Determinants of hospital costs associated with traumatic brain injury in England and Wales*

Transcription

1 Anaesthesia, 2008, 63, pages doi: /j x Determinants of hospital costs associated with traumatic brain injury in England and Wales* S. Morris, 1 S. Ridley, 2 F. E. Lecky, 3 V. Munro 4 and M. C. Christensen 5 1 Health Economics Research Group, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK 2 Glan Clwyd Hospital, Rhyl, Denbighshire, LL18 5UJ, UK 3 Trauma Audit and Research Network, University of Manchester, Eccles Old Road, Salford M6 8HD, UK 4 Novo Nordisk Ltd, Broadfield Park, Brighton Road, Crawley, West Sussex RH11 9RT, UK 5 Global Development, Novo Nordisk A S, Krogshøjvej 55, DK-2880 Bagsværd, Denmark Summary Using data from the Trauma Audit Research Network, we investigated the costs of acute care in patients 18 years of age hospitalised for traumatic brain injury between January 2000 and December 2005 in England and Wales. Traumatic brain injury patients were defined and stratified using the Abbreviated Injury Scale. A total of 6484 traumatic brain injury patients were identified; 22.3% had an Abbreviated Injury Scale score of three, 38.0% of four and 39.7% of five. Median age (IQR) was 42 years (28 59) and 76.7% were men. Primary cause of injury was motor vehicle collisions (42.4%) followed by falls (38.0%). In total 23.7% of the patients died before discharge. Hospitalisation costs averaged (SD ). Costs varied significantly by age, Glasgow Coma Score, Injury Severity Score, coexisting injuries of the thorax, spine and lower limb, hospital mortality, availability of neurosurgical services, and specialty of attendants seen in the Accident and Emergency department.... Correspondence to: Dr Stephen Morris stephen.morris@brunel.ac.uk *Presented in part at the European Association for Trauma and Emergency Surgery European Trauma Society Congress, Graz, May Accepted: 4 December 2007 At least one million patients present in hospitals in the United Kingdom (UK) each year with head injuries, representing 10% of all patients attending Accident and Emergency (A&E) departments [1]. About 90% of these patients have minor or mild head injuries, with the remainder having moderate to severe head injuries. Approximately 20% require admission for observation but fewer than 5% are transferred to specialised neurosurgical care. About one third of all adult patients admitted to an intensive care unit (ICU) for head injury die while in hospital [2]. Despite the clinical importance of head injury current treatment patterns for severe injuries are not well described in the literature. Furthermore, the costs of treatment for severe head injury have not been examined. A recent study from the Intensive Care National Audit and Research Centre (ICNARC) examined the case mix and outcome among patients admitted to the ICU with head injuries between 1995 and 2005 in the UK [2]. Mortality in the ICU was 23%, while total hospital mortality was 33.5%. The Trauma Audit and Research Network (TARN) recently compared hospitalised trauma patients with and without significant head injury and demonstrated a 10-fold higher mortality rate within the head injury cohort [3]. One-third of those with head injuries were not treated in neurosurgical centres, which was associated with a 2.15-fold increase in the odds of death. While a significant reduction in case fatality after head trauma was observed between 1989 and 2003, most of the reduction seems to have occurred before These findings are supported by results from an earlier nationally representative study on acute survival after blunt trauma from 1989 to 2000 [4]. In light of these findings, it has been recommended that public health efforts in trauma care are focussed on improving the treatment of severe head injury as this Journal compilation Ó 2008 The Association of Anaesthetists of Great Britain and Ireland 499

2 S. Morris et al. Æ Cost of TBI Anaesthesia, 2008, 63, pages appears to be the best strategy for further reduction in case fatality among hospitalised blunt trauma patients [3]. In particular, it has been recommended that neurosurgical and neurocritical care interventions play a key role in such health care improvement. The National Institute for Health and Clinical Excellence (NICE) recently published a clinical guideline on the early management of head injury [5]. The guideline covers optimal pre-hospital care including assessment, airway management and ventilation, cervical spine protection and appropriate transfer, indications for referral to hospital from pre-hospital care, secondary care with the aim of early detection of intracranial complications and appropriate transfers to neurosurgical units. The guideline is currently under revision to further update recommendations regarding pre-hospital management, selection of patients for computerised tomography (CT) scanning, pain management and use of neuroscience units. The NICE guideline follows an earlier report by the Royal College of Surgeons recommending that all patients with severe head injuries are treated in a neurosurgical centre [6]. The aims of this study were to estimate the hospital costs associated with traumatic brain injury (TBI) in England and Wales and to identify their most important predictors. The analysis will be useful for evaluating how current treatment adheres to proposed clinical guidelines and for guiding decision-makers towards an optimal use of health care resources. Methods Data source and variables Data for this study were taken from the Trauma Audit Research Network (TARN). Data from TARN have been used in a number of studies investigating, inter alia, trends in trauma care [4], the effect of neurosurgical care on head injury outcome [3], and outcome prediction in trauma [7]. This is the first study to use this dataset to investigate the acute treatment costs of TBI. TARN includes data from 50% of all hospitals receiving trauma patients in England and Wales. It collects data from participating hospitals on patients who sustain injuries resulting in immediate admission to hospital for 3 days, admission to ICU or high dependency unit (HDU), or death within 93 days. Data for the study were obtained from the TARN database. The authors did not have access to individual patient records. TARN is supported by the Healthcare Commission. Specific informed patient consent or ethical approval is not required because no patient identifiers are retained by TARN either electronically or on paper. TARN has Section 60 Patient Information Advisory Group approval. As this study involves the secondary analysis of TARN and other published data, ethical approval was not sought. We included all patients hospitalised for TBI in TARN hospitals between 1 January 2000 and 31 December Hospitals completed a data entry sheet for each patient with information on age, gender, cause and type of injuries, severity of the injuries, treatment provided at the scene of accident, en route to hospital or in A&E, and any other care received at the hospital, including diagnostic tests, surgical procedures and length of stay (LOS). TARN classifies injuries according to the 1998 revision of the Abbreviated Injury Scale (AIS), which has been widely adopted for use in studies of acute injury, including TBI [6]. TBI was defined using six-digit AIS codes beginning 14****. Each AIS injury code is allocated an AIS score ranging from one (minor injury) to six (virtually unsurvivable injury). In our study, severity of TBI was assessed for each subject by calculating the maximum AIS score of any brain injuryrelated diagnosis recorded for that patient during hospitalisation. In addition, we utilised data on gender, age, mechanism of injury, earliest recorded Glasgow Coma Score (GCS), Injury Severity Score (ISS), co-existing injuries with an AIS score of three or more by body region, discharge status and year of admission. We also report data on the specific treatment provided, including mode of arrival at A&E, time from emergency call to arrival at A&E, time spent in A&E, grade of doctor seen in A&E, specialty of doctors seen in A&E, diagnostic tests performed, TBI-related surgical interventions, admission to critical care (ICU, neurocritical units or HDU), LOS in critical care and total LOS. Finally, we used data on whether or not the treating hospital had a neurosurgical unit. We excluded from the analysis patients younger than 18 years of age at the time of injury. Measuring costs Treatment costs were estimated from the perspective of the National Health Service (NHS) in England and Wales and restricted to those for TBI. We calculated treatment costs for each patient based on the following components: transportation to the hospital, hospital stay (A&E, critical care, regular ward), and TBI-related surgical procedures. Resource use for every component was measured for each TBI patient in the TARN database. Other treatment costs were included where a clear distinction between TBI-related care and unrelated care could not be made, e.g. mode of transportation to the hospital with more than one injury. We then assigned unit costs from external sources to each item (see the Appendix for further details on the data used and methodology applied). 500 Journal compilation Ó 2008 The Association of Anaesthetists of Great Britain and Ireland

3 Anaesthesia, 2008, 63, pages S. Morris et al. Æ Cost of TBI Data analysis We examined the study population and treatment patterns stratified by AIS score. We estimated treatment costs per patient and calculated mean treatment costs by patient characteristics, treatment patterns and AIS score. We also undertook multivariate analyses of treatment costs using regression analysis to identify important predictors of costs. We estimated a full model including the full range of subject characteristics and treatment variables, and a reduced model including only those variables that had a statistically significant association with costs. These variables were identified using forwards stepwise and backwards stepwise selection procedures where the significance level for removal from the model was p 0.01, and significance level for addition was p < Robust standard errors were used to control for clustering within individuals. The models were estimated using least squares and the coefficients are marginal effects. Some of the data collected by TARN and used in the analysis are missing in a number of patients. The main variables where this occurs are the time from emergency call to arrival at A&E, whether or not the patient had a CT scan, and whether or not they had surgical procedures. The first item is available for patients who travelled to hospital by ambulance. The last item may be missing because the relevant section on the data entry sheet is completed by free text and may have been left blank. We report the numbers of observations used to calculate every statistic reported. When we calculated the acute care costs for each patient we only did so using patients with complete data. If data for one or more of the cost components were missing for a patient then we assigned a missing code to the total costs incurred by that patient and did not include the patient in the cost calculation. Results Sample characteristics We identified 6484 patients with TBI in the study period. Head injuries with AIS scores of one or two do not include brain injury; all TBI patients have an AIS score of three or more. Hence patients with an AIS score of one or two did not meet the study inclusion criteria. Only 10 patients with an AIS score of six were identified, and were as a consequence excluded from further analysis. Of the remaining 6474 patients, 1441 (22.3%) had an AIS score of three (serious TBI), 2460 (38.0%) an AIS score of four (severe TBI) and 2573 (39.7%) an AIS score of five (critical TBI). The patients demographic and clinical characteristics are detailed in Table 1. Seventy-seven percent of the Table 1 Sample characteristics of patients hospitalised for TBI, by severity. TBI AIS score All Total number Male; % Age; years Median (IQR) 38 (26 55) 42 (29 60) 43 (29 60) 42 (28 59) Cause of injury; % Vehicle incident collision Fall more than 2 m Fall less than 2 m Blow(s) Other Glasgow Coma Score Median (IQR) 12 (7 15) 12 (6 14) 7 (3 13) 10 (5 14) n Injury Severity Score Median (IQR) 14 (10 25) 17 (16 25) 26 (25 35) 25 (17 29) n Coexisting injuries by body region; %* Head (excluding TBI) or face Thorax Abdomen Spine Upper or lower limb Any Alive at hospital discharge; % The sample size is equal to the total number other than where indicated by n. *Injuries with an AIS score of 3 or more. TBI, traumatic brain injury. Journal compilation Ó 2008 The Association of Anaesthetists of Great Britain and Ireland 501

4 S. Morris et al. Æ Cost of TBI Anaesthesia, 2008, 63, pages subjects were male, and the median age (IQR) was 42 years (28 59). There was little variation in age and gender by AIS score. The predominant cause of injury was motor vehicle collisions (42.4%), followed by falls (38.0%) and blows (12.7%). Median (IQR) GCS was 10 (5 14) and median (IQR) ISS was 25 (17 29). The most frequent co-existing injuries with an AIS score of three or more were other injuries to the head (excluding TBI) or face (36.9%), thoracic injuries (20.8%) and injuries to the upper or lower limbs (17.2%). Twenty-four percent of patients died in hospital, with the highest proportion of deaths in the group with an AIS score of five (37.7%). Among those who died, the mean (SD) time to death was 6.4 days (15.8) from the date of arrival at the hospital. It was 6.3 days (10.6) for patients with an AIS score of 3, 10.8 days (25.4) for those with an AIS score of 4, and 4.8 days (10.9) for those with an AIS score of 5. There was a reasonably uniform distribution of patients in each year over the 6-year study period: the percentage of the total sample from each year ranged from 14.1% in 2005 to 20.6% in Management patterns Treatments received while in hospital are shown in Table 2. Eighty-six percent and 11% of patients arrived at the hospital by ambulance and helicopter, respectively. Helicopter transport is usually reserved for the most seriously injured patients, which includes those with TBI. TARN includes London s Air Ambulance Service, which covers all TBI patients in London. The median (IQR) time from emergency call to arrival at A&E by ambulance was 48 min (34 78), and the median (IQR) time in A&E was 70 min (0 209). Forty-two percent of patients had missing data on whether or not they had a CT scan for their head injury. Among those with a documented CT scan, 70% of these had the scan within 2 h of arrival at A&E. Twenty-nine percent of patients had TBI related surgery; the most common surgical procedures were evacuation of epidural haematoma subdural haematoma (EDH SDH) (13.5%) craniotomy (9.3%), and intracranial pressure monitoring (9.2%). Each of these procedures was more common in patients with more severe TBI. Approximately two-thirds of patients were admitted to critical care, with a median (IQR) LOS of 5 days (2 13). The median (IQR) total hospital LOS was 11 days (5 27). Patients with an AIS score of five were more likely to be admitted to critical care than less severely injured patients, but the length of stay in critical care among those who were admitted, and total length of stay was similar across the different AIS groups. Around 70% of all TBI patients were taken or transferred to a hospital with on site neurosurgery. The proportion of patients treated in a hospital with these facilities who died in the hospital was 0.227, compared with for patients treated in a hospital without these facilities (mean difference 0.033, standard error (SE) 0.012, 95% confidence interval (CI) , p = 0.005). Twenty-five percent of patients saw a consultant in A&E and around 60% saw a middle grade doctor (defined as senior registrar, registrar, specialist registrar with up to 5 years of experience, staff grade, associate specialist and research fellow). Over 50% of TBI patients were seen by a doctor with a speciality in emergency medicine; specialists in neurosurgery, anaesthesia, orthopaedics and general surgery were also common. Treatment costs The mean total cost per patient was (SD ) (Table 3). Mean costs per patient were highest in those with an AIS score of five. Length of stay in critical care accounted for 51% of mean total costs. The next most important component was length of stay on a regular ward (38%), followed by travel costs to the A&E department (5%) and TBI related surgery (4%). These proportions were similar for every AIS group. Across age groups, patients aged years incurred the highest costs. This was due to the longer mean stay in critical care and the longer mean total length of stay in this age group. There was little variation in costs by gender. Across mechanism of injury and severity of injury, costs were highest among those injured in motor vehicle collisions, those with a lower GCS (3 8) and those with a higher ISS (35 75). The higher costs for motor vehicle collisions were due to the more severe injuries sustained in this group (median GCS and ISS were 8 and 26 compared to 12 and 24 among those injured in other ways). Co-existing injuries had a positive effect on treatment costs, especially injuries to the neck, thorax, abdomen and spine, while mortality had a negative effect on costs. Costs also varied substantially by mode of arrival to the hospital, by time from emergency call to arrival at A&E (this was positively correlated with costs) (Table 4). Injuries requiring surgical interventions were generally associated with higher treatment costs. Notable exceptions were burrhole of the cranium and repair of dura, which were associated with lower costs due to less severe injuries among patients undergoing these procedures (median GCS and ISS were 14 and 25 for burrhole of cranium and 14 and 17 for repair of dura, compared with values of 10 and 25 for the whole sample). As expected, costs were positively correlated with longer lengths of stay in critical care and overall LOS. Mean treatment costs for TBI in hospitals with neurosurgical units were higher than in hospitals without neurosurgical units. 502 Journal compilation Ó 2008 The Association of Anaesthetists of Great Britain and Ireland

5 Anaesthesia, 2008, 63, pages S. Morris et al. Æ Cost of TBI Table 2 Treatment patterns for patients hospitalised for TBI, by severity. TBI AIS score All Mode of arrival; % Ambulance Helicopter Car Aircraft Walking n Time from emergency call to arrival at A&E; min* Median (IQR) 47 (33 75) 47 (34 73) 51 (35 89) 48 (34 78) n Time in A&E; min Median (IQR) 106 (0 229) 65 (0 222) 54 (0 183) 70 (0 209) n Time to CT scan after arrival at Emergency Department; min Median (IQR) 70 (47 119) 76 (47 128) 72 (46 106) 74 (47 117) n TBI-related surgery; % Evacuation of EDH SDH Craniotomy Intracranial pressure monitor Elevation of depressed fracture of cranium Burrhole of cranium Drainage of EDH SDH Any TBI-related surgery n Admitted to critical care; % n LOS in critical care; days Median (IQR) 5 (2 11) 6 (2 13) 6 (2 13) 5 (2 13) n Total length of stay; days Median (IQR) 12 (6 28) 11 (5 26) 10 (4 27) 11 (5 27) n Hospital has a neurosurgical centre; % Grade of most senior doctor seen in A&E; % Consultant Middle grade SHO n Specialty of doctors seen in A&E; % Emergency medicine Neurosurgery Anaesthesia Orthopaedics Other *Among those arriving by ambulance. Among those having a CT scan. The figures pertain only to those patients who were admitted to critical care. Including LOS in critical care. The figures pertain both to those who were admitted to critical care and those who were not. Among those with an ISS > 15. TBI, traumatic brain injury; AIS, Abbreviated Injury Scale; A&E, Accident and Emergency; CT, computerised tomography; EDH SDH, epidural haematoma subdural haematoma; LOS, length of stay. Mean treatment costs were higher if the patient was seen by a consultant, and if the patient was seen by a doctor from the specialties of anaesthesia, orthopaedics and general surgery. Note that the unit costs used in the analysis (see Appendix) did not vary by the grade or specialty of the doctors seen in A&E. Therefore, the variation in costs by doctor is a function of variations in surgery and length of stay, which in turn is affected by injury severity. Patients with missing cost data had similar severity of injuries to those with non-missing cost data (median (IQR) ISS 25 (17 29) versus 25 (17 29)). Journal compilation Ó 2008 The Association of Anaesthetists of Great Britain and Ireland 503

6 S. Morris et al. Æ Cost of TBI Anaesthesia, 2008, 63, pages Table 3 Mean treatment costs for patients hospitalised for TBI, by severity and demographic and clinical characteristics. TBI AIS score All Total cost; Mean (SD) (16 725) (16 896) (16 815) (16 844) Median (IQR) 8330 ( ) 7551 ( ) 9997 ( ) 8735 ( ) n Mean total cost; By gender Male Female By age group years years years years years By cause of injury Vehicle incident collision Fall more than 2 m Fall less than 2 m Blow(s) Other By Injury Severity Score group Coexisting injuries by body region* Neck Thorax Abdomen Spine Upper limb Lower limb Any By discharge status Alive Dead *Injuries with an AIS score of 3 or more. TBI, traumatic brain injury; AIS, Abbreviated Injury Scale. Multivariate analysis The results of the multivariate analysis are in Table 5. In the reduced model, the statistically significant cost drivers were age (those between 65 and 74 years incurred the highest cost), GCS (a lower level of consciousness was positively correlated with costs), ISS (greater severity had a positive impact on costs), co-existing injuries with an AIS score of three or more of the thorax, spine and lower limb (all of which were positively correlated with costs), and mortality (negatively correlated). Treatment costs were significantly lower in Being treated in a hospital with a neurosurgical centre had a positive impact on treatment cost, and being seen in A&E by a doctor from the specialties of anaesthesia or general surgery was also associated with higher in treatment costs. Conditional on these variables, the other patient and treatment characteristics were not statistically significant predictors of total hospital costs. Discussion This study provides a detailed description of the demographic and clinical characteristics of TBI patients in England and Wales, their causes of injury, acute treatment provided, and outcomes observed. It focuses specifically on NHS hospital costs and is the first study to provide a detailed assessment of the NHS hospital costs associated with TBI in England and Wales. The typical TBI patient was male, 45 years old, involved in a motor vehicle accident, with a moderate head injury (GCS 10) and polytraumatised (ISS 25). The most frequent co-existing injuries were other head injury, thoracic injury and 504 Journal compilation Ó 2008 The Association of Anaesthetists of Great Britain and Ireland

7 Anaesthesia, 2008, 63, pages S. Morris et al. Æ Cost of TBI Table 4 Mean treatment costs, by treatment patterns. TBI AIS score Mean total cost; By mode of arrival Ambulance Helicopter Car Walking By time from emergency call to arrival at A&E; h* By TBI-related surgery Evacuation of EDH SDH Craniotomy Intracranial pressure monitoring Burrhole of cranium Drainage of EDH SDH Any TBI-related surgery By LOS in critical care; days By total length of stay; days By whether hospital has a neurosurgical centre No Yes By grade of most senior doctor seen in A&E Consultant Middle grade SHO By specialty of doctors seen in A&E Emergency medicine Neurosurgery Anaesthesia Orthopaedics General surgery Other *Among those arriving by ambulance. Including LOS in critical care. The figures pertain both to those who were admitted to critical care and those who were not. AIS, Abbreviated Injury Scale; A&E, Accident and Emergency; TBI, traumatic brain injury; EDH SDH, epidural haematoma subdural haematoma; LOS, length of stay. damage to the upper and lower limbs. About 70% of all TBI patients were admitted to critical care for median LOS of 5 days. Median total LOS was 11 days and 23.0% of the patients died before hospital discharge. The mean cost of acute treatment to the NHS was per patient. All The observed mortality among TBI patients across the 6-year period of our study was 23.7%. It fell from 28.8% in 2000, to 23.3% in 2001, 25.2% in 2002, 22.8% in 2003, 21.5% in 2004 and 21.1% in 2005 (after controlling for injury severity in terms of AIS scores, GCS, ISS, plus age, gender, cause of injury, and coexisting injuries there was no statistically significant variation in mortality across the study period). The crude mortality rate in our study is similar to that found in other studies. For example, Patel et al. [3] reported an overall mortality rate of 25% among TBI patients treated in TARN hospitals between 1983 and In the ICNARC study of TBI patients admitted to ICU, Hyam et al. [2] reported an ICU mortality of 23.0% and in-hospital mortality of 33.5%. Our findings on the demographic and clinical characteristics of TBI in England and Wales are also consistent with findings in other European countries; about twothirds of all severe TBIs occur in men, in their early to mid-40s, with motor vehicle collisions and falls as the most common causes of injury [8]. In the United States, McGarry et al. [9] reported a detailed study on the acute treatment, outcomes and costs among 8717 patients with moderate to critical TBI. While there were no marked differences in the cause of injury by AIS, the average LOS ranged from 9.7 days for AIS 3 to 17.5 days for AIS 5, and total hospital mortality varied from 5.7% for AIS 3 to 52.0% for AIS 5. About 45% and 54% with AIS 4 and AIS 5, respectively, underwent some form of TBI related surgery compared to 26% and 42% in our study, though underreporting of surgery in the TARN database may explain at least part of this difference. No previous studies have examined the cost of acute treatment for TBI in the UK, and little is known about the cost of acute treatment in Europe [10]. A recent literature review identified only two studies, in Germany [11] and Spain [12], containing TBI related cost data, and presented new costs estimates for acute TBI treatment in Sweden [10]. Differences in costing methodology prevent a detailed comparison, but the reported average inpatient costs for patients with severe brain injury, ranging from 5622 ( 3830) in Spain to 8951 ( 6097) in Sweden, appear significantly lower than those observed in our study. Identification of substantial differences in hospital costs by specific patient characteristics generate knowledge useful for a more rational budgeting process of health care expenditures, and allow for a much better estimation of the cost-effectiveness of new public health interventions. In our multivariate analysis, we identified age, GCS, ISS, co-existing injuries of the thorax, spine and lower limb, mortality, year of admission, hospital specialisation and specialty of doctor as significant predictors of hospital Journal compilation Ó 2008 The Association of Anaesthetists of Great Britain and Ireland 505

8 S. Morris et al. Æ Cost of TBI Anaesthesia, 2008, 63, pages Full model Reduced model Table 5 Multivariate analysis of mean treatment costs for TBI. Coefficient t-statistic p-value Coefficient t-statistic p-value TBI AIS score* 4 )434.6 ) ) ) Gender; female )277.7 ) Age years years < < years < < years < Cause of injury Fall more than 2 m )650.1 ) Fall less than 2 m ) ) Blow(s) ) )3.8 < ) )3.9 < Other ) ) Glasgow Coma Score 6 8 )752.1 ) ) )6.4 < ) )7.0 < ) )13.4 < ) )16.2 < Injury Severity Score < < Coexisting injuries by body region** Head (excluding TBI) )295.7 ) Face Neck Thorax Abdomen Spine < < Upper limb Lower limb < Discharge status; dead ) )14.6 < ) )15.3 < Year of admission ) ) ) ) Hospital has a neurosurgical < < centre; yes Grade of most senior doctor seen in A&E Consultant Middle grade Specialty of doctors seen in A&E Emergency medicine )394.0 ) Neurosurgery Anaesthesia < < Orthopaedics General surgery Other Constant < < Observations Adjusted R *The omitted category in the full model is 3. The omitted category is years. The omitted category is vehicle incident collision. The omitted category is 3 5. The omitted category is **Injuries with an AIS score of three or more. The omitted category is The omitted category is SHO. TBI, traumatic brain injury; AIS, Abbreviated Injury Scale. costs. In the univariate analysis, mean treatment costs also varied by other patient and treatment characteristics (e.g. cause of injury, other coexisting injuries), yet this was due to the correlation between these characteristics and injury severity, and they were insignificant in the multivariate model. This highlights the importance of undertaking 506 Journal compilation Ó 2008 The Association of Anaesthetists of Great Britain and Ireland

9 Anaesthesia, 2008, 63, pages S. Morris et al. Æ Cost of TBI multivariate analysis when investigating the determinants of treatment costs. In our study we observed that 72% of patients were admitted to hospitals with neurosurgical expertise (neurosurgical centres). These have previously been associated with better outcomes for the severely head injured regardless of whether they actually received neurosurgery [3]. In our multivariate analysis, the conditional incremental costs of admission to a hospital with neurosurgical expertise were approximately This cost estimate can be compared to the incremental survival benefit observed in hospitals with compared to those without neurosurgical expertise to evaluate the cost-effectiveness of neurosurgical centres in treating TBI. With an incremental survival of 26% identified by Patel et al. [3], we estimate the incremental cost per hospital death averted in patients with TBI treated at a hospital with neurosurgical expertise to be approximately This study has a number of limitations. First, we were not always able to make a clear distinction between TBI related costs and costs related to other co-existing injuries; this means that the initial hospital costs of TBI may be overestimated. Second, we did not include treatment costs incurred after the initial hospitalisation period, such as the cost of rehabilitation, home care support and any subsequent hospitalisations related to TBI. Third, the retrospective nature of the study implies reliance on the quality and completeness of the data reported to TARN. We observed incomplete data on a number of treatment parameters, particularly whether or not the patient had a CT scan, and whether or not they had surgical procedures. This may mean that the costs of TBI are underestimated. Whether or not the patient had a CT scan was missing in 42% of patients. According to NHS Reference Costs [13] the mean cost per CT scan is around 100; it is therefore unlikely that the addition of these costs would have increased the total mean costs computed in this study noticeably. Given the format in which surgical procedures were recorded it was not possible to identify whether data on surgical procedures was missing or incomplete, but potentially the number of surgical procedures is higher than the figures reported in our study. Fourth, the indirect costs related to lost productivity and time spent away from other activities, as well as the costs associated with the pain and suffering by victims and relatives were not included. However, the cost of follow up care and the indirect costs can be substantial, and in fact represent the majority of the lifetime societal costs of TBI [14, 15]. In summary, our study provides the most detailed information to date on the costs of TBI in the acute care setting in England and Wales. Our findings indicate that the initial hospital costs associated with TBI vary by injury severity. Public health initiatives that aim to reduce the incidence of TBI and the severity of head injury are therefore likely to produce significant savings in acute trauma care. These data will also be important for any planned reconfiguration of trauma centres in England and Wales. Acknowledgements This study was funded by Novo Nordisk A S. S. Morris received consultancy fees and S. Ridley has received honoraria relating to lectures and other work from Novo Nordisk. M. C. Christensen and V. Munro are employees of Novo Nordisk. The authors would like to thank Omar Bouamra and Tom Jenks at TARN for providing the data used in this study and gratefully acknowledge the huge effort made by individual clinicians and hospitals in collecting and submitting raw data to the TARN database. TARN is funded by its participating hospitals. Finally, the authors would also like to thank Tina G. Nielsen, Novo Nordisk A S, for her very helpful comments relating to the statistical analyses. References 1 Kay A, Teasdale G. Head injury in the United Kingdom. World Journal of Surgery 2001; 25: Hyam JA, Welch CA, Harrison DA, Menon DK. Case mix, outcomes, and comparison of risk prediction models for admissions to adult, general and specialist critical care units for head injury: a secondary analysis of the ICN- ARC Case Mix Programme Database. Critical Care 2006; 10: S2. 3 Patel HC, Bouamra O, Woodford M, King AT, Yates DM, Lecky FE. Trends in head injury outcome from 1998 to 2003 and the effect of neurosurgical care: an observational study. Lancet 2005; 366: Lecky FE, Woodford M, Bouamra O, Yates DW. Lack of change in trauma care in England and Wales since Emergency Medical Journal 2002; 19: National Institute for Health and Clinical Excellence. Head injury. Triage, assessment, investigation and early management of head injury in infants, children and adults. (Clinical Guideline 4), London, UK: NICE, Royal College of Surgeons. Report of the Working Party on the Management of Patients with Head Injury. London, UK: The Royal College of Surgeons, Bouamra O, Wrotchford A, Hollis S, Vail A, Woodford M, Lecky F. A new approach to outcome prediction in trauma: a comparison with the TRISS model. Journal of Trauma 2006; 61: Tagliaferri F, Compagnone C, Korsic M, Servadei F, Kraus J. A systematic review of brain injury epidemiology in Europe. 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10 S. Morris et al. Æ Cost of TBI Anaesthesia, 2008, 63, pages McGarry LJ, Thompson D, Millham FH, et al. Outcomes and costs of acute treatment of traumatic brain injury. Journal of Trauma 2002; 53: Berg J, Tagliaferri F, Servadei F. Cost of trauma in Europe. European Journal of Neurology 2005; 12 (Suppl. 1): Firsching R, Woischneck D. Present status of neurosurgical trauma in Germany. World Journal of Surgery 2001; 25: Brell M, Ibanez J. Manejo del Traumaismo Craneoencefalico Leve en España. Encuesta Multicentrica Nacional Neurocirurgia 2001; 12: Department of Health. NHS Reference Costs Appendix SRC1 NHS Trust reference cost index. London: Department of Health, Dikman SS, Machamer JE, Powell JM, Temkin NR. Outcome 3 to 5 years after moderate to severe traumatic brain injury. Archives of Physical Medicine and Rehabilitation 2003; 84: Boake C, McCauley SR, Pedroza C, Levin HS, Brown SA, Brundage SI. Lost productive work time after mild to moderate traumatic brain injury with and without hospitalization. Neurosurgery 2005; 56: Curtis L, Netten A. Unit Costs of Health and Social Care Canterbury: University of Kent, London s Air Ambulance Service. londonsairambulance.com/ (accessed 23 June 2007). 18 National Institute for Health and Clinical Excellence. Technology Appraisal Guidance 83. Laparoscopic surgery for inguinal hernia repair. London: NICE, 2004: Morris S, Ridley S, Munro V, Christensen MC, on behalf of the NovoSeven Trauma Study Group. Cost effectiveness of recombinant activated factor VII for the control of bleeding in patients with severe blunt trauma injuries in the United Kingdom. Anaesthesia 2007; 62: Appendix Unit costs. Cost component Unit Unit cost ( ) Source and notes Mode of arrival at hospital Ambulance Cost per minute 5.50 Curtis and Netten [16] (p.112); cost per minute of emergency ambulance service Helicopter Mean cost per patient journey 1650 London Air Ambulance website [17]; mean cost per mission Hospital stay Emergency Department Mean cost per attender 278 NHS reference costs 2004 [13]; mean cost per attender across all A&E Healthcare Resource Groups Regular ward Mean cost per day 281 NHS reference costs 2004 [13]; mean national average unit cost per day for Healthcare Resource Group A31 (Head injury with brain injury) Critical Care Unit Mean cost per day 1328 NHS reference costs 2004 [13]; mean cost per day in Intensive Care Unit Intensive Therapy Unit Surgical procedures Duration; min Intracranial pressure monitor TARN; NICE [18]; the duration in minutes for each procedure was computed internally using the TARN database. The unit costs were then computed by multiplying the duration by the variable cost per minute from NICE [18] and adding a fixed cost per procedure also from NICE [18].* Elevation of depressed fracture of cranium Evacuation of EDH SDH Craniotomy Bur hole of cranium Drainage of EDH SDH *This method has been used in previous UK cost analyses of trauma care [19]. EDH SDH, epidural haematoma subdural haematoma. 508 Journal compilation Ó 2008 The Association of Anaesthetists of Great Britain and Ireland