Background: Magnesium therapy probably reduces the frequency of delayed cerebral ischaemia (DCI) in subarachnoid haemorrhage (SAH), but uncertainty remains about the optimal serum magnesium concentration. We assessed the relationship between serum magnesium concentrations achieved with magnesium sulphate therapy 64 mmol per day and the occurrence of delayed cerebral ischemia (DCI) and poor outcome in SAH patients.
Methods: Differences in magnesium concentrations between patients with and without DCI and with and without poor outcome were calculated. Quartiles of last serum magnesium concentrations before onset of DCI, or before median day of DCI in patients without DCI, were related with the occurrence of DCI and poor outcome at 3 months with logistic regression.
Results: Compared with the lowest quartile of serum magnesium concentration (1.10 - 1.28 mmol/L), the risk of DCI was decreased in each of the higher 3 quartiles (adjusted odds ratio (OR) in each quartile 0.2; lower 95% confidence limit 0.0 to 0.1; upper limit 0.8-0.9). The OR for poor outcome was 1.8 (95% CI 0.5-6.9) in the 2nd quartile, 1.0 (95% CI 0.2-4.5) in the 3rd quartile, and 4.9 (95% CI 1.2-19.7) in the highest quartile.
Discussion: Magnesium sulphate 64 mmol/day results in stable risk reduction of DCI in a broad range of achieved serum magnesium concentrations, and strict titration of the dosage therefore seems not necessary. However, concentrations ≤1.28 mmol/L could decrease the effect on DCI while concentrations ≥1.62 might have a negative effect on clinical outcome.
- delayed cerebral ischaemia
- magnesium sulphate
- subarachnoid haemorrhage