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Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity score–matched analysis
Journal of Critical Care xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Journal of Critical Care journal homepage: www.jccjournal.org
Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity score–matched analysis Tomoki Wada, MD a,⁎, Hideo Yasunaga, MD, PhD b, Ryota Inokuchi, MD, PhD a, Hiroki Matsui, PhD b, Takehiro Matsubara, MD, PhD a, Yoshihiro Ueda, MD a, Masataka Gunshin, MD a, Takeshi Ishii, MD a, Kent Doi, MD, PhD a, Yoichi Kitsuta, MD, PhD a, Susumu Nakajima, MD, PhD a, Kiyohide Fushimi, MD, PhD c, Naoki Yahagi, MD, PhD a a b c
Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, Tokyo, Japan Department of Clinical Epidemiology and Health Economics, School of Public Health, The University of Tokyo, Tokyo, Japan Department of Health Care Informatics, Tokyo Medical and Dental University, Tokyo, Japan
a r t i c l e
i n f o
Keywords: Traumatic rib fracture Surgical rib fixation Survival analysis Cohort study Diagnosis Procedure Combination database Propensity score matching
a b s t r a c t Purpose: We investigated whether surgical rib fixation improved outcomes in patients with traumatic rib fractures. Materials and Methods: This was a retrospective study using a Japanese administrative claim and discharge database. We included patients with traumatic rib fractures admitted to hospitals where surgical rib fixation was available from July 1 2010, to March 31, 2013. We detected patients who underwent surgical rib fixation within 10 days of hospital admission (surgical group) and those who did not (control group). The main outcome was prolonged mechanical ventilation, defined as that performed for 5 or more days, or death within 28 days. One-to-four propensity score matching was performed between the 2 groups with adjustment for possible confounders. Results: Among 4577 eligible patients, 90 (2.0%) underwent the surgical rib fixation. After the matching, we obtained 84 and 336 patients in the surgical and control groups, respectively. Logistic regression analyses showed that the surgical group was significantly less likely to receive prolonged mechanical ventilation or die within 28 days than the control group (22.6% vs 33.3%; odds ratio, 0.59; 95% confidence interval, 0.36-0.96; P = .034). Conclusions: Surgical rib fixation within 10 days of hospital admission may improve outcomes in patients with traumatic rib fractures. © 2015 Elsevier Inc. All rights reserved.
1. Introduction Most rib fractures are treated nonoperatively. In fact, a study using the National Trauma Data Bank showed that only 0.7% of patients with flail chest, which is one of the most severe conditions in multiple rib fractures, received surgical fixation for rib fractures [1]. However, patients who received conservative treatments for rib fractures often had long-lasting disability [2]. Thus, the current nonoperative treatments for rib fractures are not necessarily ideal for the patients. Several previous studies have shown the benefits of surgical rib fixation, including 3 randomized controlled trials [3–5]. Nevertheless, these studies involved small sample sizes. Consequently, operative management is not recognized as a standard treatment option, even for flail chest. A previous study in the United States involving trauma, orthopedic, and thoracic surgeons reported that only 26% had performed or assisted on surgical fixation for rib fractures [6]. Because of
⁎ Corresponding author at: Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Tel.: +81 3 5800 8681; fax: +81 3 3814 6446. E-mail address: [email protected] (T. Wada).
the potential benefits for patients with rib fractures, the effects of surgical rib fixation on outcomes need to be further evaluated. We investigated the effects of surgical fixation for rib fractures on patient outcomes in a real-world clinical setting, using a national administrative claims and discharge database in Japan.
2. Materials and methods 2.1. Study design and setting The present study was a retrospective cohort study. We used a Japanese national administrative claims and discharge abstract database called the Diagnosis Procedure Combination (DPC) database [7,8]. This database collects data for all inpatients discharged from participating hospitals. In 2013, approximately 1000 hospitals including 82 university hospitals participated in the database system. The DPC database contains the following information for individual patients: age; sex; diagnoses including primary diagnoses, complications during hospitalization, and preexisting comorbidities; medical and surgical procedures performed; drugs used; and discharge status. Diagnoses are recorded by both International Classification of Diseases,
http://dx.doi.org/10.1016/j.jcrc.2015.07.027 0883-9441/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027
2
T. Wada et al. / Journal of Critical Care xxx (2015) xxx–xxx
10th Revision (ICD-10) codes and text data written in Japanese. Procedures and drugs are recorded with the dates of use. The present study was approved by the institutional review boards and ethics committee of The University of Tokyo. Informed consent was waived because of the anonymous nature of the data. 2.2. Patient selection Among all the inpatients recorded in the DPC database, we included those who satisfying all of the following criteria: admission to hospitals with injuries including rib fractures (S223, S224, or S225) from July 1, 2010 to March 31, 2013, and admission to hospitals where surgical fixation for rib fractures was performed for at least 1 patient during the study period. We divided the patients into a surgical group and a control group. The surgical group contained patients who received surgical rib fixation within 10 days of hospital admission, whereas the control group contained those who did not. Patients who died within 10 days of hospital admission were excluded. Patients younger than 20 years were also excluded. 2.3. Variables Patients were subdivided into 3 age groups: b 59, 60-74, and ≥75 years. To adjust for injury severity, we used the following items: Japan Coma Scale (JCS) score on admission; procedures performed on admission including mechanical ventilation, chest drainage, catecholamine use, and transfusion; and interventions for associated injuries performed during hospitalization. The JCS is a scale for measuring impaired consciousness [9,10]. For the JCS, a score of 0 indicates alertness, singledigit scores of 1 to 3 indicate drowsiness, double-digit scores of 10 to 30 indicate somnolence, and triple-digit scores of 100 to 300 indicate coma. The interventions for associated injuries were as follows: craniotomy, spinal fusion, thoracotomy, laparotomy, pelvic internal fixation, open reduction and internal fixation (ORIF) for limb fractures, and transarterial
embolization. We also identified whether hospitals were tertiary trauma centers or not. The outcomes of interest were prolonged mechanical ventilation for 5 or more days or death within 28 days, tracheotomy or death within 28 days, 28-day mortality, and length of hospital stay. The definition of prolonged mechanical ventilation was derived from the finding that the median duration of mechanical ventilation was 5 days among patients with rib fractures who required mechanical ventilation in this study. 2.4. Statistical analysis We performed a 1:4 propensity score matching between the surgical group and the control group. This matching was performed to enhance the baseline comparability between the 2 groups. A logistic regression model was used to estimate a propensity score for the receipt of surgical fixation for rib fractures for each patient. The following factors were included in the model: patient age and sex; procedures performed on admission including mechanical ventilation, chest drainage, transfusion, and the use of catecholamines; the JCS scores on admission; the presence of flail chest; associated injuries requiring surgical or radiologic interventions; and hospital type. The c statistic was calculated to evaluate the goodness of fit for the model. Each patient in the control group was matched with a patient in the surgical group with the closest estimated propensity on the logit scale within a specified range (≤ 0.20 of the pooled SD of estimated logits) [11]. In both the total population and the matched population, categorical data were compared between the surgical group and the control group using the χ 2 test or Fisher exact test as appropriate, whereas continuous data were compared using the Mann-Whitney U test. In addition, we performed logistic regression analyses of surgical rib fixation for the 2 outcomes of prolonged mechanical ventilation or death within 28 days, and tracheotomy or death within 28 days. The logistic regression analyses were fitted with generalized estimating equations that accounted for the pairwise nature of the surgical patients and the controls. Because severe head and torso injuries are strong predictors of outcome in patients, we performed a
Fig. 1. Selection process of the surgical and control groups.
Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027
T. Wada et al. / Journal of Critical Care xxx (2015) xxx–xxx
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Table 1 Baseline characteristics in the surgical and control groups Total population
Sex (female), n (%) Age groups (y), n (%) b60 60-74 ≥75 Intubation on admission, n (%) Chest drainage on admission, n (%) Catecholamine use on admission, n (%) Transfusion on admission, n (%) JCS score on admission, n (%) 0 1-3 10-30 100-300 Flail chest Interventions for associated injuries, n (%) Craniotomy Spinal fusion Thoracotomy Laparotomy Pelvic ORIF Limb ORIF Transarterial embolization Admission to tertiary trauma center, n (%) Time from admission to surgical rib fixation (), median (IQR)
Matched population
Surgical group (n = 90)
Control group (n = 4487)
P
Surgical group (n = 84)
Control group (n = 336)
P
27 (30.0)
1552 (34.6)
.43
25 (29.8)
111 (33.0)
.60
38 (42.2) 28 (31.1) 24 (26.7) 21 (23.3) 31 (34.4) 9 (10.0) 23 (25.6)
1604 (35.7) 1489 (33.2) 1394 (31.1) 206 (4.6) 803 (17.9) 101 (2.3) 315 (7.0)
.43
36 (42.9) 27 (32.1) 21 (25.0) 17 (20.2) 27 (32.1) 7 (8.3) 19 (22.6)
126 (37.5) 121 (36.0) 89 (26.5) 83 (24.7) 123 (36.6) 22 (6.5) 80 (23.8)
.66
58 (64.4) 14 (15.6) 7 (7.8) 11 (12.2) 13 (14.4)
3264 (72.7) 833 (18.6) 234 (5.2) 156 (3.5) 46 (1.0)
b.001
56 (66.7) 12 (14.3) 7 (8.3) 9 (10.7) 10 (11.9)
197 (58.6) 47 (14.0) 36 (10.7) 56 (16.7) 48 (14.3)
.72
3 (3.3) 2 (2.2) 24 (26.7) 6 (6.7) 3 (3.3) 26 (28.9) 4 (4.4) 39 (43.3) 4 (2-7)
63 (1.4) 113 (2.5) 69 (1.5) 88 (2.0) 61 (1.4) 723 (16.1) 167 (3.7) 1936 (43.1) N/A
.14 1.00 b.001 .01 .13 .002 .58 1.00 N/A
3 (3.6) 2 (2.4) 19 (22.6) 4 (4.8) 3 (3.6) 25 (29.8) 3 (3.6) 36 (42.9) 4 (2-8)
13 (3.9) 5 (1.5) 65 (19.3) 22 (6.5) 17 (5.1) 111 (33.0) 17 (5.1) 176 (52.4) N/A
1.00 .63 .54 .80 .78 .60 .78 .14 N/A
b.001 b.001 b.001 b.001 b.001
.47 .53 .63 .89 .45
IQR indicates interquartile range; N/A, not applicable.
subgroup analysis for patients excluding those who received craniotomy, spinal fusion, laparotomy, pelvic ORIF, or transarterial embolization in the matched population. The threshold for significance was P b .05. The 1:4 propensity score matching was performed using the psmatch2 procedure in Stata 13.0 (StataCorp, College Station, Tex). Other statistical analyses were performed using SPSS Statistics version 20.0 (IBM SPSS, Armonk, NY). 3. Results During the study period, 34627 patients with rib fractures were admitted to participating hospitals. Of them, 4955 patients were admitted to 64 hospitals where surgical rib fixation was performed for at least 1 trauma patient during the period (Fig. 1). Surgical fixation for rib fractures was performed for 115 trauma patients during the study period. Among the 4955 patients, 378 patients were excluded in accordance with the exclusion criteria (Fig. 1). No patients who received surgical rib fixation died within 10 days of hospital admission. In the prematched population, 90 (2.0%) patients who underwent surgical rib fixation within 10 days of hospital admission were included in the surgical group, and 4487 (98.0%) patients were included in the control group (Fig. 1). In the prematched population, the JCS scores on admission in the surgical group were significantly higher than those in the control group. In addition, the patients in the surgical group were more likely to receive mechanical ventilation, chest drainage, catecholamines, and transfusions on admission than those in the control group. The proportion of patients with flail chest was also significantly higher in the
surgical group than that in the control group. Patients in the surgical group were more likely to receive surgical interventions for associated injuries such as thoracotomy, laparotomy, and limb ORIF (Table 1). By the 1:4 propensity score matching, we obtained 84 and 336 patients in the surgical group and control group, respectively (Fig. 1). The c statistic for goodness of fit was 0.82. In the matched population, the baseline characteristics were successfully balanced between the surgical and control groups (Table 1). In the matched population, the proportion of patients who underwent prolonged mechanical ventilation or died within 28 days tended to be lower in the surgical group than in the control group (22.6% vs 33.3%, P = .065; Table 2). However, the proportion of patients who underwent tracheostomy or died within 28 days, 28-day mortality, and length of hospital stay did not differ significantly between the surgical group and the control group (Table 2). In the matched population, the numbers of patients who did not receive craniotomy, spinal fusion, laparotomy, pelvic ORIF, or transarterial embolization were 69 (82.1%) of 84 in the surgical group and 279 (83.0%) of 336 in the control group (Table 3). In the subgroup analysis, the proportion of patients who underwent prolonged mechanical ventilation or died within 28 days tended to be lower in the surgical group than in the control group (18.8% vs 30.8%, P = .053). The proportion of patients who underwent tracheostomy or died within 28 days and 28-day mortality did not differ significantly between the surgical and control groups (Table 3). In the logistic regression analyses, surgical rib fixation within 10 days of hospital admission was negatively associated with prolonged
Table 2 Comparisons of the outcomes between the surgical and control groups in the 1:4 propensity-matched patients
Prolonged mechanical ventilation or death within 28 d, n (%) Tracheotomy or death within 28 d, n (%) 28-d mortality, n (%) Length of hospital stay (d), median (IQR)
Surgical group (n = 84)
Control group (n = 336)
P
19 (22.6) 13 (15.5) 3 (3.6) 33 (24-45)
112 (33.3) 74 (22.0) 6 (1.8) 42 (23-58)
.065 .229 .392 .427
IQR indicates interquartile range.
Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027
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T. Wada et al. / Journal of Critical Care xxx (2015) xxx–xxx
Table 3 Comparisons of the outcomes between the surgical and control groups of the matched patients after exclusion of those who received craniotomy, spinal fusion, laparotomy, pelvic ORIF, or TAE during hospitalization
Prolonged mechanical ventilation or death within 28 d, n (%) Tracheotomy or death within 28 d, n (%) 28-d mortality, n (%)
Surgical group (n = 69)
Control group (n = 279)
P
13 (18.8) 11 (15.9) 2 (2.9)
86 (30.8) 58 (20.8) 5 (1.8)
.053 .404 .629
TAE indicates transarterial embolization.
mechanical ventilation or death within 28 days (odds ratio, 0.59; 95% confidence interval, 0.36-0.96; P = .034; Table 4). This association persisted after exclusion of patients who received craniotomy, spinal fusion, laparotomy, pelvic ORIF, or transarterial embolization in the matched patients (odds ratio, 0.52; 95% confidence interval, 0.29-0.94; P = .031; Table 4). 4. Discussion The surgical rib fixation within 10 days of hospital admission may prevent patients with traumatic rib fractures from prolonged mechanical ventilation or death within 28 days. The matched population was more likely to include patients with severe injuries than the unmatched population in the present study. Patients in the matched population were more likely to have impaired consciousness on admission as well as flail chest than those in the total population. They also tended to receive procedures for resuscitation on admission and interventions for associated injuries. Thus, the propensity-matched analysis showed that surgical rib fixation was beneficial for patients with severe injuries. Our study has several strengths. First, we used a national inpatient database. To the best of our knowledge, previous studies related to the efficacy or effectiveness of surgical rib fixation on outcomes included 3 randomized controlled trials with small sample sizes [3–5] and retrospective studies conducted in one or a few hospitals [12,13]. Thus, our findings may be more generalizable to patients with rib fractures than those in the previous studies. Second, a propensity score–matched analysis was performed with detailed baseline characteristics as well as interventions performed for associated injuries. These characteristics were identified using not only ICD-10 codes recorded in the DPC database but also procedures performed in each patient. We believe that the identification of patient characteristics using procedures performed was more accurate than that based solely on recorded ICD-10 codes. Third, we examined 420 patients in the matched population. This sample size is the highest among those in previous studies [12,13]. The 3 randomized controlled trials as well as recent retrospective studies demonstrated that surgical rib fixation reduced the duration of mechanical ventilation in patients who had flail chest and required mechanical ventilation [3–5,14,15]. These studies support our finding that surgical rib fixation may reduce the necessity for prolonged mechanical ventilation in patients with rib fractures. We evaluated patients who underwent surgical rib fixation within 10 days in the surgical group. The period from hospital admission to
surgery varied from patient to patient in the present study. In fact, the optimal timing of surgery for rib fractures remains unknown. In a previous randomized controlled trial from Japan, the mean duration between hospital admission and surgery was 8.4 ± 4.1 days [3]. Another study suggested that earlier surgical rib fixation was associated with greater improvement in patient outcomes [15]. To identify the optimal timing for surgical rib fixation, further studies are required. Several limitations should be acknowledged. First, as a secondary data analysis using an administrative claims database, there may be some miscoding or uncoding. Second, the DPC database does not contain an established severity score such as Injury Severity Score. Also, we could not identify the extent of pulmonary contusion, which was suggested that affected the outcomes in patients who receive the surgical rib fixation [16]. In addition, we could not identify how many ribs or which ribs were fractured in each patient. Nevertheless, we adjusted several indicators for injury severity, such as mental status at admission, procedures performed at admission including mechanical ventilation and chest drainage, and interventions performed for associated injuries. We believe that the injury severities were sufficiently balanced between the surgical and control groups using these variables. Third, the indications for rib fracture surgery in each hospital could not be identified in the present study. Previous studies suggested several potential surgical indications for rib fractures including flail chest, severe chest wall deformity, and acute pain [17–19]. However, these indications for surgical rib fixation are still controversial. Thus, the indications for surgery may have differed among the participating hospitals. We were able to identify patients with flail chest, which is a well-known possible indication for surgery [17–19]. However, we could not identify the reasons why patients without flail chest received surgical rib fixation. Similarly, we could not identify the reason why patients with flail chest in the control group did not receive surgical rib fixation. Further studies are required to identify the optimal indications for surgery. Finally, we could not identify which method of rib ORIF was used for each patient in the surgical group. Despite these limitations, the present study suggested that the surgical rib fixation is beneficial for patients with severe chest injuries. We reconfirmed that most patients with rib fractures were treated conservatively. Some of these patients were mandated for prolonged mechanical ventilation, which may be prevented by receiving surgical rib fixation. The present study could not directly reach a definitive conclusion in terms of whether surgical rib fixation is beneficial for patients. However, we believe that the findings of the present study provide circumstantial evidence for a benefit. Further studies are required to
Table 4 Odds ratios of surgical rib fixation for the outcomes in the logistic regression analyses of the 1:4 propensity-matched patients
Surgical rib fixation For total patients For patients who did not receive craniotomy, spinal fusion, laparotomy, pelvic ORIF, or TAE
Prolonged mechanical ventilation or death within 28 d
Tracheotomy or death within 28 d
Odds ratio (95% CI)
P
Odds ratio (95% CI)
P
0.59 (0.36-0.96) 0.52 (0.29-0.94)
.034 .031
0.65 (0.35-1.22) 0.72 (0.36-1.46)
.176 .365
CI indicates confidence interval; TAE, transarterial embolization.
Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027
T. Wada et al. / Journal of Critical Care xxx (2015) xxx–xxx
establish reliable indications for the surgery. Furthermore, large-scale randomized control trials with reasonable indication for the surgery are also warranted. 5. Conclusions In conclusion, the present study suggested that surgical rib fixation within 10 days reduced the risk of receiving prolonged mechanical ventilation or death within 28 days in patients with rib fractures. Further studies are required to identify a reasonable indication for the surgery and to confirm the effectiveness. Acknowledgments This work was supported by grants for Research on Policy Planning and Evaluation from the Ministry of Health, Labour and Welfare, Japan (Grant No. H27-Policy-Designated-009 and H27-Policy-Strategy-011). References [1] Dehghan N, de Mestral C, McKee MD, Schemitsch EH, Nathens A. Flail chest injuries: a review of outcomes and treatment practices from the National Trauma Data Bank. J Trauma Acute Care Surg 2014;76:462–8. [2] Kerr-Valentic M, Arthur M, Mullins RJ, Pearson TE, Mayberry JC. Rib fracture pain and disability: can we do better? J Trauma 2003;54:1058–63. [3] Tanaka H, Yukioka T, Yamaguti Y, Shimizu S, Goto H, Matsuda H, et al. Surgical stabilization of internal pneumatic stabilization? A prospective randomized study of management of severe flail chest patients. J Trauma 2002;52:727–32. [4] Granetzny A, Abd El-Aal M, Emam E, Shalaby A, Boseila A. Surgical versus conservative treatment of flail chest. Evaluation of the pulmonary status. Interact Cardiovasc Thorac Surg 2005;4:583–7.
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[5] Marasco SF, Davies AR, Cooper J, Varma D, Bennett V, Nevill R, et al. Prospective randomized controlled trial of operative rib fixation in traumatic flail chest. J Am Coll Surg 2013;216:924–32. [6] Mayberry JC, Ham LB, Schipper PH, Ellis TJ, Mullins RJ. Surveyed opinion of American trauma, orthopedic, and thoracic surgeons on rib and sternal fracture repair. J Trauma 2009;66:875–9. [7] Sumitani M, Uchida K, Yasunaga H, Horiguchi H, Kusakabe Y, Matsuda S, et al. Prevalence of malignant hyperthermia and relationship with anesthetics in Japan: data from the Diagnosis Procedure Combination database. Anesthesiology 2011;114:84–90. [8] Isogai T, Yasunaga H, Matsui H, Tanaka H, Ueda T, Horiguchi H, et al. Out-of-hospital versus in-hospital Takotsubo cardiomyopathy: analysis of 3719 patients in the Diagnosis Procedure Combination database in Japan. Int J Cardiol 2014;176:413–7. [9] Ohta T, Waga S, Handa W, Saito I, Takeuchi K. New grading of level of disordered consciousness (author's transl). No Shinkei Geka 1974;2:623–7. [10] Shigematsu K, Nakano H, Watanabe Y. The eye response test alone is sufficient to predict stroke outcome—reintroduction of Japan Coma Scale: a cohort study. BMJ Open 2013;3:1–5 e002736. [11] Rosenbaum PR, Rubin DB. Constructing a control group using multivariate matched sampling methods that incorporate the propensity score. Am Stat 1985;39:33–8. [12] Leinicke JA, Elmore L, Freeman BD, Colditz GA. Operative management of rib fractures in the setting of flail chest: a systematic review and meta-analysis. Ann Surg 2013;258:914–21. [13] Slobogean GP, MacPherson CA, Sun T, Pelletier M-E, Hameed SM. Surgical fixation vs nonoperative management of flail chest: a meta-analysis. J Am Coll Surg 2013;216: 302–11. [14] Doben AR, Eriksson EA, Denlinger CE, Leon SM, Couillard DJ, Fakhry SM, et al. Surgical rib fixation for flail chest deformity improves liberation from mechanical ventilation. J Crit Care 2014;29:139–43. [15] Althausen PL, Shannon S, Watts C, Thomas K, Bain M, Coll D, et al. Early surgical stabilization of flail chest with locked plate fixation. J Orthop Trauma 2011;25:641–7. [16] Voggenreiter G, Neudeck F, Aufmkolk M, Obertacke U, Schmit-Neuerburg KP. Operative chest wall stabilization in flail chest—outcomes of patients with or without pulmonary contusion. J Am Coll Surg 1998;187:130–8. [17] Nirula R, Diaz JJ, Trunkey DD, Mayberry JC. Rib fracture repair: indications, technical issues, and future directions. World J Surg 2009;33:14–22. [18] Lafferty PM, Anavian J, Will RE, Cole P. Operative treatment of chest wall injuries: indications, technique, and outcomes. J Bone Joint Surg Am 2011;93:97–110. [19] De Jong MB, Kokke MC, Hietbrink F, Leenen LPH. Surgical management of rib fractures: strategies and literature review. Scand J Surg 2014;2:120–5.
Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027
Contents lists available at ScienceDirect
Journal of Critical Care journal homepage: www.jccjournal.org
Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity score–matched analysis Tomoki Wada, MD a,⁎, Hideo Yasunaga, MD, PhD b, Ryota Inokuchi, MD, PhD a, Hiroki Matsui, PhD b, Takehiro Matsubara, MD, PhD a, Yoshihiro Ueda, MD a, Masataka Gunshin, MD a, Takeshi Ishii, MD a, Kent Doi, MD, PhD a, Yoichi Kitsuta, MD, PhD a, Susumu Nakajima, MD, PhD a, Kiyohide Fushimi, MD, PhD c, Naoki Yahagi, MD, PhD a a b c
Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, Tokyo, Japan Department of Clinical Epidemiology and Health Economics, School of Public Health, The University of Tokyo, Tokyo, Japan Department of Health Care Informatics, Tokyo Medical and Dental University, Tokyo, Japan
a r t i c l e
i n f o
Keywords: Traumatic rib fracture Surgical rib fixation Survival analysis Cohort study Diagnosis Procedure Combination database Propensity score matching
a b s t r a c t Purpose: We investigated whether surgical rib fixation improved outcomes in patients with traumatic rib fractures. Materials and Methods: This was a retrospective study using a Japanese administrative claim and discharge database. We included patients with traumatic rib fractures admitted to hospitals where surgical rib fixation was available from July 1 2010, to March 31, 2013. We detected patients who underwent surgical rib fixation within 10 days of hospital admission (surgical group) and those who did not (control group). The main outcome was prolonged mechanical ventilation, defined as that performed for 5 or more days, or death within 28 days. One-to-four propensity score matching was performed between the 2 groups with adjustment for possible confounders. Results: Among 4577 eligible patients, 90 (2.0%) underwent the surgical rib fixation. After the matching, we obtained 84 and 336 patients in the surgical and control groups, respectively. Logistic regression analyses showed that the surgical group was significantly less likely to receive prolonged mechanical ventilation or die within 28 days than the control group (22.6% vs 33.3%; odds ratio, 0.59; 95% confidence interval, 0.36-0.96; P = .034). Conclusions: Surgical rib fixation within 10 days of hospital admission may improve outcomes in patients with traumatic rib fractures. © 2015 Elsevier Inc. All rights reserved.
1. Introduction Most rib fractures are treated nonoperatively. In fact, a study using the National Trauma Data Bank showed that only 0.7% of patients with flail chest, which is one of the most severe conditions in multiple rib fractures, received surgical fixation for rib fractures [1]. However, patients who received conservative treatments for rib fractures often had long-lasting disability [2]. Thus, the current nonoperative treatments for rib fractures are not necessarily ideal for the patients. Several previous studies have shown the benefits of surgical rib fixation, including 3 randomized controlled trials [3–5]. Nevertheless, these studies involved small sample sizes. Consequently, operative management is not recognized as a standard treatment option, even for flail chest. A previous study in the United States involving trauma, orthopedic, and thoracic surgeons reported that only 26% had performed or assisted on surgical fixation for rib fractures [6]. Because of
⁎ Corresponding author at: Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Tel.: +81 3 5800 8681; fax: +81 3 3814 6446. E-mail address: [email protected] (T. Wada).
the potential benefits for patients with rib fractures, the effects of surgical rib fixation on outcomes need to be further evaluated. We investigated the effects of surgical fixation for rib fractures on patient outcomes in a real-world clinical setting, using a national administrative claims and discharge database in Japan.
2. Materials and methods 2.1. Study design and setting The present study was a retrospective cohort study. We used a Japanese national administrative claims and discharge abstract database called the Diagnosis Procedure Combination (DPC) database [7,8]. This database collects data for all inpatients discharged from participating hospitals. In 2013, approximately 1000 hospitals including 82 university hospitals participated in the database system. The DPC database contains the following information for individual patients: age; sex; diagnoses including primary diagnoses, complications during hospitalization, and preexisting comorbidities; medical and surgical procedures performed; drugs used; and discharge status. Diagnoses are recorded by both International Classification of Diseases,
http://dx.doi.org/10.1016/j.jcrc.2015.07.027 0883-9441/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027
2
T. Wada et al. / Journal of Critical Care xxx (2015) xxx–xxx
10th Revision (ICD-10) codes and text data written in Japanese. Procedures and drugs are recorded with the dates of use. The present study was approved by the institutional review boards and ethics committee of The University of Tokyo. Informed consent was waived because of the anonymous nature of the data. 2.2. Patient selection Among all the inpatients recorded in the DPC database, we included those who satisfying all of the following criteria: admission to hospitals with injuries including rib fractures (S223, S224, or S225) from July 1, 2010 to March 31, 2013, and admission to hospitals where surgical fixation for rib fractures was performed for at least 1 patient during the study period. We divided the patients into a surgical group and a control group. The surgical group contained patients who received surgical rib fixation within 10 days of hospital admission, whereas the control group contained those who did not. Patients who died within 10 days of hospital admission were excluded. Patients younger than 20 years were also excluded. 2.3. Variables Patients were subdivided into 3 age groups: b 59, 60-74, and ≥75 years. To adjust for injury severity, we used the following items: Japan Coma Scale (JCS) score on admission; procedures performed on admission including mechanical ventilation, chest drainage, catecholamine use, and transfusion; and interventions for associated injuries performed during hospitalization. The JCS is a scale for measuring impaired consciousness [9,10]. For the JCS, a score of 0 indicates alertness, singledigit scores of 1 to 3 indicate drowsiness, double-digit scores of 10 to 30 indicate somnolence, and triple-digit scores of 100 to 300 indicate coma. The interventions for associated injuries were as follows: craniotomy, spinal fusion, thoracotomy, laparotomy, pelvic internal fixation, open reduction and internal fixation (ORIF) for limb fractures, and transarterial
embolization. We also identified whether hospitals were tertiary trauma centers or not. The outcomes of interest were prolonged mechanical ventilation for 5 or more days or death within 28 days, tracheotomy or death within 28 days, 28-day mortality, and length of hospital stay. The definition of prolonged mechanical ventilation was derived from the finding that the median duration of mechanical ventilation was 5 days among patients with rib fractures who required mechanical ventilation in this study. 2.4. Statistical analysis We performed a 1:4 propensity score matching between the surgical group and the control group. This matching was performed to enhance the baseline comparability between the 2 groups. A logistic regression model was used to estimate a propensity score for the receipt of surgical fixation for rib fractures for each patient. The following factors were included in the model: patient age and sex; procedures performed on admission including mechanical ventilation, chest drainage, transfusion, and the use of catecholamines; the JCS scores on admission; the presence of flail chest; associated injuries requiring surgical or radiologic interventions; and hospital type. The c statistic was calculated to evaluate the goodness of fit for the model. Each patient in the control group was matched with a patient in the surgical group with the closest estimated propensity on the logit scale within a specified range (≤ 0.20 of the pooled SD of estimated logits) [11]. In both the total population and the matched population, categorical data were compared between the surgical group and the control group using the χ 2 test or Fisher exact test as appropriate, whereas continuous data were compared using the Mann-Whitney U test. In addition, we performed logistic regression analyses of surgical rib fixation for the 2 outcomes of prolonged mechanical ventilation or death within 28 days, and tracheotomy or death within 28 days. The logistic regression analyses were fitted with generalized estimating equations that accounted for the pairwise nature of the surgical patients and the controls. Because severe head and torso injuries are strong predictors of outcome in patients, we performed a
Fig. 1. Selection process of the surgical and control groups.
Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027
T. Wada et al. / Journal of Critical Care xxx (2015) xxx–xxx
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Table 1 Baseline characteristics in the surgical and control groups Total population
Sex (female), n (%) Age groups (y), n (%) b60 60-74 ≥75 Intubation on admission, n (%) Chest drainage on admission, n (%) Catecholamine use on admission, n (%) Transfusion on admission, n (%) JCS score on admission, n (%) 0 1-3 10-30 100-300 Flail chest Interventions for associated injuries, n (%) Craniotomy Spinal fusion Thoracotomy Laparotomy Pelvic ORIF Limb ORIF Transarterial embolization Admission to tertiary trauma center, n (%) Time from admission to surgical rib fixation (), median (IQR)
Matched population
Surgical group (n = 90)
Control group (n = 4487)
P
Surgical group (n = 84)
Control group (n = 336)
P
27 (30.0)
1552 (34.6)
.43
25 (29.8)
111 (33.0)
.60
38 (42.2) 28 (31.1) 24 (26.7) 21 (23.3) 31 (34.4) 9 (10.0) 23 (25.6)
1604 (35.7) 1489 (33.2) 1394 (31.1) 206 (4.6) 803 (17.9) 101 (2.3) 315 (7.0)
.43
36 (42.9) 27 (32.1) 21 (25.0) 17 (20.2) 27 (32.1) 7 (8.3) 19 (22.6)
126 (37.5) 121 (36.0) 89 (26.5) 83 (24.7) 123 (36.6) 22 (6.5) 80 (23.8)
.66
58 (64.4) 14 (15.6) 7 (7.8) 11 (12.2) 13 (14.4)
3264 (72.7) 833 (18.6) 234 (5.2) 156 (3.5) 46 (1.0)
b.001
56 (66.7) 12 (14.3) 7 (8.3) 9 (10.7) 10 (11.9)
197 (58.6) 47 (14.0) 36 (10.7) 56 (16.7) 48 (14.3)
.72
3 (3.3) 2 (2.2) 24 (26.7) 6 (6.7) 3 (3.3) 26 (28.9) 4 (4.4) 39 (43.3) 4 (2-7)
63 (1.4) 113 (2.5) 69 (1.5) 88 (2.0) 61 (1.4) 723 (16.1) 167 (3.7) 1936 (43.1) N/A
.14 1.00 b.001 .01 .13 .002 .58 1.00 N/A
3 (3.6) 2 (2.4) 19 (22.6) 4 (4.8) 3 (3.6) 25 (29.8) 3 (3.6) 36 (42.9) 4 (2-8)
13 (3.9) 5 (1.5) 65 (19.3) 22 (6.5) 17 (5.1) 111 (33.0) 17 (5.1) 176 (52.4) N/A
1.00 .63 .54 .80 .78 .60 .78 .14 N/A
b.001 b.001 b.001 b.001 b.001
.47 .53 .63 .89 .45
IQR indicates interquartile range; N/A, not applicable.
subgroup analysis for patients excluding those who received craniotomy, spinal fusion, laparotomy, pelvic ORIF, or transarterial embolization in the matched population. The threshold for significance was P b .05. The 1:4 propensity score matching was performed using the psmatch2 procedure in Stata 13.0 (StataCorp, College Station, Tex). Other statistical analyses were performed using SPSS Statistics version 20.0 (IBM SPSS, Armonk, NY). 3. Results During the study period, 34627 patients with rib fractures were admitted to participating hospitals. Of them, 4955 patients were admitted to 64 hospitals where surgical rib fixation was performed for at least 1 trauma patient during the period (Fig. 1). Surgical fixation for rib fractures was performed for 115 trauma patients during the study period. Among the 4955 patients, 378 patients were excluded in accordance with the exclusion criteria (Fig. 1). No patients who received surgical rib fixation died within 10 days of hospital admission. In the prematched population, 90 (2.0%) patients who underwent surgical rib fixation within 10 days of hospital admission were included in the surgical group, and 4487 (98.0%) patients were included in the control group (Fig. 1). In the prematched population, the JCS scores on admission in the surgical group were significantly higher than those in the control group. In addition, the patients in the surgical group were more likely to receive mechanical ventilation, chest drainage, catecholamines, and transfusions on admission than those in the control group. The proportion of patients with flail chest was also significantly higher in the
surgical group than that in the control group. Patients in the surgical group were more likely to receive surgical interventions for associated injuries such as thoracotomy, laparotomy, and limb ORIF (Table 1). By the 1:4 propensity score matching, we obtained 84 and 336 patients in the surgical group and control group, respectively (Fig. 1). The c statistic for goodness of fit was 0.82. In the matched population, the baseline characteristics were successfully balanced between the surgical and control groups (Table 1). In the matched population, the proportion of patients who underwent prolonged mechanical ventilation or died within 28 days tended to be lower in the surgical group than in the control group (22.6% vs 33.3%, P = .065; Table 2). However, the proportion of patients who underwent tracheostomy or died within 28 days, 28-day mortality, and length of hospital stay did not differ significantly between the surgical group and the control group (Table 2). In the matched population, the numbers of patients who did not receive craniotomy, spinal fusion, laparotomy, pelvic ORIF, or transarterial embolization were 69 (82.1%) of 84 in the surgical group and 279 (83.0%) of 336 in the control group (Table 3). In the subgroup analysis, the proportion of patients who underwent prolonged mechanical ventilation or died within 28 days tended to be lower in the surgical group than in the control group (18.8% vs 30.8%, P = .053). The proportion of patients who underwent tracheostomy or died within 28 days and 28-day mortality did not differ significantly between the surgical and control groups (Table 3). In the logistic regression analyses, surgical rib fixation within 10 days of hospital admission was negatively associated with prolonged
Table 2 Comparisons of the outcomes between the surgical and control groups in the 1:4 propensity-matched patients
Prolonged mechanical ventilation or death within 28 d, n (%) Tracheotomy or death within 28 d, n (%) 28-d mortality, n (%) Length of hospital stay (d), median (IQR)
Surgical group (n = 84)
Control group (n = 336)
P
19 (22.6) 13 (15.5) 3 (3.6) 33 (24-45)
112 (33.3) 74 (22.0) 6 (1.8) 42 (23-58)
.065 .229 .392 .427
IQR indicates interquartile range.
Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027
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Table 3 Comparisons of the outcomes between the surgical and control groups of the matched patients after exclusion of those who received craniotomy, spinal fusion, laparotomy, pelvic ORIF, or TAE during hospitalization
Prolonged mechanical ventilation or death within 28 d, n (%) Tracheotomy or death within 28 d, n (%) 28-d mortality, n (%)
Surgical group (n = 69)
Control group (n = 279)
P
13 (18.8) 11 (15.9) 2 (2.9)
86 (30.8) 58 (20.8) 5 (1.8)
.053 .404 .629
TAE indicates transarterial embolization.
mechanical ventilation or death within 28 days (odds ratio, 0.59; 95% confidence interval, 0.36-0.96; P = .034; Table 4). This association persisted after exclusion of patients who received craniotomy, spinal fusion, laparotomy, pelvic ORIF, or transarterial embolization in the matched patients (odds ratio, 0.52; 95% confidence interval, 0.29-0.94; P = .031; Table 4). 4. Discussion The surgical rib fixation within 10 days of hospital admission may prevent patients with traumatic rib fractures from prolonged mechanical ventilation or death within 28 days. The matched population was more likely to include patients with severe injuries than the unmatched population in the present study. Patients in the matched population were more likely to have impaired consciousness on admission as well as flail chest than those in the total population. They also tended to receive procedures for resuscitation on admission and interventions for associated injuries. Thus, the propensity-matched analysis showed that surgical rib fixation was beneficial for patients with severe injuries. Our study has several strengths. First, we used a national inpatient database. To the best of our knowledge, previous studies related to the efficacy or effectiveness of surgical rib fixation on outcomes included 3 randomized controlled trials with small sample sizes [3–5] and retrospective studies conducted in one or a few hospitals [12,13]. Thus, our findings may be more generalizable to patients with rib fractures than those in the previous studies. Second, a propensity score–matched analysis was performed with detailed baseline characteristics as well as interventions performed for associated injuries. These characteristics were identified using not only ICD-10 codes recorded in the DPC database but also procedures performed in each patient. We believe that the identification of patient characteristics using procedures performed was more accurate than that based solely on recorded ICD-10 codes. Third, we examined 420 patients in the matched population. This sample size is the highest among those in previous studies [12,13]. The 3 randomized controlled trials as well as recent retrospective studies demonstrated that surgical rib fixation reduced the duration of mechanical ventilation in patients who had flail chest and required mechanical ventilation [3–5,14,15]. These studies support our finding that surgical rib fixation may reduce the necessity for prolonged mechanical ventilation in patients with rib fractures. We evaluated patients who underwent surgical rib fixation within 10 days in the surgical group. The period from hospital admission to
surgery varied from patient to patient in the present study. In fact, the optimal timing of surgery for rib fractures remains unknown. In a previous randomized controlled trial from Japan, the mean duration between hospital admission and surgery was 8.4 ± 4.1 days [3]. Another study suggested that earlier surgical rib fixation was associated with greater improvement in patient outcomes [15]. To identify the optimal timing for surgical rib fixation, further studies are required. Several limitations should be acknowledged. First, as a secondary data analysis using an administrative claims database, there may be some miscoding or uncoding. Second, the DPC database does not contain an established severity score such as Injury Severity Score. Also, we could not identify the extent of pulmonary contusion, which was suggested that affected the outcomes in patients who receive the surgical rib fixation [16]. In addition, we could not identify how many ribs or which ribs were fractured in each patient. Nevertheless, we adjusted several indicators for injury severity, such as mental status at admission, procedures performed at admission including mechanical ventilation and chest drainage, and interventions performed for associated injuries. We believe that the injury severities were sufficiently balanced between the surgical and control groups using these variables. Third, the indications for rib fracture surgery in each hospital could not be identified in the present study. Previous studies suggested several potential surgical indications for rib fractures including flail chest, severe chest wall deformity, and acute pain [17–19]. However, these indications for surgical rib fixation are still controversial. Thus, the indications for surgery may have differed among the participating hospitals. We were able to identify patients with flail chest, which is a well-known possible indication for surgery [17–19]. However, we could not identify the reasons why patients without flail chest received surgical rib fixation. Similarly, we could not identify the reason why patients with flail chest in the control group did not receive surgical rib fixation. Further studies are required to identify the optimal indications for surgery. Finally, we could not identify which method of rib ORIF was used for each patient in the surgical group. Despite these limitations, the present study suggested that the surgical rib fixation is beneficial for patients with severe chest injuries. We reconfirmed that most patients with rib fractures were treated conservatively. Some of these patients were mandated for prolonged mechanical ventilation, which may be prevented by receiving surgical rib fixation. The present study could not directly reach a definitive conclusion in terms of whether surgical rib fixation is beneficial for patients. However, we believe that the findings of the present study provide circumstantial evidence for a benefit. Further studies are required to
Table 4 Odds ratios of surgical rib fixation for the outcomes in the logistic regression analyses of the 1:4 propensity-matched patients
Surgical rib fixation For total patients For patients who did not receive craniotomy, spinal fusion, laparotomy, pelvic ORIF, or TAE
Prolonged mechanical ventilation or death within 28 d
Tracheotomy or death within 28 d
Odds ratio (95% CI)
P
Odds ratio (95% CI)
P
0.59 (0.36-0.96) 0.52 (0.29-0.94)
.034 .031
0.65 (0.35-1.22) 0.72 (0.36-1.46)
.176 .365
CI indicates confidence interval; TAE, transarterial embolization.
Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027
T. Wada et al. / Journal of Critical Care xxx (2015) xxx–xxx
establish reliable indications for the surgery. Furthermore, large-scale randomized control trials with reasonable indication for the surgery are also warranted. 5. Conclusions In conclusion, the present study suggested that surgical rib fixation within 10 days reduced the risk of receiving prolonged mechanical ventilation or death within 28 days in patients with rib fractures. Further studies are required to identify a reasonable indication for the surgery and to confirm the effectiveness. Acknowledgments This work was supported by grants for Research on Policy Planning and Evaluation from the Ministry of Health, Labour and Welfare, Japan (Grant No. H27-Policy-Designated-009 and H27-Policy-Strategy-011). References [1] Dehghan N, de Mestral C, McKee MD, Schemitsch EH, Nathens A. Flail chest injuries: a review of outcomes and treatment practices from the National Trauma Data Bank. J Trauma Acute Care Surg 2014;76:462–8. [2] Kerr-Valentic M, Arthur M, Mullins RJ, Pearson TE, Mayberry JC. Rib fracture pain and disability: can we do better? J Trauma 2003;54:1058–63. [3] Tanaka H, Yukioka T, Yamaguti Y, Shimizu S, Goto H, Matsuda H, et al. Surgical stabilization of internal pneumatic stabilization? A prospective randomized study of management of severe flail chest patients. J Trauma 2002;52:727–32. [4] Granetzny A, Abd El-Aal M, Emam E, Shalaby A, Boseila A. Surgical versus conservative treatment of flail chest. Evaluation of the pulmonary status. Interact Cardiovasc Thorac Surg 2005;4:583–7.
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Please cite this article as: Wada T, et al, Effectiveness of surgical rib fixation on prolonged mechanical ventilation in patients with traumatic rib fractures: A propensity ..., J Crit Care (2015), http://dx.doi.org/10.1016/j.jcrc.2015.07.027