Hospitalized patients frequently experience unanticipated deterioration of their clinical status, often leading to adverse clinical outcomes including mortality (1,2). A serious adverse event represents an unintended injury that occurs due to delayed or inappropriate management leading to death or disability (3). A significant number of adverse events in hospitalized patients may be preventable through early recognition of the decline in the clinical status and intervention through rescue measures. Failure to rescue represents the inability to prevent clinical deterioration and death, occurring as a result of complications arising from the underlying illness or therapeutic interventions (4). Adverse events, including cardiac arrests, are commonly preceded by antecedents that are either unnoticed or not addressed in a timely manner (5). Early recognition of abnormal vital signs may offer a window of opportunity to rescue deteriorating patients from potential complications. Rapid response systems are built around the concept of early recognition of warning signs followed by expeditious intervention. Rapid response teams (RRTs), in contrast to code blue teams, evaluate patients at an early stage of deterioration before cardiac or respiratory arrest occurs. Unexpected clinical worsening usually results from sepsis, respiratory or cardiac failure, hypotension, arrhythmias, or altered conscious level (6).
The Joint Commission in the US mandates hospitals to introduce rapid response systems to improve patient safety (7). The American Heart Association (AHA) also recommends establishment of rapid response systems to provide timely care to patients who are at risk of deterioration in general care settings (8).
Key components of rapid response systems
The efficacy of rapid response systems depends on three key elements of care, including (1) early identification of patients at risk of deterioration, (2) prompt reporting to the responder team, and (3) expeditious intervention by the RRT to enable rescue. Identification and reporting represent the afferent limb and RRT intervention, the efferent limb of the loop of care centered around rapid response systems.
Identification of patients at risk of deterioration
Medical and nursing staff play a crucial role in the timely recognition of early warning signs.
The National Patient Safety Agency report in the United Kingdom highlighted the failure to recognize clinical deterioration as a key factor that leads to hospital mortality. Nursing workload and a suboptimal nurse to patient ratio may have an adverse impact on the ability to identify patients who develop abnormal vital signs that require prompt action (9).
Early Warning Systems (EWS) have revealed a high sensitivity in identifying patients who need escalation of care (10). The National Early Warning Score (NEWS), by the Royal College of Physicians in the UK, is a nursing tool widely used in the identification and escalation of care of patients who may be deteriorating (11). It consists of six physiological parameters, including the respiratory rate, oxygen saturation, systolic BP, pulse rate, level of consciousness, and temperature. Escalation of care is triggered when the aggregate score is ≥5 or ≥3 for any individual parameter (9). The Modified Early Warning Score (MEWS), proposed by Stenhouse et al., included urine output as one of the criteria (12). A retrospective cohort study compared the efficacy of NEWS, MEWS, Systemic Inflammatory Response Syndrome (SIRS), Between the Flags (BTF), and Quick Sequential Sepsis-Related Organ Failure Assessment (qSOFA), as risk assessment tools. The relative performance of these scoring systems was compared through 1.5 million hospitalizations across 28 hospitals in the US. In this study, NEWS revealed greater discrimination in the identification of patients who were at risk of dying compared to other scoring systems in the overall cohort and in patients suspected to have infection (13).
Most rapid response systems also provide the option for activation based on the clinical judgment of the reporter even if objective criteria based on standard scoring systems are not met. The proviso for judgment-based activation has enabled the identification of patients and situations that may have been missed based on objective call-out criteria alone (14).
Reporting: relay of information
Abnormal vital signs may be noted by nursing staff, but delays in communication may lead to clinical deterioration before appropriate corrective measures are initiated (14). Nursing staff may feel reluctant to report worsening of clinical parameters due to fear of criticism or rebuke (15). A rigid, non-receptive organizational culture may discourage communication, especially among junior-level staff (16). Furthermore, a fixed, hierarchical escalation process could lead to failure in communication at various levels. Junior-level staff may be dissuaded from reporting due to concerns regarding unfavorable response from senior staff, including fear of intimidation or humiliation (17).
The efficacy of an automated advisory system based on vital parameters was evaluated in a before-after study from the UK (18). The automated system monitored vital signs and notified ward nurses and RRT members regarding possible clinical deterioration through a paging device. RRT calls increased significantly after the introduction of the automated system. Hospital mortality and the incidence of cardiac arrests reduced significantly during the intervention period. This study suggested that an automated advisory system may lead to improvement in key clinical outcomes including hospital mortality.
Delays in the activation of rapid response systems
Failure to activate rapid response systems has been associated with adverse clinical outcomes including mortality. In a retrospective observational cohort study, a delay of more than 1 hour between the documentation of an abnormal vital parameter and RRT activation led to higher mortality and a longer hospital length of stay (19). In another study, the frequency of callouts was lower during night hours and led to failure to rescue during this vulnerable period (20). These studies strongly suggest that the timely activation of rapid response systems is crucial in optimizing clinical outcomes.
Although abnormal vital signs are recognized, latency may occur in escalation and initiation of action, leading to adverse outcomes. In up to 84% of patients, physiological deterioration is identified and recorded by caregivers, but timely and appropriate action does not ensue (21,22).
The ACADEMIA study evaluated the incidence of abnormal physiological parameters that preceded adverse events including ICU admissions, cardiac arrests, and in-hospital deaths across 90 hospitals in the UK, Australia, and New Zealand (23). Hypotension and altered level of consciousness were the most common antecedents to adverse events. Cardiac arrest occurred in 22.1% of adverse events. Most patients who suffered cardiac arrest (79.4%) experienced physiological deterioration before the event; many had abnormal physiological parameters recorded for up to 4 hours before the event. A failure to escalate care in the face of worsening physiological parameters was encountered in 14% of cases.
Critically ill patients often receive suboptimal care prior to ICU transfer, resulting in adverse clinical outcomes (24). Rapid response systems aim to act speedily to address a deteriorating clinical situation by providing expertise and health care resources at the point of care, to enable a favorable transformation of the disease trajectory. Common interventions performed by the RRT include airway management, initiation of ventilator support, fluid resuscitation, and vasopressor support as appropriate.
Efficacy of rapid response systems: the evidence
Rapid response systems are expected to intervene early and prevent a downward spiral of the clinical state, thereby improving outcomes. Do rapid response systems fulfill this objective?
The MERIT cluster-randomized controlled trial (RCT) included 125,132 patients from 23 hospitals in Australia (25). A medical emergency team (MET) was introduced as a rapid response system in 12 hospitals; the existing level of care was maintained in 11 hospitals. The incidence of emergency callouts increased significantly during the study period in hospitals that introduced MET (3·1 vs 8·7 per 1000 admissions, p = 0·0001). The composite primary outcome including cardiac arrest, unexpected mortality, and unplanned admission to the ICU was not significantly different between hospitals that had MET compared to control hospitals (5·86 vs 5·31 per 1000 admissions, p=0·640). The incidence of the individual components of the composite outcome was also similar in both groups of hospitals. However, in the MET group of hospitals, 30% of patients who suffered cardiac arrest had fulfilled the callout criteria for more than 15 minutes prior to the event. Similarly, no callout was made in half of the instances that resulted in unplanned ICU admission or unexpected mortality. Thus, a substantial number of patients did not actually receive the planned escalation of care through the rapid response system; this could likely explain the lack of benefit observed (26).
Sixteen acute care wards of a UK general hospital were included in a pragmatic, cluster- randomized trial to assess the impact of a critical care outreach service. The outreach unit included nurses and doctors with experience in critical care who offered a 24-hour service. The outreach service was introduced in a phased manner across the hospital. This study, including 2903 patients, revealed a significant reduction in hospital mortality in wards where the outreach service was operational compared to those that did not [two-level odds ratio: 0.52 (95% CI 0.32–0.85)]. The hospital length of stay was unexpectedly longer in patients who received outreach service; however, this finding was not supported on confirmatory and sensitivity analysis (27).
A retrospective study from France evaluated the impact of RRT implementation in one hospital and compared outcomes with three hospitals that acted as controls. The establishment of an RRT was associated with a significant reduction in the unexpected mortality rate compared to the three control hospitals (17.4 vs. 21.9 per 1000 discharges; p = 0.002). Besides, the overall hospital mortality also decreased significantly after RRT implementation compared to the pre-RRT period (28).
Tirkonnen et al. evaluated outcomes following RRT intervention. This systematic review of 29 studies that analyzed 157,383 activations revealed that RRT review may enable decision-making regarding limitation of care. Limitation of care occurred in 8.1% of RRT callouts, while 23% led to ICU transfer. The median hospital mortality following RRT intervention was 26% with a 30-day mortality of 29% (29).
Several meta-analyses have evaluated the efficacy of rapid response systems. Maharaj et al. analyzed 29 studies. The included studies were either cluster RCTs or before-after studies. Implementation of rapid response systems was associated with an overall reduction in hospital mortality. A significant reduction in cardiopulmonary arrests was also observed. However, there was no difference in the number of ICU admissions (30). Solomon et al. included 30 before-after studies, cluster-randomized trials, or cohort studies in their meta-analysis. The introduction of an RRT or MET was associated with significantly lower hospital mortality and cardiac arrests outside the ICU (31).
- Hospitalized patients often experience unexpected deterioration in their clinical status, leading to adverse outcomes, including mortality
- Rapid response systems act as safety nets aimed at the early identification of patients who are at risk of deterioration. They provide clinical expertise and timely intervention at the point of care
- The key components of rapid response systems include early identification of patients with a declining clinical status and prompt activation of the responder team followed by appropriate intervention by the RRT to enable rescue
- The large, MERIT cluster randomized controlled trial did not reveal a significant impact on cardiac arrests, unexpected mortality, or unplanned admission to the ICU; however, rapid response activation was not performed in a relatively large number of patients who experienced clinical deterioration
- Several observational studies and meta-analyses lend support to the establishment of rapid response systems with improved clinical outcomes including a reduction in hospital mortality
- Rapid response systems may also facilitate decision-making regarding end of life care in patients who are terminally ill
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