Iron-Related Brain Damage in Patients With Intracerebral Hemorrhage
Background and Purpose— Iron plays a detrimental role after experimental intracerebral hemorrhage (ICH). This study investigates whether high-serum ferritin levels are associated with poor outcome in patients with ICH.
Methods— We studied 92 consecutive patients with primary hemispheric ICH within the first 12 hours from onset of symptoms (median, 3.3 hours). National Institute of Health Stroke Scale score, ICH, and peripheral edema volumes were measured at admission, 72 hours, and 7 days. Serum levels of ferritin and biomarkers of the inflammatory response were determined. The adjusted effect of ferritin on the full range of Rankin scale was analyzed by a general linear model.
Results— Fifty-one patients (55.4%) had poor outcome (Rankin score >2). Older age, higher stroke severity, larger hematoma volume, intraventricular extension, mass effect, and higher IL-6 and ferritin levels at baseline (270.6 [SD 81.4] vs 74.6 [SD 43.4] ng/mL; P<0.001) were associated with poor outcome. The higher the ferritin quartile, the worse the Rankin score. For every ferritin quartile, the Rankin score increased by a mean of 1.4 points (95% CI, 1.04–1.69) after adjusting for prognostic variables. Ferritin levels remained stable for 72 hours and did not correlate with acute phase reactants.
Conclusions— High-serum ferritin levels at admission are independently associated with poor outcome in patients with ICH. These findings may suggest a neurotoxic effect of increased body iron stores in patients with hemorrhagic stroke.
Iron has been involved in cerebral injury after intracerebral hemorrhage (ICH) in experimental studies. Free iron released after erythrocyte lyses and from ferritin stores may have a role in oxidative stress, glutamate release, and inflammatory response after a hemorrhagic brain injury.1–3 Iron chelators like deferoxamine can reduce brain edema and improve neurological function in experimental models of ICH.4
Few data exist about clinical evidence of iron toxicity in ICH patients.5 We collected our data with the objective to test if serum ferritin levels are associated with poor outcome in patients with ICH.
Subjects and Methods
We prospectively evaluated 100 consecutive patients with a primary supratentorial ICH admitted within the first 12 hours from onset of symptoms in 3 hospitals during 1 year. Exclusion criteria were previous disability, severe alcohol consumption, inflammatory or infectious liver, renal, hematologic diseases or cancer, secondary intracerebral hemorrhage, and coma. We further excluded 3 patients lost to follow-up and 5 patients in whom admission cranial CT was not available for volume calculations. The study was approved by the ethics committees of the participating centers and informed consent was signed by patients or their relatives. All patients were admitted at an acute stroke unit and treated according to the guidelines of the European Stroke Initiative.6 Stroke severity was quantified using the National Institute of Health Stroke Scale score. Functional outcome was evaluated at 3 months using the modified Rankin scale, and poor outcome was defined as modified Rankin scale score >2.
Cranial CT was performed at admission, 72 hours, and 7 days. ICH and peripheral hypodensity volume were measured using the formula of the ellipsoid, and edema volume was calculated by subtracting the volume of the ICH from that of the total lesion. Mass effect was considered when ventricular asymmetry or shifting of the midline structures was observed. All CT scans were centrally evaluated by an investigator who was masked to clinical data. ICH and edema growth ratios were calculated as: final volume−initial volume/initial volume.
Serum samples were obtained on admission and at 24 and 72 hours. Serum ferritin levels, IL-6, and tumor necrosis factor-α were determined by electrochemiluminescence immunoassay (ELECSYS 2010; Roche Diagnostics; and IMMULITE 1000; Diagnostic Products Corporation).
Proportions between 2 groups were compared by using the χ2 test. We used the Kolmogorov-Smirnov test to test for normality. Continuous variables were expressed as mean (SD) or median and quartiles and were compared by the Student t or the Mann-Whitney tests as appropriate. The association between ferritin levels and continuous variables was assessed with the Spearman coefficient. To assess the influence of ferritin levels on the full range of the ordinal Rankin scale, we used a general linear model adjusted for factors and covariates related to dichotomized Rankin scale (poor outcome, modified Rankin scale score >2) in the univariate analysis. We fitted the model in a customized way by means of the Enter method. Values of P<0.05 were considered statistically significant in all tests.
Poor outcome at 3 months was observed in 51 of 92 (55.4%) patients. Seventeen patients died during the study period. Table 1 shows clinical, biochemical, and radiological characteristics by outcome groups. Older age, higher stroke severity, larger hematoma volume, intraventricular extension, mass effect, and higher baseline IL-6 and ferritin levels at baseline were associated with poor clinical outcome. Notably, the higher the ferritin quartile, the poorer the Rankin score distribution (Figure). A generalized linear model showed that for every ferritin quartile, the Rankin score increased by a mean of 1.42 points (95% CI, 1.04–1.69) after adjusting for prognostic variables (Table 2). This association remained after exclusion of 26 patients enrolled in clinical trials.
Higher ferritin levels in the poor outcome group were also found when the baseline sample was obtained within 3 hours from symptoms onset (P<0.001) and showed a flat profile up to 72 hours (mean, 270 ng/mL at baseline; mean, 258 ng/mL at 24 hours; mean, 241 ng/mL at 72 hours). Baseline values did not correlate with acute phase reactants such as leukocyte count and serum glucose and fibrinogen levels.
Baseline ferritin levels showed good correlation with stroke severity, ICH, and edema volumes at baseline, 24 hours, and 7 days (all r>0.60) and showed a moderate correlation with IL-6 levels (r=0.32). Ferritin levels correlated with ICH growth at 7 days (r=0.27; P=0.04), but there was no significant correlation with edema growth at 72 hours (r=0.24; P=0.07) or at day 7.
This study shows that high-serum ferritin levels measured within 12 hours from symptoms onset predict poor outcome in patients with ICH. Likewise, high ferritin levels have been related to poor outcome in patients with acute ischemic stroke,7 and they have related to a higher risk of hemorrhagic transformation and edema development in patients treated with reperfusion therapies.8
The present findings may suggest a biological detrimental effect of increased iron stores also in hemorrhagic stroke. Baseline serum ferritin levels correlated with the initial ICH and edema volumes and, to a lesser extent, with ICH growth. Edema growth showed a nonsignificant trend. Although the biological plausibility was weak, these findings are in line with the experimental data because animal models of cerebral hemorrhage demonstrate that free iron is involved in radical hydroxyl generation, inflammatory reaction, and early edema development.1–3
Serum ferritin could be partly upregulated secondary to the acute phase response.9 However, differences in ferritin levels between patients with good and poor outcomes were seen within the first 3 hours after symptoms onset and remained stable thereafter. Moreover, in accordance with previous studies in ischemic stroke,10 no correlation between ferritin and acute phase reactants was observed, and the effect on outcome remained after adjustment for signatures of acute inflammation.
The main interest of this study links to the potential therapeutic opportunity of iron chelation. Experimental data have demonstrated a neuroprotective effect of deferoxamine in hemorrhagic cerebral damage, reducing brain edema and neurological impairment.4 This preclinical beneficial effect of iron-modifying agents supports the neurotoxic role of increased iron stores. However, this study has some limitations. Analyses of neuroimaging variables are underpowered and require a larger study, and we did not use a planimetric measurement of lesion volumes, which is a more accurate method than the estimation of the ellipsoid formula.
In conclusion, the present study demonstrates that serum ferritin level is an important predictor of clinical outcome in patients with primary ICH. These findings suggest a neurotoxic role of iron stores and may open new therapeutic strategies for the treatment of ICH. Because this is an observational study, causation must be proved in interventional clinical trials modifying iron stores.
The authors are grateful to Prof Dr Erik Cobo, biostatistician, Universidad Politécnica de Catalunya, for his helpful advice in the statistical analysis.
Sources of Funding
This project has been partially supported by grants from the Spanish Ministry of Health (Instituto de Salud Carlos III) EC07/90506, PI060788, by the Retics-RENEVAS Neurovascular Network (006/0026), and by Xunta de Galicia (Consellería de Sanidade: PS 07/14). Dr Natalia Perez de la Ossa has been a recipient of a fellowship from Instituto de Salud Carlos III of the Spanish Ministry of Health (Ayudas predoctorales de formación en investigación).
- Received October 8, 2009.
- Revision received November 9, 2009.
- Accepted November 24, 2009.
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