Pattern of injury

Throughout the UK military medical experience in Iraq and Afghanistan (Ops TELIC and HERRICK), experience was gained in treating patients who had been exposed to ballistic trauma. In particular, this included explosive injury (often concealed Improvised Explosive Devices, IEDs) or high energy transfer gunshot injury. UK service personnel universally wore body armour and helmets, and therefore extremity and limb injuries predominated in survivors. Amputation was a common sequela and the most severely injured often had bilateral high lower limb amputation, open pelvic fracture and other injuries. Service personnel were exposed to blast on foot patrol (dismounted) or within vehicles; IED were commonly buried underground and typically had low metal content.10 The victims of the Manchester Arena attack were subjected to an open air blast of a device carried by a suicide bomber and the device had been surrounded by metal objects that were energised by the blast and became projectiles. This resulted in penetrating injury (secondary blast). With high lethality of those close to the epicentre of the explosion, there were few survivors with obvious primary blast injury. Nevertheless, in one patient, pulmonary thrombosis was identified on the admission CT scan. The military experience enabled reassurance of the civilian clinicians that this was in all likelihood acute peritraumatic pulmonary thrombus (APPT). This is a phenomenon that was identified in nearly 10% of major trauma admissions in the Afghanistan war hospital.11 APPT is generally considered to be incidental and unlikely to require intervention such as anticoagulation or vena caval filter devices.

Shaping the wound

The principles of war surgery relearned in the wars in Iraq and Afghanistan have been: arrest of haemorrhage, thorough wound debridement and lavage, temporary stabilisation of fractures and a staged approach to first ‘shape’ wounds and subsequently reconstruct them.12 A key principle is that wounds can vary widely and that an arbitrary distinction into low energy wounds (with little contamination—that can be closed) and high energy wounds (with significant contamination—that must be left open) can be unhelpful, as the different wound types can coexist. Debridement can be:

• Marginal: in which all the necrotic tissue is removed but injured and potentially viable tissue is retained.

• Complete: removal of both necrosed and marginal tissue.

• Radical: which includes normal tissue within the field of excision.

Recent military experience is that meticulous repeated marginal debridement of military wounds preserves as much tissue as possible and maximises functional outcomes. ‘Complete’ debridement is hard to judge and radical debridement involves the removal of tissue which would otherwise survive. Military protocols now recommend repeated debridement every 48–72 hour until no further sign of necrosis or infection has occurred. Military protocol is to recommend delaying soft-tissue reconstruction until the wounds are macroscopically clean and remain so on two successive debridements and the patient requiring minimal physiological support. This protocol contrasts with the International Red Cross (IRC) guidelines that recommend an initial (radical) debridement followed by application of gauze dressings, which are then left undisturbed until a delayed primary closure is performed at 4–7 days: ‘once the exudative phase of trauma inflammation has subsided and the proliferative phase begun’.13

A further recent development in military surgery has been the concept of damage control operations particularly for laparotomy14 but also for other anatomical regions, such as the chest and head, and the use of vascular shunts for vascular injury.15–17 The QEHB/RCDM delegation discussed our experience with the Manchester clinicians and we were able to compare and contrast the clinical challenges faced. The stance of the QEHB/RCDM delegation was that of ‘humble learners’ and we acknowledged that not only were the patterns of wounding different from ‘Afghan standard’, but that considerable, high level expertise was widespread among the Manchester clinicians. The largely concrete concourse of the Arena is obviously different to the ‘Green Zone’ of Helmand and the nature of the device (man-portable IED packed with metallic objects) meant that survivors sustained little primary blast injury, but had extensive ballistic injury from the metal nuts and cable packed around the device. The nature of the event targeted by the perpetrator meant that significant numbers of survivors were children and young people.

The impact of terrorism on children

In a review of mass casualty incidents in Israel, injuries among teenagers (ages 10–17 years) were twice as likely as those of younger children (ages 0–9 years), (67% and 33%, respectively (p<0.05)). The head, face and neck (HFN) region was the most common to be injured (67%), followed by upper and lower extremities (62%).18 A review of paediatric blast casualties at Camp Bastion Role 3 Medical Facility confirmed that children are more likely to sustain severe HFN injuries than adults.19

Lessons learnt

There was recognition that the Manchester major trauma network had performed exceptionally well and that individual clinical interactions were consistently undertaken to a very high standard. Operationally, the Greater Manchester dispersal plan worked very well; however, there were certain factors that will require further work to be fully incorporated into future plans. The incident produced a much longer clinical ‘tail’ than had been anticipated; it took 2 months for the operational performance of the most impacted hospitals in Manchester to return to ‘business as usual’. Evaluation of the Greater Manchester response to the Arena bombing also highlighted a potential additional role for Local Emergency Hospitals (LEH), beyond caring for patients with ‘low-acuity’ traumatic injuries. Acute medical patients could be redirected to LEHs in the immediate aftermath of a mass casualty incident, thereby clearing pressure in the Major Trauma Centres. To accept the number of acute medical admissions will require a structured response; however, staff at the LEHs felt that, in this way, they could offer a further valuable part of the response to any such incident in the future. The issue of consent for sharing clinical information was also highlighted. This was not so much between NHS organisations or clinicians, but information governance was a concern when there were requests for clinical information between NHS and non-NHS organisations. This included social care or third parties such as the trustees or the ‘fourth estate’.

There was recognition that the MCR pattern of injury differed from the typical injuries experienced by UK servicemen after IED strike in Afghanistan and that surgical care was excellent across the board. Nevertheless, there were minor inconsistencies in surgical protocols (some primary closure of a few minor ballistic wounds occurred). The MCR clinicians identified a high yield of significant nerve and tendon injuries on secondary and tertiary surveys. The invited delegation felt that some overenthusiastic relooking of wounds and surgery to retrieve missile fragments had occurred. There was also some enthusiasm for ‘hyper acute’ complex reconstruction and this was counselled against. There was a recognition that pneumoperitoneum can occur after blast injury without visceral injury20 and negative laparotomy can occur (but also that negative laparotomy is a ‘lesser evil’ that a missed injury). There was a requirement identified for clear recommendations for management of risk of blood-borne viruses and policies concerning management of noise induced hearing loss and antimicrobial prophylaxis after blast injury.21–23 In addition to these clinical factors, it was realised that there was a requirement for enhanced welfare support for patients’ relatives and for members of staff, both those who had directly treated patients and those who had not.

Defence otology contribution

Properties of the ear that allow it to act as a biological pressure transducer make it inherently susceptible to damage as a result of blast. Disruption of the soft tissues within the ear canal, the ear drum and ossicular chain can be managed in relatively ‘slow time’. Recent evidence, however, supports interventions capable of rescuing some hearing loss associated with sensorineural damage. The immediate otological challenge of the Arena bombing concerned the possible practicalities of determining the presence and extent of any hearing loss in a potentially large number of people including many children. There was also the possibility of a cohort of patients presenting late to their general practitioner (GP) with no injury other than hearing loss, and the need for a proportionate response. A military-led team at QEHB undertook a rapid literature review to develop protocols for adults and children forthe management of hearing loss in a mass casualty situation and these were provided to the Manchester team. Flow diagrams included detailed advice on the medical options available, the role of intratympanic steroids and special considerations as to the use of high dose steroids particularly in multiply injured patients and in children. The protocols were designed to be used by GPs to help triage those with possible acoustic injury and also to inform definitive assessment and treatment of both forms of hearing loss in a secondary care setting.22

Defence imaging contribution

CT was introduced to forensic sciences in 1977 by Wüllenweber et al to aid in the assessment of patients who had died after gunshot injuries.24 Experience with forensic CT in the understanding of unnatural death was first used in the UK in Manchester in the 1990s in response to local religiously motivated objection to autopsy.25 The UK Defence Medical Services have accumulated significant experience in forensic radiology after blast injury and a Defence imaging team consisting of three radiologists and four radiographers was tasked to support the forensic process following the MCR bombing. The team utilised cross-sectional imaging with CT, standard radiographic imaging with small portable X-ray machines and ultrasound. While the overarching cause of death was largely understood for the Arena victims, forensic radiological analysis supported the pathologist in resolving the de facto cause of death and served to support the forensic investigation. In the absence of imaging, the pathologist must serially and methodically explore relevant body cavities and fascial compartments—a process which may take several hours. In a mass casualty event such as the MCR bombing, with 22 victims, a conventional forensic process could have lasted several weeks. In addition to speeding up the forensic examination, radiology allows the pathologist to minimise the otherwise necessary dissection of the deceased; a fact that can provide some small comfort to the relatives. Forensic imaging started with a CT scan of the victim and subsequent body mapping of fragments with a detailed assessment of injuries and wounding tracts. Prior to conventional autopsy, a case conference allowed detailed discussion and direction so the pathologist knew where to look when the autopsy was undertaken. During the autopsy, radiographers with portable X-ray equipment were able to correlate the CT body map to the victim and further refine the forensic process. Ultrasound was used to further facilitate localisation within organs.