The present study demonstrated a higher contamination rate of blood cultures and bacteremia incidence in patients with OHCA, compared with those without OHCA at the ED. Notably, significant differences in bacteremia sources, causative microorganisms, and susceptibilities between two patient groups were evident. Compared with the matched non-OHCA patient with community-onset bacteremia, the OHCA patient exhibited a greater likelihood of having bacteremia due to lower respiratory tract infections and a lower likelihood of having urosepsis. Furthermore, more bacteremic events due to anaerobes and streptococci, but fewer events due to E. coli were observed in OHCA patients, and AROs more often existed among such patients. More importantly, the survival benefit of early administration of appropriate antimicrobials in OHCA patients was firstly recognized. Accordingly, the clinical practice of blood culture samplings should be encouraged and the incorporation of broad-spectrum antimicrobials as empirical therapy into the antibiotic stewardship program should be considered as the first aids for OHCA patients.
Generally, the etiologies of cardiac arrest are presumed to be of cardiac origins, regardless of the presenting cardiac rhythm. However, the fact that non-cardiac origins account for up to 30% of cardiac arrest population should not be ignored . Recent investigations dealing with non-cardiac etiologies have indicated that asphyxia, respiratory failure, and comorbid respiratory diseases are the leading etiologies [9, 10, 24], but information available on infectious etiologies is limited in the literature. In our OHCA cohort, lower respiratory tract infections were the most common etiology of bacteremia. Moreover, risk factors linked to the development of lower respiratory tract infections, such as the elderly, comorbid neurological diseases, and bed-ridden status, were frequently observed in OHCA patients. Accordingly, we reasonably infer that lower respiratory tract infection is the leading etiology in the frail elderly presenting with OHCA.
Although optimization in the “chain of survival” has been evidenced to improve survival and neurological outcomes in patients with OHCA [24, 25], the appropriateness of empirical antimicrobial therapy has not been address during the formulation of strategies to reduce morbidity and mortality. Generally, a delay in the administration of appropriate antimicrobials increases the risk of unfavorable prognoses in adults with community-onset bacteremia, particularly in those who are critically ill [5, 7]. In the latter presenting with cardiac arrest, the prognostic benefit of prompt administration of appropriate antimicrobials was recognized herein. Because of a higher extent of antimicrobial resistance among the etiological pathogens, a longer elapse of the TAA in patients with OHCA who had community-onset bacteremia was not surprised.
Studies have identified several prehospital predictors of survival from OHCA, such as bystander CPR [24, 25],, witnessed cardiac arrest , EMS transport time , ambulance response time , and EMS scene time . Although two predictors, namely bystander CPR and witnessed cardiac arrest, were demonstrated to be independent determinants of survival outcomes, the time-related EMS variables, in terms of the response time, transport time, and scene time, were not associated with patient fatality in our cohort. The cohorts in previously established studies differ from those in our study because we included only patients with documented BSIs. Notably, our work is the first to together investigate the effects of pre-hospital factors and antimicrobial therapy on the prognosis of patients experiencing OHCA. We believe that impacts of any time-related EMS variable on patient prognoses might be negligible, because the elapsed TAA was found to be considerably greater than any of the values for time-related EMS variables. Accordingly, efforts to provide prompt treatment for patients with OHCA through the administration of appropriate antimicrobial therapy should be emphasized.
Contaminated blood cultures was widely known to adversely affect health care and medical expenditures, causing unnecessary hospitalizations, antimicrobial administration, and microbiological studies . Furthermore, ED overcrowding is a growing problem worldwide and is associated with blood culture contamination , delayed administration of appropriate antibiotics [32, 33], and unfavorable patient outcomes . Patients with cardiac arrest are emergently resuscitated and comprehensively evaluated, which substantially increases the utilization of emergency care resources and the degree of ED overcrowding. Therefore, a high contamination rate of blood culture samples in patients experiencing OHCA is not unexpected.
As the study controls, our non-OHCA patients with BSI were selected at a ratio of 6:1, according to the arrival timing of each patient with OHCA. Such ED encounters were sufficiently representative of the comparators of community-onset bacteremia for the following reasons. First, the main causative microorganisms, namely E. coli, S. aureus, Streptococcus species, and Klebsiella species, as well as common bacteremia sources, such as urosepsis, intra-abdominal infections, and soft-tissue infections, in the matched non-OHCA patients, were compatible with those in previously published cohorts with community-onset bacteremia [2, 5, 7, 34]. Second, the proportion of critically ill patients at bacteremia onset (approximate 20%) and the crude mortality rate (approximate 15%) in the present cohort were also similar to the corresponding data reported in other studies [2, 5, 7, 34].
Of AROs in the community, ESBL-producers have well known adverse effects on the prognoses of bacteremic patients in the literature . Clinical predictors of ESBL-producers in community-onset bacteremia, including healthcare facility residents, urinary catheter use, previous antimicrobial therapy, frequent ED visits , and previous hospitalization have been reported . Because of the retrospective nature of the present study, some variables were difficult to assess. However, studies assessing the frequency of ED visits have suggested that it may be correlated with increased healthcare use, serious ill health, and socioeconomic distress [37, 38]. It was rightfully understandable that etiologic microorganisms in bacteremic patients experencing OHCA were more likely to be antimicrobial-resistant because of frequent utilization of medical care.
Our findings should be interpreted with cautions for several limitations inherent to the study design. First, the recall basis could not be completely abolished because of the retrospective and observational nature. Therefore, two authors recorded information to ensure data accuracy and minimize record discrepancies. Second, the present study was conducted at three hospitals located in southern Taiwan, and our findings may not be applicable to other areas or hospitals. However, we included approximately 3,000 adults that could be regarded as representative of community-onset bacteremia in southern Taiwan. Third, although bacterial translocation raised from intestinal ischemia during the periarrest period might result in secondary bloodstream infections, OHCA patients simultaneously experiencing systemic infections were proven for the high level of C-reactive protein herein. Finally, our cohort represents 56% of all patients experiencing OHCA sampled for blood cultures at EDs. Selection bias may have exerted a certain influence on the results and reflects the inadequate alertness of sepsis as one of the causes of OHCA, as observed in the literature [9, 10]. We believe a multicenter, prospective study to evaluate the incidence and significance of BSIs are warranted in the future.