Ceftriaxone to PRevent pneumOnia and inflammaTion aftEr Cardiac arresT (PROTECT): study protocol for a randomized, placebo-controlled trial

Microbiological Profiles after Out-of-Hospital Cardiac Arrest: Exploring the Relationship between Infection, Inflammation, and the Potential Effects of Mechanical Circulatory Support

Background: Cardiogenic shock (CS) following an out-of-hospital cardiac arrest (OHCA) poses significant management challenges, exacerbated by inflammatory responses and infectious complications. This study investigates the microbiological profiles and impacts of mechanical circulatory support (MCS) on inflammation and infection in OHCA patients. Methods: We retrospectively analyzed microbiological data from various specimens of 372 OHCA patients, who were treated at the Cardiac Arrest Center of the University Hospital of Marburg from January 2018 to December 2022. Clinical outcomes were evaluated to investigate the potential impact of MCS on infection and inflammation. Results: Of the study cohort, 115 patients received MCS. The microbiological analysis revealed a higher incidence of positive blood cultures in the MCS group vs. the non-MCS group (39% vs. 27.7%, p = 0.037), with predominantly Gram-positive bacteria. Patients with positive microbiological findings had longer in-hospital stays and prolonged periods of mechanical ventilation. The levels of inflammatory markers such as C-reactive protein (CRP) and procalcitonin (PCT) differed, suggesting a more pronounced inflammatory response in MCS patients, especially in the later ICU stages. Notably, despite the higher infection rate in the MCS group, the survival rates did not significantly differ in the two groups. Conclusions: MCS appears to influence the microbiological and inflammatory landscape in OHCA patients, increasing the susceptibility to certain infections but not affecting the overall mortality. This study underscores the complexity of managing post-resuscitation care and highlights the need for tailored therapeutic strategies to effectively mitigate infectious and inflammatory complications.

Delayed CCL23 response is associated with poor outcomes after cardiac arrest

Chemokines, a family of chemotactic cytokines, mediate leukocyte migration to and entrance into inflamed tissue, contributing to the intensity of local inflammation. We performed an analysis of chemokine and immune cell responses to cardiac arrest (CA). Forty-two patients resuscitated from cardiac arrest were analyzed, and twenty-two patients who underwent coronary artery bypass grafting (CABG) surgery were enrolled. Quantitative antibody array, chemokines, and endotoxin quantification were performed using the patients blood. Analysis of CCL23 production in neutrophils obtained from CA patients and injected into immunodeficient mice after CA and cardiopulmonary resuscitation (CPR) were done using flow cytometry. The levels of CCL2, CCL4, and CCL23 are increased in CA patients. Temporal dynamics were different for each chemokine, with early increases in CCL2 and CCL4, followed by a delayed elevation in CCL23 at forty-eight hours after CA. A high level of CCL23 was associated with an increased number of neutrophils, neuron-specific enolase (NSE), worse cerebral performance category (CPC) score, and higher mortality. To investigate the role of neutrophil activation locally in injured brain tissue, we used a mouse model of CA/CPR. CCL23 production was increased in human neutrophils that infiltrated mouse brains compared to those in the peripheral circulation. It is known that an early intense inflammatory response (within hours) is associated with poor outcomes after CA. Our data indicate that late activation of neutrophils in brain tissue may also promote ongoing injury via the production of CCL23 and impair recovery after cardiac arrest.

The immunology of the post-cardiac arrest syndrome

Patients successfully resuscitated from cardiac arrest often have brain injury, myocardial dysfunction, and systemic ischemia-reperfusion injury, collectively termed the post-cardiac arrest syndrome (PCAS). To improve outcomes, potential therapies must be able to be administered early in the post-arrest course and provide broad cytoprotection, as ischemia-reperfusion injury affects all organ systems. Our understanding of the immune system contributions to the PCAS has expanded, with animal models detailing biologically plausible mechanisms of secondary injury, the protective effects of available immunomodulatory drugs, and how immune dysregulation underlies infection susceptibility after arrest. In this narrative review, we discuss the dysregulated immune response in PCAS, human trials of targeted immunomodulation therapies, and future directions for immunomodulation following cardiac arrest.