Temporal profile of the effects of intracisternal injection of magnesium sulfate solution on vasodilation of spastic cerebral arteries in the canine SAH model.

PURPOSE: the temporal profiles of the effects of intracisternal injection of magnesium sulfate (MgSO(4)) on vasodilation and cerebrospinal fluid (CSF) magnesium ion (Mg(2+)) concentration were investigated in the canine subarachnoid hemorrhage (SAH) model.

METHOD: cerebral vasospasm was induced using the two-hemorrhage model in seven female beagles. On day 7, 0.5 ml/kg of 15 mmol/l MgSO(4) in Ringer solution was injected into the cerebellomedullary cistern. Angiography was performed on day 1 (before SAH), and before and 1, 3, and 6 h after the intracisternal injection on day 7. CSF Mg(2+) was measured at the same time.

RESULTS

the diameters of the basilar artery (BA), vertebral artery (VA), and superior cerebellar artery (SCA) before the intracisternal injection on day 7 were 0.59 ± 0.15, 0.41 ± 0.17, and 0.35 ± 0.17 mm, respectively, and were significantly decreased (p < 0.01) compared with the baseline diameters on day 1. The BA diameters at 1 h (0.74 ± 0.16 mm) and 3 h (0.73 ± 0.13 mm), the VA diameter at 1 h (0.64 ± 0.14 mm), and the SCA diameter at 3 h (0.54 ± 0.08 mm) after the injection were significantly increased (p < 0.05). The CSF Mg(2+) concentration was significantly increased (p < 0.01) at 1 h (3.59 ± 0.76 mEq/l) and 3 h (2.00 ± 0.31 mEq/l) after the injection compared with the baseline value (1.35 ± 0.23 mEq/l).

CONCLUSIONS

the reversible effect of intracisternal MgSO(4) solution injection on the spastic artery depends on maintenance of the optimal CSF Mg(2+) concentration.