Eur J Trauma Emerg Surg DOI 10.1007/s00068-013-0292-4
ORIGINAL ARTICLE
Symptomatic venous thromboembolism in Asian major trauma patients: incidence, presentation and risk factors T. H. Wong • M. P. Koh • J. Ng
Received: 25 September 2012 / Accepted: 15 April 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract Background Trauma patients are known to be at increased risk of venous thromboembolism (VTE), and pulmonary embolism (PE) is one of the preventable causes of mortality in trauma patients. The incidence of VTE in Asian populations was believed to be lower than in Caucasians, but the recent literature suggests that this is not the case. The purpose of this study was to assess the incidence of VTE in Asian major trauma patients and to examine the manner of presentation, use of prophylaxis and risk factors for VTE. While other studies of VTE have addressed general and high-risk populations within Asia, our study is one of the few to examine Asian major trauma patients. Methods Data for all patients with VTE were extracted from the Singapore General Hospital trauma database over a 10-year period from 1998 to 2007. Patient profiles and clinical factors were compared to patients without a diagnosis of VTE admitted with injuries in the same time period. Results There were 8,615 patients entered into our database in this 10-year period. Thirty-four patients had VTE, with an overall incidence of 0.39 %. Thirteen patients had pulmonary embolism, an incidence of 0.15 %. Of note, 30 % of patients with deep vein thrombosis (DVT) presented with fever alone without limb symptoms. Almost all 34 patients who developed VTE had either head injury, a spinal cord injury or a pelvic/extremity injury. Eighteen patients had head injury, 22 patients sustained pelvic or extremity injury, and three patients had spinal cord injury with paraplegia. Head injury and spinal cord injury with T. H. Wong (&) M. P. Koh J. Ng Department of General Surgery, Singapore General Hospital, Block 6 Level 7, Outram Road, Singapore 169608, Singapore e-mail: [email protected]
neurologic sequelae were statistically significant risk factors for VTE (p \ 0.05). Conclusion The incidence of symptomatic VTE in the Asian trauma population is no lower than in the West. The incidence found in this study is similar to the incidence of VTE according to a study using data from the American national trauma data bank using similar study methods and with a similar study population. It is also higher than the incidence in the literature for general post-surgical Asian patients. Fever was the presenting factor in some patients and screening for VTE should not be forgotten when assessing fever in the trauma patient. The strong association between head injury, spinal cord injury and VTE confirms that we should pay special attention to VTE prophylaxis for our patients with these injuries. Keywords Venous thromboembolism Pulmonary embolism Deep vein thrombosis Race Asia Trauma Injury
Introduction Trauma patients are known to be at increased risk of venous thromboembolism (VTE), and pulmonary embolism (PE) is one of the preventable causes of morbidity and mortality in trauma patients [1]. The overall incidence of VTE in Asian populations was previously believed to be lower than in Western populations [2, 3]. However, recent studies suggest that the real incidence of asymptomatic VTE, especially after high-risk elective orthopaedic surgery, is comparable to Western populations [4, 5]. Even studies published from the West show variation in VTE incidence. The largest retrospective published study to date of VTE from North America has shown that the
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overall VTE incidence in general trauma patients may be lower than expected, finding an incidence of only 0.36 % for VTE and 0.13 % for PE [6]. These variations in findings may reflect study design (whether all patients are screened or just symptomatic patients; how they are screened) and the risk profile of the population under study (e.g. spontaneous VTE, orthopaedic elective patients, all surgical patients) [6–14]. It has been theorised that Asian patients do form calf clots, but most remain asymptomatic, leading to a lower incidence of symptomatic VTE. One hypothesis is that Asians have a more active or efficient fibrinolytic system [3, 12]. The purpose of this study was to assess the incidence of VTE in Asian major trauma patients and to examine the risk factors for VTE in this group. While the above-mentioned studies of VTE address various general and highrisk populations within Asia, we believe that ours is one of the few studies to examine the incidence and clinical risk factors in the Asian major trauma patient.
Table 1 Inclusion criteria for our trauma database Period
Inclusion
Exclusion
Year 1998–2000
All trauma resuscitation patients (P1)
Burns, electrocution, drowning
2001 to Feb 2005
ICD codes 800 to 959.9
Neck of femur fracture from same-level fall Burns, electrocution, drowning
Mar 2005 to present
ICD codes 800 to 959.9
Neck of femur fracture from same-level fall
Length of stay C3 days
Burns, electrocution, drowning
TTA (trauma team activation) Died from trauma
Table 2 Trauma team activation criteria Physiologic
Anatomical
Mechanism
Airway compromise
Penetrating injury to head, neck or torso
Fall from more than 6m (20 feet)
Respiratory rate \10/ min or [30/min
Pelvic fracture (excluding isolated neck of femur fracture in the elderly)
Prolonged entrapment ([20 min)
Pulse [130 per min
Two or more proximal long bone fractures
Ejection from vehicle
Systolic blood pressure \90 mmHg
Two or more body region injuries
GCS B13
Spinal cord injury
Patients and methods Data for all patients with VTE were extracted from the Singapore General Hospital trauma database over the 10-year period from 1 January 1998 to 31 December 2007 by text search. They were compared to patients without a diagnosis of VTE admitted with injuries in the same time period. All data were entered by a single dedicated nurseclinician conducting systematic review and follow-up of trauma patients. All patients were followed up till discharge or death and re-admissions were flagged in the system. The inclusion criteria for our trauma database during this period are listed in Table 1. The criteria used at our hospital for trauma team activation are listed in Table 2. The team may also be activated at the duty senior emergency doctor’s discretion. Data were analysed with SPSS v16.0, using Fisher’s exact test for discrete variables, Mann–Whitney U-test for continuous variables and logistic regression for multivariate analysis.
Results Incidence There were 8,615 patients entered into our database during the 10-year period. Thirty-four patients had VTE, with an overall incidence of 0.39 %. This included 13 patients with pulmonary embolism, an incidence of 0.15 %. Seven patients had both PE and deep vein thrombosis (DVT). All
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Proximal limb amputation
cases of DVT were diagnosed or confirmed by duplex ultrasound and all PE patients were diagnosed by highresolution computed tomography of the chest. Presentation The 13 patients with PE presented with: shortness of breath (eight patients), low oxygen saturations (four) or chest pain (one patient). Of the 21 patients with DVT alone, 12 presented with leg swelling and six were detected when screening for causes of fever. For the other patients, one patient presented with arm swelling, at which point DVT was found in the arm veins as well as in both legs, one patient was asymptomatic when the DVT was detected on computed tomography of the abdomen and pelvis, showing the DVT extending into the pelvic veins, and one patient had a suspicion of a PE when investigated for breathlessness and, while that result was equivocal, a DVT scan subsequently showed DVT.
Symptomatic venous thromboembolism
Use of prophylaxis Only one out of 20 patients admitted prior to 2004 received any documented prophylaxis (TED stockings or pharmacoprophylaxis) and the single patient who did receive pharmacoprophylaxis was a patient with a high cervical spine injury with neurologic deficits. From 2004, almost half (6 of the 14 patients) received some form of prophylaxis, and those that had not were either not deemed to be at high risk (e.g. isolated penetrating upper limb injury and able to walk) or had some form of contra-indication (e.g. intracranial bleeding). While the increased usage of VTE prophylaxis did not translate to a statistically significant decrease in the incidence of VTE post-2004, all three deaths due to VTE occurred prior to 2004, even if only one death was directly related to the PE. This suggests that the increasing vigilance post-2004 contributed to lower mortality from VTE, although the study was not designed to assess this and data are not available. This timeframe of increased VTE prophylaxis use coincides with the participation of our institution in a large multi-centre study [4], suggesting that there was increased awareness of clinicians after participation. Risk factors Demographics The age of patients with VTE ranged from 14 to 87 years, with a median age of 39 years. There were 12 females and 22 males. All but one were blunt trauma patients. There were three deaths among these patients: one in a 48-yearold with severe head injury and multi-organ failure and an Injury Severity Score (ISS) of 38; two elderly patients (aged 81 and 82 years, respectively): one suffered an ischaemic cerebrovascular accident prior to a minor fall, and the decision was conservative management of the pulmonary embolism in view of his poor prognosis from the cerebrovascular accident, and the other patient died from severe intracranial haemorrhage. Injury pattern As expected, patients with VTE (median ISS 19, range 1–43) were more severely injured than those without (median ISS 4, range 1–75, p \ 0.005). There was no significant differences in gender or age between the two groups (Table 3). Almost all 34 patients who developed VTE had some form of head injury, pelvic/lower extremity injury or spinal cord injury (Table 3). Three patients suffered spinal cord injury with neurological deficit. Seventeen patients had
Table 3 Demographics and injury pattern VTE
No VTE
Significance
Age (years)a
39 (14–87)
38 (0–100)
Not significant
Gender
22 males, 12 females
6,105 males, 2,476 females
Not significant
ISSa AIS score for heada
19 (1–43) 3 (0–5)
4 (1–75) 0 (0–6)
p \ 0.005 p \ 0.005
AIS score for pelvis and extremitya
2 (0–5)
1 (0–5)
p = 0.007
Spinal cord injury with neurological deficit
a
Present
3
84
No spinal cord injury
31
8,531
p \ 0.005
Median and range
head injury, 21 patients sustained pelvic or lower extremity injury and five patients had both types of injury. Only four patients had no spinal cord injury, head injury or pelvic/ lower extremity injury. One 81-year-old patient was bedbound from previous cerebrovascular accidents and had only severe abrasions over the arm. Another had suffered severe self-inflicted major burns to the face, head and neck regions, and had severe depression, possibly contributing to her lack of mobility. One patient suffered only a humerus fracture but had two third-degree relatives with a history of spontaneous DVT; she developed DVT and pulmonary embolism on post-operative day one after internal fixation of the humerus fracture. The final patient had a penetrating upper limb injury that required lengthy and complex neurovascular operative repair under general anaesthesia. In our population, head injury and pelvis and extremity injuries increased patients’ risks of acquiring VTE (p \ 0.005). There was also a strong association between spinal cord injury with neurologic deficit and VTE (p \ 0.05). On multivariate analysis, head injury score, pelvis and extremity injury score, and spinal cord injury with neurologic deficit remained significant predictors of VTE. Time to diagnosis The time to diagnosis of thromboembolism ranged from 1 to 46 days, with a median of 8 days. The outlier patient diagnosed on day 46 of injury had just been transferred after 45 days in a hospital abroad, so this could have been related to the air transfer and/or was missed by the referring hospital (Fig. 1). Race There were two Caucasians in our series, eight Malays, three Indians and the remainder (20) were ethnically
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follow-up of our patients and we believe that we should have detected almost all clinically significant VTE in our population. Post-mortems are routinely conducted for all major trauma patients in Singapore and the results entered into our database. Incidence of VTE in Asia—East vs. West, trauma vs. non-trauma
Fig. 1 Time from injury to diagnosis of thromboembolism
Chinese. There was no statistical difference when compared to the overall race proportions in the database. Thrombophilia Three patients showed some form of thrombophilia upon screening (one patient had protein S deficiency, one was positive for anticardiolipin, one 30-year-old patient had a past history of recurrent juvenile cerebrovascular accidents despite a negative laboratory screen). Other risk factors One patient had a documented past history of DVT in pregnancy. She was not given prophylaxis on admission as she had a small sub-galeal haematoma and was mobilising well on crutches. Another patient had two third-degree relatives with spontaneous VTE, despite no known laboratory-detected cause of thrombophilia. Five patients (15.2 %) had been transferred after initial care overseas, ranging from transfer on the day of injury to 45 days after the injury. This was not statistically significantly different from the overall rate of transferred patients in the trauma database (9.74 %). On multivariate analysis, ISS and spinal cord injury with neurological deficit remained independent risk factors for VTE.
Discussion Our study was interesting from two perspectives—the similar incidence of VTE in Asian trauma patients compared to Western data when similar methods were used and for identifying risk factors for VTE that could potentially be targeted in our trauma population. While we do not routinely screen asymptomatic patients, we do have good
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The overall incidence of symptomatic VTE in our Singaporean trauma population is similar to Knudson’s largest retrospective registry-based study on trauma patients from the North American trauma database (0.36 % VTE, 0.13 % PE). One explanation for the low incidence of VTE in this large Western retrospective study was that only 7 % of the study population (national trauma data bank of the American College of Surgeons) had an ISS of 25 or more. We believe that our study population is fairly comparable, with 5 % of our cohort having an ISS of 25 or more. Both of our registry-based studies would suffer from the same weakness in that asymptomatic VTE would be missed and there may be drop-out in follow-up due to a minority of nonresident trauma patients continuing treatment in a different location. Nevertheless, with the studies using similar methodology, our similar results suggest that there is no difference between VTE risk in Asians and Westerners. Our conclusions are similar to those of a large multicentre Asian study targeting a different study population which showed comparable VTE rates to the West if similar methods and study populations were used. In this case, asymptomatic VTE were screened for in all elective lower limb surgery patients [4] and similar rates were found in both populations. While some have hypothesised that Asians have a more active or efficient fibrinolytic system [3, 11], leading to lower clinically significant manifestation, our data do not support this hypothesis. Our VTE rates are approximately triple the rates in another Asian retrospective study that examined multidiscipline elective and emergency post-surgical patients (0.13 % VTE, 0.4 % PE in multi-disciplinary surgical patients including neurosurgery, obstetrics and gynaecology, urology, orthopaedics and cardiothoracic surgery) [2]. This suggests that trauma (even apparently minor trauma) is an independent risk factor for VTE. Thirty percent (6 out of 20) patients with DVT were diagnosed while screening for fever and had no other limb symptoms, emphasising the need to include DVT in the differentials when screening a trauma patient for fever. VTE presented as early as one day post-injury, in keeping with increasing data showing that VTE can present as early as a few hours after trauma [1, 15, 16]. As such, early VTE prophylaxis should be encouraged [17].
Symptomatic venous thromboembolism
Recent studies, including a trans-national study in 2006–2007, have shown that clinician usage can be suboptimal, even in high-risk patients [17, 18]. We hope that the apparent rise in prophylaxis (either compression stockings or pharmacologic) when comparing the patients diagnosed with VTE pre-2004 (hardly receiving any prophylaxis) and post-2004 reflects the increasing awareness of the importance of VTE prophylaxis among healthcare staff. While our study was not designed to study this (we do not have the data on prophylaxis in the non-VTE group), we believe that this is due to the growing body of evidence in the literature that VTE in Asians is not as rare as previously thought [4, 12, 13, 19]. Injury pattern We found that our spinal cord-injured patients with neurologic deficit were significantly at increased risk of VTE. In spite of the lack of association in meta-analyses between head injury and VTE [20], and between pelvic/extremity injuries and VTE, we did find a strong association between pelvis and extremity injury, head injury and VTE. While this difference in risk may be due to the small overall numbers of patients with VTE in our study, it may also suggest that we are not giving enough prophylaxis to these groups compared to the other at-risk groups due to fear of the increased risk of bleeding. Hence, we should pay special attention to VTE prophylaxis for our patients with these injuries and be vigilant in this group. Recent data suggest that pharmacoprophylaxis may be safe in head-injured patients [21]. We believe that our findings add to the growing body of evidence showing that Asian patients at are similar risk of DVT compared to their Western counterparts and that trauma patients from Asia should be considered for thromboprophylaxis.
Conclusion Our study confirms that venous thromboembolism (VTE) in trauma populations is a significant and potentially preventable cause of morbidity and mortality among trauma patients in Asia. The increased risk of VTE in extremity-/ pelvis-, spine- and head-injured patients suggests that we need to be more consistent in applying prophylactic measures in these groups. Acknowledgements We would like to thank Ms. Stephanie Fook of the Singapore General Hospital Division of Research for her assistance in the statistical analysis. We affirm that our study was approved by our institution’s ethics committee and was, therefore, performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments, as well as the
local laws governing research. The results in their current form in this study have not been published in any form in any journal, although preliminary results were part of an oral presentation at the Austrauma conference in Sydney, Australia, February 2011. Conflict of interest On behalf of all authors, the corresponding author states that there is no conflict of interest.
References 1. Menaker J, Stein DM, Scalea TM. Pulmonary embolism after injury: more common than we think? J Trauma. 2009;67(6): 1244–9. 2. Cheuk BL, Cheung GC, Cheng SW. Epidemiology of venous thromboembolism in a Chinese population. Br J Surg. 2004;91(4): 424–8. 3. White RH, Keenan CR. Effects of race and ethnicity on the incidence of venous thromboembolism. Thromb Res. 2009; 123(Suppl 4):S11–7. 4. Piovella F, Wang C-J, Lu H, Lee K, Lee LH, Lee WC, et al. Deep-vein thrombosis rates after major orthopedic surgery in Asia. An epidemiological study based on postoperative screening with centrally adjudicated bilateral venography. J Thromb Haemost. 2005;3:2664–70. 5. Cohen AT; Asia-Pacific Thrombosis Advisory Board. AsiaPacific Thrombosis Advisory Board consensus paper on prevention of venous thromboembolism after major orthopaedic surgery. Thromb Haemost. 2010;104(5):919–30. 6. Knudson MM, Ikossi DG, Khaw L, Morabito D, Speetzen LS. Thromboembolism after trauma: an analysis of 1602 episodes from the American College of Surgeons National Trauma Data Bank. Ann Surg. 2004;240(3):490–6; discussion 496–8. 7. Lee CH, Lin LJ, Cheng CL, Kao Yang YH, Chen JY, Tsai LM. Incidence and cumulative recurrence rates of venous thromboembolism in the Taiwanese population. J Thromb Haemost. 2010;8(7):1515–23. 8. Jang MJ, Bang SM, Oh D. Incidence of venous thromboembolism in Korea: from the Health Insurance Review and Assessment Service database. J Thromb Haemost. 2011;9(1):85–91. 9. Roberts LN, Patel RK, Arya R. Venous thromboembolism and ethnicity. Br J Haematol. 2009;146(4):369–83. 10. Chua K, Kong KH, Chan SP. Prevalence and risk factors of asymptomatic lower extremity deep venous thrombosis in Asian neurorehabilitation admissions in Singapore. Arch Phys Med Rehabil. 2008;89(12):2316–23. 11. Rathore MF, Hanif S, New PW, Butt AW, Aasi MH, Khan SU. The prevalence of deep vein thrombosis in a cohort of patients with spinal cord injury following the Pakistan earthquake of October 2005. Spinal Cord. 2008;46(7):523–6. 12. White RH. The epidemiology of venous thromboembolism. Circulation. 2003;107(23 Suppl 1):14–8. 13. Lee LH, Gu KQ, Heng D. Deep vein thrombosis is not rare in Asia—the Singapore General Hospital experience. Ann Acad Med Singapore. 2002;31(6):761–4. 14. Liew NC, Moissinac K, Gul Y. Postoperative venous thromboembolism in Asia: a critical appraisal of its incidence. Asian J Surg. 2003;26(3):154–8. 15. Spencer Netto F, Tien H, Ng J, Ortega S, Scarpelini S, Rizoli SB, et al. Pulmonary emboli after blunt trauma: timing, clinical characteristics and natural history. Injury. 2012;43(9):1502–6. 16. Menaker J, Stein DM, Scalea TM. Incidence of early pulmonary embolism after injury. J Trauma. 2007;63(3):620–4.
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T. H. Wong et al. 17. Nathens AB, McMurray MK, Cuschieri J, Durr EA, Moore EE, Bankey PE, et al. The practice of venous thromboembolism prophylaxis in the major trauma patient. J Trauma. 2007;62(3): 557–62; discussion 562–3. 18. Kakkar AK, Cohen AT, Tapson VF, Bergmann JF, Goldhaber SZ, Deslandes B, et al. Venous thromboembolism risk and prophylaxis in the acute care hospital setting (ENDORSE survey): findings in surgical patients. Ann Surg. 2010;251(2):330–8. 19. Ng HJ, Lee LH. Trends in prevalence of deep venous thrombosis among hospitalised patients in an Asian institution. Thromb Haemost. 2009;101(6):1095–9.
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20. Rogers FB, Cipolle MD, Velmahos G, Rozycki G, Luchette FA. Practice management guidelines for the prevention of venous thromboembolism in trauma patients: the EAST practice management guidelines work group. J Trauma. 2002;53(1):142–64. 21. Koehler DM, Shipman J, Davidson MA, Guillamondegui O. Is early venous thromboembolism prophylaxis safe in trauma patients with intracranial hemorrhage. J Trauma. 2011;70(2): 324–9.
ORIGINAL ARTICLE
Symptomatic venous thromboembolism in Asian major trauma patients: incidence, presentation and risk factors T. H. Wong • M. P. Koh • J. Ng
Received: 25 September 2012 / Accepted: 15 April 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract Background Trauma patients are known to be at increased risk of venous thromboembolism (VTE), and pulmonary embolism (PE) is one of the preventable causes of mortality in trauma patients. The incidence of VTE in Asian populations was believed to be lower than in Caucasians, but the recent literature suggests that this is not the case. The purpose of this study was to assess the incidence of VTE in Asian major trauma patients and to examine the manner of presentation, use of prophylaxis and risk factors for VTE. While other studies of VTE have addressed general and high-risk populations within Asia, our study is one of the few to examine Asian major trauma patients. Methods Data for all patients with VTE were extracted from the Singapore General Hospital trauma database over a 10-year period from 1998 to 2007. Patient profiles and clinical factors were compared to patients without a diagnosis of VTE admitted with injuries in the same time period. Results There were 8,615 patients entered into our database in this 10-year period. Thirty-four patients had VTE, with an overall incidence of 0.39 %. Thirteen patients had pulmonary embolism, an incidence of 0.15 %. Of note, 30 % of patients with deep vein thrombosis (DVT) presented with fever alone without limb symptoms. Almost all 34 patients who developed VTE had either head injury, a spinal cord injury or a pelvic/extremity injury. Eighteen patients had head injury, 22 patients sustained pelvic or extremity injury, and three patients had spinal cord injury with paraplegia. Head injury and spinal cord injury with T. H. Wong (&) M. P. Koh J. Ng Department of General Surgery, Singapore General Hospital, Block 6 Level 7, Outram Road, Singapore 169608, Singapore e-mail: [email protected]
neurologic sequelae were statistically significant risk factors for VTE (p \ 0.05). Conclusion The incidence of symptomatic VTE in the Asian trauma population is no lower than in the West. The incidence found in this study is similar to the incidence of VTE according to a study using data from the American national trauma data bank using similar study methods and with a similar study population. It is also higher than the incidence in the literature for general post-surgical Asian patients. Fever was the presenting factor in some patients and screening for VTE should not be forgotten when assessing fever in the trauma patient. The strong association between head injury, spinal cord injury and VTE confirms that we should pay special attention to VTE prophylaxis for our patients with these injuries. Keywords Venous thromboembolism Pulmonary embolism Deep vein thrombosis Race Asia Trauma Injury
Introduction Trauma patients are known to be at increased risk of venous thromboembolism (VTE), and pulmonary embolism (PE) is one of the preventable causes of morbidity and mortality in trauma patients [1]. The overall incidence of VTE in Asian populations was previously believed to be lower than in Western populations [2, 3]. However, recent studies suggest that the real incidence of asymptomatic VTE, especially after high-risk elective orthopaedic surgery, is comparable to Western populations [4, 5]. Even studies published from the West show variation in VTE incidence. The largest retrospective published study to date of VTE from North America has shown that the
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overall VTE incidence in general trauma patients may be lower than expected, finding an incidence of only 0.36 % for VTE and 0.13 % for PE [6]. These variations in findings may reflect study design (whether all patients are screened or just symptomatic patients; how they are screened) and the risk profile of the population under study (e.g. spontaneous VTE, orthopaedic elective patients, all surgical patients) [6–14]. It has been theorised that Asian patients do form calf clots, but most remain asymptomatic, leading to a lower incidence of symptomatic VTE. One hypothesis is that Asians have a more active or efficient fibrinolytic system [3, 12]. The purpose of this study was to assess the incidence of VTE in Asian major trauma patients and to examine the risk factors for VTE in this group. While the above-mentioned studies of VTE address various general and highrisk populations within Asia, we believe that ours is one of the few studies to examine the incidence and clinical risk factors in the Asian major trauma patient.
Table 1 Inclusion criteria for our trauma database Period
Inclusion
Exclusion
Year 1998–2000
All trauma resuscitation patients (P1)
Burns, electrocution, drowning
2001 to Feb 2005
ICD codes 800 to 959.9
Neck of femur fracture from same-level fall Burns, electrocution, drowning
Mar 2005 to present
ICD codes 800 to 959.9
Neck of femur fracture from same-level fall
Length of stay C3 days
Burns, electrocution, drowning
TTA (trauma team activation) Died from trauma
Table 2 Trauma team activation criteria Physiologic
Anatomical
Mechanism
Airway compromise
Penetrating injury to head, neck or torso
Fall from more than 6m (20 feet)
Respiratory rate \10/ min or [30/min
Pelvic fracture (excluding isolated neck of femur fracture in the elderly)
Prolonged entrapment ([20 min)
Pulse [130 per min
Two or more proximal long bone fractures
Ejection from vehicle
Systolic blood pressure \90 mmHg
Two or more body region injuries
GCS B13
Spinal cord injury
Patients and methods Data for all patients with VTE were extracted from the Singapore General Hospital trauma database over the 10-year period from 1 January 1998 to 31 December 2007 by text search. They were compared to patients without a diagnosis of VTE admitted with injuries in the same time period. All data were entered by a single dedicated nurseclinician conducting systematic review and follow-up of trauma patients. All patients were followed up till discharge or death and re-admissions were flagged in the system. The inclusion criteria for our trauma database during this period are listed in Table 1. The criteria used at our hospital for trauma team activation are listed in Table 2. The team may also be activated at the duty senior emergency doctor’s discretion. Data were analysed with SPSS v16.0, using Fisher’s exact test for discrete variables, Mann–Whitney U-test for continuous variables and logistic regression for multivariate analysis.
Results Incidence There were 8,615 patients entered into our database during the 10-year period. Thirty-four patients had VTE, with an overall incidence of 0.39 %. This included 13 patients with pulmonary embolism, an incidence of 0.15 %. Seven patients had both PE and deep vein thrombosis (DVT). All
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Proximal limb amputation
cases of DVT were diagnosed or confirmed by duplex ultrasound and all PE patients were diagnosed by highresolution computed tomography of the chest. Presentation The 13 patients with PE presented with: shortness of breath (eight patients), low oxygen saturations (four) or chest pain (one patient). Of the 21 patients with DVT alone, 12 presented with leg swelling and six were detected when screening for causes of fever. For the other patients, one patient presented with arm swelling, at which point DVT was found in the arm veins as well as in both legs, one patient was asymptomatic when the DVT was detected on computed tomography of the abdomen and pelvis, showing the DVT extending into the pelvic veins, and one patient had a suspicion of a PE when investigated for breathlessness and, while that result was equivocal, a DVT scan subsequently showed DVT.
Symptomatic venous thromboembolism
Use of prophylaxis Only one out of 20 patients admitted prior to 2004 received any documented prophylaxis (TED stockings or pharmacoprophylaxis) and the single patient who did receive pharmacoprophylaxis was a patient with a high cervical spine injury with neurologic deficits. From 2004, almost half (6 of the 14 patients) received some form of prophylaxis, and those that had not were either not deemed to be at high risk (e.g. isolated penetrating upper limb injury and able to walk) or had some form of contra-indication (e.g. intracranial bleeding). While the increased usage of VTE prophylaxis did not translate to a statistically significant decrease in the incidence of VTE post-2004, all three deaths due to VTE occurred prior to 2004, even if only one death was directly related to the PE. This suggests that the increasing vigilance post-2004 contributed to lower mortality from VTE, although the study was not designed to assess this and data are not available. This timeframe of increased VTE prophylaxis use coincides with the participation of our institution in a large multi-centre study [4], suggesting that there was increased awareness of clinicians after participation. Risk factors Demographics The age of patients with VTE ranged from 14 to 87 years, with a median age of 39 years. There were 12 females and 22 males. All but one were blunt trauma patients. There were three deaths among these patients: one in a 48-yearold with severe head injury and multi-organ failure and an Injury Severity Score (ISS) of 38; two elderly patients (aged 81 and 82 years, respectively): one suffered an ischaemic cerebrovascular accident prior to a minor fall, and the decision was conservative management of the pulmonary embolism in view of his poor prognosis from the cerebrovascular accident, and the other patient died from severe intracranial haemorrhage. Injury pattern As expected, patients with VTE (median ISS 19, range 1–43) were more severely injured than those without (median ISS 4, range 1–75, p \ 0.005). There was no significant differences in gender or age between the two groups (Table 3). Almost all 34 patients who developed VTE had some form of head injury, pelvic/lower extremity injury or spinal cord injury (Table 3). Three patients suffered spinal cord injury with neurological deficit. Seventeen patients had
Table 3 Demographics and injury pattern VTE
No VTE
Significance
Age (years)a
39 (14–87)
38 (0–100)
Not significant
Gender
22 males, 12 females
6,105 males, 2,476 females
Not significant
ISSa AIS score for heada
19 (1–43) 3 (0–5)
4 (1–75) 0 (0–6)
p \ 0.005 p \ 0.005
AIS score for pelvis and extremitya
2 (0–5)
1 (0–5)
p = 0.007
Spinal cord injury with neurological deficit
a
Present
3
84
No spinal cord injury
31
8,531
p \ 0.005
Median and range
head injury, 21 patients sustained pelvic or lower extremity injury and five patients had both types of injury. Only four patients had no spinal cord injury, head injury or pelvic/ lower extremity injury. One 81-year-old patient was bedbound from previous cerebrovascular accidents and had only severe abrasions over the arm. Another had suffered severe self-inflicted major burns to the face, head and neck regions, and had severe depression, possibly contributing to her lack of mobility. One patient suffered only a humerus fracture but had two third-degree relatives with a history of spontaneous DVT; she developed DVT and pulmonary embolism on post-operative day one after internal fixation of the humerus fracture. The final patient had a penetrating upper limb injury that required lengthy and complex neurovascular operative repair under general anaesthesia. In our population, head injury and pelvis and extremity injuries increased patients’ risks of acquiring VTE (p \ 0.005). There was also a strong association between spinal cord injury with neurologic deficit and VTE (p \ 0.05). On multivariate analysis, head injury score, pelvis and extremity injury score, and spinal cord injury with neurologic deficit remained significant predictors of VTE. Time to diagnosis The time to diagnosis of thromboembolism ranged from 1 to 46 days, with a median of 8 days. The outlier patient diagnosed on day 46 of injury had just been transferred after 45 days in a hospital abroad, so this could have been related to the air transfer and/or was missed by the referring hospital (Fig. 1). Race There were two Caucasians in our series, eight Malays, three Indians and the remainder (20) were ethnically
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follow-up of our patients and we believe that we should have detected almost all clinically significant VTE in our population. Post-mortems are routinely conducted for all major trauma patients in Singapore and the results entered into our database. Incidence of VTE in Asia—East vs. West, trauma vs. non-trauma
Fig. 1 Time from injury to diagnosis of thromboembolism
Chinese. There was no statistical difference when compared to the overall race proportions in the database. Thrombophilia Three patients showed some form of thrombophilia upon screening (one patient had protein S deficiency, one was positive for anticardiolipin, one 30-year-old patient had a past history of recurrent juvenile cerebrovascular accidents despite a negative laboratory screen). Other risk factors One patient had a documented past history of DVT in pregnancy. She was not given prophylaxis on admission as she had a small sub-galeal haematoma and was mobilising well on crutches. Another patient had two third-degree relatives with spontaneous VTE, despite no known laboratory-detected cause of thrombophilia. Five patients (15.2 %) had been transferred after initial care overseas, ranging from transfer on the day of injury to 45 days after the injury. This was not statistically significantly different from the overall rate of transferred patients in the trauma database (9.74 %). On multivariate analysis, ISS and spinal cord injury with neurological deficit remained independent risk factors for VTE.
Discussion Our study was interesting from two perspectives—the similar incidence of VTE in Asian trauma patients compared to Western data when similar methods were used and for identifying risk factors for VTE that could potentially be targeted in our trauma population. While we do not routinely screen asymptomatic patients, we do have good
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The overall incidence of symptomatic VTE in our Singaporean trauma population is similar to Knudson’s largest retrospective registry-based study on trauma patients from the North American trauma database (0.36 % VTE, 0.13 % PE). One explanation for the low incidence of VTE in this large Western retrospective study was that only 7 % of the study population (national trauma data bank of the American College of Surgeons) had an ISS of 25 or more. We believe that our study population is fairly comparable, with 5 % of our cohort having an ISS of 25 or more. Both of our registry-based studies would suffer from the same weakness in that asymptomatic VTE would be missed and there may be drop-out in follow-up due to a minority of nonresident trauma patients continuing treatment in a different location. Nevertheless, with the studies using similar methodology, our similar results suggest that there is no difference between VTE risk in Asians and Westerners. Our conclusions are similar to those of a large multicentre Asian study targeting a different study population which showed comparable VTE rates to the West if similar methods and study populations were used. In this case, asymptomatic VTE were screened for in all elective lower limb surgery patients [4] and similar rates were found in both populations. While some have hypothesised that Asians have a more active or efficient fibrinolytic system [3, 11], leading to lower clinically significant manifestation, our data do not support this hypothesis. Our VTE rates are approximately triple the rates in another Asian retrospective study that examined multidiscipline elective and emergency post-surgical patients (0.13 % VTE, 0.4 % PE in multi-disciplinary surgical patients including neurosurgery, obstetrics and gynaecology, urology, orthopaedics and cardiothoracic surgery) [2]. This suggests that trauma (even apparently minor trauma) is an independent risk factor for VTE. Thirty percent (6 out of 20) patients with DVT were diagnosed while screening for fever and had no other limb symptoms, emphasising the need to include DVT in the differentials when screening a trauma patient for fever. VTE presented as early as one day post-injury, in keeping with increasing data showing that VTE can present as early as a few hours after trauma [1, 15, 16]. As such, early VTE prophylaxis should be encouraged [17].
Symptomatic venous thromboembolism
Recent studies, including a trans-national study in 2006–2007, have shown that clinician usage can be suboptimal, even in high-risk patients [17, 18]. We hope that the apparent rise in prophylaxis (either compression stockings or pharmacologic) when comparing the patients diagnosed with VTE pre-2004 (hardly receiving any prophylaxis) and post-2004 reflects the increasing awareness of the importance of VTE prophylaxis among healthcare staff. While our study was not designed to study this (we do not have the data on prophylaxis in the non-VTE group), we believe that this is due to the growing body of evidence in the literature that VTE in Asians is not as rare as previously thought [4, 12, 13, 19]. Injury pattern We found that our spinal cord-injured patients with neurologic deficit were significantly at increased risk of VTE. In spite of the lack of association in meta-analyses between head injury and VTE [20], and between pelvic/extremity injuries and VTE, we did find a strong association between pelvis and extremity injury, head injury and VTE. While this difference in risk may be due to the small overall numbers of patients with VTE in our study, it may also suggest that we are not giving enough prophylaxis to these groups compared to the other at-risk groups due to fear of the increased risk of bleeding. Hence, we should pay special attention to VTE prophylaxis for our patients with these injuries and be vigilant in this group. Recent data suggest that pharmacoprophylaxis may be safe in head-injured patients [21]. We believe that our findings add to the growing body of evidence showing that Asian patients at are similar risk of DVT compared to their Western counterparts and that trauma patients from Asia should be considered for thromboprophylaxis.
Conclusion Our study confirms that venous thromboembolism (VTE) in trauma populations is a significant and potentially preventable cause of morbidity and mortality among trauma patients in Asia. The increased risk of VTE in extremity-/ pelvis-, spine- and head-injured patients suggests that we need to be more consistent in applying prophylactic measures in these groups. Acknowledgements We would like to thank Ms. Stephanie Fook of the Singapore General Hospital Division of Research for her assistance in the statistical analysis. We affirm that our study was approved by our institution’s ethics committee and was, therefore, performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments, as well as the
local laws governing research. The results in their current form in this study have not been published in any form in any journal, although preliminary results were part of an oral presentation at the Austrauma conference in Sydney, Australia, February 2011. Conflict of interest On behalf of all authors, the corresponding author states that there is no conflict of interest.
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