The aim of this study was to compare the demographics, 30-day mortality, rate and type of spinal injuries and other time-critical injuries between patients trapped and not trapped following an MVC from a UK based national trauma registry.
Is being trapped associated with an increased mortality?
This study demonstrates a significantly higher mortality in the trapped population. This difference in mortality between the groups remains when known confounders considered in the Ws statistic are accounted for. Our results likely underestimate the effect of entrapment on mortality as patients who died on scene were not included in our analyses.
Are spinal injuries common in patients who are trapped?
In high-income countries, patients who are trapped are extricated primarily by the FRS. The principles of extrication have developed without significant medical input (18) and they are based around movement minimization – specifically movement of the spine. Current FRS guidance suggests that even small movements are intolerable and all patients who have undergone trauma should be considered to have a spinal injury until proven otherwise (14). This guidance accepts that other life-threatening injuries may be present, but the focus in extrication practice remains on the minimization of spinal movement.
Spinal injuries were infrequent in this study population, with trapped patients with a spinal cord injury representing just 0.29% (or one in 345) of all extrications performed. Interestingly the rate of cord injury was higher in the un-trapped population. For the very small proportion of patients whom extrication techniques are targeted towards there is a very large number of patients with no or minor injuries (patients not on the TARN registry) whom as a result of application of movement minimization techniques consume significant resources. In addition, there is a large number of severely injured patients who have non-spinal or spinal and additional injuries who extrication approaches are not optimised for.
Do patients with spinal injuries have other injuries which may dictate extrication needs?
In the context of prevention of secondary spinal injury, those patients who may benefit from movement minimization are those who have both a spinal cord injury and do not have other time-critical injuries that may take precedence when planning an extrication. This is a rare patient group; just 232 patients over the six years that this study covers, or 0.53% of the 43,633 total extrications that occurred. As isolated cord injury represents a small proportion of those who are trapped in their vehicles with injuries, extrication principles should therefore be reconsidered with a wider appreciation of the mortality and morbidity associated with other common injuries and injury patterns e.g. blood loss and tension pneumothorax. Within our data, for example, a trapped patient is five times more likely to have a chest AIS of 3+ than a spine AIS of the same severity (Table 3).
The findings of increased number and severity of injuries in those who are trapped are consistent with previous evidence. Palanca et al performed univariate and multivariate analysis on 621 patients involved in road traffic collisions presenting to a single centre. Two hundred and fifty-three patients had major injury defined as ISS >15 (8). They identified the need for extrication as an independent risk factor for severe injury (p<0.0001; OR 2.9 (1.9-4.5)). In another large prospective study of 2363 patients, Lerner et al examined numerous pre-hospital factors associated with motor vehicle collisions (10). They found that prolonged extrication (>20 minutes) predicted MTC need with a sensitivity of 11% and a specificity of 98%, likelihood ratio 3.6 (2.2 – 5.9).
Injuries in context of intervention when the patient remains trapped?
A large number of patients in our study required life-saving interventions (OR (95% CI), such as intubation (2.02 (1.90-2.15)), decompression of a tension pneumothorax (1.79 (1.64-1.96), or blood product transfusion (2.92 (2.72-3.14), and trapped patients were more likely to require these interventions than their not trapped counterparts (p<0.001). It is challenging to deliver these interventions safely and effectively to a patient that is trapped, due to the working environment, space constraints and inability to do a detailed physical examination. It has been suggested that rapid extrication, minimising the time the patient is trapped, may offer significant benefits. Kaiser et al reinforce this need in their report on 446 traumatically injured patients where they performed a regression analysis to predict the need for urgent surgery (19). They identified that prolonged extrication (> 30 minutes) was associated with an increased need for emergency surgery (odds ratio 2.3 (1.2-4.6)).
Severe chest injuries are common in the trapped patients reported here. Chest injuries are often time sensitive and though they may be temporised by interventions such as supplemental oxygen, decompression of tension pneumothorax and analgesia, they are generally not amenable to definitive pre-hospital treatment. Delivering interventions is further hampered when a patient remains trapped in a vehicle, where oxygen may be contraindicated (due to ignition risk), technical procedures are difficult (20) and pauses for medical assessment and/or intervention further lengthen the time of extrication (21).
Those caring for patients who are trapped in cars should be aware of the frequency, severity and type of injuries which affect this patient group. FRS are often present at the scene prior to the arrival of an ambulance crew. Consideration should be given to how these personnel are trained and how their trauma skillset is relevant and proportional to this patient group.