Factors affecting mortality of hospitalized chest trauma patients in United Arab Emirates

Injury is a leading cause of death worldwide and is the second cause of death in the United Arab Emirates (UAE). The mortality rate of patients having chest trauma ranges between 4% and 20% worldwide [1]. The pattern of chest trauma and its clinical presentation vary between different countries [2]. Consequently, predictors of mortality vary in different settings. When chest trauma is not life threatening, management decisions become less clear [1]. Clinical presentations alone have a low predictive value of mortality and may not be enough to guide the decision making process [3].

Studies on predictors of mortality of chest trauma are limited. Majority studied specific age groups like children and elderly, or studied specific chest injuries. Predictors of mortality of chest trauma have been defined in different settings [1]. Significant factors included the age, presence of flail chest, co-morbidities, number of fractured ribs, Glasgow Coma Scale (GCS), Injury Severity Score (ISS) and quality of pre-hospital care [1, 4–7]. There are no similar studies from the Middle East. We aimed to define the factors affecting mortality of hospitalized chest trauma patients in Al-Ain, UAE.

Patients with chest trauma who were admitted for more than 24 hours in Al-Ain Hospital or who died after arrival to the hospital were included in the study. Al-Ain Hospital is one of the two major public hospitals in Al-Ain City. The hospital has a catchment population of more than 350 000 inhabitants. During the study period, Al-Ain Hospital treated 80% of the trauma patients of Al-Ain City.

Data for patients were retrieved from Al-Ain Hospital Trauma Registry and were collected prospectively over 3 years (March 2003 to march 2006). The details of the development of the registry and its content were described elsewhere [8, 9]. Injury Severity Scale (ISS) was calculated manually using the Abbreviated Injury Scale handbook [10]. Data which were required to score the AIS and ISS were available for all patients except for one who died in the Emergency room. The Local Ethics Committee of Al-Ain Health District Area has approved data collection for the Trauma Registry. All patients admitted to Al-Ain Hospital or their caregivers signed a general consent form giving permission to use their anonymous data for research and audit.

Demography of patients, mechanism of injury, systolic blood pressure and Glasgow Coma Scale (GCS) on arrival, the need for ventilation, ISS, presence of head or chest injury, Abbreviated Injury Scale (AIS) for both the chest and head injuries, and mortality were analyzed.

Statistical analysis included Fisher’s exact test for categorical data for two independent groups, Mann–Whitney U-test for continuous or ordinal data for two independent groups. Univariate analysis was used to compare patients who survived and those who died. Significant factors were then entered into a backward stepwise likelihood ratio logistic regression. A p value of ≤ 0.05 was considered significant. Data were analyzed with PASW Statistics 18, SPSS Inc, USA.

474 patients were studied, 425 (90%) were males. Median (range) age was 35 (1–90) years. Eighty six patients (18.1%) were UAE nationals. The most common mechanism of injury was road traffic collision (RTC) in 313 patients (66%) followed by falls in 111 patients (23.4%). Penetrating trauma occurred in only 4 patients (0.8%), all were stab wounds and all survived. 304 (64.1%) patients were injured in the street or highway, 90 (19%) at work place, and 45 (9.5%) at home. Two hundred sixty five (55.9%) patients arrived at hospital by ambulance.

The Receiver Operating Characteristic (ROC) curve has shown that best cut off points for predictors of mortality were systolic blood pressure of less than 103 mmHg on presentation (Figure 1), GCS of less than 10.5 (Figure 2) and ISS of more than 11.5 (Figure 3).

Our study has shown that significant predictors for mortality of chest trauma patients were low GCS, hypotension on presentation and increased severity of injury. Old age was reported as a predictor of mortality for chest trauma [2, 4, 5, 11]. Liman et al. have shown that an age of more than 60 years significantly increased mortality [5]. Patients’ demographics (age, gender and nationality) did not predict mortality in our logistic regression model. The UAE population is a very young population composed mainly of male workers [12, 13]. Elderly expatriate patients prefer to retire at their homeland. Having small number of elderly patients in our study may have resulted in the non significant effect of age on mortality.

Majority of chest trauma in our community is blunt in nature. There is less than 1% penetrating trauma. The strong law enforcement in our community contributes to the reduction of domestic violence because aggressors may be deported to their homeland if they cause physical injury to others.

Univariate analysis has shown that the mechanism of injury, mechanical ventilation, and admission to the ICU, head and chest AIS, ISS, GCS and systolic blood pressure on arrival to hospital were significantly different between those who died and those who survived. The multivariate logistic regression model excluded all these factors except ISS, GCS and systolic blood pressure as significant predictors of mortality.

Our cut off values for prediction were systolic blood pressure of less than 103 mmHg, GCS lower than 10.5 and an ISS score higher than 11.5. In contrast, Emircan et al. found the same significant factors with different cut off values. These were hypotension (in general), GCS lower than 13 and an ISS higher than 22 [2]. Patients having a lower ISS, compared with Emircan et al., died in our setting. We think that this occurred because our prehospital care is relatively not well developed. Lack of pre-hospital care increases mortality [14] while improved pre-hospital care reduced mortality in chest trauma patients [7].

RTC is the most common mechanism of chest trauma [5]. Abbas et al. have described the biomechanics of chest trauma in RTC [15]. They defined three mechanisms of injury occurring in front impact collisions of unrestrained drivers. This includes the impact of the chest to steering wheel, and the head injury to the wind shield. A recent prospective study has shown that more than 80% of RTC patients in the UAE were unrestrained [16]. This finding explains the high frequency and severity of head injury in our study. Seatbelt usage reduces severity of head injury [17]. Emircan et al. highlighted that the mechanism of injury is a significant predictor of mortality. The most common associated extra-thoracic injury in our study was to the head; which reflects the low usage of seatbelts [18].

Similar to others, our study has shown that chest injuries associated with extra-thoracic injuries were more common than isolated chest injuries [2, 5]. In contrast, Demirhan et al. reported the opposite [6]. This can be explained by selection bias. Presence of associated extrathoracic injuries, especially abdominal injuries increases the mortality [2, 11]. Splenic and hepatic injuries increase the risk of death by threefold [8]. In contrast, the type of intra-thoracic injury per se was not a predictor for mortality in chest trauma patients [7].

Road traffic collision is the main cause of chest trauma in Al-Ain City, United Arab Emirates. The mortality of patients presenting with chest trauma is high in our setting (7.2%). This was significantly related to the severity of injury and hypotension on arrival. Extra-thoracic injuries are the main cause of death in chest trauma patients. Improvement in the pre-hospital care and enforcement of seatbelt compliance may reduce this mortality.