06/05/2009 - Articles

A Higher Blood Calcium Minimizes Stroke

By: Robert W. Griffith, MD

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Lower serum calcium on admission to hospital for an ischemic stroke is predictive of a larger volume of damaged brain tissue than that seen in people with a higher serum calcium. This may have implications for managing people at risk of having a stroke.

Summary

Higher serum calcium levels on admission of patients with an ischemic stroke are linked with smaller volumes of dead brain tissue, suggesting that serum calcium may serve as a prognosticator for stroke severity.

Introduction

Ischemic stroke is the most common type of stroke - accounting for almost 80% - and is caused by a clot or some other blockage of a blood vessel supplying the brain. The remaining 20% of strokes are hemorrhagic strokes, caused by a burst blood vessel. Previous studies have suggested that higher serum calcium levels at admission are associated with better clinical outcomes after ischemic stroke. To analyze this finding further, with the hope of providing more information on the pathology, a Canadian study was done to determine the size (or rather, volume) of the infarcted (dead) tissue in ischemic stroke, in relation to the serum calcium level at the time. The findings are reported in the Archives of Neurology , and summarized here.

What was done

Consecutive admissions to hospital of ischemic stroke patients provided the data for analyses; there were 322 patients in all, but some were excluded because 24 hours had elapsed between the onset of symptoms and admission, or there were no serum calcium or MRI imaging results. This left 173 patients in the study for full analysis.

Diffusion-weighted magnetic resonance imaging (DWI) was used to determine the volume of the infarcted tissue. Diffusion-weighted imaging measures the diffusion of water molecules in tissues; nerve cell death offers a barrier to water diffusion, so that the area of cell death can be clearly depicted.

Serum total calcium was determined on admission. The patients were classified into 4 groups (called quartiles) depending on their serum calcium levels, and the volumes of the infarcts compared for each quartile.

What was found

The average age of the patients was 70 years; 58% of them were women, and 66% were white, 13% Asian, 12% black, and 8% Hispanic. The serum calcium levels were obtained, on average, 10 hours after the onset of symptoms. MRIs were done, on average, 8 hours after symptom onset.

The four quartiles for calcium levels were: below 8.7 mg/dL, 8.7 to 8.9 mg/dL, 9.0 to 9.3 mg/dL, and above 9.3 mg/dL. The first analysis showed that the median infarct volumes for the 4 quartiles of calcium levels (lowest to highest) were 9.42, 2.11, 1.03, and 3.68 mL. (The 'median' value is the number separating the upper half of a sample from the lower half.) Although the volume in the lowest quartile was significantly greater from a statistical viewpoint than the other three, there wasn't a clear-cut 'dose-dependent' relationship. However, adjustments were made for average differences in age, stroke subtype, previous stroke, a history of diabetes, statin use, or atrial fibrillation, and blood pressure. This resulted in a 'smoothing' of the volume/calcium relationship: 8.9, 5.8, 4.5, and 3.8 mL for the 4 quartiles (lowest to highest), respectively. Again, the volume in the lowest calcium quartile was significantly greater than the other three quartile volumes.

Conclusions

This study shows that higher serum calcium levels at admission for patients with an ischemic stroke are linked with smaller volumes of dead brain tissue. This suggests that serum calcium may serve as a prognosticator for stroke severity. The authors of the study go even further. They suggest that serum calcium levels above a certain level may be a therapeutic target in patients at risk of an ischemic stroke.

Laboratory studies have shown that there is a rise in calcium in the brain cells in ischemia, which is accompanied by a decrease in the calcium levels in the tissue fluid outside the cells. It might be predicted, therefore, that raising serum calcium levels (and hence the tissue fluid calcium levels) might have a neuroprotective effect. This seems to work in rats fed a diet high in calcium, which had a decreased lesion volume after experimentally-induced ischemic stroke.

The next step is to see if raising the serum calcium levels in people at risk of ischemic stroke will minimize the effects of a stroke, if they have one...

Source

Association of higher serum calcium levels with smaller infarct volumes in acute ischemic stroke. BH. Buck, DS. Liebeskind, JL. Saver,  et al. , Arch Neurol , 2007, vol. 64, pp. 1287 --1291

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Created on: 11/08/2007
Reviewed on: 06/05/2009

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