The management of traumatic cardiac arrest has been a popular topic over the past few years and featured in numerous social media and conferences. We’ve talked about here at St.Emlyn’s too1. Various algorithms exist and I’m sure those working in the field of trauma are au fait with them. Outcomes from this procedure are variable, with a significantly worse outcome in the blunt trauma group. A paper has been released this week from the Journal of Trauma and Acute Care Surgery comparing open cardiac massage2 vs. closed chest compressions in traumatic cardiac arrest3. The study was performed by some famous names (Deborah Stein et al.) at the R Adams Cowley Shock Trauma Centre in Baltimore, Maryland.
In major trauma centres around the world end-tidal CO2 (etCO2) monitoring 4 is near ubiquitous. It allows real time feedback on the quality of cardio-pulmonary resuscitation4,5,5and its use is recommended by ILCOR. Given that CO2 is a by-product of metabolism, rising levels indicate good perfusion of tissues whereas falling levels can indicate poor perfusion (a good overview can be found at LITFL). No studies have previously compared the quality of resuscitation by either open cardiac massage (OCM) or closed chest compressions (CCC) using etCO2 in the trauma population.
Patients were included in the study if they presented directly to the centre and had either OCM or CCC. Patients who were pronounced dead on arrival or had a REBOA catheter placed were excluded from the trial. The investigators enrolled 33 patients into the trial, mainly male in the traditional demographics seen in trauma literature. 17 were in the CCC group and 16 in the OCM group, and approximately half the patients had a witnessed arrest. That last bit is somewhat confusing (at least to me) as it is unclear where exactly the patient arrested; was it en route to hospital or in the ED? Half of the patients (8) in the CCC group had a blunt mechanism of injury, compared to only 2 patients in the OCM group. The OCM group had 100% mortality and the CCC group had 88.2% mortality (p=0.49). Annoyingly the exact pattern of injury was not described, although in the OCM group most of the patients had sustained a gunshot wound, which can be particularly destructive to a number of anatomical regions given the penchant of bullets to cut a wild trajectory. Despite this knowing whether the patient had a directly treatable injury, cardiac laceration for example, would have been useful when considering ones own patients. Imagine a solitary cardiac injury, by stabbing for arguments sake, one would imagine that a thoracotomy and repair of the injury would be far better than CCC. Knowing the mean or median ISS in each group would have also helped clarify this further, as unless you know the patient group in this study one can’t draw too many conclusions.
So what did they find?
The investigators were able to measure etCO2 every 6 seconds during resuscitation. Ultimately they used initial, peak and final etCO2 values to compare the groups. The OCM group underwent CCC prior to thoracotomy for a mean of 66 seconds. Overall there was an increase in etCO2 in both groups, but there was no significant difference between the groups at any time point. Furthermore there was no significant difference in the rates of ROSC (OCM 23.5% vs. CCC 38.9%, p=0.53). In both the blunt and penetrating sub-groups there were also no significant differences between OCM and CCC. In the penetrating group who underwent OCM the etCO2 values went from averagely lower to averagely higher, whereas the same was true of the CCC group with blunt mechanism.
What does this mean?
Difficult to say. They numbers in this study were very small and whilst it promotes an interesting debate, it provides no definitive answers. This is a significant problem with conducting research in trauma, and in specifically with trauma patients in extremis. The number of cases seen by most institutions is relatively low, and to collect sufficiently large data requires time. The problem with collecting data over years is that it can be confounded by temporal changes in practice. REBOA6 is now being utilised in some services in zone 1 of the aorta7, thus offering an alternative to thoracotomy and cross clamping of the aorta. As this is less invasive we may see an increase in this application over the coming years. Ultimately though, most institutions are not using REBOA and thoracotomy remains the most viable approach to gain proximal control of the aorta. The mortality data for blunt traumatic cardiac arrest is poor and has been for some time. The majority of survivors from traumatic cardiac arrest have historically come from the isolated penetrating thoracic injury cohort, and as such it is still unknown how best to achieve an improvement in mortality from the blunt mechanism group. Additionally, some institutions/services are performing resuscitative thoracotomy in the pre-hospital environment8 and sometimes the procedure is delivered before the patient arrests, which may make the relevance of this paper difficult to interpret.
This is a great study for provoking debate, although is not sufficient to change practice for most institutions. There is an element of the paper that could be interpreted as advocacy for the employment of REBOA in such cases, given that R Cowley Adams Shock Trauma is a world leader in the use of the technique. Let’s hope we see more research in this area and continue to improve outcomes!
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