Abstract
Background and Aims:
Blunt thoracic injury is a common cause for hospital admission after trauma. The effect of the number of rib fractures on the outcome is controversial. In this study, our hypothesis was that an increasing number of rib fractures correlates with mortality and hospital resource utilization. In addition to mortality, our focus was on the length of stay at hospital and in the intensive care unit, ventilator days, and the days in continuous positive airway pressure.
Material and Methods:
The present investigation is a retrospective study from a single trauma center. The study includes patients with severe thoracic injury (thoracic Abbreviated Injury Scale (AIS) > 2) admitted to hospital after blunt trauma. Patients with isolated thoracic spine injuries and patients who were dead on arrival were excluded. Vital signs, laboratory results on admission, given care, intensive care unit and hospital length of stay, injuries, and in-hospital mortality were collected for the study.
Results:
A total of 594 patients from a 5-year period (2003–2007) were included in the study. The mean age of the patients was 45 years, and 76.9% of the patients were males. The average Injury Severity Score was 22, and the patients had on average 5.5 injuries. Overall mortality was 6.4%. In the multivariate analysis, the mortality was associated with base excess and tromboplastin time in admission. The number of rib fractures did not correlate with the outcome measures, but the presence of bilateral rib fractures correlated with the outcome measures other than mortality.
Conclusions:
The number of rib fractures does not correlate with mortality or the length of stay in the intensive care unit in blunt trauma patients with severe thoracic injury. Mortality in these patients correlated with the degree of hypoperfusion (base excess) and coagulation abnormalities (tromboplastin time) on admission.
Introduction
Blunt thoracic injury is a common major trauma often combined with multiple other injuries such as intracranial, intra-abdominal, pelvic, spinal, and extremity injuries (1). More than 10% of all trauma patients presenting to the emergency departments worldwide are due to blunt thoracic injuries, and about 25% of all traumatic deaths are caused by blunt thoracic injuries (2). The mortality due to these injuries is relatively high ranging from 3% to 20% (2, 3). Although many patients with blunt thoracic injuries seem to manage relatively well at the initial phase, they often develop complications within the following 24–72 h or even later (4, 5). Adequate pain control, including epidural analgesia, and allowing early aggressive respiratory care to prevent the development of pulmonary complications are essential, particularly in elderly blunt thoracic injury patients (6).
An increasing number of rib fractures in blunt trauma patients has been shown to be associated with increased morbidity and mortality. The presence of more than three rib fractures on chest X-ray in adults is a marker for potential associated solid visceral trauma and mortality, and has, thus, been used as criterion for trauma center transfer (7). Elderly blunt trauma patients with multiple rib fractures are particularly at risk of delayed deterioration (3, 8). Bulger et al. (9) found that elderly patients who sustain blunt chest trauma with rib fractures have twice the mortality and thoracic morbidity compared to younger patients with similar injuries. For each additional rib fracture in the elderly, the mortality increases by 19% and the risk of pneumonia by 27% (9). On the contrary, Whitson et al. (10) found out that the number of rib fractures was not an independent predictor of outcome. Rather, the age and overall trauma burden seem to be more powerful predictors of a poor outcome (10). In a meta-analysis, the risk factors for mortality in patients with blunt thoracic injury were as follows: age of 65 years or more, three or more rib fractures, and the presence of a preexisting disease, particularly a cardiopulmonary disease (11). The development of pneumonia post injury was also a significant risk factor for mortality (11).
As blunt chest injuries are relatively common and often cause significant morbidity and mortality, attention should be focused on the predicting factors contributing to the complications. Clinical symptoms are not considered an accurate predictor of the outcome following non-life-threatening blunt chest trauma (4). Associated injuries and comorbidities should be expected and looked for when dealing with blunt thoracic injuries patients. The difficulty of identifying the high-risk patients in such a population has been an area of interest in the past two decades.
The aim of this study was to identify factors associated with the outcome of patients with severe thoracic injury. Our focus was on mortality, the length of stay (LOS) at hospital and in the intensive care unit (ICU), as well as days in ventilator and in continuous positive airway pressure (CPAP). Our hypothesis was that the number of rib fractures correlates with these parameters.
Methods
The study population consisted of 594 patients with blunt thoracic trauma treated at Töölö Hospital, which is a regional trauma center and part of the Helsinki University Central Hospital. The study period was from 1 January 2003 to 31 December 2007. The inclusion criteria used were thoracic Abbreviated Injury Scale (AIS) > 2 after blunt trauma and hospital admission. Isolated thoracic spine injuries and patients who were dead on arrival were excluded.
The in-hospital records (admission diagnoses, discharge diagnoses, diagnoses during the ICU stay, and operation room diagnoses) were searched to identify patients with chest injuries. A total of 1192 patients were identified with thoracic injuries. Plain chest films and computed tomography (CT) scans of the chest (when available) as well as written radiological reports were used to identify patients with chest AIS > 2. Body CT was done on 521 (88%) patients. After exclusion of patients with chest AIS 1 or 2, a total of 594 patients were identified. For these patients, all medical records were reviewed to ensure thoracic AIS > 2. Blunt cardiac injury is defined as any cardiac injury requiring surgical or radiological intervention, cardiac injury found in autopsy, and clinical diagnosis based on changes in the electrocardiogram (ST changes, acute arrhythmias, and acute blocks) together with an increase in serum/plasma cardiac enzyme (Troponin T).
The data collected from the 594 patients included patient demographics, mechanism of injury (MOI), prehospital treatment, vital signs on admission, physical examinations, given care at hospital, hospital LOS, ICU LOS, ventilator days, days in CPAP, all injuries, 30-day mortality at Töölö Hospital or survival to discharge if earlier than 30 days, and autopsy reports. The ventilator days included only the time ventilated in the ICU. For all patients, the Injury Severity Score (ISS) and New Injury Severity Score (NISS) were calculated using the AIS (2005 version).
The statistical analysis was completed by using the IBM SPSS Statistics for MAC version 21.0 (IBM Corp., Armonk, NY, USA). For statistical analysis, an α-value of 0.05 was considered statistically significant. The Pearson’s chi-square test was used for noncontinuous parameters and the Spearman’s ρ for correlation between continuous parameters. A multivariate logistic regression analysis was performed to identify independent predictors for mortality. The data are presented as mean ± standard deviation, unless otherwise mentioned.
The study protocol was approved by the Institutional Review Board (Helsinki University Central Hospital); according to the Finnish law, an ethical board review is not necessary for study of medical records.
Results
Patient Demographics
The majority of the 594 patients included in the study were males (457 out of 594, 76.9%). The mean age (range 2–90 years) of the male and female patients was 44 ± 17 and 48 ± 19 years, respectively (p = 0.053). The most common mechanisms of injury were motor vehicle accident (45.5%) and falls (26.9%). Low-energy injuries were seen in 28 patients (fall from standing height). On admission, 25 patients had systolic blood pressure (SBP) < 90 and 88 patients had base excess (BE) < −5 (69 patients with BE < −5 had SBP ≥ 90). The demographics of the patients are shown in Table 1. The majority of the patients were brought from the scene (n = 443, 74.6%), and 116 (19.5%) patients were intubated at scene. Most of the patients arriving with spontaneous airway had Glasgow Coma Scale (GCS) of 14–15 on arrival (402 out of 478, 84.0%). In all, 40 patients were intubated at the emergency department.
Patient demographics, N = 594.
high fall: fall from over standing height of the patient; MVA: motor vehicle accident; MOI: mechanism of injury; ISS: Injury Severity Score; NISS: New Injury Severity Score.
Average ± standard deviation.
Injuries
There were 3292 injuries in the 594 patients, resulting in an average of 5.5 injuries per patient (Figs 1 and 2). The average number of thoracic injuries (including wing of the scapula) per patient was 2.4 (rib fractures counted as one injury, regardless of the number of fractured ribs). Fractured ribs were diagnosed in 506 patients (85.1%). The average number of rib fractures in these patients was 6.3. Isolated blunt thoracic injury (maximum AIS = 1 in other body regions) was seen in 115 patients (19.4%) (fractures of the wing of scapula were considered to be part of thoracic injuries). Hemothorax, pneumothorax, and hemopneumothorax were seen in 51 (8.6%), 81 (13.6%), and 114 (19.2%) patients, respectively. The other common thoracic injuries were fractures of the thoracic spine, scapula, and sternum in 117 (19.7%), 70 (11.8%), and 55 (9.3%) of the patients, respectively. Injuries to the thoracic aorta were seen in 16 (2.7%) patients and one of these patients died due to aortic injury.
Axial contrast-enhanced CT image of patient with severe pulmonary injury.
Coronal view of contrast-enhanced CT of patient with chest wall injury resulting severe deformity.
Treatment
The chest drain was inserted in 325 patients and 111 (18.7%) patients required emergency surgery within 24 h of admission. The emergency procedures included 10 thoracotomies (10 out of 111, 9%), 29 laparotomies (29%), 30 orthopedic operations (28%), 7 embolizations (6%), 6 craniotomies (6%), and 26 intracranial pressure measurement-placements (24%). The indications of chest drain insertions were hemo- and/or pneumothorax in 246 patients and prophylactic (in patients who had occult pneumothorax and were mechanically ventilated) in 36 patients. In 43 cases, the indication of chest drain insertion was not obvious from the medical records. The chest drain was kept on average for 7 ± 5 days (median: 6 days).
The average LOS in hospital was 11.6 ± 11.8 days and the average LOS in ICU (n = 428, 72.1%) 8.5 ± 8.6 days. Altogether, 306 (51.5%) patients were intubated and 225 (37.9%) patients needed noninvasive ventilatory support. A total of 427 (71.9%) patients were treated in the ICU. During the stay, 268 patients needed surgery (including emergency surgery). Thoracotomy was done on 21 patients and thoracoscopy on 3 patients. In one patient, the thoracoscopy was converted to thoracotomy. The reasons for thoracic operations were cardiac injury in 3 patients, suspicion of cardiac injury in 1 patient, diaphragmatic injury in 2 patients, aortic injury in 1 patient, and bleeding or retained hemothorax in 14 patients. All operated patients with cardiac injury had a pericardial rupture resulting in dislocation of the heart. A minority of the patients were discharged home (n = 208, 35.0%). Of these patients, 348 were transferred to further care to other health care facilities. Transfer to other facilities was done after all acute surgical interventions were done and the patient did not need care in the ICU. The overall mortality was 6.4% (38 patients).
Factors Associated with Outcome (Mortality, Hospital LOS, ICU LOS, and Ventilator Days)
The parameters with a statistically significant association with ICU LOS and ventilator days and days in CPAP are shown in Table 2. A longer time in the ICU and in the ventilator or CPAP was higher in males, in patients with admission SBP < 90, bilateral rib fractures, or spine operation. There were no gender differences in age or ISS or admission values of SBP, BE, or tromboplastin time % (TT%). The only gender difference was seen in admission hemoglobin (Hb), 116 g/L versus 128 g/L (p < 0.001), for females and males, respectively. None of the parameters studied was associated with hospital LOS.
Factors associated with outcome measures (other than mortality) in univariate analysis.
The values are expressed as mean ± standard deviation.
SBP < 90, systolic blood pressure < 90 mmHg on arrival; SBP ≥ 90, systolic blood pressure ≥ 90 on arrival.
The parameters associated with mortality in the univariate analysis were SBP on admission and the first measured values of BE, Hb, and TT% (Table 3). In the multivariate analysis, only BE and TT% were found to associate to mortality. BE ranged from 5 mmol/L to −21.7 mmol/L and TT% from 168% to 10%. The odds ratio (OR) for BE was 1.139 (per 1 mmol/L decrement), and for TT% the OR was 1.029 (per 1% decrement) (Table 4.). There were no statistically significant differences in age, sex, ISS, AIS grade, NISS, or MOI between the survivors and nonsurvivors (Table 3).
Comparison between survivors and nonsurvivors.
BE: base excess; Hb: hemoglobin on arrival; TT%: tromboplastin time; SBP: systolic blood pressure; ISS: Injury Severity Score.
p < 0.001 between survivors and nonsurvivors in univariate analysis. Values are expressed as mean ± standard deviation, unless otherwise mentioned.
Factors associated with mortality in multivariate analysis.
BE: base excess; TT%: tromboplastin time; OR: odds ratio; 95% CI: 95% confidence interval.
The number of rib fractures did not associate with mortality (p = 0.751) and was weakly correlated with the LOS in hospital (correlation coefficient = 0.198) in the whole study group. When analyzing only the patients with rib fractures, no association was found between the number of rib fractures and mortality, hospital LOS, ICU LOS, or time in the ventilator or CPAP. We also analyzed the effect of bilateral versus unilateral rib fractures but found no statistically significant difference (p = 0.068) in mortality between the three groups of patients: (1) no rib fractures, (2) unilateral rib fractures, and (3) bilateral rib fractures. Also, when comparing only patients with unilateral rib fractures to patients with bilateral rib fractures, no differences were found (p = 0.255). There was also no statistically significant correlation found in the effect of rib fractures on mortality, ICU LOS, days ventilated, and days in CPAP in patients who did not have body CT scans taken on admission.
Discussion
In this study population, the number of rib fractures was not associated with mortality or the LOS in the ICU or at hospital. The finding is similar to that by Whitson et al. (10) in National Trauma Data Bank study. However, our study population is slightly different, as we included only hospitalized patients with severe (thoracic AIS > 2) injuries, whereas Whitson et al. (10) included all patients with rib fractures, regardless of the thoracic AIS. The results of both of these studies clearly suggest that the number of rib fractures per se is not determinant for the outcome when severely injured patients are evaluated as one population. In a recent meta-analysis (11), three or more rib fractures were found to associate with higher mortality. Severe intrathoracic injuries and polytrauma patients without reference to chest wall trauma were excluded from the meta-analysis, whereas this study included these patients, as did also the study by Whitson et al. (10). Also, we analyzed the effect of rib fractures on mortality in the whole study population (including patients without rib fractures) and in a subgroup of patients with rib fractures. In both cohorts, the number of rib fractures did not correlate with mortality or other outcome measures. In a previous study (12), the presence of bilateral rib fractures increased the risk of death (OR = 3.43), but we did not find any effect of bilateral rib fractures on mortality.
CT is more accurate in diagnosing rib fractures (13) compared to plain chest films. Livingstone et al. (13) found a better correlation with outcome with rib fractures seen in plain chest films on admission than with the number of rib fractures in CT. In our study population, the number of rib fractures was mostly based on CT findings, as 88% of our patients had the body CT done on admission. In addition, we did not find any correlation between the number of rib fractures and outcome when analyzing only patients without body CT on arrival. The use of CT increases the number of rib fractures, but it also seems to decrease the predictive power of the number of rib fractures. Our results support the conclusion by Livingstone et al. (13): “In addition, attempting to isolate one part of the information stream (rib fractures in this study) from the rest of the data obtained by CT scan is difficult and prone to differing interpretation.”
We did not find any factor correlating with hospital LOS. This can be at least partly explained by local circumstances. The patients were discharged home when they were fit enough, though this could be done only in a minority of the patients (35%). The remaining 65% of the patients were transferred to other units such as local hospital wards, nursing homes, and so on. We have no information from these units; therefore, the total hospital LOS of 65% of our patients is not known. Moreover, sometimes patients have to wait at our hospital for several days before getting acceptance to the admitting hospital (usually due to lack of available beds). Also, only 19% of the patients had isolated thoracic injuries, and the reason for prolonged hospital LOS can be related to nonthoracic injuries. However, we did not see any association between the AIS grade in any region of the body and the hospital LOS.
In this study, we found that male gender, hypotension on admission, bilateral rib fractures, and spinal operation were associated with ICU LOS, ventilator days, and days in CPAP. Contrary to hospital LOS, the patients were transferred from the ICU as soon as possible, and there are usually no problems in bed availability for these in-hospital transfers. Hypotension on admission is often a strong indicator of severe injury, and thus, it is not surprising that it correlated with ICU LOS, ventilator days, and days in CPAP. Gender had a statistically significant association with the days in the ICU, ventilator days, and days in CPAP, but the differences were small, males being 1.2, 0.6, and 0.9 days longer in the ICU, ventilator, and in CPAP, respectively. Male gender was associated with a longer ICU stay in other previous studies (14, 15). The gender differences on post-traumatic sepsis are associated with a longer ICU stay in males (14, 15), and this might be related to sex steroids (16).
Previously, increasing age and ISS have been shown to correlate with ICU LOS and days in the ventilator (10). However, in the study by Whitson et al. (10), the patients with eight or more rib fractures were analyzed as one group. We analyzed the number of rib fractures both as continuous variable and as divided into different categories. In either way, we did not see any correlation with the outcome measures (data not shown).
In our institution, the patients with spinal fractures are mobilized if the fractures are considered stable and operated if considered unstable. Bed rest is not a considered option. Spinal injuries requiring single-level instrumented fusion in the lower spine (Th10-S1) are operated by the trauma unit and other injuries by spinal (orthopedic) surgeons. The lack of available spine surgeon can sometimes delay the operative treatment. Patients with severe chest injury and unstable spinal fracture (with or without neurological deficits) are often monitored in the ICU, even if they do not have any organ dysfunctions requiring intensive care. These factors could partly explain the longer ICU LOS in patients who needed spinal operation. However, these factors do not explain the longer ventilator and CPAP time in patients needing spinal operation, as they are affected only by the condition of the patients. Thus, patients with severe thoracic injury (AIS > 2) and unstable spine fracture can be expected to need a longer time in the ventilator and CPAP due to injuries.
In our study population, 52% of the patients were intubated. Half of these patients were intubated at the scene or on admission. The other half deteriorated during the following days and required intubation. We did not find any factor that could be associated with the timing of the intubation (prehospital or on admission, later during hospital stay, or not intubated during hospital stay).
The overall mortality in our study population with severe thoracic trauma (thoracic AIS > 2) was 6.4%. It is similar to that in a recent meta-analysis, 9.3% (11) as well as to that in the National Trauma Data Bank study, 8.1% (10). These two recent studies include close to 88,000 patients. In previous studies, the number of rib fractures (11), increasing age, and ISS have been associated with mortality in patients with thoracic trauma (10). We did not find any association of age, number of rib fractures, or ISS with mortality. In our study, mortality was associated with admission BE and coagulation status.
The limitation of our study is its retrospective data collection, leading to missing data, nonuniform measurement times of different parameters, and unavailability of some information, for example, causes for intubation. Also, the collected patient cohort is old, ranging from 2003 to 2007. We decided to limit the cohort to the end of 2007, as there have been several changes in our protocol in the following years, such as surgical rib stabilization and implementation of massive transfusion protocol.
Conclusion
The number of rib fractures does not correlate with mortality or the LOS in ICU in blunt trauma patients with severe thoracic injury. Hypotension on admission, male gender, bilateral rib fractures, and spine fracture operation were associated with higher hospital resource utilization. Mortality in these patients correlated with the degree of hypoperfusion (BE) and coagulation abnormalities (TT%) on admission. The present findings can be used to identify patients at risk of prolonged utilization of the ICU, mechanical ventilation, and CPAP.
Footnotes
Declaration of Conflicting Interests
None (all authors).
Funding
No outside funding received.