Prehospital survival after non-traumatic cardiopulmonary resuscitation with intra-arrest echocardiography: a propensity score matching analysis

Abstract Background The use of point-of-care ultrasound during cardiopulmonary resuscitation (CPR) may help to detect the reversible causes of cardiac arrest. Furthermore, it allows visualization of organized myocardial movements in patients with no palpable pulse but electrical activity still visible on ECG. Purpose In this study, we aimed to compare the prehospital survival of patients with pseudo pulseless electric activity (pseudo-PEA) and with cardiac standstill. Methods 2,715 CPR cases are available in a structured form from the database of the digital case reports of the Helicopter Emergency Medical Service (HEMS) in our country from 2019 to 2024. Of them, 908 non-traumatic CPR cases were included, in which point-of-care echocardiography was performed during CPR, and the documentation was clear and complete. The endpoint of the study was hospital admission with spontaneous circulation. Patients who were admitted to the hospital with continuous CPR were not included in this analysis (n=16). Pseudo-PEA was documented in 125 cases (13.77%). Using 1:1 nearest neighbour propensity score-matching analysis (PSM), 125 patients with documented cardiac standstill were matched to the pseudo-PEA patients, using the available baseline and procedural characteristics of patients. Balance on baseline covariates between the pseudo-PEA and cardiac standstill groups was evaluated using absolute standardized mean differences. A value less than 0.15 was considered as an acceptable standardized bias. Binary outcomes were analysed using 2x2 crosstabs comparative measures. Results An acceptable balance on baseline covariates was achieved by the propensity score matching. Hospital admission with spontaneous circulation was observed in 46/125 (36.8%) pseudo-PEA cases, while 11/125 (8.8%) cases with cardiac standstill chi-square p0.001, OR=6.03 (95% CI: 2.94-12.4). Conclusion During non-traumatic out-of-hospital CPR, if pseudo-PEA is detected during point-of care echocardiogram, the probability of admission to the hospital with spontaneous circulation may be higher than in the case of a cardiac standstill, even if other relevant baseline covariates are balanced. Further studies are needed to compare possible diagnostic and therapeutic alternatives to improve survival chances.Balance plot Outcomes after PSM