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with sudden, critical abnormalities in vital signs, a failure to react promptly or commensurately escalate care constitutes a “failure to rescue” and may result in a serious adverse event.1 There are many reasons for sudden critical illness and for failure to rescue (Table 2), and they help to explain why serious adverse events are surprisingly frequent. The New England Journal of Medicine Downloaded from nejm.org at UNIVERSITY OF PITTSBURGH on May 30, 2012. For personal use only. No other uses without permission. Copyright © 2011 Massachusetts Medical Society. All rights reserved. T h e n e w e ngl a nd j o u r na l o f m e dic i n e 140 n engl j med 365;2 nejm.org july 14, 2011 The Epidemiology of Serious Adverse Events Serious adverse events expose patients to an increased risk of death. Many such events appear to result from insufficient, delayed, or incorrect medical care. Studies in the United States2,15,16 and other countries17-19 show that serious adverse events are relatively common and often iatrogenic and that they are associated with disability and death. Research also shows that such events occur after failure to rescue.20 Collectively, these studies present robust evidence that improvements are needed to overcome failure to deliver optimal care rapidly in hospital wards and that most serious adverse events due to such failure are preceded by clinically observable warning signs.21-23 Conditions that are commonly associated with failure to rescue include acute respiratory failure, acute cardiac failure, acute changes in consciousness, hypotension, arrhythmias, pulmonary edema, and sepsis.24 In studies of rapid-response systems, the most commonly measured serious adverse events include cardiac arrest, unexpected death, and unplanned ICU admission.25 Warning Signs Several studies show that abnormal vital signs can help identify clinical deterioration in patients minutes to hours before a serious adverse event occurs.21,26 Thus, in most cases, there is sufficient time to identify patients at risk and deliver an intervention. A logical preventive step would appear to be frequent and accurate measurement and reporting of vital signs.27 What is less well established, however, is the proportion of hospitalized patients in whom abnormal vital signs develop but do not lead to a serious adverse event. In addition, the optimal thresholds for activation criteria in specific patient cohorts should be assessed to prevent excessive assessment of patients who have abnormal vital signs but who are not at risk for serious adverse events. Failure to Monitor The measurement of vital signs is risk-free, inexpensive, and reproducible, and it identifies clinical deterioration in many patients.28 However, studies have shown that such measurements may not be performed predictably, accurately, or completely.25,29,30 The case of respiratory-rate monitoring is particularly striking.30,31 This “failure to monitor” probably contributes to the risk of failure to rescue. Unfortunately, a major impediment to providing adequate monitoring is the cost of staffing and automated monitoring equipment. Failure to Escalate An analysis of the actions of hospital-ward personnel during patient instability suggests problems such as triage error and inappropriate placement of severely ill patients on the hospital ward,5 delays in doctor notification,32 failure to attend to and assess the patient’s deteriorating condition,20 inadequate clinical assessment,15,19,20,22 medication errors,20 suboptimal response to the urgency of the symptoms,20 and failure to seek help or advice.20 Many investigators have concluded that objective criteria for deterioration are needed; such criteria would clarify the expectations of staff.1,33 In addition, these criteria should act as triggers for rapid referral to personnel with appropriate expertise and equipment. Deficiencies in identifying and responding to patients in crisis have been singled out for improvement and used to provide a rationale for rapid-response systems.33 Table 1. Comparison between a Traditional Code Team and a Rapid-Response Team.* Feature Traditional Code Team Rapid-Response Team Typical criteria for calling the team No recordable pulse, no recordable blood pressure,