Relevance of Cerebral Interleukin-6 After Aneurysmal Subarachnoid Hemorrhage
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This study examines the inflammatory response via interleukin-6 (IL-6) in aneurysmal subarachnoid hemorrhage (aSAH) patients and its association with their clinical course (occurrence of acute focal neurological deficits, AFND; and delayed cerebral ischemia, DCI).
A total of 38 consecutive aSAH patients were studied prospectively within 14 days after admission and classified as asymptomatic (n = 9; WFNS grade 1 (1–2), median and quartiles) and symptomatic (n = 29; WFNS grade 4 (2–5)); the latter presenting with AFND (n = 13), DCI (n = 10) or both (n = 6). Levels of pro-inflammatory cytokine IL-6 were determined in cerebral extracellular fluid (ECF, using cerebral microdialysis), cerebrospinal fluid (CSF) and plasma for 10 days after aSAH. Additionally, C-reactive protein (CRP) levels were measured in plasma.
High IL-6 levels in CSF, ECF and plasma were found in all patients, reflecting a pronounced local inflammatory response after aSAH, followed only in symptomatic patients by a delayed systemic inflammation (CRP P < 0.025, days 7–9 after aSAH). In all compartments, IL-6 levels appeared to be higher in symptomatic patients, accompanied also by a higher ECF lactate–pyruvate ratio (P = 0.04). Cerebral, but not plasma IL-6, levels were indicative of the development of DCI in symptomatic patients (ECF P = 0.003; CSF P = 0.001).
A pronounced initial cerebral inflammatory state was observed in patients of all WFNS grades, suggesting that IL-6 elevations are not necessarily detrimental. Cerebral, but not plasma IL-6, levels were predictive of the development of delayed ischemic deficits in symptomatic patients, suggesting that CSF or ECF are the best sampling media for future studies.
KeywordsInflammation Interleukin-6 Cerebral metabolism Microdialysis Subarachnoid hemorrhage Infection
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