To the best of our knowledge, this is the first study to describe the characteristics of IHCAT and comparing OHTCA and IHCAT. Previous studies of OHTCA or pre-hospital traumatic cardiac arrest have included trauma patients with evidence of pre-hospital cardiac arrest or CPR [19]. However, some traumatic cardiac arrest studies have combined patients, defined as CPR either in the pre-hospital phase and/or during trauma room treatment [9, 20]. Few studies have reported on cardiac arrest in trauma patients in ED only [9, 21]. None of the studies, however, has designated IHCAT as a separate study population with different pathophysiology of delayed cardiac arrest occurring in-hospital in a trauma patient.
The majority of the traumatic cardiac arrest studies have included patients either from a cardiac arrest registry or a trauma registry [19, 22]. We defined traumatic cardiac arrest to include IHCAT and OHTCA and demonstrated that IHCAT is a distinct type of traumatic cardiac arrest that is different from OHTCA in terms of epidemiology, etiology, pathophysiology, and outcomes.
IHCAT patients have delayed cardiac arrest in the ED and in-hospital phase compared to OHTCA patients who suffer cardiac arrest in the pre-hospital phase. The postulated pathophysiology of delayed cardiac arrest in IHCAT patients is varied and further studies need to be undertaken to determine the causes of their delayed cardiac arrest. The trauma in IHCAT patients always precedes the cardiac arrest in contrast to OHCTA which may include some cases where cardiac arrest precedes secondary trauma. It is unclear how many of the OHTCA cases might be primarily cardiac in origin (i.e., a cardiac event that precedes or causes the traumatic event).
In contrast to previous literature that bemoans the “dismal” survival of trauma patients who suffer from a cardiac arrest, our results show these patients are actually 2 distinct populations with significantly different survival rates, more so after adjusting for confounders [23]. For trauma systems, we have reiterated the importance of getting the patient to the “right care in the right time,” as well as ‘scoop and run’ rather than ‘stay and play.’ A patient who arrests in a trauma center has 6 times higher odds of survival when compared to one that arrests in the pre-hospital phase. For clinical prognostication, we have shown that a trauma patient who arrests, in-hospital, does not have as dismal prognosis as reported in previous literature that did not differentiate this entity from OHTCA. For future reports on trauma patient survival from arrest, we recommend that the practice of ‘lumping’ together all trauma patients be stopped and all the proper classification of such patients be made.
The mean annual crude incidence of IHCAT was 2.0 per 100,000 population compared to 4.0 per 100,000 population for OHTCA, in Qatar. The incidence of cardiac arrest in trauma patients is significant such that it should be recognized as a separate sub-type of cardiac arrest and not simply as an “arrest in special situations.” Since there are no studies of IHCAT, we could not compare the incidence rates with other populations. However, the mean annual crude incidence of OHTCA in Melbourne, for example, was 6.0 per 100,000 [8]. Extrapolating our results, the incidence of IHCAT would be half of OHTCA; giving an incidence of 3.0 per 100,000 for IHCAT in Melbourne.
There were no significant differences noted in the demographic nor injury characteristics of the OHTCA and IHCAT patients. Those that seemed initially significant, i.e. Far Eastern ethnicity, did not persist after multi-variate adjustment. This is different from another study of all out-of-hospital cardiac arrest (OHCA) in Qatar concentrating only on Middle Eastern Arabs and North Africans, and which found that the latter had better chances of survival as they were generally younger with decreased risk factors, more favorable cardiac rhythms, shorter EMS response times, received more Advanced Cardiac Life Support (ACLS) interventions and had longer scene times [24]. The consistent predominance of males, South Asian, and Middle Eastern populations in this study population is simply reflective of the demographic breakdown of the national population of Qatar [25].
The interval between initial trauma and IHCAT is expected to follow the pattern of trauma death described by Sauaia et al., in the USA, and Abdelrahman et al., in Qatar [26, 27]. This work takes the analysis further by separating pre- and in-hospital arrests in trauma patients, therefore providing the evidence that more than two-thirds (67%) of all traumatic arrests, in Qatar during the study period, occur in the pre-hospital setting. This has major implications for healthcare policy prioritization and future research. More resources must be earmarked for quality improvement in pre-hospital care and the primary prevention of trauma through proven programs that will prevent the leading causes of OHTCA [28,29,30].
Road traffic injuries were the leading mechanism of injury of IHCAT and OHTCA patients. However, IHCAT patients had higher odds of injury due to ‘falls,’ compared to OHTCA patients, in univariate analysis. Greater than ninety percent of OHTCA and IHCAT patients had blunt injuries. The high percentage of blunt injuries was similar to OHTCA injury pattern with very few assaults and gunshot penetrating injuries. (9) This may be unique to Qatar, where trauma registry data over the years has shown a less than 5% of injuries due to a penetrating mechanism (ACS TQIP Benchmark report: Fall 2020. American College of Surgeons, Committee on Trauma, Trauma Quality Improvement Program, 2021) [31, 32].
Patients with IHCAT were associated with delayed cardiac arrest in ED and in-hospital.
IHCAT patients had a greater proportion of anatomically localized injuries indicating solitary injuries compared to greater polytrauma in OHTCA. In contrast, OHTCA patients had a higher proportion of diffuse blunt non-localizable polytrauma injuries that were severe enough to cause immediate or earlier onset of cardiac arrest.
The difference in anatomical injury pattern was statistically significant for a spinal injury and abdominal injury that persisted after multivariable analysis. Abdominal and spinal injury patterns may indicate different pathophysiological pathways, for example, involving the thoracoabdominal autonomic nervous system causing bradycardia leading to cardiac arrest [33]. These two isolated anatomical injury patterns may also be surrogate indicators for less immediately fatal mechanisms of injury in IHCAT patients leading to delayed onset of cardiac arrest in the hospital.
Despite a comparable proportion of head injuries, the mean GCS score for IHCAT was nearly twice that for OHTCA patients. The difference in mean GCS score was statistically significant even after adjustment and underlines the finding that OHTCA patients had more severe traumatic brain injury (TBI) and were more likely to be recipients of greater energy transfer during the initial traumatic event. Again, this has implications for efforts to prevent this energy transfer for the most common mechanisms of injury (i.e. seatbelts and helmets for motor vehicle collisions [MVC] or helmets and harnesses for falls) and what treatment or interventions they may benefit from in the pre-hospital setting and once in the ED or Trauma Center [34, 35].
Hypoxia secondary to airway and respiratory compromise in OHTCA and IHCAT patients were comparable. Hypovolemia had a statistically significantly higher proportion in IHCAT patients compared to OHTCA patients that did not persist after adjustment. Hypovolemia, as a result of massive hemorrhage, is either massive and lethal at the scene (i.e., aortic transection) or is initially survivable but aggravated by the time it is left unidentified as the fluids infused and the coagulopathy of trauma ensues. It is the latter that would comprise the population of IHCAT patients with hemorrhagic shock.
Overall, the proportions of OHTCA and IHCAT patients with an initial shockable rhythm was low, 2.9% and 7.5%, respectively. While these proportions were much lower than what we noted for presumed cardiac origin OHCA, 19.7%, an initial shockable rhythm still predicted a more favorable outcome for both.
IHCAT was associated with a greater proportion of cardiac re-arrest after adjustment. Cardiac re-arrest has been reported to be associated with decreased survival in OHCA patients [36]. In contrast, this study determined that cardiac re-arrest was associated with IHCAT patients who had greater survival compared to OHTCA patients. Further studies are required to explore re-arrest in traumatic cardiac arrest (TCA), OHTCA, and IHCAT.
After multivariate adjustment, IHCAT patients had higher survival rates compared to OHTCA. The Donabedian model for healthcare quality measures in this setting emphasizes that even in the presence of structural measures, including EMS personnel that are not only BLS/ACLS/ATLS certified but are even augmented by critical care paramedics, there is a survival benefit to expediting transport to a trauma center [15, 37]. This highlights the need for prevention and process measures, the implementation of proven interventions that will prevent the crashes and falls from occurring in the first place or reduce the force/s that are imparted on the victims, i.e., speed limits, high-visibility law enforcement, and enhanced seat belt laws for MVCs and tighter enforcement of occupational safety regulations on safety harnesses and helmets for falls [30, 34, 35].
