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Experience was found to count in recognising and acting on patient deterioration. National guidelines recommend the use of “track and trigger” systems to monitor seriously ill patients for the signs of deterioration. Following their identification, prompt referral to critical care teams is suggested, for example, but this does not always happen reliably. This realist review explored the organisational factors within UK hospitals that influence how and why these alert systems work in practice.

Experienced nurses used the protocols effectively, alongside their clinical judgment in knowing when to refer for specialist assessment and to quantify concerns. Standard protocols were found to be useful; however, reluctance to challenge staff hierarchy still prevented junior staff referring directly when they suspected deterioration.

The culture where monitoring tasks are frequently delegated to junior nursing staff was noted. Incomplete or inaccurate observations and lack of experience to judge the importance of clinical signs were also linked with failure to seek a rapid response.

This highlights the need for training including simulation and improved teamwork between healthcare disciplines to empower staff to use track and trigger systems effectively.


Why was this study needed?

It is essential that signs of deterioration in people admitted to hospital are recognised quickly and acted upon appropriately. This gives the best outcomes for patients and reduces the need for cardiopulmonary resuscitation.

NICE recommends identifying acutely ill patients using “track and trigger” systems. This involves monitoring people’s physiological condition (“track”) and knowing when to “trigger” a response, such as increased monitoring or calling for critical care assessment.

The evidence for the effectiveness of these track and trigger systems has been mixed. This “realist” review is the first to bring together the evidence to understand for whom, under what circumstances, how and why track and trigger systems work in practice. Realist reviews are useful for exploring the contextual factors and mechanisms that can influence outcomes when the same intervention is implemented in different localities.


What did this study do?

The study began with a scoping review to identify the underlying logic and key components of track and trigger systems (called rapid response systems in the review). An expert steering group verified these assumptions, and then researchers undertook systematic searches to identify studies relevant to these components. Like realist reviews, they also purposively searched the grey literature looking for articles supporting, refuting or explaining the theories of how these components work.

The findings of 275 studies were used to elaborate on the contextual, social, cultural and organisational factors associated with system outcomes. The review both looked at studies evaluating the impact of track and trigger systems on better recognition of high-risk patients, and associated research on how these systems worked in practice.

The review systematically identified and appraised the studies using an internationally recognised checklist. Of the 275 studies, most were judged low to medium quality.


What did it find?

  • Evidence supports the reliability of physiological variables such as heart rate, blood pressure and respiratory rate to predict intensive care admission or mortality risk. However, local modifications to track and trigger protocols may inadvertently reduce their accuracy for predicting patient deterioration and make it difficult to draw overarching conclusions on their effectiveness.
  • The availability of standardised protocols empowered experienced nurses to call rapid response teams and to organise the most relevant information when asking for help. Nurses with education and experience of critical care had greater confidence in decision-making and were more likely to refer patients. Experienced nurses tended to use track and trigger protocols flexibly in combination with clinical judgement. Delayed referrals are sometimes caused by nurse uncertainty, especially when their clinical judgment that a patient is deteriorating is not corroborated by the track and trigger system, but the protocols helped with this.
  • Nurses remain reluctant to call for help when it would breach hierarchical systems. Fear of criticism, calling for junior ward doctors first or waiting for the ward team review was also associated with delays. This suggests a need for improved communication and cohesion between healthcare teams.
  • Incomplete or inaccurate recording of physiological observations was also associated with failure to recognise deterioration. Due to workload, these tasks are often delegated to student nurses or healthcare assistants who may not be able to understand the significance of these signs and trigger the appropriate response. Although the systems are standardised, there remains a need for training and support for all staff using them.


What does current guidance say on this issue?

NICE 2007 guidelines recommend that adults have physiological observations upon admission to acute wards. These should be repeated at least 12 hourly, unless the senior decision is made otherwise, using a track and trigger system. All staff using these systems should be trained to ensure they can correctly interpret clinical signs and act appropriately.

NICE recommends that trigger thresholds are set locally and regularly reviewed to ensure sensitivity and specificity. This involves a three-tiered response strategy where patients at risk of clinical deterioration are graded from low (increased frequency of observations) to high score (immediate response from critical care teams). Patients considered a “clinical emergency” should bypass the graded response and receive immediate attention.


What are the implications?

This highlights some key issues that need to be considered when implementing track and trigger systems to ensure prompt recognition and response for deteriorating patients.

In keeping with guideline recommendations, staff need training in using the systems. Furthermore, nurses need to feel empowered and supported to overcome the barriers to referral that staffing hierarchies can create.

Trusts that adjust trigger thresholds should also consider regular reviews to ensure the appropriateness of these thresholds.


Citation and Funding

McGaughey J, O'Halloran P, Porter S, Blackwood B. Early warning systems and rapid response to the deteriorating patient in hospital: a systematic realist review. J Adv Nurs. 2017. [Epub ahead of print].

This realist review was completed as part of a PhD fellowship funded by the School of Nursing and Midwifery at Queen’s University Belfast.



NICE. Acutely ill adults in hospital: recognising and responding to deterioration. CG50. London: National Institute for Health and Care Excellence; 2007.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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