Outcome after vascular trauma in a deployed military trauma system

Original article

Outcome after vascular trauma in a deployed military trauma system A. Stannard, K. Brown, C. Benson, J. Clasper, M. Midwinter and N. R. Tai Academic Department of Military Surgery and Trauma, Royal Centre for Defence Medicine, Birmingham Research Park, Vincent Drive, Birmingham B15 2SQ, UK Correspondence to: Lieutenant Colonel N. R. Tai (e-mail: [email protected])

Background: Military injuries to named blood vessels are complex limb- and life-threatening wounds that pose significant difficulties in prehospital and surgical management. The aim of this study was to provide a comprehensive description of the epidemiology, treatment and outcome of vascular injury among service personnel deployed on operations in Afghanistan and Iraq. Methods: Data from the British Joint Theatre Trauma Registry were combined with hospital records to review all cases of vascular trauma in deployed service personnel over a 5-year interval ending in January 2008. Results: Of 1203 injured service personnel, 110 sustained injuries to named vessels; 66 of them died before any surgical intervention. All 25 patients who sustained an injury to a named vessel in the abdomen or thorax died; 24 did not survive to undergo surgery and one casualty in extremis underwent a thoracotomy, but died. Six of 17 patients with cervical vascular injuries survived to surgical intervention; two died after surgery. Of 76 patients with extremity vascular injuries, 37 survived to surgery with one postoperative death. Interventions on 38 limbs included 19 damage control procedures (15 primary amputations, 4 vessel ligations) and 19 definitive limb revascularization procedures (11 interposition vein grafts, 8 direct repairs), four of which failed necessitating three amputations. Conclusion: In operable patients with extremity injury, amputation or ligation is often required for damage control and preservation of life. Favourable limb salvage rates are achievable in casualties able to withstand revascularization. Despite marked progress in contemporary battlefield trauma care, torso vascular injury is usually not amenable to surgical intervention.

Presented in part to the Annual Meeting of the Vascular Society of Great Britain and Ireland, Bournemouth, UK, November 2008, and published in abstract form as Br J Surg 2009; 96(Suppl 1): 6 Paper accepted 19 October 2010 Published online 19 November 2010 in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.7359

Introduction

Among soldiers who die from combat injury, exsanguination from major vascular trauma endures as the leading cause of death1 – 3 . Many of these injuries prove fatal well before the casualty reaches organized surgical care, and survivorship bias ensures that only a small minority of combat casualties need treatment for vascular injury. Two of the largest series from the recent conflicts in Afghanistan and Iraq have documented a 4·4–7 per cent prevalence of vascular trauma3 – 5 . These and other contemporary reports are generally limited to descriptions of patients who survived to reach surgical care6 – 11 . As a consequence, the casualties who die  2010 British Journal of Surgery Society Ltd Published by John Wiley & Sons Ltd

before the opportunity for surgical intervention are poorly described. Any systematic effort to improve salvageability from vascular trauma must include the entire population in order to understand where gains in survival of life and limb can be made. British servicemen and women have been deployed to Afghanistan since 2001 and to Iraq since 2003. Acute trauma care for these troops from the point of injury, through initial resuscitation, surgery, evacuation and definitive treatment, has been organized into an integrated United Kingdom Joint Theatre Trauma System (JTTS)12 . A central part of this effort concerns the improvement of injury mitigation systems, surgical British Journal of Surgery 2011; 98: 228–234

Outcome after vascular trauma in a deployed military trauma system

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education and protocols of care by capture of robust injury data and analysis of performance indicators13 . A unique part of this information capture system includes centralized post-mortem examination of all UK military casualties held under the auspices of Her Majesty’s (HM) Coroner. The aim of this study was to assist maturation of the JTTS by providing an account of the epidemiology, treatment and early outcomes of troops sustaining vascular trauma on deployment in Afghanistan and Iraq. The burden of vascular trauma was described among all injured service personnel whether there was a surgical intervention or not.

to affected limbs. The study encompassed a 5-year interval ending in January 2008. Data were analysed according to injury location and whether there was a surgical intervention or not. Injuries were categorized as those to the extremities (limbs), trunk (abdomen and thorax) or cervical regions. Case-note review allowed further categorization of peripheral injury by treatment category: where limb revascularization was not performed owing to physiological or anatomical disruption, and where definitive repair and revascularization could be undertaken. Mechanism of injury was categorized as caused by blast weaponry (improvised explosive device, indirect fire, rocket-propelled grenade) or non-blast weapon systems.

Methods

The clinical details of personnel who had sustained combat vascular injuries while serving with HM Armed Forces were abstracted retrospectively from a prospectively maintained database, the Joint Theatre Trauma Registry (JTTR), held and maintained at the Academic Department of Military Emergency Medicine, Royal Centre for Defence Medicine. Basic data on casualty demographics were recorded from the registry, with subsequent interrogation of medical records to delineate further mechanisms and patterns of injuries, management (including intraoperative details) and outcome data (including limb salvage and complications). In addition to these basic data and descriptive details, the Injury Severity Score (ISS)14 and Mangled Extremity Severity Score (MESS)15 were recorded in order to stratify further the gravity of injuries both globally and specifically

Statistical analysis Statistical analyses were performed using the Mann– Whitney U test and Fisher’s exact test, by means of TM software (GraphPad Software, La Jolla, GraphPad California, USA). Results

Of 1203 casualties entered in the JTTR, 110 (9·1 per cent) had injury to a named vessel. Seventy-six patients sustained extremity vascular injury, whereas 42 sustained central (torso or cervical) injury (Fig. 1). Eight patients sustained combination vascular injury to more than one body zone; none of these survived to reach surgical intervention. The intervention group consisted of 44 patients who Torso

Torso

18 1

0

6

0

37

0

Extremity

a

Surgical intervention

0 0

0 6

9

2

31

Extremity

Cervical

b

Cervical

No surgical intervention

Venn diagrams demonstrating the numbers with isolated and coexisting torso, extremity and cervical vascular injuries among a 44 casualties who underwent a surgical intervention and b 66 who did not

Fig. 1

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A. Stannard, K. Brown, C. Benson, J. Clasper, M. Midwinter and N. R. Tai

Table 1 Injury severity, anatomical pattern and outcome for casualties with central vascular injuries (cervical, thoracic and abdominal)

Blast injury Injury Severity Score* Vessel injured Aorta Arch branches Visceral branches Cervical Survivors

No surgical intervention (n = 35)

Surgical intervention (n = 7)

20 75 (75–75)

3 23 (11–75)

20 3 1 11 0

1 0 0 6 4

*Values are median (interquartile range).

underwent a surgical procedure, four of whom died (perioperative mortality rate 9 per cent). Seven of 44 casualties in this cohort had a central vascular injury compared with 35 of 66 in the group that did not have surgery (P < 0·001). No patient in the no-surgery cohort was found to have been deprived of an indicated surgical intervention.

Central vascular injury Of the 42 patients with central vascular injury, 35 had no surgical intervention or opportunity for surgical intervention (Table 1). As expected, this group had a much higher burden of injury than patients who underwent surgical intervention (median ISS 75 versus 23; P < 0·001). The rate of blast as a causative mechanism was similar in the surgery and no-surgery groups (P = 0·684). Of 25 casualties with a vascular injury to the trunk, 24 did not survive to surgical intervention. Twenty died from wounds to the main aorta, three from wounds to the arch vessels and one from a visceral branch vessel injury. One casualty with a thoracic aortic injury survived to undergo resuscitative thoracotomy but died before definitive repair could be achieved. Eleven of 17 casualties with injuries to the major neck vessels died before surgical intervention. Of six casualties with cervical injuries who survived to surgical intervention, three sustained carotid artery injuries. Two died following operative repair; one of these had an extensive head injury (with injuries to the ipsilateral internal, external carotid and vertebral arteries) and the other died from a hemispheric stroke following direct repair of a posterior wall injury at the bifurcation of the common carotid artery. All three casualties with jugular vein injuries survived following vessel ligation.  2010 British Journal of Surgery Society Ltd Published by John Wiley & Sons Ltd

Table 2 Injury severity, anatomical pattern and outcome for casualties with peripheral vascular injuries

Blast injury Injury Severity Score* Named vessel injured Femoral Popliteal Crural Brachial Radial/ulnar Survivors

No surgical intervention (n = 39)

Surgical intervention (n = 37)

35 75 (75–75)

23 17 (13–20)

15 2 6 11 5 0

6 6 15 7 4 36

*Values are median (interquartile range).

Peripheral vascular injury Of 76 casualties with peripheral vascular injury, 39 (51 per cent) had no surgical intervention (Table 2). The prevalence of blast injury was higher in this group than in the surgery group (P = 0·006). This group also had a much higher injury burden than patients who had surgery (median ISS 75 versus 17; P < 0·001). Leg wounds accounted for 65 per cent of all extremity vascular injuries. The proportion of arm injuries was greater in the nosurgery group, although this did not reach statistical significance (16 of 39 versus 11 of 38; P = 0·341). Eight of the 39 patients in the no-surgery group had coexisting vascular trauma to other body regions: two had associated carotid injury and six had aortic injury (Fig. 1). In addition, 38 of the 39 had significant trauma to the central nervous system (22), cardiopulmonary system (11) or abdominal organs (5). One casualty died from bilateral injuries to the common femoral arteries without coexisting trauma to the trunk or head. The surgical intervention group comprised 37 patients with 38 injured limbs. In 19 limbs revascularization was not possible and primary amputation (15) or vessel ligation (4) was performed. There were 19 definitive repairs where the limb was revascularized. Patients without revascularization had higher ISS and MESS (P = 0·054 and P = 0·001 respectively). Two patients in this group subsequently died. In the group that had definitive repair, eight limbs had direct vascular repair (suture repair, patch angioplasty) and 11 underwent reversed vein bypass grafting (Fig. 2, Table 3). Four of the 11 bypass grafts subsequently thrombosed before casualty evacuation. One was salvaged with preservation of the limb; in the remaining three, limb perfusion could not be restored and all patients underwent major amputation. There was a non-significant trend (P = 0·072) towards a higher prevalence of blast injury in the group that had vessel ligation or primary amputation. www.bjs.co.uk

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Table 3 Mechanism and severity of peripheral vascular injury, intervention and outcomes for patients with no attempt at revascularization and those in whom revascularization was undertaken

a

Initial wound

Blast injury Injury Severity Score* MESS* Intervention Primary amputation Vessel ligation Direct vessel repair Bypass graft Secondary amputation Limb loss Death

No revascularization (n = 19)

Revascularization (n = 19)

16 17 (13–25) 9 (8–9)

10 10 (5–17) 6 (6–7)

15 4 — — 0 15 2

— — 8 11 3 3 0

*Values are median (interquartile range). MESS, Mangled Extremity Severity Score.

Discussion

b

Axial incision

c

Restoration of perfusion

Intraoperative images of the left shoulder of a casualty with a fragmentation injury to a segment of the left axillary artery and vein, following a rocket-propelled grenade attack: a initial wound, b axial incision to expose proximal axillary and brachial arteries, and c restoration of perfusion using an interposition reversed vein graft. The casualty also sustained a median nerve injury, which was noted and, following aeromedical evacuation, subsequently repaired at Selly Oak Hospital, Royal Centre for Defence Medicine. Images courtesy of Wing Commander D. Nott

Fig. 2

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Contemporary military operations in Afghanistan and Iraq have led to the need for innovative battlefield trauma treatments in coalition and UK forces16 . Prehospital advances have included the introduction of novel haemostatic agents such as HemCon (HemCon Medical Technologies, Portland, Oregon, USA) and QuikClot (Z-Medica, Wallingford, Connecticut, USA)17 , the re-emergence of tourniquet use for control of massive limb bleeding18 , and physiciandelivered definitive airway control and blood transfusion (via the helicopter-borne Medical Emergency Response Team). Surgical and critical care teams working in the deployed military hospital are trained to deliver damage control interventions hand-in-hand with haemostatic resuscitation, to avoid the often fatal development of acute coagulopathy of trauma. Finally, robust and responsive strategic aeromedical evacuation facilitates rapid return of casualties for tertiary-level hospital care in the UK. Current UK operational medical doctrine does not compel specialist vascular surgical support to deployed forces. The skill mix of deployed field surgical teams typically includes one consultant general and one consultant orthopaedic surgeon, although the numbers of surgical teams deployed is a function of the mission at hand, predicted casualty rates and other variables. The deployed general surgeon may or may not have a vascular background, depending on training and the requirements of his or her substantive consultant appointment within the National Health Service. For non-vascular surgeons, appropriate vascular surgical competencies are refreshed before deployment via the Definitive Surgical Trauma www.bjs.co.uk

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Skills course and the Military Operational Surgical Training course, both held at the Royal College of Surgeons of England. The aim was to examine the outcomes of service personnel inflicted with fatal and non-fatal vascular trauma, in order to assist a performance improvement programme and ‘end-to-end’ efforts in preventing such injuries and treating the wounded. Only by describing both the fatally injured and the surviving cohorts can the effect of weapons systems, protective body armour and treatment strategies be gauged properly. Patients treated within the deployed British field hospitals in Iraq and Afghanistan over the study interval included non-combatant civilians, coalition troops from allied nations and captured insurgents. However, complete JTTR data sets – in particular post-mortem descriptions and data pertaining to late outcomes – were available only for injured HM Armed Forces servicemen and women. Therefore this group constituted the study population. With regard to the fatally injured, troops are usually classified as having died before reaching a hospital facility (killed in action, KIA) or afterwards (died of wounds, DOW)2 . In the present study these populations were classified according to the domains of surgical intervention or no surgical intervention. This retrospective series suffers from the usual disadvantages of such analyses, but potential bias was minimized by grouping patients according to explicit and unambiguous definitions. Patients were not classified as KIA or DOW, as these terms did not necessarily depict the influence of surgical intervention, and may be mutable depending on what constitutes a hospital, and therefore what is defined as prehospital care. The present data suggest that major vessel injury remains a highly lethal injury complex, particularly in patients with torso vascular trauma. All 25 patients with thoracic or abdominal vascular injury and 13 of 17 with cervical vascular trauma died. Discounting casualties with a jugular vein injury, only one of 39 patients with major central (torso or cervical) arterial injury survived overall. Even in patients with extremity vascular trauma amenable to tourniquet control, a combination of either coexisting vascular trauma to the central vessels, or severe trauma to other vital non-vascular structures, led to death in more than half before surgical intervention could be undertaken. These data reflect the immediate efficacy of modern munitions on human tissue; advances in non-surgical resuscitation, even if commenced within minutes of injury, may never be able to address disruption to the large central vessels of the torso and coexisting trauma to the brain, heart or lungs. Notably, the incidence of torso vessel trauma is less

in populations with access to body armour4 ; it is likely that continued advances in vehicle and personal protection will always be of greater value than new surgical techniques or processes of care19 . Casualties with injury to the cervical vessels appeared less likely to die before surgical intervention than those with torso trauma, although two of three patients with carotid injuries died after surgery. One of these casualties had an ipsilateral combination of internal and external carotid trauma, together with a vertebral artery injury; post-mortem examination also revealed significant brain injury, remote from the missile track, consistent with shock wave transmission. Poor outcome would be the norm given this constellation of injuries. Casualties with peripheral vascular injury accounted for 69·1 per cent of patients; 65 per cent of wounded vessels were located in the leg. Although the extremities are more vulnerable to injury, as protective personal body armour is confined to the torso, the injuries are correspondingly less fatal as they may be controllable with non-surgical treatments, such as a tourniquet or novel haemostatic agents18 . The overall amputation rate among all patients with extremity vascular injury was 47 per cent (18 of 38). However, this figure should be interpreted cautiously, as it included patients only suitable for damage control surgery who had a median MESS of 9. No patient scored less than 7, indicating very significant limb trauma. The observed case-fatality rate of 11 per cent (2 of 19) suggests that patients in this group had been correctly identified as requiring damage control, and that the strategy was successful in minimizing mortality. A better description of the success of revascularization strategies may be obtained by examining the limb salvage rate in patients fit enough to undergo definitive surgery. In this group, extensive vessel destruction necessitated reversed vein bypass graft in the majority. Failure of repair was confined to the vein graft group, with restoration of graft perfusion in one of four thrombosed grafts. The primary (assisted) patency (and limb salvage rate) in these patients was 84 per cent (16 of 19). Although vascular shunting has been popularized as a damage control technique8,9 , and the training of UK military surgeons has been focused concordantly, no patient received a shunt in this series. This is explained only partly by the fact that, although previous reports have described the value of this technique for patients treated in far-forward and isolated surgical resuscitation sites, such facilities have not been required to support UK military operations in either Afghanistan or Iraq. It is difficult to compare the present data with those in previous reports, as the subset declared as KIA is

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Outcome after vascular trauma in a deployed military trauma system

frequently not analysed. Among the recent literature, two papers from US military vascular surgeons summarized their contemporary experiences. Clouse and colleagues4 reported a 2-year experience from the Balad Vascular Registry, compiled from a database maintained at the Air Force Theatre Hospital north of Baghdad, Iraq. Vascular injury was found in 4·8 per cent of battlewounded casualties presenting to surgical staff, with a central (neck and torso) vascular injury rate of 25 per cent and an overall perioperative mortality rate of 4·3 per cent. The authors were able to confirm that the distribution of central wounds was lower in US casualties issued with body armour than in local nationals who did not wear personal protective equipment. Sohn and colleagues6 , who were based in a Baghdad combat support hospital, treated 153 patients with vascular injury (many of whom were evacuated to Balad) and reported a prevalence of 4·4 per cent with a 6 per cent mortality rate. They noted an overall limb salvage rate of 80 per cent and described an overwhelming preponderance of extremity injury; no patient with vascular trauma to the aorta or inferior vena cava survived injury, although four of six patients with injury to the subclavian–axillary axis and all seven with an iliac artery injury survived surgery. Fox and co-workers5 reviewed 106 patients with combat vascular injuries treated at Walter Reed Army Medical Center in Washington, DC, from 2001 to 2004. The prevalence of vascular trauma in their cohort of 1524 combat-injured patients who survived evacuation to the USA was 7 per cent. The numerator included patients in whom covert vascular injury was found upon further investigation at their institute. Only one patient with torso vascular trauma (to an iliac vessel) was recorded in the Walter Reed cohort, suggesting that patients with this injury complex almost always died before repatriation. Continued collation of data from both the surviving and the mortally injured populations with vascular injury will inform ongoing analysis and comparison of battlefield data. Future effort needs to be directed at harmonizing terms and definitions across the medical services of allied nations whose deployed armed forces serve together in operational theatres. Acknowledgements

The authors thank the staff of the Academic Department of Military Emergency Medicine for their continuing efforts in the development and maintenance of the JTTR, which has played a central role in the realization of this paper. The authors declare no conflict of interest.  2010 British Journal of Surgery Society Ltd Published by John Wiley & Sons Ltd

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British Journal of Surgery 2011; 98: 228–234