Comprehensive post-resuscitation care is important for survivors of out-of-hospital cardiac arrest (OHCA) [1
]. Because the care for post-cardiac arrest syndrome (PCAS) is specialized and complex, various treatment strategies, including a range of specialists and resources, should be available in a multi-disciplinary fashion. When the index hospital to which the victim is initially transported cannot provide comprehensive PCAS care, including coronary angiography, patients with return of spontaneous circulation (ROSC) should be relocated to a different hospital. Even index hospitals that provide PCAS care may not always be able to provide comprehensive post-resuscitation care because of limited resources.
Inter-hospital transfer (IHT) after ROSC is a time-consuming process. When patients who achieve ROSC are transferred to other hospitals, PCAS care can be delayed. The International Liaison Committee on Resuscitation (ILCOR) recommends that emergent coronary angiography (CAG) be performed in OHCA patients with a suspected etiology of cardiac arrest and ST elevation on electrocardiography (ECG) [1
]. Several studies have reported good neurological outcomes after transfer to cardiac arrest centers (CACs) [2
]. Therefore, the ILCOR has suggested that all post-arrest patients be transported to a CAC; however, CACs are not always accessible [5
In Korea, patients with sudden cardiac arrest are transported to the closest emergency department (ED) by the emergency medical service (EMS) with basic life support. Because the rate of ROSC before arrival at the ED is low, it is difficult to triage patients on the basis of ECG results after ROSC, and ECG results are usually examined after ROSC at the index hospital. For these reasons, patients who achieve ROSC should be transferred to a CAC for emergent CAG and comprehensive post-resuscitation care. Park et al. reported that the overall rate of IHT was 16.88% among patients who achieved sustained ROSC at an ED in Korea [7
]. Previous studies on IHT have focused on the regionalization of cardiac arrest patients. Nevertheless, IHT is needed, and little is known about the neurological outcomes of patients who undergo IHT to a CAC after achieving ROSC. In this study, we sought to determine whether IHT to a CAC after achievement of ROSC was associated with poor outcomes in cardiac arrest patients treated with targeted temperature management (TTM) based on ECG results. We also compared the time from ROSC to TTM induction according to the type of ED visit to determine the effect of delayed TTM on neurological outcomes in post-cardiac arrest patients.
Treatment of PCAS patients in CACs is beneficial in terms of survival and neurological outcomes. Therefore, it is rational for patients with ROSC at low-volume hospitals to be transferred to CACs for comprehensive PCAS care. Nevertheless, there is a concern that the transfer of patients with ROSC could be harmful because active treatment could be delayed, and adverse events might occur during transport [9
]. Previous studies on IHT focused on the effect of IHT from low-volume hospitals to high-volume hospitals or from a non-CAC to a CAC [2
]. Therefore, in this study, we investigated the effect of IHT on the neurological outcomes of patients who were treated with comprehensive PCAS care in a CAC. In this study, 30% of patients were transferred from the index hospital (Figure 1
). IHT was not an independent predictor of neurological outcomes after 6 months in either the STE or non-STE group (Table 3
The participating hospitals in this study were generally equipped with the important components of a CAC, such as 24/7 access to interventional cardiology facilities, TTM, diagnostic imaging, and neurologic care. We found that neither IHT itself nor a delay in active PCAS care caused by IHT affected neurological outcomes. In Korea, the public EMS system does not have guidelines regarding the transportation of cardiac arrest patients to a CAC. Usually, the EMS transports OHCA patients to the nearest emergency medical center capable of providing basic and advanced life support. For these reasons, IHT should be required to provide comprehensive post-resuscitation care and to treat the underlying causes of cardiac arrest when cardiac arrest victims achieve ROSC at the index hospital and when the index hospital is a low-volume hospital or cannot provide appropriate treatment. These transfers from low-volume to high-volume hospitals or a non-CAC to a CAC are necessary to improve neurological outcomes. However, few studies have investigated how the delay in comprehensive PCAS care due to IHT could affect the neurotological outcomes of PCAS patients.
Because TTM is a treatment modality for comprehensive PCAS care, we hypothesized that TTM time could serve as an indicator for the implications of comprehensive post-resuscitation care. When patients with ROSC are transferred from index hospitals, physicians consider the possible effects of treatment delay and adverse events during transfer. However, in the present study, we found that IHT after ROSC was not related to poor neurological outcomes at 6 months, even though the TTM time may have been prolonged (Table 1
, Figure 2
). These findings support the recommendation that cardiac arrest patients with ROSC could be transferred to a CAC as soon as possible when the index hospital cannot provide comprehensive PCAS care and management.
Regionalization of care to specialized centers is important for managing time-critical illnesses by concentrating both services and providers with greater experience [13
]. Several studies have shown that management after ROSC at high-volume hospitals is associated with better survival; improved neurological outcomes were also seen in patients transferred from low-volume hospitals to high-volume hospitals [2
]. These findings suggest that the regionalization of care for cardiac arrest results in good neurological outcomes [11
]. On the basis of the results of these studies, the ILCOR recommends transport of all post-arrest patients to a CAC [6
]. One of the purposes of regionalization of cardiac arrest care is rapid management of the cause of arrest, especially the use of coronary angiography. Early intervention for coronary artery disease is important for treating PCAS. Several studies have reported on the effects of transfer to a CAC stratified by ECG rhythm (ST elevation or non-ST elevation) [3
]. In the present study, only 23.8% (316/1326) of patients underwent CAG within 24 h after ROSC (Table 1
). Although early CAG within 24 h after ROSC was more common in the STE group (94/149) than in the non-STE group (222/1177), early CAG was not an independent predictor of poor neurological outcomes (Table 3
). When regionalization of cardiac arrest care is based on ECG findings after ROSC, confounding may be present due to the interpretation of ST elevation after ROSC. In the present study, only 411 (31%) patients achieved ROSC before arrival at the hospital; 915 (69%) patients had been resuscitated upon arrival to the hospital and achieved ROSC in the ED (Table 1
). Regarding these patients, a decision on whether transport them to the nearest emergency medical center or CAC was needed, for early CAG could not be made.
Comprehensive post-resuscitation care is important for improving survival and neurological outcomes in patients achieving ROSC [6
]. Regionalization to a CAC could be helpful in providing early comprehensive PCAS care. However, IHT should be required when the index hospital cannot provide PCAS care. We suggest that in these situations, patients who achieve ROSC at the index hospital be transferred to a CAC for comprehensive PCAS care because IHT itself did not show any association with neurological outcomes 6 months after cardiac arrest.
This study has several limitations. The KORHN-pro registry did not include detailed information regarding the index hospitals, such as volume of cardiac arrest patients, the hospitals’ ability to manage PCAS patients, or the reason for transfer after achieving ROSC. Therefore, this was designed as a retrospective study based on the database collected by KORHN prospective observational study. We recorded the TTM time on the basis of ROSC because the cardiac arrest may have occurred while the patient was not under observation, and therefore, the timing of cardiac arrest could have been based on the surmise of the caregiver. In IHT patients, the time for transportation from the index hospital was not recorded in the KORHN-pro registry. Therefore, the transportation time could not be calculated and analyzed for its effect on neurological outcomes. Nevertheless, we compared TTM time (the time from ROSC to TTM induction), including the transportation time from the index hospital to a CAC, to analyze the effect of a delay in active PCAS care in transferred patients.
In conclusion, we found that IHT after achieving ROSC showed no association with neurologic outcomes at 6 months in post-OHCA patients treated with TTM, even though TTM induction was delayed in transferred patients. Therefore, when comprehensive PCAS care is not available at the index hospital, physicians could consider transferring patients with ROSC to a CAC.