The reform of major trauma care in the NHS over the past two decades, with the establishment of regional major trauma networks, has been one of the most significant developments in the care of major trauma patients in the UK. A series of influential reports such as the National Confidential Enquiry into Patient Outcome and Death's (2007)Trauma—Who Cares? and the National Audit Office's (2010)Major Trauma Care in England highlighted systemic inadequacies in trauma care and helped guide these improvements.
The creation of a hierarchy of trauma services — major trauma centres, trauma units and local emergency hospitals—and careful development of prehospital triage tools to determine which of these services is required are two interventions that have been key to improving outcomes (McCullough et al, 2014).
This organisation of trauma systems has had a demonstrable benefit on morbidity and mortality for the most severely injured patients (MacKenzie et al, 2010), with Celso et al (2006) and Chesser et al (2019) showing 15% and 20% mortality reduction with their implementation respectively. Historically, this improvement was only seen a decade after their establishment (Nathens et al, 2004) but modern regional trauma networks have been shown to produce improvements within two years (Claridge et al, 2013).
However, this development has been accompanied by a loss of resuscitative skills in non-major trauma centres. This is problematic if the capacity of trauma centres is overwhelmed in the event of a mass casualty incident (David et al, 2019).
The development of specific triage tools that partnered the inception of trauma networks has been key to improving outcomes. This involves striking a difficult balance, with the rates of under-triage (a patient with major trauma (Injury Severity Score (ISS) >15) being sent to a non-trauma centre) and over-triage (a patient without major trauma (ISS <16) being sent to a major trauma centre) both ideally being minimised. Although ISS is calculated retrospectively, it remains the gold standard for defining major trauma (Cassignol et al, 2019). There is no defined acceptable rate of these triage errors in the UK but trauma systems in the US typically allow 5% under-triage and 50% over-triage (Voskens et al, 2018).
Rapid on-scene prediction tools have shown potential to reduce under-triage rates, particularly among the elderly population with seemingly innocuous mechanisms of injury (Delgado et al, 2014). Reducing this is clearly beneficial for patients experiencing major trauma; triage of moderate and severe head injuries to level I US trauma centres rather than non-trauma centres has been shown to reduce mortality (MacKenzie et al, 2006).
However, this safety improvement comes at the expense of increased over-triage (Shanahan et al, 2021), which leads to significant costs (Bukur et al, 2018) and resources being stretched in major trauma centres. Research following the 2001 terrorist attack on the World Trade Center showed a direct correlation between over-triage and mortality rates in severely injured patients (Frykberg, 2002).
Although paramedics are expected to follow triage protocols uniformly, adherence varies across regions enormously and a prospective cohort study in the US showed that the subjective judgement of the emergency provider was the most commonly adopted triage tool (Newgard et al, 2016). It has been suggested this may be because triage tools have poor sensitivity, particularly for elderly patients (van Rein et al, 2018).
Efforts to improve this triage process are continuous, with some emergency services attempting to refine it by actively anticipating changes in trauma demographics (Farah et al, 2020). Nonetheless, the importance of these triage systems and their value to the coordination of trauma services is widely agreed upon (Fuller et al, 2014).
Exsanguination places an enormous burden on trauma systems worldwide. Epidemiological studies typically document it is involved in 20–40% of trauma deaths, the majority of which occur within a few hours of injury (Holcomb et al, 2013; 2015). The immediate control of the exsanguinating trauma patient is a source of much ongoing research and deliberation (Curry and Davenport, 2019) and covers an enormous scope of clinical practice.
Efforts to reduce this burden on healthcare systems began with structural changes, as described above, and preventive strategies such as the mandatory use of seat belts and improved car and airbag construction. The other elements of this, which will be explored in this article, are prehospital interventions, damage control resuscitation and interventional radiology (IR).
Prehospital care
The commonest and most immediate setting of trauma-related mortality is the scene of the incident. Pfeifer et al's (2019) systematic review of more than 7000 trauma deaths found up to 47.6% of these occurred in the prehospital setting. It can therefore be argued that prehospital care is the most important facet of trauma treatment.
Historically, two distinct philosophies existed: either an intervention and procedure-scarce strategy, which minimises the time spent at a scene in an attempt to initiate definitive resuscitation and operative/radiological management in a major trauma centre—known as ‘scoop and run’; or an intervention-heavy approach, where highly trained paramedics, anaesthetists or emergency physicians are able to provide high-level care including intubation and induction of general anaesthesia—known as ‘stay and play’ (Smith and Conn, 2009).
These two methods were debated by the American Association for the Surgery of Trauma in 1982 (Border et al, 1983) and have been compared ever since. The majority of evidence has supported a scoop-and-run policy in major trauma; however, a third category of ‘play without extending play’ has been suggested. This technique, where skilled emergency providers perform only life-saving prehospital interventions, was found not to increase time at the scene nor total prehospital time and decreased mortality rates in the most severely injured patients by 50% in a retrospective analysis of prehospital interventions of 3733 consecutive trauma patients attending a US level I trauma centre (Meizoso et al, 2015).
Although, historically, the presence of doctors in the prehospital setting was shown to improve intubation rates and patient satisfaction for pain control (Eckstein et al, 2000), contemporaneous literature has demonstrated pain relief administration by paramedics is effective (Yousefifard et al, 2019) and there is no good-quality evidence showing higher successful intubation rates in comparisons between paramedics and non-anaesthetic doctors (Peters et al, 2015). There is also insufficient evidence to show that improved prehospital pain relief and intubation rates improve mortality, particularly in the setting of major haemorrhage (Wilson and Gangathimmaiah, 2017).
One of the paradoxes of the two approaches to prehospital trauma care is the distribution of expertise in urban versus rural settings. The scoop-and-run strategy is associated with improved outcomes for trauma patients in urban environments where transfer times are short; this is the setting where most experience and competency in advanced skills are concentrated but also where they are least likely to be used. Another factor to be considered is that, because of the higher populations in urban areas, paramedics will generally have fewer exposures to critically unwell patients requiring these advanced skills. Even when exposed, paramedics in urban areas are likely to receive less educational benefit than from an equivalent encounter in a rural setting because treatment is likely to be led by other assets deployed to the scene (Mulholland, 2010). This is also problematic for maintaining skills as nobody is able to sufficiently preserve skills if they practise them only a few times a year (Smith and Conn, 2009).
As stated above, significant early haemorrhage accounts for a substantial proportion of trauma morbidity and mortality. Consequently, innovations in methods to mechanically control haemorrhage have advanced rapidly. This is particularly relevant to military settings as battlefield analyses have associated haemorrhage with 90% of survivable injuries (Winstanley et al, 2019).
Tourniquets for extremity haemorrhage were first documented in the Roman era and their use is common today, albeit with practitioners having a greater appreciation of the complications of prolonged tourniquet times than their Roman counterparts (Saied et al, 2015). War has been the primary driver for their advancement, with the training of all military personnel in tourniquet application in recent conflicts in Afghanistan and Iraq contributing to unprecedented survival rates for battlefield injury (Goodwin et al, 2019).
In patients not suitable for tourniquet application—mainly those with junctional haemorrhage, such as in the neck, axilla and inguinal regions, which accounted for 19.2% of injuries causing death in US soldiers in Iraq and Afghanistan between 2001 and 2011—topical haemostatics are invaluable (Güven, 2017). A host of different compounds are available for this, with the most recent Tactical Combat Casualty Care (2020) guidelines stipulating the use of a ‘combat gauze’ dressing (surgical gauze with kaolin) (Ran et al, 2010) in association with a kaolin-based topical haemostat (which augments the activation of factors XI and XII) and a chitosan-based agent used as second line (this positively charged surface recruits erythrocytes, physically closing the haemorrhage site and causing vasoconstriction) (Güven, 2017; Tactical Combat Casualty Care, 2020).
Civilian mass casualty events, such as terrorist bombings in which injury patterns mirror those seen in military settings, have created a requirement to transfer this haemorrhage control practice to emergency providers (Gulland, 2017). It has taken time to translate this to the civilian setting; although the use of topical haemostatics among emergency crews is increasing, retrospective surveys of US paramedics showed fewer than half had used a topical haemostatic in the previous year. The causes for this appear to be a lack of clear indications for their use, low availability and a lack of experience and comfort with the products (Sigal et al, 2017).
Another direction for the prehospital control of major haemorrhage has been endovascular interventions. These have been developed for non-compressible bleeds that are not amenable to tourniquets or topical haemostats. One such example is resuscitative endovascular balloon occlusion of the aorta (REBOA). This involves cannulation of the femoral artery and inflation of an endovascular balloon at various points of the aorta (zone 1=between the left subclavian and coeliac trunk; zone 2=between the coeliac trunk and the origin of the renal arteries; zone 3=between the origin of the renal arteries and the bifurcation of aorta) to reduce the volume of haemorrhage and risk of hypovolaemic cardiac arrest.
Early studies have shown promise with its use in exsanguinating pelvic trauma (Lendrum et al, 2019) alongside established methods of pelvic splinting and immobilisation of long-bone fractures. This demonstrates a significant survival improvement compared to other methods of controlling severe subdiaphragmatic haemorrhage, namely resuscitative thoracotomy (Brenner et al, 2018).
This procedure does have complications, particularly hypoperfusion and ischaemia distal to the site of balloon occlusion. REBOA is only used in zones 1 and 3 as mesenteric and renal ischaemia can result from complete aortic occlusion in zone 2 (Russo et al, 2016). This can also be caused by zone 1 placement; however, partial REBOA (P-REBOA) can be used to maintain low-volume flow to distal tissues whilst maintaining arterial control and preserving blood pressure (Lendrum et al, 2019).
The optimal inflation time of the balloon is an area of ongoing research, with Bekdache et al's (2019) systematic review stating the ideal time is 20 minutes, after which the catheter should be removed or an alternating inflation-deflation mode should be adopted (Bekdache et al, 2019).
Damage control resuscitation
Damage control resuscitation (DCR) is a term coined around the turn of the century, once again off the back of military experience. It describes a focus on the early control of bleeding, with particular attention being paid to coagulopathy, hypothermia and acidosis—an often fatal group of trauma sequelae (Rotondo and Zonies, 1997; Holcomb, 2007).
Coagulopathy in particular has historically been a troublesome issue for emergency doctors and trauma surgeons (Güven, 2017). Over the past two decades, the practice of haemostatic resuscitation has been developed specifically to counteract this. This involves a 1:1:1 ratio of packed red cells to fresh frozen plasma to platelets, and avoiding diluting crystalloid solutions: this has been demonstrated as the best approach to the immediate resuscitation of trauma patients (Van et al, 2017). For the purposes of this essay, DCR is being discussed separately from prehospital care although DCR is frequently initiated in this setting.
While maintaining ideal ratios of blood products is important, other crucial interventions are the use of tranexamic acid (TXA) and thromboelastography (TEG) to guide transfusion requirements.
With regards to TXA, it has been shown to reduce the risk of death from exsanguination with early administration in trauma (Roberts et al, 2013), traumatic brain injury (Cap, 2019) and post-partum haemorrhage (WOMAN Trial Collaborators, 2017). It acts through diminution of a maladaptive activation of the fibrinolytic pathway in response to injury that results in the breakdown of haemostatic clots, increasing the permeability of endothelial cells, oedema and inflammation (Cap, 2016).
TEG is a way of measuring the efficacy of blood coagulation and was developed at the University of Heidelberg in 1948. It overcomes the limitations of conventional testing of coagulation through platelet count, fibrinogen levels, prothrombin time and activated partial thromboplastin time, which are static, timely and often analysed in isolation. The main strengths of TEG are its dynamic analysis of clot formation, applicability as a bedside test, rapid turnaround of results and cost-effectiveness in identifying patients who are at a low risk of haemorrhage (Karon, 2014). Its main limitation is its inability to investigate hypercoagulable states postoperatively, which still require conventional haemostatic measurements (Bolliger et al, 2012).
An area of future exploration in DCR is the use of whole blood. Indeed, this is a return to past practice, with whole blood being the resuscitative tool of choice prior to the separation of blood components in 1965 (Barnes, 1980). The rationale behind this is that even a perfect 1:1:1 ratio of red cells, platelets and plasma delivers a solution that is anaemic (with a haemoglobin of approximately 9 g/dl), is thrombocytopenic (platelet count approximately 88 000/ml), has significantly decreased fibrinogen levels and has a 35% reduction in coagulation activity compared to whole blood (Zielinski et al, 2014; Van et al, 2017).
The use of whole blood in a military setting is supported by a wealth of evidence (Keneally et al, 2015). However, translation of this to the civilian population is limited because of concerns over acute haemolytic transfusion reactions. Low-titre anti-A and anti-B type O whole blood (LTOWB) has been demonstrated to be safe in military settings (Nadler et al, 2020). Another impediment to the widespread use of LTWOB in civilian trauma is a lack of consensus over the definition of low titre, with Norwegian and Swedish military services limiting immunoglobulin M (IgM) titres to <100, although some US divisions allow IgM titres as high as 256 (Fisher et al, 2015).
Despite this difficulty in civilian application, a 2019 survey revealed its use in one Norwegian and 24 US hospitals and two air ambulance services—one in Israel and Bart's Health NHS Trust in London (Yazer and Spinella, 2019). Unrefrigerated whole blood has been used as part of initial resuscitative efforts in Australia (Pivalizza et al, 2018). An aspect of this incorporation that needs clarification across healthcare providers is whole-blood wastage. This has been linked to its 21-day shelf life as well as potential unfamiliarity with its availability and hospital procedures surrounding its use (Pivalizza et al, 2018).
In the 2019 survey referred to above, some units had waste reduction strategies such as creating units of red cells once LTOWB reached its storage deadline. Other strategies included prehospital services returning LTOWB units to the hospital after 14 days, extending their shelf life to 35 days for trauma patients or reserving LTOWB between 21–35 days old for haemorrhaging non-trauma patients (Yazer and Spinella, 2020).
Larger studies investigating the use of whole blood against traditional component therapy are certain. Incorporating these into trauma algorithms could mitigate severe coagulopathy and significantly aid operative treatment of the most severely injured patients or prevent the need for surgery at all.
Interventional radiology
IR has an important role in trauma management. Training in transcatheter techniques and experience in multimodal imaging makes interventional radiologists capable of identifying significant internal haemorrhage and treating this in a timely manner.
For this to benefit patients, clear communication between members of the resuscitative multidisciplinary team, accurate initial assessment and prioritisation of injuries are essential.
IR therapies in trauma patients most commonly include:
IR has typically been reserved for haemodynamically stable trauma patients (Radwan and Abu-Zidan, 2006). However, a wealth of ongoing research is being carried out into the application of IR to the most severely injured unstable patients.
An example of such work is Matsumoto et al's (2015) PRESTO protocol (prompt and rapid endovascular strategies in trauma occasions). This is a standardised algorithm activated when a resuscitation team receives a pre-alert from the prehospital emergency team. This protocol initiates prompt initial decision-making regarding the patient's suitability for IR, a rapid CT scan to identify severe pre-selected injuries in no more than 3 minutes and expert damage control IR (DCIR), with no individual procedure lasting more than 5 minutes. The aim is to change IR from being viewed as an adjunct to surgery in the trauma setting to it being a distinct, primary treatment method in itself (Matsumoto et al, 2015).
Another proposed advance of IR's role in trauma is that of a hybrid or RAPTOR (resuscitation with angiography, percutaneous techniques and operative repair) suite. These are specialised units where CT scanning, IR facilities and surgical management can all be performed with minimal time-wasting as a patient is transferred from one location to another (D'Amours et al, 2013). Delay to radiological intervention has been repeatedly proven to increase mortality; Howell et al (2010) showed this effect can be as high as 47% for every hour delay (Howell et al, 2010).
However there are clear difficulties associated with establishing these units; they come at enormous costs to healthcare providers, in terms of both designing and building them and staffing them. This cost is increased through maintenance of technology needed in these suites, and their reliance on multiple cooperating IT systems is another potential limitation. Further problems arise with loss of service provision through the extensive education of staff required, in the procedures, image analysis and the triaging of patients directly to the hybrid suites (Martin et al, 2012).
With regards to triage, the lack of large-scale studies to guide this (as hybrid units have been introduced only recently) makes this difficult. An adaptation of existing triage tools to include when transfer to a RAPTOR suite would be appropriate would be an excellent addition to treatment algorithms in major trauma centres (Kinoshita et al, 2019).
Conclusion
The burden of exsanguinating patients on trauma systems worldwide is extensive and huge advancements in all aspects of trauma care have been made to minimise its impact.
These begin at an organisational level with structuring services and can be seen throughout the patient journey: in prehospital care with the development of local haemostatic compounds for junctional haemorrhage and endovascular tools such as REBOA; the advancement of damage control resuscitation with a possible shift back to whole blood in the coming years; and the use of IR with its application broadening to a primary method of haemorrhage control for haemodynamically unstable patients.
An interesting future direction is hybrid resuscitation suites, where operative and non-operative management are combined in a dedicated unit. These have clear limitations but have shown promising initial data with regards to 28-day mortality for trauma patients in Tokyo (Kinoshita et al, 2019). Further studies analysing cost-effectiveness will be required if they are to be used more widely.