Influence of mild therapeutic hypothermia on the inflammatory response after successful resuscitation from cardiac arrest☆
Introduction
After successful cardiopulmonary resuscitation (CPR) from out-of-hospital cardiac arrest (OHCA) in patients who have ventricular fibrillation (VF), the use of mild therapeutic hypothermia (MTH) is advocated to reduce neurologic dysfunction [1]. Although survivors of OHCA exhibit a systemic inflammatory response [2], some animal data suggest that MTH does not alter this cascade [3]. In settings other than CPR, the use of hypothermia yielded conflicting results, and experimentally, MTH is associated with a marked increase of proinflammatory cytokines, which is linked to brain and heart failure [4], [5], [6]. Although cytokine activation is essential for optimal immune response to microbial pathogens, excessive production can also induce shock and progression of organ failure leading to death [7], [8]. In this preliminary study, we compared the time course of the inflammatory cytokines interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α), and the biomarkers C-reactive protein (CRP) and procalcitonin (PCT) in patients resuscitated from OHCA and treated with or without MTH. We hypothesized that the use of MTH would result in increased serum cytokine and biomarker levels.
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Material and methods
Seventy-one patients (>18 years) with nontraumatic arrest cause were enrolled in this observational study. Demographical and CPR-related data were collected at the emergency department immediately after hospital admission and after 6, 24, and 120 hours at the intensive care unit using a Web-based data entry system as part of a quality assurance initiative of the German Society of Anesthesia and Intensive Care Medicine [9]. At the same time, serum samples for the determination of IL-6, TNF-α,
Results
No differences between patients treated with or without MTH were found with regard to most of the demographical and arrest-related data (Table 2). Patients treated with MTH were significantly more prone to bacterial colonization and required significantly more often catecholamines to maintain arterial pressures (Fig. 1). Bacterial colonization was predominantly found in bronchoalveolar lavage (48.8% of all cases), blood cultures (30.2%), and urine (11.6%), with Gram-positive cocci (58.5%) and
Discussion
Survivors of OHCA exhibit a “sepsis like syndrome” including high levels of circulating cytokines, which are associated with dismal outcomes [2]. Our results are in accordance with this observation and extend our knowledge in that MTH per se results in significant alterations in IL-6, CRP, and PCT levels. In settings of regional ischemia/reperfusion injury in the central nervous system, that is, acute ischemic stroke, there is evidence that high IL-6 serum levels are associated with early
Uncited reference
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This study was supported by a grant to Dr Michael Fries from the Laerdal Foundation for Acute Medicine, Stavanger, Norway. Test kits for the determination of Procalcitonin and C-reactive protein serum levels were kindly provided by BRAHMS AG, Hennigsdorf, Berlin, Germany. Michael Fries has received honoraria as speaker by the same company.
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These authors contributed equally to this study.