The rapid expansion of medical knowledge and the advances in surgical techniques, drug treatments, and interventions make it possible to treat conditions that would have been untreatable only 50 years ago. Progress has also led to a change in demographics, with an unparalleled increase in the age of patients treated and, as a result, an increasing level of illness severity.
These medical and social changes have coincided with alterations in hospital care. Such trends include health-care budget containments, cuts in the number of beds available, shortages of trained nurses, and working time directives. These new imperatives, which are associated with fewer and less experienced staff at hand to manage a larger workload of more complex patients, do not match the rising demand for admissions. Intensive care units (ICUs) have a proportionately limited number of beds to deal with such complex patients. Furthermore, the general wards, which lack sufficient monitoring, vigilance, and staffing resources, are being asked to provide care at levels usually reserved for ICUs. As a result of these system characteristics, patients whose condition deteriorates while on the general ward may not be identified and may not receive an appropriately high level of care in a timely manner.
Rapid Response Systems (RRSs) have been adopted in different forms worldwide to address the needs of such deteriorating patients in general wards. The RRS is an organized approach to improve patient safety by bridging care across hierarchies and specialties. RRSs facilitate the delivery of intensive care knowledge outside of the walls of the ICU, benefiting ward patients regardless of their location. The purpose is to detect and treat deviating physiology in time to prevent progression to irreversible conditions such as cardiac arrest or death.
Although intuitively appealing, some have questioned the evidence on which the implementation of an RRS rests. In this chapter, we present the concept of identifying and treating patients at risk using early warning scores (EWS) and RRSs as well as the emerging body of evidence in which these systems are evaluated.
Do Early Warning Scores Help Identify Patients at RISK?
Adverse Events
Hospitals are dangerous places. In the early 1990s, several reports highlighted the occurrence of unexpected and potentially avoidable serious adverse events in hospitals. These reports were not confined to a specific health-care system but were emerging from different parts of the world, thus forming the picture of a global problem. Adverse events, defined as unintended injuries or complications caused by medical management rather than by the underlying disease and leading to death, disability, or prolonged hospital stays, were identified in between 2.9% and 16.6% of hospitalizations. Up to 13.6% of such events were reported to lead to death and, importantly, 37% to 70% of these complications were deemed preventable. An in-hospital cardiac arrest is an example of a serious adverse event that is likely to have dire consequences. Despite dedicated efforts to improve resuscitation routines during cardiac arrest, mortality has remained unaltered at 85% to 90% over the past 30 years. This lack of improvement could be explained by the fact that in-hospital cardiac arrests occurring in general wards are mostly related to noncardiac processes, with the arrest representing the common final pathway of various underlying disturbances. As such, it is logical to hypothesize that outcome will improve with appropriate recognition and management of the precipitating disorder. Indeed, retrospective chart reviews suggest that this approach may well make it possible to avoid cardiac arrest altogether. In many, if not most, patients, signs of deterioration such as changes in pulse, blood pressure, respiratory rate, and mental status were present many hours before an actual arrest occurred. Several studies have confirmed that this slow deterioration in vital signs may be present up to 48 hours before serious adverse events such as cardiac arrest, unanticipated ICU admission, or death. These reports imply that the development of critical illness is not so much “sudden” but rather “suddenly recognized.”
Early Warning Scores
The classic vital signs are temperature, pulse rate, blood pressure, and respiratory rate. Oxygen saturation, as measured by pulse oximetry, and level of consciousness may also constitute useful vital signs. Development of a score/numerical value quantifying derangements of these easily measured physiologic markers, the so-called EWSs, thus has potential. The UK National Early Warning Score (NEWS) is shown for illustration ( Fig. 5-1 ).
Assessment of a patient’s vital signs is a routine component of in-hospital care. However, only rarely are detected abnormalities linked to specific responses. In the formulation of such a closed-loop system, it is essential to define assessment parameters that trigger a response. Trigger systems can be categorized as single-parameter, multiple-parameter, aggregate weighted scoring, or combination systems. The two most common are the single-parameter and the aggregate weighted scoring systems.
The first RRS was a single-parameter system. The triggers were acute change in respiratory rate, pulse oximetry saturation, heart rate, systolic blood pressure, or conscious state or that the staff was simply worried about the patient because of specific conditions, physiologic abnormalities, and the subjective criterion “any time urgent help is needed or medical and nursing staff are worried.” A deviation of any single parameter from its predefined cutoff level was enough to alert the team. These original RRS activating criteria are, with slight modifications, still in use in Australia, the United States, and parts of Europe. Advantages of the single-parameter system are ease of implementation and use and the provision of a binary response (call for help or not). The criteria consist of the observation of an acute change in respiratory rate, pulse oximetry saturation, heart rate, systolic blood pressure, conscious state, or that the staff are simply worried about the patient.
The subjective “worried” criterion is designed to empower the staff to activate a response whenever they are concerned about a patient. This approach relies on the intuition and experience of nurses and other providers and should not be underestimated because subtle symptoms or small changes observed by vigilant practitioners often turn out to be precursors to more objective physiologic changes. Studies on several systems demonstrated that the worried criterion activated nearly half of RRS calls.
In the aggregate weighted scoring systems, deviations of vital signs are assigned points. The sum of these points constitutes total scores that have been referred to as the EWS or Modified EWS. Once a threshold score is reached, a response is triggered. Alternatively, a trend in the score can be followed and an increase over time can then be used to direct a graded escalation of care. However, this approach is relatively complex and time-consuming and depends on accurate calculation. Variations of scoring systems with different triggers or additional parameters (e.g., urinary output) have been used. The Royal College of Physicians of the United Kingdom has recently proposed the application of a national standard, the NEWS, to increase consistency and reproducibility.
EWS have been shown to predict the development of critical illness. Prospective prevalence studies of entire hospital populations have demonstrated that fulfilling criteria for abnormal vital signs is clearly associated with a worse outcome. Most studies have focused on mortality, but derangements in vital signs also presage cardiac arrest and the need for ICU transfer. However, the accuracy of scores can vary as a function of the chosen outcome parameter. In a comparison by Churpek et al., the areas under the curve for different EWSs ranged from 0.63 to 0.88, with prediction of mortality being the most accurate. A recent systematic review by Alam et al. concluded that introduction of EWSs was associated with better clinical outcomes (improved survival and decreases of serious adverse events), although meta-analysis could not be performed because of the heterogeneity of the patient populations and lack of standardization of the scores used in the included studies.
There is no clear evidence to indicate which form of warning system is best or even what frequency of monitoring is ideal. One study found a median duration of 6.5 hours for vital sign deteriorations before cardiac arrest, whereas other studies found an even longer period. Patients clearly respond better to earlier than delayed interventions. In general, all systems provide reasonable specificity and negative predictive values but low sensitivity and positive predictive values. Sensitivity can be improved by reducing the trigger threshold but not without compromising specificity, thus increasing workload. Including other parameters such as age, comorbidities, or laboratory data may improve predictive value.
Although many systems are in use, they differ primarily in details. Virtually all are based on the same concept: vital signs can provide clinicians with useful clues in evaluating a patient’s condition or trajectory of illness. Implementing the use of any form of EWS conveys an important message: patients need to be checked. Placing the focus on monitoring and educating staff on when to react heightens awareness across the whole hospital; thus, it is likely to improve patient safety. In all probability, the value of an RRS lies not in the exact cutoffs or form of scores but rather in providing clear and objective tools to aid in assessing patients and in encouraging and empowering front-line providers to seek help when needed.
Do Rapid Response Systems Improve Outcome?
General Principles of Rapid Response Systems
The usefulness and predictive value of EWSs must always be seen within the context of the response they can trigger. This response typically emanates from ICUs: dedicated teams that can be summoned to respond early to deteriorating patients, removing the usual boundaries of specialties and locations and centering care instead around the patients’ needs.
Systems were simultaneously starting to take form in several parts of the world. An RRS is activated in Pittsburgh under the denotation “Condition C” (crisis) as opposed to “Condition A” (arrest), whereas in Australia the RRS is referred to as the “Medical Emergency Team” (MET). The first description in the literature appeared from an Australian center in 1995. This report described the use of the team, its triggers, and the interventions provided. In the United Kingdom, a similar model was named the “Patient-at-Risk Team.” In 2005, the first international conference on METs was held in Pittsburgh, and faculty consensus findings were published. The report from this meeting defined a common nomenclature and composition and set the framework for future research.
The term Rapid Response System refers to an entire network for responding to patients with a critical medical problem. The system comprises an afferent limb that detects the problem and triggers a response ( Table 5-1 ). The responding team constitutes the efferent limb. This aspect may be of different designs, reflecting local culture and resources.
| Physiologic Parameters | 3 | 2 | 1 | 0 | 1 | 2 | 3 |
|---|---|---|---|---|---|---|---|
| Respiration rate | ≤8 | 9–11 | 12–20 | 21–24 | ≥25 | ||
| Oxygen saturation | ≤91 | 92–93 | 94–95 | ≥96 | |||
| Any supplemental oxygen | Yes | No | |||||
| Temperature | ≤35.0 | 35.1–38.0 | 38.1–39.0 | ≥39.1 | |||
| Systolic blood pressure | ≤90 | 91–100 | 101–110 | 111–219 | ≥220 | ||
| Heart rate | ≤40 | 41–50 | 51–90 | 91–110 | 111–130 | ≥131 | |
| Level of consciousness | A | V, P, or U |
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