The ‘chain of survival’ has proven to be useful in improving the understanding of, and the quality of the response to, cardiac arrest, both outside and in hospital.1 In the 2005 European Resuscitation Council Guidelines the importance of recognising critical illness and preventing cardiac arrest was highlighted by their inclusion as the first link in a new four-ring ‘chain of survival’.2 In the in-hospital setting, patient deterioration is often insidious and potentially preventable, with failure of recognition being a frequent problem.3, 4 However, recognising critical illness and preventing cardiac arrest are complex tasks, each requiring the presence of several essential steps to ensure clinical success. Failures have been reported in each of these steps, many resulting in adverse outcomes for patients.3, 4 This article proposes the use of an additional chain for in-hospital settings – a ‘chain of prevention’ – to assist hospitals in structuring their care processes to prevent and detect patient deterioration and cardiac arrest.
2. The ‘chain of prevention’
The proposed ‘chain of prevention’ (Fig. 1) consists of five rings linked in series. As no chain is stronger than its weakest link, weakness of one or more of the components (rings) of the chain will inevitably result in failure of the whole system. This would be manifest by patient deterioration and cardiac arrest. If the components of the chain are present and strong, the chain will work perfectly, and this should be measurable as a reduction in the number of preventable cardiac arrests. The chain and the rationale behind it are described below.
Fig. 1. The chain of prevention. © Gary Smith.
2.1. First ring of the chain: Education
In general, such education needs to include: how to observe patients, including vital signs measurement and recording; interpretation of observed signs; recognition of the signs of deterioration; the use of an early warning score (EWS) or medical emergency team (MET) calling criteria; appreciating clinical urgency; when and how to utilise simple interventions (airway opening, oxygen therapy, intravenous fluid administration, etc.); knowing how to seek help from other staff; successful teamwork and organization; knowing how to use a systematic approach to information delivery, and end-of-life care.
Evidence supporting the role of education in preventing deterioration and cardiac arrest already exists. For example, virtually all of the observed decrease in the hospital cardiac arrest rate in an Australian, prospective before-and-after trial of a MET occurred before the introduction of the MET during the period when ward staff were being educated about, and prepared for, its implementation.5, 6 Additionally in hospitals with established rapid response teams (RRTs), the introduction of specific, objective criteria for ward staff to activate the RRT has been associated with improved use of the RRTs and significant reductions in cardiac arrest rates.7, 8 Recently, a Portuguese group concluded that the effectiveness of a rapid response system (RRS) programme “…is dependent not only on the existence of an MET but mainly on the periodic and continued education and training of the entire hospital staff …”.9
Suitable audit criteria that would identify whether this ring of the chain was in place might include: the presence of a specific education programme for the recognition and management of the acutely ill patient in the hospital10; the percentage of hospital staff successfully completing such a course per annum; and the number of staff possessing agreed levels of competencies relating to the deteriorating patient.11
2.2. Second ring of the chain: Monitoring
This includes patient assessment and the measurement and recording of patient vital signs, which may include the use of electronic monitoring devices. However, evidence suggests that vital signs monitoring occurs infrequently and that observation sets are often incomplete. The UK report “An Acute Problem” found that the notes of medical patients seldom contained written requests regarding the type and frequency of physiological observations to be measured.4 Pulse rate, blood pressure and temperature were the most frequently recorded variables and breathing rate the least.4 Improved vital signs monitoring might be achievable using technology, but the consequence of failing to staff clinical areas appropriately should not be minimised. Studies of nurse staffing levels suggest that the incidence of deterioration, cardiac arrest and failure-to-rescue is likely to be less in areas with increased levels of trained staff, probably due to enhanced patient surveillance.12 Improvements in monitoring can be achieved by documenting a vital signs monitoring plan for each patient that identifies the variables to be measured and the frequency of measurement.13 Using an EWS and/or a MET can also increase the frequency of vital signs measurements.14, 15
Criteria that would identify whether this ring of the chain was in place might include the percentage of patients who have a written vital signs plan that identifies the variables to be measured and dictates the frequency of measurement number of patients,13 the number of patients whose vital signs measurements occur with the agreed frequency and the number of vital signs datasets that include an agreed core dataset of vital signs parameters.
2.3. Third ring of the chain: Recognition
Recognizing patient illness can be difficult, and is a common feature of adverse incidents.3 Improving the tools available to staff on general wards may help them to identify better those patients in need of additional monitoring or intervention. The design of vital signs charts has an important role in the detection of deterioration,16 but, at present, the optimal layout is unknown. The use of colour-coded or colour-banded vital signs charts are believed to assist in the recognition of patient deterioration, but again technology may have a future role to play. Within a given institution a starting point for improvement could be the use of a single chart format.
Many hospitals now also use a set of predetermined ‘calling criteria’ to ‘flag’ the need to escalate monitoring or to call for more expert help. These calling criteria, or ‘track and trigger’ systems, can be categorized as single-parameter systems, multiple-parameter systems, aggregate weighted scoring systems or combination systems. The aggregate weighted track and trigger systems offer a graded escalation of care, whereas single-parameter track and trigger systems provide an all-or-nothing response. The performance of these systems is variable.17, 18
A simple criterion that would identify whether this ring of the chain was in place might be whether the hospital used either standardized calling criteria18 or a standardized, uniform early warning score17 to assist ward staff in the early recognition of patient deterioration for all adult patients.
2.4. Fourth ring of the chain: Call for help
All hospitals should have a universally known and understood, mandated, unambiguous, activation protocol for summoning a response to a deteriorating patient. The culture of the organisation should be such that staff are never criticised for calling. However, data from Australia has demonstrated that, even when patients had documented physiological MET calling criteria present, the team is not always called.19 In such circumstances, failures to call may result from a lack of recognition of patient deterioration, lack of knowledge of the escalation protocol, incorrect clinical judgement, a lack of confidence in escalating or worry on the part of the caller that they might receive criticism. Using quantifiable evidence appears to be the most effective means for nurses to refer patients to doctors, but the use of a standardized method of communication, such as the RSVP (Reason-Story-Vital Signs-Plan) system20 may also improve communication about patient deterioration. In some hospitals, the RRT can be called directly by the patient's family or visitors; their intimate knowledge of the patient often provides an additional method for recognizing the subtle changes of early deterioration.21
One criterion that would identify whether this ring of the chain was in place might be whether the hospital uses an unambiguous, activation protocol for summoning a response to a deteriorating patient, such as RSVP.20 Spot audits of clinical notes might be used to determine the number of times that calls for help were made after a patient's physiology met criteria that should trigger a call for help.
2.5. Final ring of the chain: Response
So far this is the area of practice that has seen the greatest investment in terms of time, money and education. In many countries of the world, hospitals have attempted to solve the problem of patient deterioration by introducing RRTs. Although several, single-centre studies using historical control groups have suggested a positive impact of RRTs, others have been unable to prove a benefit.19, 22 However, having recognized that a patient is deteriorating or has deteriorated, it makes perfect sense to escalate the patients monitoring status and care. In certain institutions, doing so may include calling an RRT.
Criteria that would identify whether this ring of the chain was in place might include whether a specific response team for medical crises exists in the hospital, whether a team response occurs following a call for help and the time taken from “call for help” to team response.
3. A better alternative?
There has been a prior attempt to develop a structure for the components necessary to prevent and respond to deterioration.23 In June 2005, a publication resulting from the first International Conference on Medical Emergency Teams described the essential characteristics of rapid response systems, using the concept similar to that of the neurological reflex arc.23 As a minimum, it was suggested that the system should have an afferent limb (for event detection and response triggering) and an efferent limb (the response to identified deterioration), although two other components – (a) an evaluative, patient safety, and process improvement limb and (b) a governance and administrative structure – were described.23 To date, the use of the afferent and efferent limb concepts have not been widely adopted outside the MET community.
The use of afferent and efferent limbs seems unnecessarily complex, using ‘special’ terminology most appropriate for those who understand the function of nervous system physiology. Most vital signs are now documented by nurse aides or assistants, who may find this concept confusing. The beauty of using a ‘chain’ concept is that it is simple, using common everyday language. The components – rings and links – and the consequence of ‘breaks in the chain’ can be easily understood and memorised by all. The proposed ‘chain of prevention’ has the potential of being better understood by hospital clinical staff of all grades, disciplines and specialties, patients, and their families and friends.
This short paper proposes the introduction of a five-ringed ‘chain of prevention’ to assist hospitals in structuring their care processes to best prevent and detect patient deterioration and cardiac arrest. The rings represent ‘staff education’, ‘monitoring’, ‘recognition’, the ‘call for help’ and the ‘response’. It is believed that a ‘chain of prevention’ has the potential to be understood well by hospital clinical staff of all grades, disciplines and specialties, patients, and their families and friends. Suggestions for auditing the robustness of the chain are proposed.
The chain provides a structure for research to identify the importance of each of the various components of rapid response systems.
Conflicts of interest statememt
Professor Smith is a member of the Executive Committee of the Resuscitation Council (UK) and contributed to the 2005 European Resuscitation Council Guidelines for Resuscitation. He is the Director of the Acute Life-threatening Events: Recognition and Treatment (ALERT) course, which is run by his employers, Portsmouth Hospitals NHS Trust. His wife hold shares in The Learning Clinic Ltd., which markets an electronic vital signs capturing and charting system (VitalPAC). VitalPAC is a collaborative development of The Learning Clinic Ltd. and Portsmouth Hospitals NHS Trust.
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Department of Critical Care, Queen Alexandra Hospital, Cosham, Portsmouth PO6 3LY, United Kingdom