Predicting the Outcome of Limb Revascularization in Patients With Lower-extremity Arterial Trauma: Development and External Validation of a Supervised Machine-learning Algorithm to Support Surgical Decisions.

OBJECTIVES: Estimating the likely success of limb revascularization in patients with lower-extremity arterial trauma is central to decisions between attempting limb salvage and amputation. However, the projected outcome is often unclear at the time these decisions need to be made, making them difficult and threatening sound judgement. The objective of this study was to develop and validate a prediction model that can quantify an individual patient's risk of failed revascularization. METHODS: A BN prognostic model was developed using domain knowledge and data from the US joint trauma system. Performance (discrimination, calibration, and accuracy) was tested using ten-fold cross validation and externally validated on data from the UK Joint Theatre Trauma Registry. BN performance was compared to the mangled extremity severity score. RESULTS: Rates of amputation performed because of nonviable limb tissue were 12.2% and 19.6% in the US joint trauma system (n = 508) and UK Joint Theatre Trauma Registry (n = 51) populations respectively. A 10-predictor BN accurately predicted failed revascularization: area under the receiver operating characteristic curve (AUROC) 0.95, calibration slope 1.96, Brier score (BS) 0.05, and Brier skill score 0.50. The model maintained excellent performance in an external validation population: AUROC 0.97, calibration slope 1.72, Brier score 0.08, Brier skill score 0.58, and had significantly better performance than mangled extremity severity score at predicting the need for amputation [AUROC 0.95 (0.92-0.98) vs 0.74 (0.67-0.80); P < 0.0001]. CONCLUSIONS: A BN (https://www.traumamodels.com) can accurately predict the outcome of limb revascularization at the time of initial wound evaluation. This information may complement clinical judgement, support rational and shared treatment decisions, and establish sensible treatment expectations.

Management and outcome of 597 wartime penetrating lower extremity arterial injuries from an international military cohort.

OBJECTIVE: Vascular injury is a leading cause of death and disability in military and civilian settings. Most wartime and an increasing amount of civilian vascular trauma arises from penetrating mechanisms of injury due to gunshot or explosion. The objective of this study was to provide a comprehensive examination of penetrating lower extremity arterial injury and to characterize long-term limb salvage and differences related to mechanisms of injury. METHODS: The military trauma registries of the United States and the United Kingdom were analyzed to identify service members who sustained penetrating lower limb arterial injury (2001-2014). Treatment and limb salvage data were studied and comparisons made of patients whose penetrating vascular trauma arose from explosion (group 1) vs gunshot (group 2). Standardized statistical testing was used, with Bonferroni corrections for multiple comparisons. RESULTS: The cohort consisted of 568 combat casualties (mean age, 25.2 years) with 597 injuries (explosion, n = 416; gunshot, n = 181). Group 1 had higher Injury Severity Score (P < .05) and Mangled Extremity Severity Score (P < .0001), required more blood transfusion (P < .05), and had more tibial (P < .01) and popliteal (P < .05) arterial injuries; group 2 had more profunda femoris injuries (P < .05). Initial surgical management for the whole cohort included vein interposition graft (33%), ligation (31%), primary repair with or without patch angioplasty (16%), temporary vascular shunting (15%), and primary amputation (6%). No difference in patency of arterial reconstruction was found between group 1 and group 2, although group 1 had a higher incidence of primary (13% vs 2%; P < .05) and secondary (19% vs 9%; P < .05) amputation. Similarly, longer term freedom from amputation was lower for group 1 than for group 2 (68% vs 89% at 5.5 years; Cox hazard ratio, 0.30; P < .0001), as was physical functioning (36-Item Short Form Health Survey data; mean, 39.80 vs 43.20; P < .05). CONCLUSIONS: The majority of wartime lower extremity arterial injuries result from an explosive mechanism that preferentially affects the tibial vasculature and results in poorer long-term limb salvage compared with those injured with firearms. The mortality associated with immediate limb salvage attempts is low, and delayed amputations occur weeks later, affording the patient involvement in the decision-making and rehabilitation planning. We recommend assertive attempts at vascular repair and limb salvage for service members injured by explosive and gunshot mechanisms.

Emergency Abdominal Surgery in the Elderly: Can We Predict Mortality?

BACKGROUND: The United Kingdom population is ageing. Half of patients requiring an emergency laparotomy are aged over 70, 20 % die within 30 days, and less than half receive good care. Frailty and delay in management are associated with poor surgical outcomes. P-POSSUM risk scoring is widely accepted, but its validity in patients aged over 70 undergoing emergency laparotomy is unclear. AIMS: To assess if P-POSSUM risk stratification reliably predicts inpatient mortality in this group and establish whether those who died within 30 days received delayed care. METHODS: Observational study of consecutive patients aged 70 and over fulfilling the National Emergency Laparotomy Audit criteria from a tertiary hospital. The predictive value of pre-operative P-POSSUM, ASA, lactate and other routine variables was assessed. Surgical review, decision to operate, consultant surgical review, antibiotic prescription, laparotomy and discharge or death time points were assessed by 30-day survival. RESULTS: One hundred and ninety-three patients were included. This represented 46.28 % of those undergoing an emergency laparotomy in our centre. Pre-operative P-POSSUM scoring, ASA grade and lactate were moderate predictors of mortality (AUC 0.784 and 0.771, respectively, lactate AUC 0.705, all p ≤ 0.001). No correlation existed between pre-operative P-POSSUM and days to death (p = 0.209), nor were there delays in key management timings in those who died in 30 days. CONCLUSIONS: P-POSSUM scoring may predict inpatient mortality with moderate discrimination. Addition of frailty scoring in this high-risk group might better identify those with a high risk of mortality after emergency laparotomy and would be a fertile area for further research.

Using Fully-Immersive Simulation Training with Structured Debrief to Improve Nontechnical Skills in Emergency Endovascular Surgery.

OBJECTIVE: Assess whether fully-immersive simulation training with structured debriefing of a standardized emergency thoracic endovascular aortic repair (TEVAR) scenario improves team-work performance of the lead surgeon. Secondary aims: assess whether technical skills (TS) and radiation safety behaviors (RSB) improved concurrently. DESIGN: Pre-post study. SETTING: UK-based training days. PARTICIPANTS: General and vascular surgical trainees (n = 16). INTERVENTION(S): Fully-immersive simulation training with structured debriefing of a standardized emergency TEVAR scenario. Following standardized emergency TEVAR technical training, trainees led 2 standardized fully-immersive endovascular surgery simulations, with scripted support from a passive surgical team. A non-TS (NTS) structured debrief was delivered following simulations. NTS were assessed using the validated observational teamwork assessment for surgery tool post hoc using video recordings of simulations. TS were assessed through time taken to complete each step of the procedure, as defined during technical training. RSB were assessed through checking for presence of pre-defined actions and the length of time fluoroscopy was used during each simulation. RESULTS: Total observational teamwork assessment for surgery scores improved following structured debrief (p = 0.005, median 52.55/90 vs 73.0/90), alongside all constituent domains - communication (p < 0.001, median 11.7/20 vs 16.6/20), coordination (p < 0.001, median 8.6/15 vs 13.4/15), cooperation (p < 0.001, median 13.15/20 vs 16.35/20), leadership (p < 0.001, median 8.70/15 vs 11.30/15) and monitoring (p < 0.001, median 9.85/20 vs 14.85/20). TS improved; time to complete 12 of 13 procedural steps improved (p < 0.027). Fluoroscopy time (seconds) decreased (p = 0.339, 543.6 vs 495.5), frequency lead surgeons checked the team were wearing leads increased (p = 0.125, 3 vs 7) and asked the team to step back before screening increased (p = 0.003, frequency team asked to step back/total angiography runs before = 2/36 vs after = 14/44). CONCLUSIONS: fully-immersive endovascular simulation with structured debrief is a robust tool to improve NTS and TS. Incorporation into surgical training may reduce operating theatres errors, increase efficiency, and improve RSB. However effective translation into the clinical workplace must be demonstrated to see these benefits.

Combat vascular injury: Influence of mechanism of injury on outcome.

BACKGROUND: Haemorrhage is the leading cause of death on the battlefield. Seventy percent of injuries are due to explosive mechanisms. Anecdotally, these patients have had poorer outcomes when compared to those with penetrating mechanisms of injury (MOI). We wished to test the hypothesis that outcomes following vascular reconstruction were worse in blast-injured than non blast-injured patients. METHODS: Retrospective cohort study. British and American combat casualties with arterial injuries sustained in Iraq or Afghanistan (2003-2014) were identified from the UK Joint Theatre Trauma Registry (JTTR). Eligibility included explosive or penetrating MOI, with follow-up to UK hospital discharge, or death. Outcomes were mortality, amputation, graft thrombosis, haemorrhage, and infection. Statistical analysis was performed using Pearson Chi-Square test, t-tests, ANOVA or non-parametric equivalent, and survival analyses. RESULTS: One hundred and fifteen patients were included, 80 injured by explosive and 35 by penetrating mechanisms. Evacuation time, ISS, number of arterial injuries, age and gender were comparable between groups. Seventy percent of arterial injuries resulted from an explosive MOI. The explosive injuries group received more blood products (p = 0.008) and suffered more regions injured (p < 0.0001). Early surgical interventions in both were ligation (n = 36, 31%), vein graft (n = 33, 29%) and shunting (n = 9, 8%). Mortality (n = 12, 10%) was similar between groups. Differences in limb salvage rates following explosive (n = 17, 53%) vs penetrating (n = 13, 76.47%) mechanisms approached statistical significance (p = 0.056). Nine (28%) vein grafted patients developed complications. No evidence of a difference in the incidence of vein graft thrombosis was found when comparing explosive with non-explosive cohorts (p = 0.154). CONCLUSIONS: The recorded numbers of vein grafts following combat arterial trauma in are small in the JTTR. No statistically-significant differences in complications, including vein graft thrombosis, were found between cohorts injured by explosive and non-explosive mechanisms.

A proposed surgical training pathway for the 21st century.

Numerous problems have been identified with current UK surgical training. These include the balance between generalist and specialist practice, service provision and training time, and work-life balance. This article proposes modifications to the current training pathway. A three-stage training model is discussed using modular training to clearly identify training aims and endpoints and allow flexibility in training and working practices. This will help with workforce planning and work-life balance and support high quality patient-focused surgical training in the 21st century.

Cross-sectional study of the financial cost of training to the surgical trainee in the UK and Ireland.

OBJECTIVES: Applications for surgical training have declined over the last decade, and anecdotally the costs of training at the expense of the surgical trainee are rising. We aimed to quantify the costs surgical trainees are expected to cover for postgraduate training. DESIGN: Prospective, cross-sectional, questionnaire-based study. SETTING/PARTICIPANTS: A non-mandatory online questionnaire for UK-based trainees was distributed nationally. A similar national questionnaire was distributed for Ireland, taking into account differences between the healthcare systems. Only fully completed responses were included. RESULTS: There were 848 and 58 fully completed responses from doctors based in the UK and Ireland, respectively. Medical students in the UK reported a significant increase in debt on graduation by 55% from £17 892 (2000-2004) to £27 655 (2010-2014) (p<0.01). 41% of specialty trainees in the UK indicated that some or all of their study budget was used to fund mandatory regional teaching. By the end of training, a surgical trainee in the UK spends on average £9105 on courses, £5411 on conferences and £4185 on exams, not covered by training budget. Irish trainees report similarly high costs. Most trainees undertake a higher degree during their postgraduate training. The cost of achieving the mandatory requirements for completion of training ranges between £20 000 and £26 000 (dependent on specialty), except oral and maxillofacial surgery, which is considerably higher (£71 431). CONCLUSIONS: Medical students are graduating with significantly larger debt than before. Surgical trainees achieve their educational requirements at substantial personal expenditure. To encourage graduates to pursue and remain in surgical training, urgent action is required to fund the mandatory requirements and annual training costs for completion of training and provide greater transparency to inform doctors of what their postgraduate training costs will be. This is necessary to increase diversity in surgery, reduce debt load and ensure surgery remains a popular career choice.

A Single 9-Colour Flow Cytometric Method to Characterise Major Leukocyte Populations in the Rat: Validation in a Model of LPS-Induced Pulmonary Inflammation.

The rat is a commonly used model for immunological investigation. Yet basic research and characterisation of leukocyte populations and sub-sets lags far behind murine research, with inconsistency on reported leukocyte markers and their overlap. These shortcomings limit the opportunity for more complex and advanced rat immunology research. In this study, we developed a robust 9-colour flow-cytometric protocol to elucidate the major blood and tissue rat leukocyte populations, and validated it in a model of LPS-induced pulmonary inflammation. Blood and tissues (lung, BALF, spleen, liver, bone marrow) from naïve Sprague-Dawley rats were collected and analysed by flow cytometry (FCM). Rats were exposed to aerosolised saline or LPS (1 mg/mL), at 3 and 24 hrs thereafter blood, lung and BALF were collected and analysed using FCM and ELISA. Neutrophils, two monocyte subsets, NK Cells, B Cells, CD4+, CD8+ T Cells and alveolar macrophages can be identified simultaneously across different tissues using a 9-colour panel. Neutrophils and monocytes can be distinguished based upon differential expression of CD43 and His48. Neutrophils and CD43Lo/His48Hi monocyte-macrophages are elevated in the lung at 3 and 24 hrs during LPS-induced pulmonary inflammation. This validated method for leukocyte enumeration will offer a platform for greater consistency in future rat immunology and inflammation research.

CD43Lo classical monocytes participate in the cellular immune response to isolated primary blast lung injury.

BACKGROUND: Understanding of the cellular immune response to primary blast lung injury (PBLI) is limited, with only the neutrophil response well documented. Moreover, its impact on the immune response in distal organs remains poorly understood. In this study, a rodent model of isolated primary blast injury was used to investigate the acute cellular immune response to isolated PBLI in the circulation and lung, including the monocyte response, and investigate distal subacute immune effects in the spleen and liver 6 hours after injury. METHODS: Rats were subjected to a shock wave (~135 kPa overpressure, 2 ms duration) inducing PBLI or sham procedure. Rat physiology was monitored, and at 1, 3, and 6 hours thereafter, blood, lung, and bronchoalveolar lavage fluid (BALF) were collected and analyzed by flow cytometry, enzyme-linked immunosorbent assay, and histologic examination. In addition, at 6 hours, spleen and liver were collected and analyzed by flow cytometry. RESULTS: Lung histology confirmed pulmonary barotrauma and inflammation. This was associated with rises in CXCL-1, interleukin 6 (IL-6), tumor necrosis factor α and albumin protein in the BALF. Significant acute increases in blood and lung neutrophils and CD43Lo/His48Hi (classical) monocytes/macrophages were detected. No significant changes were seen in blood or lung "nonclassical" monocyte and in natural killler, B, or T cells. In the BALF, significant increases were seen in neutrophils, CD43Lo monocyte-macrophages and monocyte chemoattractant protein-1. Significant increases in CD43Lo and Hi monocyte-macrophages were detected in the spleen at 6 hours. CONCLUSION: This study reveals a robust and selective response of CD43Lo/His48Hi (classical) monocytes, in addition to neutrophils, in blood and lung tissue following PBLI. An increase in monocyte-macrophages was also observed in the spleen at 6 hours. This profile of immune cells in the blood and BALF could present a new research tool for translational studies seeking to monitor, assess, or attenuate the immune response in blast-injured patients.

Prolonged but not short-duration blast waves elicit acute inflammation in a rodent model of primary blast limb trauma.

BACKGROUND: Blast injuries from conventional and improvised explosive devices account for 75% of injuries from current conflicts; over 70% of injuries involve the limbs. Variable duration and magnitude of blast wave loading occurs in real-life explosions and is hypothesised to cause different injuries. While a number of in vivo models report the inflammatory response to blast injuries, the extent of this response has not been investigated with respect to the duration of the primary blast wave. The relevance is that explosions in open air are of short duration compared to those in confined spaces. METHODS: Hindlimbs of adult Sprauge-Dawley rats were subjected to focal isolated primary blast waves of varying overpressure (1.8-3.65kPa) and duration (3.0-11.5ms), utilising a shock tube and purpose-built experimental rig. Rats were monitored during and after the blast. At 6 and 24h after exposure, blood, lungs, liver and muscle tissues were collected and prepared for histology and flow cytometry. RESULTS: At 6h, increases in circulating neutrophils and CD43Lo/His48Hi monocytes were observed in rats subjected to longer-duration blast waves. This was accompanied by increases in circulating pro-inflammatory chemo/cytokines KC and IL-6. No changes were observed with shorter-duration blast waves irrespective of overpressure. In all cases, no histological damage was observed in muscle, lung or liver. By 24h post-blast, all inflammatory parameters had normalised. CONCLUSIONS: We report the development of a rodent model of primary blast limb trauma that is the first to highlight an important role played by blast wave duration and magnitude in initiating acute inflammatory response following limb injury in the absence of limb fracture or penetrating trauma. The combined biological and mechanical method developed can be used to further understand the complex effects of blast waves in a range of different tissues and organs in vivo.