In the early 1960s, some medical centers began to develop intensive care unit (ICU) information systems to monitor critically ill patients. These used a combination of devices to obtain measurements and derive variables. One generated a severity index to guide treatment and compute the probability of survival; another saved data to use in analysis and educational simulations. Studies of the clinical effectiveness of such systems were mixed, despite fi ndings that variations in hospital death rates were associated with variations in care processes. While few hospitals had emergency department (ED) subsystems installed by the end of the 1980s, some participated in community emergency medical systems that routed patients to hospitals for treatment. Despite progress in intervening years, recent studies fi nd that both settings face continued challenges. The data-intensive ICU faces interoperability issues arising from incompatible piece of monitoring equipment. For the ED, exchange of patient information from other settings remains diffi cult and evidence as to the impact of health information technology remains limited.Keywords Intensive care unit information system s • Emergency department information system s • Specialized information system s • Interoperability • Clinical effectiveness • Medical device s • Community emergency medical system s Two hospital settings have an undeniable hold on the mass media and the public imagination: the intensive care unit (ICU) and the emergency department (ED). Both of these specialized high-intensity environments rely on health information technology (IT) and an array of health informatics applications to treat patients who are severely ill or injured and potentially at risk of death. Beyond those commonalities, there are signifi cant differences. The ICU treats critically ill patients transferred in from other care settings; the ED admits patients from the community to treat
