Novel vasodilatory effect of intracisternal injection of magnesium sulfate solution on spastic cerebral arteries in the canine two-hemorrhage model of subarachnoid hemorrhage.

OBJECT: The extracellular Mg++ has a vasodilatory effect on the cerebral artery. The present study investigated the effect of intracisternal injection of MgSO4 solution on cerebral vasospasm in a canine model of subarachnoid hemorrhage (SAH).
METHODS: Subarachnoid hemorrhage was induced in 10 beagles using the two-hemorrhage model. Angiography of the vertebrobasilar artery was performed on Day 1 (baseline values before SAH) and on Day 7 (during cerebral vasospasm after induced SAH) before and after intracisternal injection of 0.5 ml/kg of 15 mmol/L MgSO4 solution into the cerebellomedullary cistern.
RESULTS: The cerebrospinal fluid Mg++ concentration was significantly increased to 3.15 +/- 1.14 mEq/L after intracisternal injection from the preinjection value (1.45 +/- 0.09 mEq/L; p < 0.01). The diameters of the basilar artery, vertebral artery, and superior cerebellar artery on Day 7 were significantly decreased to 58.0 +/- 10.9%, 71.0 +/- 10.1%, and 60.9 +/- 13.8%, respectively, of their baseline diameters on Day 1 (p < 0.01). After intracisternal injection of MgSO4, these diameters significantly increased to 73.8 +/- 14.3%, 83.0 +/- 14.8%, and 74.1 +/- 13.5%, respectively (p < 0.01).
CONCLUSIONS: Intracisternal injection of MgSO4 solution causes significant dilation of spastic cerebral arteries in the canine two-hemorrhage model of SAH.