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Personal view
Triage in the Defence Medical Services Simon T Horne,1 J Vassallo2 ABSTRACT Triage of patients into categories according to their need for intervention is a core part of military medical practice. This article reviews how triage has evolved in the Defence Medical Services and how it might develop in the context of recent research. In particular, a simple model demonstrates that the ideal sensitivity and specificity of a triage system depends upon the availability of transport and the capacity of the receiving units. As a result, we may need to fundamentally change the way we approach triage in order to optimise outcomes—especially if casualty evacuation timelines become longer and smaller medical units more prevalent on future operations. Some pragmatic options for change are discussed. Finally, other areas of current research around triage are highlighted, perhaps showing where triage may go next.
UNDERSTANDING THE HISTORY OF TRIAGE Triage as a concept has been extensively covered in the medical literature. In the National Health Service (NHS) it is used to describe the sorting of patients in a variety of contexts, such as: telephone triage for appointments in General Practice;1 prioritising unselected patients in emergency departments2 and deciding whether to bypass trauma units in order to go straight to the major trauma centre (MTC) of a trauma network.3 These developments potentially distract from its primary role in the military context—quickly sifting through battlefield casualties to identify those needing surgery. While Napoleon’s Surgeon General (Larrey) is often credited with the concept,4 it was Wilson (a British naval surgeon) who first explicitly divided patients into three groups in 1846.5 Wilson described sorting those who needed to be saved from those who could not be saved, or who do not need saving —serious, from slight or fatal. This represents the first conceptualisation of the T category system currently in use in NATO (in civilian practice, P categories). The key 1
Emergency Department, Derriford Hospital, Plymouth, UK; 2Institute of Naval Medicine, Gosport, UK
Correspondence to Lt Col Simon T Horne, Emergency Department, Derriford Hospital, Plymouth PL6 8DH, UK; [email protected] 90
difference between Wilson’s triage and current practice is that he simply tried to discriminate between the expectant casualties who would die regardless (T4 in the NATO system), those who would survive even if their treatment were delayed (T3) and those who needed intervention in order to prevent significant morbidity or mortality (T1 and T2). The NATO system tiptoes around the concept of expectancy and concentrates on separating immediate need (T1) from urgent (T2). Wilson’s concept appears to have changed little over the subsequent 100 years. In the Boer War, patients were triaged on the table by the surgeons. Increased workload in the field hospitals led to forward ‘Clearing Hospitals’ with a basic dressing facility and sorting being introduced, allowing P3 patients to be either expedited direct to the unit rear echelons or returned to duty. Early in World War I, these became casualty clearing stations (CCS) with enhanced surgical capability—prior to this, some patients had been transferred back to England before their surgery. These CCSs even specialised so that the less wounded could be diverted to one, while the surgical cases were managed at another.6 This ‘triage to destination’ rather than simply triage by priority was a forerunner of the current bypass system for major trauma centres.3 The process itself was still largely based on the assessment of the anatomical nature of the patient’s injuries and survivability.7 In Korea8 and the Falklands,9 a more familiar system was described with Priority (P) 1 being assigned to casualties in need of immediate resuscitation and surgery, P2 to those needing early surgery and P3 to those requiring no resuscitation and in whom surgery could be delayed. At this stage, there was still no formal description of how a triage category might be assigned. As to who should do it—experienced doctors, nurses and dentists are variously described. In 1989, Champion described the Triage—Revised Trauma Score.10 This represented decades of derivation and refinement of predictors of injury severity in cohorts of trauma patients. This system was based on three physiological variables, the systolic BP (SBP), respiratory rate (RR) and Glasgow coma score (GCS).
The patient is given a score from 1 to 4 for each variable, 4 being within the normal range. Thus, a patient with minimal physiological derangement will score 12. This was correlated to a triage category of T3. Moderate derangement (a score of 3 for one variable, eg, a RR over 29) results in a total score of 11, and a category of T2. Profound derangement in one variable (eg, SBP29 and GCS 12) will score 10 or below and be categorised as T1. This was developed by the Major Incident Medical Management and Support11 course into the Triage Sort (Figure 1)—where the casualty’s physiology forms the basis of the triage categorisation at a CCS or hospital, which can then be augmented by the anatomical findings of an experienced clinician if necessary. A simpler version has been derived from the same parameters for use at the scene of an incident, the Triage Sieve (Figure 2). This is widely taught across the Defence Medical Services (DMS). Recent modifications included the presence of a tourniquet or ‘Unconscious’—both an automatic T1. Champion’s data is robust, but questions have been raised about whether it is identifying the wrong patients—‘T-RTS correctly identified more than 97% of non-survivors as requiring trauma center care.’ Wilson would have disputed whether this was effective triage. As he said, ‘in fatal cases…it would be useless or unjust to delay or put off time in the presence of others as urgent and pressing, but not without hope’; non-survivors should not be the basis of clinical prioritisation— rather we should seek to identify patients who are badly injured, but salvageable. In terms of detecting seriously injured ‘Major Trauma’ patients (widely defined as an Injury Severity Score (ISS) >15), the T-RTS was insensitive—identifying only 59%. However, not all ISS >16 patients need immediate intervention, and so, this itself might not be the correct patient group to seek out. Baxt13 suggested that instead of looking at mortality or the ISS, we should try to identify the patients who needed a time-critical intervention in order to remain a survivor. This was further developed by Garner14 and Horne15—the latter using a small Delphi study of military consultants at the Role 3 Hospital at Camp Bastion, Afghanistan, to identify a list defining these interventions. The exact nature of the interventions and their timing in order to be ‘Immediate’ (therefore, meeting the MIMMS and NATO P1/
Horne ST, et al. J R Army Med Corps June 2015 Vol 161 No 2
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Personal view saving intervention would probably drop the specificity below 75% (Vassallo, unpublished data). This would mean that in an incident generating 10 ‘real’ T1s and 22 T2s, the tool would prioritise 14 casualties as T1, 6 of whom would be false positives. In the context of a major incident being supported by a large civilian hospital, this is perfectly acceptable, and it may be that for civilian major incident management, studies into the physiology associated with the need for life-saving intervention can improve the triage sort significantly. The ability to augment the physiological sort with ‘as much relevant anatomical information as can be obtained in the time and conditions’11 is largely intended to influence destination (eg, head injuries prioritised to neurosurgical resources) but could improve specificity as well, if the triaging clinicians feel confident to downgrade the T category.
A SIMPLE MODEL OF THE IMPACT OF TRIAGE ON CAPACITY Figure 1 The Triage sort (from CGOs12). T1 definition) remains hotly debated. However, there is a consistent theme throughout the various studies—that physiology is a poor predictor of severity of injury on its own, whether using the sieve or the sort. Other systems (START in the USA and Careflight in Australia) do equally badly (Vassallo, unpublished data).
IMPROVING PHYSIOLOGICAL ASSESSMENT While the ‘optimal’ ranges for physiological variables such as RR and GCS can be derived from the data, in developing adequate sensitivity the tools become very non-specific. Adaptation of the triage sort to capture 80% of those needing life-
Figure 2 The military Triage Sieve (from CGOs12). Horne ST, et al. J R Army Med Corps June 2015 Vol 161 No 2
Medical treatment facility (MTF) trauma capability comes from combination of resuscitation (often, initiated prehospital) with damage control surgery, and frontdoor capacity largely depends on the number of resuscitation bays and operating tables. However, with the increasing use of helicopters as a medevac platform, the number of patients delivered at once impacts on capacity; when large numbers are involved, the resuscitation bays and operating tables need to be kept for the T1s first. The current preferred platform, the CH47, nominally carries a maximum of eight stretcher cases. Consider a scenario where 32 stretcher casualties are brought from the scene with a 30 min return flight time. Ten are genuinely in need of immediate intervention (T1) and 22 are less urgent (T2). The sensitivity and specificity of the triage sort are used in the first example, and there is no clinical discretion applied on scene. In the first CH47 delivery, there will be a mix of genuine T1s and T2s who were false positives (and so were incorrectly prioritised as T1). The sort is insensitive (60%) and so will only identify six of the critically ill correctly as T1. However, as it is nearly 90% specific, it is likely that only two of the T2s will be incorrectly upgraded to T1—the tool will only identify a total of eight casualties as ‘Probably T1’. In this case, six genuine T1s are likely to arrive at the MTF with the first CH47, and the ones missed by the tool will arrive evenly distributed in subsequent deliveries, every 30 min. This 91
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Personal view is shown graphically at (Figure 3A), which shows in green correctly identified patients at the MTF, incorrectly identified patients at the MTF are in yellow and critical patients still on scene are in red. Contrast this with a tool that is more sensitive for critically ill patients, but less specific (Sens 80%, Spec 75%). It would identify eight of the genuine T1s immediately, but would also falsely upgrade six T2s to T1. As a total of 14 casualties were identified as T1, the first flight would probably bring four true T1s and four T2s. In this model, a Role 2 forward surgical unit will be filled (and in reality overwhelmed) by the first delivery. And yet four more genuine T1s have been selected for the second flight. The last two were missed by the tool, and will arrive one each on the subsequent two flights. Given the current medevac system where primary retrieval is common, the specificity is more important to the efficient functioning of a small MTF than the sensitivity of an improved physiological triage system. How then can this gap be closed?
ANATOMY AND SENIORITY One solution is to try to reintroduce anatomical triage and some assessment of injury severity. The US SALT triage system attempts to address this by describing injuries as minor or unlikely to be survivable, given the available resources.16 While anatomical triage has been out of favour because of its poor reproducibility, low sensitivity in isolation, and impracticality (it involves the need to undress),11 this may be a very sensible course—Israeli experience after bombings showed that while rapid senior clinician assessment alone had sensitivity of only 60%, it had a specificity of over 80%.17 It may be that combining optimised physiological
parameters with a senior clinician making an early on-scene assessment, and downgrading where appropriate, may improve the sensitivity without vastly diluting the specificity. Key here is that the clinicians involved in this study had some experience in the management of blast injured casualties. The assessment by a combat medical technician or paramedic, may not have comparable results, as it is likely to be experience of the subsequent patient journey that informs this decision. The solution might be to move towards a policy of immediate delivery of senior medical triage to the scene, probably by the first CH47, to overlay some element of clinical experience onto the physiological triage performed by the first responders. While triage has been considered recently to be a generic skill, in the Falklands and before, these decisions were made at as senior a level as possible.9 To optimise accuracy, we may need to move to a model where instead of triage solely by those already on scene, we proactively deploy experienced triage capability forward. In terms of what injuries to include, we may learn from the evidence accruing around MTC triage tools. They usually include a combination of mechanistic, anatomical and physiological variables (which are commonly based on Champion’s data). Mechanistic variables are unlikely to add value in major incidents, as by definition, many people have suffered the same mechanism of injury. We may, however, be able to learn from the anatomical triggers. While these were generally identified by consensus, there is data to support some of them. Having been designed for prehospital use they do not involve undressing the patient completely. Interobserver variability persists and is inevitable to a degree, but
unpublished work on the MTC triage tool in our region has shown that some descriptors may be more effective than others—flail chest is very poorly detected (1.4% sensitivity),18 whereas ‘extensive chest wall tenderness’ performs much better—and that using these with more evidence-based physiological parameters improves the tool significantly.
PREALERTING THE MTF: ‘THERE’S A T1 COMING IN....’ As most DMS personnel are trained to use the triage sieve, it has become common practice to assign priority to a casualty even if they were the only one injured. The implication is that (like bypass decisions to a MTC in civilian practice) there is a need for a higher level of care—either in the MTF chosen or the level of experience in the team readied prepared to receive them. Obviously in most military contexts there is little or no choice in the destination MTF, but there might be benefit if the tool worked well in triggering a higher level of trauma team response. Two-tiered trauma responses, with a reduced team mobilised to receive patients expected to be of lower acuity, are now well accepted.19 They are safe and reduce resources wasted on less-injured casualties. So there may be value in seeking a more accurate DMS triage system, even outside major incident management.
RESOURCE MODELLING AND MEDICAL PLANNING: ‘THIS COMPLEX CAN MANAGE 10 T1S...’ Matching MTF capability with expected demand is the holy grail of medical planning—ensuring that adequate resources are in place to treat casualties, without overstaffing or wasting supplies. Achieving this requires that we understand the
Figure 3 (A and B) Accuracy of triage categorisation at R2 after arrival of helicopters 1, 2, 3 and 4, and number of missed T1 casualties still on scene.
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Horne ST, et al. J R Army Med Corps June 2015 Vol 161 No 2
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Personal view correlation between the severity of injury and the procedures and consumables that will be needed. Unpublished data (Glasgow S, 2013) linking total blood product usage and T category has shown that there is a correlation, but T category is neither sensitive nor specific. This probably simply reflects the poorly performing triage system; there is likely to be a strong correlation between severely injured patients requiring immediate life-saving intervention, and the need for, and even quantity of blood. Unfortunately, we have seen that current tools do not reliably identify these patients. Should we reach the stage where we can reliably identify genuine T1 casualties, we may be able to model the resources that they need (blood, theatre consumables, ITU time, etc). Then an MTF will be able to declare a genuine capability to manage, for example, ‘10 T1s’ before it needs resupply.
SUMMARY Military triage has evolved considerably in the last two centuries, in the way categories are assigned, and the types of casualties that the system aims to identify. Current systems based almost entirely on physiological scoring are relatively insensitive for patients needing life-saving interventions. While they may be adapted to be more sensitive by applying evidence-based adjustments to the criteria or addition of anatomical findings, the subsequent reductions in specificity (manageable in most civilian situations) become problematic in a military context. A solution to this might be to consider
routinely deploying specific triage experience forward to multiple casualty incidents, in the form of senior clinicians. Accurate prehospital triage categorisation may inform better usage of resources at MTFs, and may even allow accurate modelling of MTF capability in future. Contributors The paper is a result of long collaboration and discussion between STH and JV. STH undertook the majority of the initial draft, while much of the theoretical component and in press research was undertaken by JV. STH is the guarantor.
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Competing interests None.
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Provenance and peer review Not commissioned; externally peer reviewed.
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To cite Horne ST, Vassallo J. J R Army Med Corps 2015;161:90–93. Received 24 March 2014 Revised 13 May 2014 Accepted 17 May 2014 Published Online First 20 June 2014
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REFERENCES
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Bunn F, Byrne G, Kendall S. Telephone consultation and triage: effects on health care use and patient satisfaction (Review). The Cochrane Library 2009;(1). http://onlinelibrary.wiley.com/doi/10.1002/14651858. CD004180.pub2/full Cooke M, Jinks S. Does the Manchester triage system detect the critically ill? J Accid Emerg Med 1999;16:179–81. Potter D, Kehoe A, Smith JE. The sensitivity of pre-hospital and in-hospital tools for the identification of major trauma patients presenting to a major trauma centre. JRNS 2013;99:16–9.
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Rignault D, Wherry D. And finally…: Lessons from the past worth remembering: larrey and triage. Trauma 1999;1:85–9. Wilson J. Outlines of naval surgery. MacLachan Stewart and Co. Edin, 1846:24–6. Bricknell MCM. The evolution of casualty evacuation in the British Army 20th Century (Part 1) –Boer war to 1918. J R Army Med Corps 2002;148:200–7. Dearden H. Medicine and duty. London: William Heinemann. 1928:152. King B. The Mobile Army Surgical Hospital (MASH): a Military and Surgical Legacy. J Natl Med Assoc 2005;97:648–56. Ryan JM. The Falklands war—Triage. Ann RCSE 1984;66:195–6. Champion H, Sacco W, Copes W, et al. A revision of the trauma score. J Trauma 1989;29:623–9. Advanced Life Support Group. Major incident medical management and support: the practical approach. 3rd edn. London: BMJ Publishing, 2011. Ministry of Defence. Clinical Guidelines for Operations ( JSP 999). 2013. https://www.gov.uk/ government/publications/ jsp-999-clinical-guidelines-for-operations Baxt W, Jones G, Fortledge D. The trauma triage rule: a new, resource-based approach to the prehospital identification of major trauma victims. Ann Emerg Med 1990;19:1401–6. Garner A, Lee A, Harrison K, et al. Comparative analysis of multiple-casualty incident triage algorithms. Ann Emerg Med 2001;38:541–8. Horne S, Vassallo J, Read J, et al. UK triage—an improved tool for an evolving threat. Injury 2013;44;23–8. Lerner EB, Schwartz R, Coule P, et al. Use of SALT triage in a simulated mass-casualty incident. Prehosp Emerg Care 2010;14:21–5. Ashkenazi I, Kessel B, Khashan T, et al. Precision of in-hospital triage in mass-casualty incidents after terror attacks. Prehosp Disaster Med 2006;21:20–3. Lerner EB, Roberts J, Guse C, et al. Does EMS perceived anatomic injury predict trauma centre need? Prehosp Emerg Care 2013;17:312–16. Jenkins P, Kehoe A, Smith JE. Is a two-tier trauma team activation system the most effective way to manage trauma in the UK? Trauma 2013;15:322–30.
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Triage in the Defence Medical Services Simon T Horne and J Vassallo J R Army Med Corps 2015 161: 90-93 originally published online June 20, 2014
doi: 10.1136/jramc-2014-000275 Updated information and services can be found at: http://jramc.bmj.com/content/161/2/90
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Personal view
Triage in the Defence Medical Services Simon T Horne,1 J Vassallo2 ABSTRACT Triage of patients into categories according to their need for intervention is a core part of military medical practice. This article reviews how triage has evolved in the Defence Medical Services and how it might develop in the context of recent research. In particular, a simple model demonstrates that the ideal sensitivity and specificity of a triage system depends upon the availability of transport and the capacity of the receiving units. As a result, we may need to fundamentally change the way we approach triage in order to optimise outcomes—especially if casualty evacuation timelines become longer and smaller medical units more prevalent on future operations. Some pragmatic options for change are discussed. Finally, other areas of current research around triage are highlighted, perhaps showing where triage may go next.
UNDERSTANDING THE HISTORY OF TRIAGE Triage as a concept has been extensively covered in the medical literature. In the National Health Service (NHS) it is used to describe the sorting of patients in a variety of contexts, such as: telephone triage for appointments in General Practice;1 prioritising unselected patients in emergency departments2 and deciding whether to bypass trauma units in order to go straight to the major trauma centre (MTC) of a trauma network.3 These developments potentially distract from its primary role in the military context—quickly sifting through battlefield casualties to identify those needing surgery. While Napoleon’s Surgeon General (Larrey) is often credited with the concept,4 it was Wilson (a British naval surgeon) who first explicitly divided patients into three groups in 1846.5 Wilson described sorting those who needed to be saved from those who could not be saved, or who do not need saving —serious, from slight or fatal. This represents the first conceptualisation of the T category system currently in use in NATO (in civilian practice, P categories). The key 1
Emergency Department, Derriford Hospital, Plymouth, UK; 2Institute of Naval Medicine, Gosport, UK
Correspondence to Lt Col Simon T Horne, Emergency Department, Derriford Hospital, Plymouth PL6 8DH, UK; [email protected] 90
difference between Wilson’s triage and current practice is that he simply tried to discriminate between the expectant casualties who would die regardless (T4 in the NATO system), those who would survive even if their treatment were delayed (T3) and those who needed intervention in order to prevent significant morbidity or mortality (T1 and T2). The NATO system tiptoes around the concept of expectancy and concentrates on separating immediate need (T1) from urgent (T2). Wilson’s concept appears to have changed little over the subsequent 100 years. In the Boer War, patients were triaged on the table by the surgeons. Increased workload in the field hospitals led to forward ‘Clearing Hospitals’ with a basic dressing facility and sorting being introduced, allowing P3 patients to be either expedited direct to the unit rear echelons or returned to duty. Early in World War I, these became casualty clearing stations (CCS) with enhanced surgical capability—prior to this, some patients had been transferred back to England before their surgery. These CCSs even specialised so that the less wounded could be diverted to one, while the surgical cases were managed at another.6 This ‘triage to destination’ rather than simply triage by priority was a forerunner of the current bypass system for major trauma centres.3 The process itself was still largely based on the assessment of the anatomical nature of the patient’s injuries and survivability.7 In Korea8 and the Falklands,9 a more familiar system was described with Priority (P) 1 being assigned to casualties in need of immediate resuscitation and surgery, P2 to those needing early surgery and P3 to those requiring no resuscitation and in whom surgery could be delayed. At this stage, there was still no formal description of how a triage category might be assigned. As to who should do it—experienced doctors, nurses and dentists are variously described. In 1989, Champion described the Triage—Revised Trauma Score.10 This represented decades of derivation and refinement of predictors of injury severity in cohorts of trauma patients. This system was based on three physiological variables, the systolic BP (SBP), respiratory rate (RR) and Glasgow coma score (GCS).
The patient is given a score from 1 to 4 for each variable, 4 being within the normal range. Thus, a patient with minimal physiological derangement will score 12. This was correlated to a triage category of T3. Moderate derangement (a score of 3 for one variable, eg, a RR over 29) results in a total score of 11, and a category of T2. Profound derangement in one variable (eg, SBP29 and GCS 12) will score 10 or below and be categorised as T1. This was developed by the Major Incident Medical Management and Support11 course into the Triage Sort (Figure 1)—where the casualty’s physiology forms the basis of the triage categorisation at a CCS or hospital, which can then be augmented by the anatomical findings of an experienced clinician if necessary. A simpler version has been derived from the same parameters for use at the scene of an incident, the Triage Sieve (Figure 2). This is widely taught across the Defence Medical Services (DMS). Recent modifications included the presence of a tourniquet or ‘Unconscious’—both an automatic T1. Champion’s data is robust, but questions have been raised about whether it is identifying the wrong patients—‘T-RTS correctly identified more than 97% of non-survivors as requiring trauma center care.’ Wilson would have disputed whether this was effective triage. As he said, ‘in fatal cases…it would be useless or unjust to delay or put off time in the presence of others as urgent and pressing, but not without hope’; non-survivors should not be the basis of clinical prioritisation— rather we should seek to identify patients who are badly injured, but salvageable. In terms of detecting seriously injured ‘Major Trauma’ patients (widely defined as an Injury Severity Score (ISS) >15), the T-RTS was insensitive—identifying only 59%. However, not all ISS >16 patients need immediate intervention, and so, this itself might not be the correct patient group to seek out. Baxt13 suggested that instead of looking at mortality or the ISS, we should try to identify the patients who needed a time-critical intervention in order to remain a survivor. This was further developed by Garner14 and Horne15—the latter using a small Delphi study of military consultants at the Role 3 Hospital at Camp Bastion, Afghanistan, to identify a list defining these interventions. The exact nature of the interventions and their timing in order to be ‘Immediate’ (therefore, meeting the MIMMS and NATO P1/
Horne ST, et al. J R Army Med Corps June 2015 Vol 161 No 2
Downloaded from http://jramc.bmj.com/ on March 30, 2017 - Published by group.bmj.com
Personal view saving intervention would probably drop the specificity below 75% (Vassallo, unpublished data). This would mean that in an incident generating 10 ‘real’ T1s and 22 T2s, the tool would prioritise 14 casualties as T1, 6 of whom would be false positives. In the context of a major incident being supported by a large civilian hospital, this is perfectly acceptable, and it may be that for civilian major incident management, studies into the physiology associated with the need for life-saving intervention can improve the triage sort significantly. The ability to augment the physiological sort with ‘as much relevant anatomical information as can be obtained in the time and conditions’11 is largely intended to influence destination (eg, head injuries prioritised to neurosurgical resources) but could improve specificity as well, if the triaging clinicians feel confident to downgrade the T category.
A SIMPLE MODEL OF THE IMPACT OF TRIAGE ON CAPACITY Figure 1 The Triage sort (from CGOs12). T1 definition) remains hotly debated. However, there is a consistent theme throughout the various studies—that physiology is a poor predictor of severity of injury on its own, whether using the sieve or the sort. Other systems (START in the USA and Careflight in Australia) do equally badly (Vassallo, unpublished data).
IMPROVING PHYSIOLOGICAL ASSESSMENT While the ‘optimal’ ranges for physiological variables such as RR and GCS can be derived from the data, in developing adequate sensitivity the tools become very non-specific. Adaptation of the triage sort to capture 80% of those needing life-
Figure 2 The military Triage Sieve (from CGOs12). Horne ST, et al. J R Army Med Corps June 2015 Vol 161 No 2
Medical treatment facility (MTF) trauma capability comes from combination of resuscitation (often, initiated prehospital) with damage control surgery, and frontdoor capacity largely depends on the number of resuscitation bays and operating tables. However, with the increasing use of helicopters as a medevac platform, the number of patients delivered at once impacts on capacity; when large numbers are involved, the resuscitation bays and operating tables need to be kept for the T1s first. The current preferred platform, the CH47, nominally carries a maximum of eight stretcher cases. Consider a scenario where 32 stretcher casualties are brought from the scene with a 30 min return flight time. Ten are genuinely in need of immediate intervention (T1) and 22 are less urgent (T2). The sensitivity and specificity of the triage sort are used in the first example, and there is no clinical discretion applied on scene. In the first CH47 delivery, there will be a mix of genuine T1s and T2s who were false positives (and so were incorrectly prioritised as T1). The sort is insensitive (60%) and so will only identify six of the critically ill correctly as T1. However, as it is nearly 90% specific, it is likely that only two of the T2s will be incorrectly upgraded to T1—the tool will only identify a total of eight casualties as ‘Probably T1’. In this case, six genuine T1s are likely to arrive at the MTF with the first CH47, and the ones missed by the tool will arrive evenly distributed in subsequent deliveries, every 30 min. This 91
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Personal view is shown graphically at (Figure 3A), which shows in green correctly identified patients at the MTF, incorrectly identified patients at the MTF are in yellow and critical patients still on scene are in red. Contrast this with a tool that is more sensitive for critically ill patients, but less specific (Sens 80%, Spec 75%). It would identify eight of the genuine T1s immediately, but would also falsely upgrade six T2s to T1. As a total of 14 casualties were identified as T1, the first flight would probably bring four true T1s and four T2s. In this model, a Role 2 forward surgical unit will be filled (and in reality overwhelmed) by the first delivery. And yet four more genuine T1s have been selected for the second flight. The last two were missed by the tool, and will arrive one each on the subsequent two flights. Given the current medevac system where primary retrieval is common, the specificity is more important to the efficient functioning of a small MTF than the sensitivity of an improved physiological triage system. How then can this gap be closed?
ANATOMY AND SENIORITY One solution is to try to reintroduce anatomical triage and some assessment of injury severity. The US SALT triage system attempts to address this by describing injuries as minor or unlikely to be survivable, given the available resources.16 While anatomical triage has been out of favour because of its poor reproducibility, low sensitivity in isolation, and impracticality (it involves the need to undress),11 this may be a very sensible course—Israeli experience after bombings showed that while rapid senior clinician assessment alone had sensitivity of only 60%, it had a specificity of over 80%.17 It may be that combining optimised physiological
parameters with a senior clinician making an early on-scene assessment, and downgrading where appropriate, may improve the sensitivity without vastly diluting the specificity. Key here is that the clinicians involved in this study had some experience in the management of blast injured casualties. The assessment by a combat medical technician or paramedic, may not have comparable results, as it is likely to be experience of the subsequent patient journey that informs this decision. The solution might be to move towards a policy of immediate delivery of senior medical triage to the scene, probably by the first CH47, to overlay some element of clinical experience onto the physiological triage performed by the first responders. While triage has been considered recently to be a generic skill, in the Falklands and before, these decisions were made at as senior a level as possible.9 To optimise accuracy, we may need to move to a model where instead of triage solely by those already on scene, we proactively deploy experienced triage capability forward. In terms of what injuries to include, we may learn from the evidence accruing around MTC triage tools. They usually include a combination of mechanistic, anatomical and physiological variables (which are commonly based on Champion’s data). Mechanistic variables are unlikely to add value in major incidents, as by definition, many people have suffered the same mechanism of injury. We may, however, be able to learn from the anatomical triggers. While these were generally identified by consensus, there is data to support some of them. Having been designed for prehospital use they do not involve undressing the patient completely. Interobserver variability persists and is inevitable to a degree, but
unpublished work on the MTC triage tool in our region has shown that some descriptors may be more effective than others—flail chest is very poorly detected (1.4% sensitivity),18 whereas ‘extensive chest wall tenderness’ performs much better—and that using these with more evidence-based physiological parameters improves the tool significantly.
PREALERTING THE MTF: ‘THERE’S A T1 COMING IN....’ As most DMS personnel are trained to use the triage sieve, it has become common practice to assign priority to a casualty even if they were the only one injured. The implication is that (like bypass decisions to a MTC in civilian practice) there is a need for a higher level of care—either in the MTF chosen or the level of experience in the team readied prepared to receive them. Obviously in most military contexts there is little or no choice in the destination MTF, but there might be benefit if the tool worked well in triggering a higher level of trauma team response. Two-tiered trauma responses, with a reduced team mobilised to receive patients expected to be of lower acuity, are now well accepted.19 They are safe and reduce resources wasted on less-injured casualties. So there may be value in seeking a more accurate DMS triage system, even outside major incident management.
RESOURCE MODELLING AND MEDICAL PLANNING: ‘THIS COMPLEX CAN MANAGE 10 T1S...’ Matching MTF capability with expected demand is the holy grail of medical planning—ensuring that adequate resources are in place to treat casualties, without overstaffing or wasting supplies. Achieving this requires that we understand the
Figure 3 (A and B) Accuracy of triage categorisation at R2 after arrival of helicopters 1, 2, 3 and 4, and number of missed T1 casualties still on scene.
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Personal view correlation between the severity of injury and the procedures and consumables that will be needed. Unpublished data (Glasgow S, 2013) linking total blood product usage and T category has shown that there is a correlation, but T category is neither sensitive nor specific. This probably simply reflects the poorly performing triage system; there is likely to be a strong correlation between severely injured patients requiring immediate life-saving intervention, and the need for, and even quantity of blood. Unfortunately, we have seen that current tools do not reliably identify these patients. Should we reach the stage where we can reliably identify genuine T1 casualties, we may be able to model the resources that they need (blood, theatre consumables, ITU time, etc). Then an MTF will be able to declare a genuine capability to manage, for example, ‘10 T1s’ before it needs resupply.
SUMMARY Military triage has evolved considerably in the last two centuries, in the way categories are assigned, and the types of casualties that the system aims to identify. Current systems based almost entirely on physiological scoring are relatively insensitive for patients needing life-saving interventions. While they may be adapted to be more sensitive by applying evidence-based adjustments to the criteria or addition of anatomical findings, the subsequent reductions in specificity (manageable in most civilian situations) become problematic in a military context. A solution to this might be to consider
routinely deploying specific triage experience forward to multiple casualty incidents, in the form of senior clinicians. Accurate prehospital triage categorisation may inform better usage of resources at MTFs, and may even allow accurate modelling of MTF capability in future. Contributors The paper is a result of long collaboration and discussion between STH and JV. STH undertook the majority of the initial draft, while much of the theoretical component and in press research was undertaken by JV. STH is the guarantor.
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Competing interests None.
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Provenance and peer review Not commissioned; externally peer reviewed.
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To cite Horne ST, Vassallo J. J R Army Med Corps 2015;161:90–93. Received 24 March 2014 Revised 13 May 2014 Accepted 17 May 2014 Published Online First 20 June 2014
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Triage in the Defence Medical Services Simon T Horne and J Vassallo J R Army Med Corps 2015 161: 90-93 originally published online June 20, 2014
doi: 10.1136/jramc-2014-000275 Updated information and services can be found at: http://jramc.bmj.com/content/161/2/90
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