagnostic and therapeutic management using tools such as protocol-driven therapy) produce equivalent or better results (e.g., patient outcomes, LOS, costs, and adverse events) compared with routine inpatient care?

3. 3: In the adult emergency department (ED), does use of an OU improve key measures of department efficiency, such as decreases in ED LOS, door-to-doctor time, ambulance diversion, and the left-without-being-seen rate?