ROSC rates and live discharge rates after cardiopulmonary resuscitation by different CPR teams - a retrospective cohort study

For patients with cardiac arrest, outcomes and survival depend greatly on timely and effective cardiopulmonary resuscitation (CPR) by experienced healthcare workers [1]. Improving patient outcomes by improving the quality of CPR has been crucial in the fields of critical care medicine and resuscitation [2, 3].

In an effort to improve CPR outcomes, many hospitals have designated professional CPR teams [4]; however, the most effective resuscitation models for improving outcomes remain controversial [5, 6]. Several studies have reported that having either a medical emergency team or a rapid response (RR) team designated for CPR could increase the quality of CPR [7, 8]. Unfortunately, most of these studies have been limited in that they compared patients “before” and “after” implementation of either RR or medical emergency team [7, 8].

Seoul National University Bundang Hospital (SNUBH) is a tertiary academic hospital that implemented a part-time RR team in October 2012 to conduct in-hospital CPR covering 47.6% of the week [9], while the on-call residents were responsible for the remaining 52.4% of the week. Separate from these teams, the emergency medicine (EM) team responded to all of the out-of-hospital CPR cases, as well as the in-hospital CPR cases occurring in the emergency department. The aim of this study was to compare patient CPR outcomes across the RR, resident, and EM teams. Specifically, we wanted to examine whether CPR performed by the RR team yielded superior patient outcomes than that performed by the EM and resident teams.

During the study period, there were a total of 1148 CPR cases. Three cases were excluded due to incomplete data; of the remaining 1145 CPR cases, 444 (39%) were conducted by the resident team, 431 (38%) by the RR team, and 270 (23%) by the EM team. The baseline characteristics of the patients attended by the three teams are shown in Table 1. The mean Charlson comorbidity scores did not significantly differ among patients treated by the three teams (RR team: 2.61 ± 1.32; resident team: 2.58 ± 1.06; EM team: 2.69 ± 1.35; P = 0.512). The outcomes of CPR according to the variables are shown in Table 2.

In the present study, we found that only the ROSC rates and 10-day survival after ROSC varied between patients who had received CPR from the RR and resident teams from 2013 through 2016. Our findings suggest that the RR team was able to improve patient CPR outcomes by delivering better quality CPR than the resident team that was composed of trainees. Further, while the CPR outcomes between those treated by the EM and RR teams were not significantly different, patients that received CPR in the surgical department had higher rates of ROSC and 10-day survival than those that received it in the non-surgical department.

The first important point to consider while interpreting our findings is whether the difference observed in ROSC rates between patients that were administered CPR by the RR and resident teams was due to the difference in their operating times, and not due to the difference in the proficiency of the teams. Considering the similar nurse-to-patient ratios during the daytime and nighttime in SNUBH, it is unlikely that the occurrence of sudden cardiopulmonary arrests in patients was detected late during the nighttime. However, it is likely that the optimal performance of the resident team was affected because there may have been more fatigue or carelessness in nighttime or during weekends.

The differences in CPR outcomes between the RR and the resident teams might be attributed to either patient-related factors that we were unable to control for, or effects occurring during the night and over weekends. Previous studies have reported that hospitals tend to attend to patients with a greater severity of illness at night; hence, the in-hospital CPR conducted during the night yielded lower ROSC rates [10]. Further, because these studies [11, 12] analyzed the nighttime or weekend effects within the same CPR system, it is likely that patient-related factors and fatigue levels of the medical staff contributed to the lower ROSC rates.. In our study, it is unlikely that severity of illness contributed to the differences in the CPR outcomes; this is supported by the non-significant differences in the Charlson comorbidity scores between the three teams. However, since the effects of the time of the day and day of the week (nighttime and weekend effects) were not considered in this study, a follow-up study investigating these factors would be beneficial.

Second, when interpreting our findings, it is important to note that the EM team has been primarily responsible for CPR for out-of-hospital cardiac arrests. In general, out-of-hospital cardiopulmonary arrests are known to be worse than in-hospital cardiopulmonary arrests [13, 14]. Furthermore, the initial CPR was likely to be provided by the Public EMS team rather than the EM team from the hospital. As a result, the incidence of defibrillation and the placement of an advanced airway were fewer for patients treated by the EM team compared to those for in-hospital cardiac arrest patients treated by the RR or resident teams. Nevertheless, the initial outcome of CPR (rate of ROSC) administered by the EM team for the out-of-hospital cardiopulmonary arrests did not differ from that of CPR administered by the RR team for in-hospital cardiopulmonary arrests in covariates-adjusted multiple regression analysis (Table 3). This result shows the superiority compared to other teams of the systematic CPR implemented by the combination of the public EMS system and the EM team. However, considering that the EM team is not generally responsible for CPR for in-hospital cardiopulmonary arrest, further study is needed to investigate the quality of CPR provided by the EM team.

Other potential confounding factors in the present study were the numbers of individuals who performed CPR, and the numbers of CPR leaders. It is well known that CPR performed immediately following detection of cardiac arrest contributes to better patient outcomes [15]. However, we did not find a significant association between CPR outcomes and the length of time between detection of cardiac arrest and the CPR initiation. This is likely attributed to the fact that most of the CPR cases examined in this study had CPR performed within a minute of detection of cardiac arrest. As for the number of staff members performing CPR, an accurate comparison between the three teams would be difficult due to the retrospective nature of this study; however, all three teams in the study were designed to have at least five individuals participating in CPR implementation. Therefore, it is not likely that the number of staff members per team exerted any decisive influence on the CPR outcomes.

Furthermore, the medical personnel in charge of leading the CPR could potentially play a more decisive factor on the outcomes of the three teams. An experienced SNUBH intensivist (anesthesiologist, pulmonologist, thoracic surgeon, or emergency physician) is typically put in charge of leading the CPR for the RR team [9]. However, for the resident team, an on-call resident, in the second or third year of residency, is typically put in charge of leading the CPR; this introduces an experience gap between the RR and resident teams. Similarly, an experienced physician typically leads the EM team’s CPR, likely contributing to the high-quality CPR observed from that team. A previous study reported that having an experienced medical doctor as a CPR team leader can improve ROSC rates [16]. The presence of highly-trained nurses in the RR team, who generally have more experience than regular nurses, and the presence of emergency medical technicians in the EM team, likely contributed to higher-quality CPR, due to more organized role allocation and effective performance in these teams [17].

Finally, better patient outcomes were observed in the surgery department, regardless of which team (RR or resident team) administered in-hospital CPR. Cardiac arrest among patients in surgery departments are likely to be related to postoperative complications [18]. However, because the present study did not compare the characteristics of in-hospital CPR patients between surgical and non-surgical departments, it is highly likely that these characteristics had an impact on the CPR outcomes. Thus, more research is needed to determine the factors influencing the differences in patient outcomes between those receiving CPR in surgical and non-surgical departments.

This study was subject to several limitations. As this was a retrospective study, bias was inevitable. The time of day during which CPR was performed differed between the RR and resident teams; and nighttime and weekend effects could not be considered. Additionally, since the EM team’s CPR was limited to the emergency department, the emergency room settings may have influenced outcomes; further, records detailing how many individuals performed the CPR or the timing of defibrillation were unavailable. Finally, assessment of the EM team’s CPR quality via a direct comparison of parameters with the RR and resident teams was limited because the EM team responded mostly to out-of-hospital CPR cases, whereas the RR and resident teams’ CPR cases were in-hospital. Nevertheless, this was the first study comparing CPR outcomes across different CPR teams within a single tertiary hospital during the same study period, rather than as a before-and-after study.

In conclusion, CPR performed by the RR team may result in superior ROSC rates and 10-day survival after ROSC compared to that performed by the resident team. Thus, it may be beneficial if in-hospital CPR is performed by a more experienced team that uses a systematic approach to CPR regardless of the time of day or the day of week. However, our results should be applied with caution owing to the aforementioned limitations, and follow-up studies investigating the optimal composition of CPR teams are recommended.