Medical pre-hospital management reduces mortality in severe blunt trauma: a prospective epidemiological study

In France, two rescue systems are involved in the pre-hospital management of trauma patients. In the event of an accident, both the fire brigade and pre-hospital medical emergency dispatching centre (SAMU: Service d'Aide Médicale Urgente) can be alerted. A fire brigade is systematically dispatched to the scene. The SAMU may decide to send a pre-hospital medical emergency team (SMUR), either directly, as a result of the phone evaluation of the accident, or later, as a result of the on-scene evaluation by the fire brigade. If there is no request for SMUR support, the fire brigade will provide only basic life support and take the patient to the closest hospital. However, according to French regulations, when the vital signs of a patient transported by the fire brigade cease, the fire brigade vehicle has to stop; the staff has to call the SMUR and begin cardio-pulmonary resuscitation with chest compression and ventilation while waiting for the arrival of the SMUR. The French SAMU/SMUR system is well described in the literature [2]. Briefly, when the SMUR is present on the scene, the EP may decide to refer the patient either to the closest hospital or to a university hospital trauma centre if a major trauma is suspected [5]. Each SMUR unit is staffed by an EP, a nurse and a specially trained ambulance driver. Depending on the clinical assessment of the patient, the emergency physician may initiate early life-sustaining treatment. According to French guidelines, tracheal intubation is systematically performed for patients with severe brain trauma (GCS: Glasgow Coma Scale <8), with respiratory distress syndrome and/or with haemorrhagic shock. Rapid sequence intubation is systematically used for tracheal intubation and sedative infusion is started early to prepare the patient for mechanical ventilation. Fluid infusion is performed on the basis of clinical assessment and mean arterial pressure (MAP). The haemodynamic target depends on whether patients have neurological injury (cerebral and/or medullar) (MAP: 85 to 90 mmHg) or not (MAP: 65 mmHg). In order to achieve the MAP target, the EP uses careful crystalloid infusion. If the initial MAP is very low (mean arterial pressure <60 mmHg), patients receive a bolus infusion of colloid and/or hypersaline solution. Continuous norepinephrine infusion can start quickly for patients with initial collapse, or in order to limit an excess of fluid loading. According to French guidelines, it is necessary to begin continuous norepinephrine infusion when fluid loading exceeds 2,000 ml and/or after beginning sedative infusion. Mannitol may be used if clinical intracranial hypertension exists or appears. Medical monitoring includes invasive arterial blood pressure, the use of continuous capnometry and on-board arterial blood gas measurement [6]. The patient's response to treatment is used by the dispatching physician to determine the most appropriate facility for the patient [7].

The FIRST prospective study involved intensive care units (ICU) and emergency departments from 14 university hospitals located throughout France. University hospitals in France correspond to Level 1 trauma centres in the United States. Between December 2004 and March 2007, study centres were asked to record data regarding consecutive patients with severe blunt trauma in a computerized and anonymous database. Inclusion criteria were age (18 years or over) and severe blunt trauma, defined as trauma requiring admission into a university hospital ICU within 72 hours after injury or, in the case of early death before ICU admission, trauma managed by SMUR units from university hospitals. Exclusion criteria were penetrating traumas, and deaths occurring before the implementation of any advanced life-sustaining treatment. The latter condition means that trauma patients managed by fire brigades who died before admission to an ICU were not included in the study. A total of 3,205 patients were eligible for inclusion in the FIRST study.

After checking for data quality, patients with either incomplete (n = 97) or poor quality data (aberrant or illogical data, n = 281) regarding hospital of first admission, injury severity score (ISS) and vital status were subsequently excluded. Patients with unknown information about SMUR/non-SMUR management (n = 124) were also excluded. Thus, the present analysis was restricted to 2,703 patients suffering from severe trauma, alive upon arrival at the hospital, for whom complete and high quality data on the major variables of interest were available. According to French law (law 88-1138 relative to Biomedical Research of 20 December 1988 modified on 9 August 2004), this non-interventional study did not require approval by an Ethics Committee nor informed signed consent from patients. The study was declared to, and approved by, the National Commission for Data Processing and Civil Liberties (authorization n° 05-1059 obtained on 24 February 2005). However, according to French law, all patients or their families were informed about the study by the ICU physician[8].

ICU physicians collected data from the medical records of SMUR units, emergency divisions and ICUs, regardless of the hospital of first admission. In each centre, ICU physicians entered data into the FIRST database with the help of local research assistants. The eligibility criteria were checked online by the research assistants of the Coordination Centre in Dijon. Every month, the Coordination Centre extracted data for quality control. In cases of missing, aberrant or illogical mandatory data, queries were sent to local research assistants. At the end of the inclusion period, data monitoring was performed by the Coordination Centre in order to validate data quality on a random sample of 7% of patients. Unreliable variables were discarded from the analysis.

ICU physicians collected the following data: 1 - patient characteristics; 2 - data about accident circumstances, condition of victims in traffic-related accidents, and rescue services mobilized for patient transport (SMUR units or fire brigade units); 3 - hospital units involved in early care of the patient before admission to the ICU; 4 - clinical and biological data on the pre-hospital phase, if available, at first hospital admission and at 24 h and 72 h after trauma; 5 - a summary of clinical variables at patient discharge or death.

During the pre-hospital phase, the following data were recorded for SMUR patients: initial physiological variables (arterial pressure, respiratory rate, SpO₂), pupil status, GCS and life-sustaining treatments (venous line, fluid loading and catecholamine administration, tracheal intubation, ventilation, blood products, chest tube).

For all patients, information on physiological variables and life sustaining treatments was also collected upon arrival at the first hospital, and 24 h and 72 h after the injury. The first available measurement, either at the pre-hospital phase or upon hospital admission, was used to describe the initial physiological status of the patient. At patient discharge from the ICU or death (within 30 days), anatomic injury diagnoses with corresponding Abbreviated Injury Scale (AIS) codes, and the ISS were recorded from medical records. The AIS was coded according to the 1998 updated classification [9] by local research assistants using medical, radiological and surgical reports. Local ICU physicians reviewed all problematic cases.

The main outcome measurement was the vital status at 30 days or at ICU discharge, if discharge occurred within the first 30 days. A secondary outcome was 72-h mortality.

Given their non-Gaussian distribution, quantitative variables were a priori categorized as follows: GCS score (<8, 8 to 13, >13), ISS (<25, 25 to 34, >34), systolic arterial blood pressure (<90, 90 to 110, >110 mmHg), SpO₂ (<90, 90 to 95.9, ≥96%), respiratory rate (<10, 10 to 29, >29 minutes^-1). Descriptive characteristics were expressed as percentages, or means with standard deviations (SD), or medians with interquartile range (IQR). Univariate comparisons between groups were performed using chi-square tests or Fisher exact tests, when appropriate, for qualitative variables, and using Kruskal-Wallis tests for quantitative variables. Multivariable analyses were performed using logistic regression models, where the outcomes (30-day mortality and 72-h mortality) were introduced as the dependent variables. Independent variables were: pre-hospital management (SMUR/non-SMUR), age, sex, injury severity score, systolic blood pressure, SpO₂, respiratory rate, GCS score (model 1); and secondly, hospital of first admission or hospital admission delay (model 2). Interaction terms between SMUR/non-SMUR management and other independent variables were systematically tested. As none were significant, they were dropped from the final model. The Hosmer-Lemeshow test was used to check model goodness-of-fit. The significance level was P < 0.05. The Coordination Centre performed all analyses using SAS™ version 9.1 (SAS Institute Inc, Cary, NC, USA).