For patients with a GCS between 6 and 8, we found that intubation was associated with increased odds of mortality. This association was consistent irrespective of the presence of head injury. Furthermore, intubation was associated with longer ICU and hospital length of stay. These findings bring into question the established dogma that mandates intubation for GCS ≤ 8.
As stated in the Introduction, EAST gives a level 1 recommendation to intubate this cohort of patients [2, 3]. However, many of the studies cited in the PMG were designed to answer different questions or study different subsets of these patients, including the safety of cricothyroidotomy  or neuromuscular blockade,  and a comparison of early vs late intubation . Of the 31 studies cited as supporting evidence for this recommendation, 16 were for the purposes of studying prehospital intubation. This is not to say that these studies (or the guidelines based on them) are not valuable, but they do not constitute direct evidence that there is an outcome benefit to intubating all trauma patients presenting with GCS ≤ 8.
However, there is some existing evidence for the potential harms of intubation in trauma patients. One study examining the effect of intubating patients for “combativeness” found that these patients, as compared to a matched non-intubated group, incurred longer hospital length of stay, increased rates of pneumonia, and poorer discharge status . Furthermore, there is some literature to suggest that it may be appropriate to observe some patients with a GCS less than 8 without intubation. A small observational study, noting that many emergency department providers advocate intubation for GCS ≤ 8 in intoxicated (non-trauma) patients, reported safe management without intubation in all of the included GCS ≤ 8 patients . There may be a similar cohort of trauma patients who, despite impaired cognition, may be safely managed without intubation. However, this is the first study to our knowledge of the effect of intubation on trauma patients with a marginal GCS.
As a retrospective cohort study with a small effect size, this work could be categorized as Level III evidence . However, this modest increase in mortality risk is less impactful for practice than the knowledge that there is no decrease in mortality risk. This, after all, is the presumed goal of intubating those with a GCS of 8. Our use of inverse probability weighting was intended to help mitigate the risk of confounding. This statistical method may be a helpful tool in answering a question that is inherently difficult to study. Beyond this, our use of a large national dataset allowed the sample size and power necessary to detect this result and generate a statistically sound study.
We chose to define “intubation” as those who were intubated within an hour of arrival. This may prompt questions about those who potentially undergo slightly delayed intubations in the trauma bay or in the operating room soon after trauma bay evaluation. To determine whether we were missing a significant number of patients intubated outside of the first hour, we re-examined the data for the codes listed in Table 5 in Appendix 1, timestamped for the 2nd and 3rd hours after arrival. Of the 2598 patients who did not meet our initial criteria for ED intubation, 133 (5.1%) were intubated in the ensuing two hours. This relatively small number of delayed intubations is reassuring.
There are a few limitations to address. The GCS provided in the NTDB is at the time of arrival to the emergency department; we do not know whether this is the best or worst GCS for that patient, nor whether some of these patients may have received sedating medications on route. However, prehospital intubations were excluded and it seems unlikely that many non-intubated patients would have received drugs in the field. Secondly, we are not able to exclude confounding by indication as a possible reason for the association between intubation and mortality we describe. For instance, some physical findings that may be considered indications for intubation (e.g., anisocoria, vomiting with concerns for aspiration, evidence of smoke inhalation) are not captured in the data but are associated with mortality. However, as the NTDB does not contain data on indication for intubation, this a known limitation of the dataset. The fact that similar results were shown on an analysis stratified by head injury is encouraging. The 23.3% missingness rate for intoxication is also limiting, as this might be an additional confounder. Despite this limitation, we are encouraged by the similarity between the stratified and overall results.
We do not intend to suggest that there are no trauma patients with a GCS between 6 and 8 who would benefit from intubation. Furthermore, it should be emphasized that this data only applies to those with a marginal GCS, and not those with a severely depressed mental status. We do, however, believe that this data should prompt trauma providers to question the blanket recommendation that all patients with a GCS of 8 be intubated and use clinical judgement to determine which ones will benefit. Though some patients in this category will surely benefit, we have demonstrated here that for patients who have a GCS of 6–8, after adjustment for severity of injury, those who were observed without intubation suffered no increase in mortality risk and may have in fact been subject to a lower risk. Future directions to further elucidate the appropriate indications for intubation should include dedicated prospective studies that not only question what GCS score is the most appropriate threshold, but also investigate which other, more nuanced factors are appropriate to factor in to the decision of whether or not to intubate.