Multicenter Canadian Study of Prehospital Trauma Care

Moishe Liberman, MD, David Mulder, MD, André Lavoie, PhD, Ronald Denis, MD, John S. Sampalis, PhD

Disclosures

Annals of Surgery. 2003;237(2) 

In This Article

Methods

This observational study was based on three cohorts of patients treated for severe injuries between January 1, 1993, and December 31, 1997, in three Canadian cities (Montreal, Quebec City, and Toronto). The three cohorts were exposed to different prehospital trauma care, but all received in-hospital care at designated level I tertiary trauma centers. The type of on-site care provided depended on the prehospital system in place in the respective city and the availability of ALS personnel within the city.

The study sample from each site was identified from patients who were treated for severe injury at one of the four tertiary trauma centers in the three cities: the Montreal General Hospital and Hôpital Sacré-Coeur in Montreal, Hôpital Enfant-Jésus in Québec City, and Sunnybrook Health Sciences Trauma Center in Toronto. To identify patients with major trauma, the following inclusion criteria were applied: death as a result of the injury, hospitalization for more than 3 days, treatment in an intensive care unit, surgery requiring admission, or an ISS of more than 12.

The outcome measure for the present study was mortality, defined as death as a result of the injury. The cohorts were followed up to discharge from the trauma centers. The exposure or independent variable used was dependant on the objective addressed. For the first objective, the independent variable was the city, which defined the type of prehospital services available as EMTs only (Quebec City), PMD-ALS (Toronto), and MD-ALS (Montreal). For the second objective the exposure variable described the type of on-site crew managing the patient as EMT, PMD, or MD. Finally, the exposure variable for the third objective described the type of on-site care received by the patient as ALS or BLS.

Between-group differences with respect to categorical variables were evaluated for statistical significance with the chi-square statistic. For continuous variables, one-way analysis of variance was used to evaluate the significance of between-group differences. For all estimates 95% confidence intervals were calculated. Between-group differences with respect to mortality rates were described by the relative risk using Quebec City, EMT-BLS, or BLS as the baseline, depending on the specific analysis conducted. For each estimate of the relative risk, 95% confidence intervals were used to assess precision and statistical significance.

Logistic regression models were used to produce adjusted estimates of the relative risk for each one of the exposure variables studied. The logistic regression model was developed by first including all of the following variables as predictors of death: age (years); gender; body region injured (yes/no): head/neck, face, thorax, abdomen, extremities; mechanism of injury (yes/no): motor vehicle collision, fall, firearm, stabbing, blunt object, sharp object (accidental), other; ISS; and penetrating trauma. A backwards selection process was used to identify those variables that were the strongest independent predictors of mortality. A significance level of 15% was set as the minimum for the variable to be kept in the final model. The variables maintained in the model by this backwards selection procedure defined the basic logistic regression models that were used in the final analyses.

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