Comparison of open and closed chest compressions after traumatic arrest
I read, with great interest, the study by Bradley et al.1 that compared end-tidal carbon dioxide (ETCO2) values obtained during closed chest compressions (CCCs) and open chest cardiac massage (OCCM). The authors analyzed 17 patients who underwent CCC only and 16 patients who underwent CCC followed by OCCM and concluded that “thoracotomy solely for performing open chest cardiac massage may not provide any benefit to the patient over closed chest compressions.” Importantly, emergency department (ED) or resuscitative thoracotomy serves several functions that benefit critically injured patients presenting in extremis, including relief of pericardial tamponade, direct control of exsanguinating hemorrhage, temporary occlusion of the descending thoracic aorta to limit infradiaphragmatic hemorrhage and improve coronary and cerebral blood flow, prevention of further air embolism, and finally, perhaps most pertinent to the aforementioned manuscript, the performance of OCCM. As such, resuscitative or ED thoracotomy “solely for performing open chest cardiac massage” without these other therapeutic adjuncts is exceedingly uncommon.
Indeed, the limited to nonexistent role of external chest compressions in the exsanguinating trauma patient is hardly controversial. In 1982, Mattox and Feliciano2 reviewed 100 cases of truncal trauma and found external compressions to be of no clinical value in patients who have sustained cardiac arrest after torso injury. Numerous reports over the ensuing 35 years only supported their conclusions. Well-designed animal studies have provided a much more detailed assessment of the benefits of OCCM over CCC during exsanguination. With the use of invasive hemodynamic monitoring, Rubertsson et al.3 randomized swine to CCC versus OCCM cardiopulmonary resuscitation and demonstrated improved mean arterial pressures and double the cardiac output in OCCM versus CCC resuscitations. Human studies have also been reported. Boczar et al.4 reported on 10 patients who underwent CCC followed by OCCM. As Bradley et al.1 has once again effectively demonstrated in Tables 2 and 3 of the current study, Boczar improved perfusion after converting from CCC to OCCM. Importantly though, the benefits of OCCM versus CCCs are further enhanced when hemorrhagic shock is also considered. External compressions rely on increased intrathoracic pressure and competent venous valves to provide approximately 25% of baseline cardiac output while OCCM is more efficient by compressing the cardiac pump itself and is able to generate 60% to 70% of baseline cardiac output.2 Unless new methods and adjuncts to CPR are created, these physiologic parameters will not change with passing time.
It is imperative that we recognize the methodological and data limitations of the current study. The Bradley report was described as a prospective observational study that utilized video review of monitors and resuscitations to capture data. As such, the authors should have been able to analyze the necessary data on CCC rates, OCCM rates, ventilation rates, and sodium bicarbonate or epinephrine administration. Reported variables however were extremely limited—only gender, age, injury mechanism, presence of a witnessed cardiopulmonary arrest, ETCO2, and resuscitation duration were reported. Once again, physiologic variables—the variables most predictive of outcomes after traumatic cardiopulmonary arrest, are nearly absent in this manuscript. There is no mention of location of cardiopulmonary arrest (prehospital vs. in-hospital), duration of cardiopulmonary arrest, the performance of prehospital CPR, the presence of prehospital or ED signs of life, the presence of prehospital or ED vital signs, prehospital or ED cardiac electrical activity, or the presence of cardiac motion on ultrasound.
The absence of these variables raises a question that is essential to the interpretation of this article. What was the presenting physiology in these critically injured patients? Careful review of the manuscript reveals that data after return of spontaneous circulation (ROSC) was included in the analysis.