Adverse events present on arrival to the emergency department: the ED as a dual safety net.

Trigger tools are one approach to identifying adverse events. This retrospective cohort study developed an emergency department (ED) trigger tool to characterize adverse events that are present on arrival (POA). The majority (60.8%) of adverse events identified in the ED were POA, accounting for an estimated 7.6% of ED visits. The most comment POA adverse events were medication-related (55.6%).