Prehospital and emergency department airway management of severe penetrating trauma in Sweden during the past decade

Trauma is a leading cause of mortality and morbidity in the young and healthy.[1, 2] Gunshot wounds (GSWs) and stab wounds (SWs) constitute up to 20 percent of all trauma in the US.[3] The incidence of penetrating trauma is lower in western Europe, accounting for approximately 10 percent of all injuries.[3, 4] The incidence of homicide and gun homicide has increased in Sweden in the past decade and is now well above the European average, despite a decline in the majority of European countries.[5] .

Delay, or failure in securing an airway is a preventable cause of death in trauma patients,[6‐8] and emergency airway management is more challenging when needed outside the operating theater. Consequently, prehospital and out-of-theater emergency tracheal intubations (TI) may be associated with a lower success rate and a higher incidence of complications than TI in operating theatres.[9, 10] Nevertheless, prehospital TI can meet the standard of in-hospital emergency intubations when performed by experienced airway providers.[9, 11] In addition to risks with TI, anesthesia drugs and positive pressure ventilation may increase mortality in hypovolemic patients. [12‐14] Positive pressure ventilation leads to an increased intra-thoracic pressure, which may decrease venous return and subsequently cardiac output in a hypovolemic state. Trauma patients are heterogeneous, and optimal airway management depends on the patient’s specific condition, airway provider experience and environmental factors.[3, 8, 15] TI in patients with penetrating trauma is associated with increased mortality,[9, 16, 17] specifically in patients with hemorrhagic shock.[12, 13] The increased incidence of deadly violence in Sweden warrants a comprehensive evaluation of current airway management for patients with penetrating trauma in the prehospital environment and in the ED.

The aims of this study were to present the characteristics associated with TI, its associated causes of mortality and to compare prehospital and ED intubations in patients with penetrating trauma in Sweden between 2011 and 2019, during which time the incidence of gun violence increased.[18] We analyzed data from the nationwide trauma registry in Sweden (SweTrau) and hypothesized that prehospital TI was associated with increased mortality.

The study analyzed 4965 patients with penetrating trauma between 2011 and 2019, and 816 patients (16.4%) met the inclusion criteria.

In this observational multicenter study, we showed that prehospital TI was associated with a higher 30-day mortality rate than intubations performed in the ED, even after adjustment for ISS. This was specifically related to TCA, and in patients without cardiac arrest, prehospital TI did not affect the mortality rate when compared with intubations in the ED. Previous studies have shown that increased mortality was associated with prehospital advanced airway management (69.2%) when compared with in-hospital airway management (35.9%) in patients with penetrating trauma.[16] Taghavi et al. found prehospital TI to be the strongest predictor of mortality in patients with penetrating trauma (OR 11.88, p < 0.001) compared with ISS (OR 1.07) and GSW (OR 7.08).[23] A meta-analysis of undifferenced trauma with TCA excluded observed an increased mortality of 48% with prehospital TI compared to 29% for TI in the ED, with an OR of 2.59 when adjusted for ISS.[9] We showed that this association was also present in the Swedish context. However, no difference in mortality was detected when excluding patients with TCA (OR 2.07, p  = 0.068). The rationale for this subgroup analysis was the finding that the majority (64%) of prehospital TI was performed without medication, compared with 16% in the ED, as TI without medication is likely to be performed in a situation of cardiac arrest.

A total of 154 (18.9%) patients suffered from TCA, 133 (86.4%) of whom required TI either prehospital or in the ED, and 9 (5.8%) patients survived. The frequency of cardiac arrests was substantially higher than previously reported.[14, 17] As registration in SweTrau is restricted to patients arriving at participating hospitals, the high frequency of TCA may represent an unwillingness to terminate prehospital resuscitation efforts in a cohort of young patients, but the cause is unclear and requires further study. Heffner et al. found cardiac arrest as a complication of anesthesia in 12% of cases in a mixed cohort of medical and trauma patients with hypotension, and Stausberg et al. observed TCA in 3.2% of all patients in a cohort of severely injured trauma patients managed by physicians.[14, 17] Excluding TCA reduced the difference in ISS and systolic blood pressure between prehospital and ED intubations, although the GCS score in patients with prehospital TI remained substantially lower than those with intubations in the ED. It is known that patients who require prehospital TI have higher ISS than those with TI in the ED [9, 16, 24, 25], which we could confirm in our cohort (ISS 33 versus 25). It is likely that a higher ISS predisposed patients to a higher risk of TCA. We could not determine whether the TCAs were preexistent or occurred after anesthesia. Systolic hypotension and shock prior to anesthesia induction have been observed as risk factors for cardiac arrest.[13, 14] In addition, anesthesia and positive pressure ventilation in patients with hemorrhagic shock are debated and may have contributed to the observed increase in mortality in patients with prehospital TI where the majority of intubated patients were in circulatory collapse or shock.[14, 26, 27] Furthermore, positive pressure ventilation decreases venous return and cardiac output.[28, 29] Hemorrhagic shock represents a low flow state with reduced capacity for transportation of produced CO₂, and normal respiratory rates may reduce pCO₂ with subsequent further reductions in venous return, mean arterial pressure and cardiac output.[13, 25].

Patient parameters associated with prehospital TI were analyzed using multivariate models, with and without TCA. Hemodynamic collapse (≤ 40 mmHg) and low GCS score (≤ 8) were the parameters most associated with prehospital TI with TCA included, compared with low GCS score (≤ 8) and hypotension (≤ 90 mmHg) with TCA excluded. We have previously shown that a substantial proportion of these patients suffered head injuries, which can also be reflected in the low GCS score.[18] Hypotension, related to injury or anesthesia, may exacerbate existing brain injury and contribute to increased mortality.[30] The correct indication and timing of TI in penetrating trauma are still under discussion.[9, 13, 16] Prehospital TI is an experience dependent, hazardous procedure that can and should be performed according to in-hospital standards.[11, 12, 31] Prehospital TI may increase the scene time which have been associated with an increased mortality[32], although experienced providers are capable of administering prehospital anesthesia in patients with hemorrhagic shock with short scene time.[13, 17, 33] The scene time was significantly longer (median 21 versus 12 min) when prehospital TI was required, which may have contributed to the increased mortality, although this is not clear. It is likely that the severity of the clinical situation required TI, and the observed increase in mortality reflected severely injured patients. High mortality in patients receiving prehospital TI was observed both when performed by physicians (70%) and nurses (85%). When TCA was excluded, the mortality was reduced for both physicians (30%) and nurses (50%). In comparison, Stausberg et al. observed increased mortality associated with prehospital TI in a physician-based emergency medical service (EMS), and Fevang et al. observed increased mortality associated with prehospital TI in trauma patients despite similar first pass success rates.[9, 17] While quality indicators of airway management (such as first pass success, etc.) are not registered in SweTrau, our results suggest that increased mortality associated with prehospital TI in trauma patients was not primarily driven by the experience of airway providers.

Prehospital anesthesia in hemodynamically unstable penetrating trauma patients is challenging. Emergency medical services are heterogeneous in organization and available competence, which therefore complicate comparisons.[34‐37] Notably, Anglo-American EMS teams are largely comprised of paramedics while EMS teams in parts of Europe are a physician-based system.[34, 36, 38] Each ambulance in Sweden is staffed with a registered or specialist nurse, and several regions have access to physician-staffed, second tier EMS units.[39] Several interventions involving these second-tier EMS units have recently been initiated to counteract the challenges associated with severe, penetrating trauma. These include blood transfusions during anesthesia in trauma patients with hemorrhagic shock and a focus on shortening the scene time.[33] The effects of these new interventions in the Swedish context will be analyzed in future studies.

This study has some limitations to be discussed. First, it is an observational study with inherent biases, and inferences regarding the causation of prehospital TI and mortality could not be made. Second, SweTrau is primarily a trauma registry, and quality indicators of airway management were not registered, which limits the analysis. Third, the coverage of SweTrau increased during the study period, which could confound incidence. However, we did not analyze incidence trends. Fourth, the transcription of ordinal data (blood pressure) limits the multivariate analysis, which was primarily intended as a visualization of associations. Fifth, as registration in SweTrau was limited to patients who arrived at a participating hospital, prehospital deaths are a possible source of selection bias.

Prehospital TI was associated with a higher mortality rate than intubations performed in the ED, which was related to TCA; intubation did not affect mortality in patients without cardiac arrest. The mortality rate was substantial when airway management was needed, regardless of TCA, demonstrating the lethality of severe, penetrating trauma and the challenges posed when anesthesia is needed. Several interventions, including whole blood transfusions, implementation of second-tier EMS units and measures to shorten the scene time, have been initiated to counteract challenges with penetrating trauma in Sweden. The effects of these new interventions will be analyzed in future studies.