Page 18 - JSOM Summer 2023

FIGURE 1 Flow diagram of casualties included in this study. also highlight that intubation remains the primary airway inter-
vention despite lack of recommendation by TCCC guidelines.
Total dataset
28,950 The DoDTR, while incredibly useful to explore associations,
is limited in the granularity and completeness of prehospital
Pediatric data. Data on the severity of initial airway compromise (e.g.,
8
(excluded) degree of airway obstruction by fluid and debris and first pass
3,053 success rate) is infrequently documented. Simple but effective
Adults procedures to limit aspiration such as casualty positioning and
(included) suction are also rarely documented. Additionally, the location
of events in combat settings as well as training and expertise
25,897 of the personnel involved in the airway management are not
documented. This may limit the generalizability further. Other
limitations include the data collected for the DoDTR, while
Airway prospectively captured, was reviewed in a retrospective pro-
intervention cess. Given the lack of a requisite comparative standard, we
1,509 do not have fidelity on the amount of omitted data. The low
event rate of aspiration in prehospital intubations in this data
set also adds to the limitations of this study. However, we did
use Firth bias-adjusted estimates to compensate for the low
Aspiration incidence. Our study population consisted of mainly young
pneumonia adult males and may have limited generalizability to the gen-
41 eral population. Unmeasured confounding variables may also
exist as this is an observational study.
these studies may be attributed to the increased ISS seen in the
aspiration cohort. Our median ISS for the aspiration cohort Our study suggests several areas for future research. Future
was 25; this may reflect a difference in injuries sustained in the investigations seeking to clarify any causal relationship be-
combat setting including mixed penetrating and blunt trauma tween aspiration pneumonia and patient outcomes would
from the signature explosive injury. Other studies have also benefit from additional data collection to improve the ability
found a positive correlation between ISS and development of to control for potential confounders. Given that documenta-
aspiration complications. 33,34 In a retrospective study of trau- tion errors are likely to remain a challenge for DoDTR data
ma-associated pneumonia, Mangum et al. determined that an collected in combat zones, this might be an ideal avenue of
ISS greater than 18 was associated with increased ICU and inquiry for prospectively collected registry data, such as the
hospital length of stay. 35 National Emergency Airway Registry (NEAR). 40–42 Next, stud-
ies will ideally clarify the relationship between paralytic use
Of the interventions compared, succinylcholine was the only and patient outcomes, a clinical question unlikely to be ad-
intervention associated with a significant difference between dressed by future randomized trials. 43,44 Despite using a Firth
the groups, 28% of the non-aspiration group received the drug bias model, we can only account for measurable confounders
versus 5% of the aspiration group (p = 0.031). We observed that are often limited in prehospital documentation. Fourth,
an association between administration of succinylcholine and we must highlight that the majority of the casualties in this
reduced risk of aspiration pneumonia. Several studies assert analysis were non-NATO and humanitarian associated. It is
that the use of this depolarizing agent reduces complications not clear how this can be extrapolated to the US and NATO
of intubation including aspiration. The authors also point out forces as other factors such as preinjury health, nutrition, and
that out-of-hospital intubations overwhelming occur on more other factors may have influenced their outcomes in a way
severely injured patients than in hospital RSI intubations. 36–39 that we cannot adjust for. Finally, these registry studies may
Our data supported the findings of reduction in the rate of aspi- also prove useful for clarifying the effect modification result-
ration in patients receiving succinylcholine as part of RSI. More ing from operator experience, intubation modality, and other
studies are needed to deduce the complex interplay of ISS and characteristics of airway management.
RSI in prehospital intubation of trauma patients. Moreover, our
increased survivability in the aspiration cohort receiving succi- Conclusion
nylcholine may be a result of a selection bias of patients: this
agent is generally used by prehospital clinicians with a higher Overall, the incidence of aspiration pneumonia was low in our
level of training and skill, and often in semi-fixed locations such military cohort. Succinylcholine was associated with lower
as an aid station. That is, casualties not getting succinylcholine odds of developing aspiration pneumonia.
may be cared for by prehospital personnel with less training in
more austere conditions. We must also note that the most fre- Funding
quently seen non-depolarizing paralytic in the deployed setting We received no funding for this study.
is vecuronium, which has a substantially slower time to onset
compared to succinylcholine. This may suggest that the more Disclosures
rapid onset time has a protective factor. Alternatively, it may None.
be possible that vecuronium was only used post-intubation and
was not used for facilitating intubation and therefore had no Disclaimer
effect. Since we do not have time-stamp data, we can only hy- The views expressed in this article are those of the authors and
pothesize. While not the primary aim of this analysis, we must do not reflect the official policy or position of the US Army

16 | JSOM Volume 23, Edition 2 / Summer 2023