Thomas Lawrence

The association between admission systolic blood pressure and mortality in significant traumatic brain injury: A multi-centre cohort study

INTRODUCTION Low systolic blood pressure (SBP) is an important secondary insult following traumatic brain injury (TBI), but its exact relationship with outcome is not well characterised. Although a SBP of <90 mmHg represents the threshold for hypotension in consensus TBI treatment guidelines, recent studies suggest redefining hypotension at higher levels. This study therefore aimed to fully characterise the association between admission SBP and mortality to further inform resuscitation endpoints. METHODS We conducted a multicentre cohort study using data from the largest European trauma registry. Consecutive adult patients with AIS head scores >2 admitted directly to specialist neuroscience centres between 2005 and July 2012 were studied. Multilevel logistic regression models were developed to examine the association between admission SBP and 30 day inpatient mortality. Models were adjusted for confounders including age, severity of injury, and to account for differential quality of hospital care. RESULTS 5057 patients were included in complete case analyses. Admission SBP demonstrated a smooth u-shaped association with outcome in a bivariate analysis, with increasing mortality at both lower and higher values, and no evidence of any threshold effect. Adjusting for confounding slightly attenuated the association between mortality and SBP at levels <120 mmHg, and abolished the relationship for higher SBP values. Case-mix adjusted odds of death were 1.5 times greater at <120 mmHg, doubled at <100 mmHg, tripled at <90 mmHg, and six times greater at SBP<70 mmHg, p<0.01. CONCLUSIONS These findings indicate that TBI studies should model SBP as a continuous variable and may suggest that current TBI treatment guidelines, using a cut-off for hypotension at SBP<90 mmHg, should be reconsidered.

Resuscitative endovascular balloon occlusion of the aorta (REBOA): a population based gap analysis of trauma patients in England and Wales

Introduction Non-compressible torso haemorrhage (NCTH) carries a high mortality in trauma as many patients exsanguinate prior to definitive haemorrhage control. Resuscitative endovascular balloon occlusion of the aorta (REBOA) is an adjunct that has the potential to bridge patients to definitive haemostasis. However, the proportion of trauma patients in whom REBOA may be utilised is unknown. Methods We conducted a population based analysis of 2012–2013 Trauma Audit and Research Network (TARN) data. We identified the number of patients in whom REBOA may have been utilised, defined by an Abbreviated Injury Scale score ≥3 to abdominal solid organs, abdominal or pelvic vasculature, pelvic fracture with ring disruption or proximal traumatic lower limb amputation, together with a systolic blood pressure <90 mm Hg. Patients with non-compressible haemorrhage in the mediastinum, axilla, face or neck were excluded. Results During 2012–2013, 72 677 adult trauma patients admitted to hospitals in England and Wales were identified. 397 patients had an indication(s) and no contraindications for REBOA with evidence of haemorrhagic shock: 69% men, median age 43 years and median Injury Severity Score 32. Overall mortality was 32%. Major trauma centres (MTCs) received the highest concentration of potential REBOA patients, and would be anticipated to receive a patient in whom REBOA may be utilised every 95 days, increasing to every 46 days in the 10 MTCs with the highest attendance of this injury type. Conclusions This TARN database analysis has identified a small group of severely injured, resource intensive patients with a highly lethal injury that is theoretically amenable to REBOA. The highest density of these patients is seen at MTCs, and as such a planned evaluation of REBOA should be further considered in these hospitals.

A profile of suspected child abuse as a subgroup of major trauma patients

Introduction Non-accidental injury (NAI) in children is an important cause of major injury. The Trauma Audit Research Network (TARN) recently analysed data on the demographics of paediatric trauma and highlighted NAI as a major cause of death and severe injury in children. This paper examined TARN data to characterise accidental versus abusive cases of major injury. Methods The national trauma registry of England and Wales (TARN) database was interrogated for the classification of mechanism of injury in children by intent, from January 2004 to December 2013. Contributing hospitals’ submissions were classified into accidental injury (AI), suspected child abuse (SCA) or alleged assault (AA) to enable demographic and injury comparisons. Results In the study population of 14 845 children, 13 708 (92.3%, CI 91.9% to 92.8%) were classified as accidental injury, 368 as alleged assault (2.5%, CI 2.2% to 2.7%) and 769 as SCA (5.2%, CI 4.8% to 5.5%). Nearly all cases of severely injured children suffering trauma because of SCA occurred in the age group of 0–5 years (751 of 769, 97.7%), with 76.3% occurring in infants under the age of 1 year. Compared with accidental injury, suspected victims of abuse have higher overall injury severity scores, have a higher proportion of head injury and a threefold higher mortality rate of 7.6% (CI 5.51% to 9.68%) vs 2.6% (CI 2.3% to 2.9%). Conclusions This study highlights that major injury occurring as a result of SCA has a typical demographic pattern. These children tend to be under 12 months of age, with more severe injury. Understanding these demographics could help receiving hospitals identify children with major injuries resulting from abuse and ensure swift transfer to specialist care.

The accuracy of existing prehospital triage tools for injured children in England--an analysis using trauma registry data.

Objectives To investigate the performance characteristics of prehospital paediatric triage tools for identifying seriously injured children in England. Design Eight prehospital paediatric triage tools were identified by literature review and by survey of the Lead Trauma Clinicians across English Strategic Health Authorities. Retrospective clinical registry data from the Trauma Audit and Research Network were used to determine the performance characteristics of each tool, using ‘gold standards’ for under- and over-triage of <5% and <25–50%, respectively, as benchmarks for performance. Participants 701 patient records were included. Inclusion criteria were all injured patients aged <16 years admitted to a receiving unit direct from the scene of accident in the period 2007–2010, for whom all key discriminator fields were recorded in the Trauma Audit and Research Network database. Outcome measures The main outcome measure was how each tool functioned with regard to their under- and over-triaging features. Other performance characteristics, for example, predictive values and likelihood ratios were also calculated. Results Two (of eight) triage tools demonstrated acceptable under-triage rates (3% and 4%) but had unacceptably high over-triage rates (83% and 72%). Two tools demonstrated acceptable over-triage rates (7% and 16%), but with unacceptably high under-triage rates (61% and 63%). Four tools had unacceptably high under- and over-triage rates. Conclusions None of the prehospital triage tools currently used or being developed in England meet recommended criteria for over- and under-triage rates. There is an urgent need for the development of triage tools to accurately risk-stratify injured children in the prehospital setting.

Prediction modelling for trauma using comorbidity and ‘true’ 30-day outcome

Background Prediction models for trauma outcome routinely control for age but there is uncertainty about the need to control for comorbidity and whether the two interact. This paper describes recent revisions to the Trauma Audit and Research Network (TARN) risk adjustment model designed to take account of age and comorbidities. In addition linkage between TARN and the Office of National Statistics (ONS) database allows patients outcome to be accurately identified up to 30 days after injury. Outcome at discharge within 30 days was previously used. Methods Prospectively collected data between 2010 and 2013 from the TARN database were analysed. The data for modelling consisted of 129 786 hospital trauma admissions. Three models were compared using the area under the receiver operating curve (AuROC) for assessing the ability of the models to predict outcome, the Akaike information criteria to measure the quality between models and test for goodness-of-fit and calibration. Model 1 is the current TARN model, Model 2 is Model 1 augmented by a modified Charlson comorbidity index and Model 3 is Model 2 with ONS data on 30 day outcome. Results The values of the AuROC curve for Model 1 were 0.896 (95% CI 0.893 to 0.899), for Model 2 were 0.904 (0.900 to 0.907) and for Model 3 0.897 (0.896 to 0.902). No significant interaction was found between age and comorbidity in Model 2 or in Model 3. Conclusions The new model includes comorbidity and this has improved outcome prediction. There was no interaction between age and comorbidity, suggesting that both independently increase vulnerability to mortality after injury.

Traumatic brain injury in England and Wales: prospective audit of epidemiology, complications and standardised mortality

Objectives To provide a comprehensive assessment of the management of traumatic brain injury (TBI) relating to epidemiology, complications and standardised mortality across specialist units. Design The Trauma Audit and Research Network collects data prospectively on patients suffering trauma across England and Wales. We analysed all data collected on patients with TBI between April 2014 and June 2015. Setting Data were collected on patients presenting to emergency departments across 187 hospitals including 26 with specialist neurosurgical services, incorporating factors previously identified in the Ps14 multivariate logistic regression (Ps14n) model multivariate TBI outcome prediction model. The frequency and timing of secondary transfer to neurosurgical centres was assessed. Results We identified 15 820 patients with TBI presenting to neurosurgical centres directly (6258), transferred from a district hospital to a neurosurgical centre (3682) and remaining in a district general hospital (5880). The commonest mechanisms of injury were falls in the elderly and road traffic collisions in the young, which were more likely to present in coma. In severe TBI (Glasgow Coma Score (GCS) ≤8), the median time from admission to imaging with CT scan is 0.5 hours. Median time to craniotomy from admission is 2.6 hours and median time to intracranial pressure monitoring is 3 hours. The most frequently documented complication of severe TBI is bronchopneumonia in 5% of patients. Risk-adjusted W scores derived from the Ps14n model indicate that no neurosurgical unit fell outside the 3 SD limits on a funnel plot. Conclusions We provide the first comprehensive report of the management of TBI in England and Wales, including data from all neurosurgical units. These data provide transparency and suggests equity of access to high-quality TBI management provided in England and Wales.

The accuracy of alternative triage rules for identification of significant traumatic brain injury: a diagnostic cohort study

Introduction Traumatic brain injury (TBI) is a leading cause of death and disability in young adults. Reorganisation of trauma services with direct triage of suspected head injury patients to trauma centres may improve outcomes following TBI. This study aimed to determine the sensitivity of principal English triage tools for identifying significant TBI. Methods We performed a diagnostic cohort study using data prospectively collated from the Trauma Audit and Research Network database between 2005 and 2011. Adult head injury patients were retrospectively classified according to London Ambulance Service (LAS) and Head Injury Transportation Straight to Neurosurgery study (HITS-NS) triage criteria. Sensitivity and specificity were then calculated against a reference standard of significant TBI, comprising head region abbreviated injury score (AIS) ≥3 or neurosurgical operation. Results 6559 patients were included in complete case analyses. The LAS and HITS-NS triage tools demonstrated sensitivities of 44.5% (95% CI 43.2 to 45.9) and 32.6% (95% CI 31.4 to 33.9), respectively, for identifying significant TBI patients. False negative significant TBI cases were relatively older, more likely to be female, more frequently secondary to low-level falls, and were less likely to have very severe AIS five or six head injuries, p<0.01. Conclusions A considerable proportion of significant head injury patients may not be triaged directly to trauma centres. Investment is therefore necessary to improve the accuracy of existing triage rules and maintain expertise in TBI diagnosis and management in non-specialist emergency departments.

The diagnostic accuracy of the HITSNS prehospital triage rule for identifying patients with significant traumatic brain injury: a cohort study.

Diversion of suspected traumatic brain injury (TBI) patients to trauma centres may improve outcomes by expediting access to specialist neurosurgical care. This study aimed to determine the accuracy of the Head Injury Straight to Neurosurgery (HITSNS) triage rule for identifying patients with significant TBI. A diagnostic cohort study was performed using data from the HITSNS trial, the Trauma Audit and Research Network registry and the North East Ambulance service database. Sensitivity and specificity of the HITSNS triage rule were calculated against a reference standard of significant TBI, defined by a cranial Abbreviated Injury Scale score of at least 3 or by the performance of a neurosurgical procedure. A total of 3628 patients were included in the complete case analyses. The HITSNS triage tool demonstrated a sensitivity of 28.3% (95% confidence interval 21.8–35.4) and a specificity of 94.4% (95% confidence interval 93.6–95.2). The low sensitivity of the HITSNS triage rule suggests that a considerable proportion of patients with significant TBI may not be triaged directly to trauma centres, and further research is needed to improve the accuracy of bypass protocols.

Do Prolonged Primary Transport Times for Traumatic Brain Injury Patients Result in Deteriorating Physiology? A Cohort Study

Abstract Background. Recent interest has focused on reorganizing emergency medical services (EMS) for traumatic brain injury (TBI) patients, with bypass of nonspecialist hospitals and direct transportation to distant neuroscience centers. Although this could expedite neurosurgery and neurocritical care, deteriorating physiology could be deleterious. Methods. We performed a multicenter cohort study examining adult patients with significant TBI enrolled in the English National Trauma Registry. The distributions and correlation of first recorded prehospital and emergency department (ED) vital signs were compared, and the effect of time on changes in vital signs was examined in bivariate and multivariate analyses. Results. A total of 7149 eligible patients were studied. No clinically significant differences were apparent between distributions of prehospital and ED vital signs. Moderate linear correlation was observed for field and ED pulse rate (r2 = 0.34) and GCS values (Spearmans rho = 0.76), with weak correlation apparent for systolic blood pressure (r2 = 0.28) and respiratory rate (r2 = 0.28). Eight percent of cases’ vital signs deteriorated in the prehospital interval; however, odds of deterioration in vital sign status did not vary significantly with duration of EMS interval. Conclusion. The similarity between prehospital and ED vital signs, and lack of association between EMS interval and physiological deterioration, may support a strategy of direct transportation of TBI cases to specialist centers. Further research is necessary to identify patients at risk from deterioration during bypass and to investigate effects on mortality.

Emergency medical services interval and mortality in significant head injury: a retrospective cohort study

Objectives Recent interest has focused on reorganizing emergency medical services (EMS) for English traumatic brain injury (TBI) patients, with bypass of nonspecialist hospitals and direct transportation to distant neuroscience centres. This may expedite specialist neurocritical care and neurosurgical interventions, but risks harms from prehospital deterioration and delayed resuscitation. We therefore aimed to investigate the effect of EMS interval on outcome following head injury. Methods We performed a multicentre cohort study examining adult patients with significant TBI (head region abbreviated injury scale ≥3) enrolled in the Trauma Audit and Research Network trauma registry between 2005 and 2011. The association between EMS interval and mortality in patients directly admitted to specialist neuroscience centres was explored using bivariate and multivariate logistic regression and propensity score matching analyses. Results In all, 7149 eligible patients presented directly to specialist neuroscience centres during the study period. Adjusted odds ratios for mortality showed no association between EMS interval and mortality, varying from 0.46 (95% confidence interval 0.1–2.6) for EMS intervals under 20 min to 0.67 (95% confidence interval 0.4–1.2) for EMS intervals more than 120 min (reference EMS interval 40–60 min). This lack of association was also observed following matching using propensity scores, with no significant difference apparent in mortality between EMS intervals less than 60 min and more than 60 min (17.85 vs. 17.0%, P=0.826). These results were unaffected in sensitivity analyses examining missing covariate data or unmeasured outcomes. Conclusion The lack of observed association between EMS interval and mortality may not preclude bypass of significant TBI patients, with concomitantly prolonged primary transfers from the scene of injury to distant specialist centres. However, given the limitations of registry data, our results should be interpreted with caution.