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

Results

A total of 9,405 patients were included in the study. Table 1 shows that 5,096 (54% of the patients in the study sample) were from Montreal, 2,530 (27%) were from Toronto, and 1,779 (19%) were from Quebec City. The reason that there are approximately twice as many patients from Montreal is explained by the fact that two trauma centers participated from this region.

Montreal had 801 (16%) patients who received on-site ALS by a physician, while 1,000 (40%) of the Toronto patients received ALS by a paramedic at the scene. None of the patients from Quebec City received on-site ALS. In total, 1,801 (19%) patients received on-site ALS and 7,604 (81%) received BLS only at the scene. Of the 1,801 patients receiving ALS at the scene, 801 (44%) were treated by a physician and 1,000 (56%) were treated by a paramedic.

The data in Table 1 describe the demographic and injury characteristics of the study sample. The overall mean age of the sample was 44 years, and 72% of patients were male. Compared to Quebec City and Toronto, the Montreal patients had a significantly higher mean age (P < .001). Although the proportion of male patients was slightly higher in Quebec City, this difference was not statistically significant.

The overall mean ISS was 26, with 43% of patients having an ISS between 25 and 49 and 6% having an ISS over 49. The mean ISS of the Toronto patient cohort was 28 compared to 26 for Montreal and 25 for Quebec City. This difference was statistically significant (P < .001). The Toronto cohort had a significantly higher proportion of patients with an ISS between 25 and 49 compared to the patients from Montreal and Quebec City (P < .001).

Most of the patients (57%) were injured in motor vehicle accidents; 28% were injured in falls. Injuries due to firearms, stabbing, blunt object, sharp object, or other causes comprised approximately 15% of the remaining injuries, with blunt objects and firearms representing 5% and 3% of the total, respectively. The proportion of patients injured in motor vehicle collisions was significantly higher in Toronto (74%) compared to Montreal (50%) and Quebec City (54%) (P < .001). The proportion of patients injured in falls was significantly lower in Toronto (12%) compared to Montreal (33%) and Quebec City (33%) (P < .001). All other mechanisms of injury were statistically similar between cities.

Most patients had at least one injury to the head or the extremities. The proportion of patients with injuries to the head was significantly lower for Montreal (P < .01). The proportion of patients with facial injuries was significantly lower in Toronto (P < .01). The Toronto patients had significantly higher rates of thoracic and abdominal injuries (P < .01). The proportion of patients with penetrating injuries was significantly higher in Toronto, followed by Montreal and lowest in Quebec (P = .01) ( Table 2 ).

The overall mortality rates for Montreal, Toronto, and Quebec City were 23%, 20%, and 19% (Fig. 1). The mortality rate for Quebec City was significantly lower compared to Montreal and Toronto (P < .001). For patients with mild to moderate injury severity (ISS 1-24), there was a significant trend of lower mortality in Toronto followed by Quebec City, with Montreal having the highest rate (P = .001). There were no statistically significant differences between the three cities with respect to the mortality rates for patients with major (ISS 25-49) or fatal (ISS 50-79) injury severity.

Mortality by city stratified by Injury Severity Score (ISS). , Montreal; , Toronto; , Quebec. *P = .001, **P < .01.

Table 3 summarizes the demographic and injury characteristics of the patients by the type of crew that was present at the scene. These data show that 7,604 patients received on-site care by a BLS crew, 801 were treated by a physician at the scene, and 1,000 were treated by a paramedic. Both physicians and paramedics were capable of providing ALS at the site. The patients treated by paramedics were younger compared to those treated by a BLS crew and by physicians (P = .001). The proportion of male patients was just over 70% for all three groups.

The mean ISS was significantly higher for the patients treated by a physician at the scene compared to the other two groups (P = .001). In addition, the mean ISS of the patients treated by paramedics was higher than that of the patients treated by an EMT crew (P = .01). The ISS distribution shows that a significantly higher proportion of the patients treated by a physician had an ISS between 50 and 75, while the proportion of patients with an ISS between 24 and 49 was significantly lower for the patients treated by a BLS crew (P = .001). A significantly higher proportion of patients injured in motor vehicle collisions were treated by paramedics (72%) compared to physicians (52%) and EMTs (56%) (P = .001) and a lower proportion injured in falls (PMD 11%, MD-ALS 52%, BLS 29%) (P = .001). Other mechanisms of injury were statistically similar between groups.

Concerning body regions injured, the prevalence of injuries to the head or neck regions was not different between the three groups. However, the proportion of patients with injuries to the face was lower for the patients treated by paramedics (PMD 27%, MD 44%, BLS 42%), while significantly more patients in this group had injuries to the thorax (PMD 59%, MD 49%, BLS 45%) and abdomen (PMD 45%, MD 32%, BLS 29%)(P = .001). Finally, the incidence of penetrating injuries was higher in the patients treated by paramedics (PMD 12%, MD 7%, BLS 5%) (P = .001).

The overall mortality rate was significantly higher for the patients treated by a physician at the scene (P = .001). However, for the subgroup of patients with an ISS between 1 and 24, the mortality rate was low and not different for the three groups. For the patients with an ISS between 25 and 49, the mortality rate for the MD-ALS group was 32% compared to 28% for the PMD-ALS group and 26% for the BLS group. The difference between the MD-ALS and the other two groups was statistically significant (P = .001) (Fig. 2).

Mortality by on-site crew. , Montreal; , Toronto; , Quebec; BLS, Basic Life Support; MD-ALS, physician-provided Advanced Life Support; PMD-ALS, paramedic-provided Advanced Life Support. *P = .001.

Table 4 summarizes the demographic information and ISS of the patients depending on whether ALS or BLS care was administered on site. For these two groups, the mean age and proportion of male patients were similar, but the mean ISS was significantly higher for the ALS patients (P = .001). The ISS distribution showed that the ALS group had a significantly higher proportion of patients with an ISS between 24 and 49 and between 50 and 75 (P = .001). The ALS group had a significantly lower proportion of patients injured in falls (n = 379 [21%]) compared to the BLS group (n = 2,214 [29%]) (P = .001), but the other mechanisms were similar between ALS and BLS. The prevalence of injuries to the head was similar for the two groups (P = .37), although the proportion of patients with injuries to the thorax (ALS 55%, BLS 45%), abdomen (ALS 39%, BLS 29%), and extremities (ALS 88%, BLS 70%) was higher in the ALS group (P = .001). The proportion of ALS patients with penetrating injuries was twice that of the BLS patients (ALS 10%, BLS 5%). This difference was statistically significant (P = .001).

The overall mortality rate was 29% for the ALS group and 18% for the BLS group. The crude odds ratio was 1.86 (95% confidence limits 1.65-2.09). These data show a significant increase in the risk of dying associated with on-site ALS (P = .001) (Fig. 3). Stratification by ISS categories showed that for patients with minor to moderate injury (ISS 1-24), the mortality rates for the ALS and BLS groups were similar. For the patients with an ISS between 24 and 49, the mortality for the ALS group was 30% compared to 26% for the BLS group. The odds ratio for this stratum was 1.23 (95% confidence limits 1.04-1.45). This difference and odds ratio were statistically significant (P = .01).

Mortality by on-site care. , Advanced Life Support (ALS); , Basic Life Support (BLS). *P = .01, **P = .001.

The final logistic regression model was derived by the backward selection process and included the following variables as covariates: age, body region injured, mechanism of injury, and ISS. The first logistic regression model ( Table 5 ) tested the adjusted association between city and the odds of dying. This analysis showed that the adjusted odds of dying in Quebec City were 20% lower compared to Montreal; this was statistically significant (P = .01). The odds ratio for Toronto versus Quebec City indicated a 14% increase in the risk of dying for Toronto; this was not statistically significant. Compared to Toronto, the odds of dying in Montreal were 27% greater (P = .003).

The second logistic regression model tested the association between the on-site crew and the odds of dying. The results of this analysis showed that compared to being treated by an EMT, being treated by an MD at the scene was associated with a 36% increase in the adjusted odds of dying (P = .001). The odds ratio comparing physicians to paramedics was also elevated, indicating a 20% increase in the odds of dying; however, this did not reach statistical significance (P = .22). Finally, the odds ratio of paramedics versus EMTs showed a 6% increase in the odds of dying; this was not statistically significant (P = .61).

The third multiple logistic regression analysis compared on-site ALS to BLS only. This analysis showed that when patients received any type of ALS on the scene, the adjusted odds of dying increased significantly by 21% (P = .01).

The mean scene times for the three different types of on-site crews differed. MD-ALS crews had significantly longer mean scene time (24.9 minutes) compared to BLS crews (21.9 minutes) and PMD-ALS crews (19.3 minutes) (P = .01). The mean scene time for the PMD-ALS crew was significantly shorter compared to the BLS and the MD-ALS crews (P = .01).

To adjust for the effect of scene time on the association between the exposure variables and mortality, the logistic regression analyses were repeated with scene time included as a covariate in the models. The inclusion of scene time did not significantly change the odds ratio estimated (data not shown), although a longer scene time was significantly associated with an increased chance of dying in all models.

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