Magnesium Sulfate Does Not Increase Ventricular Cerebrospinal Fluid Ionized Magnesium Concentration in Patients with Intracranial Hypertension
Background: Magnesium sulfate (MgSO4) has attracted interest as a neuroprotective agent during cerebral ischemia. Passage of Mg ion into the CNS has been poorly examined. The present study assessed the passage of ionized (physiologically-active)Mg into the cerebrospinal fluid (CSF) of patients with intracranial hypertension after MgSO4 infusion. Design: After IRB approval, patients requiring CSF drainage received IV MgSO4 (5g)in 125 cc NS over 30 min. Plasma and CSF samples were taken hourly for 4 hrs. Intraventricular catheter placement was confirmed by CT. Data analysis involved ANOVA followed by Dunnet’s post hoc test for a significant F statistic (p < 0.05). Results: Nine patients (5/4, male/female; mean age=52) with closed head injury (n=3), subarachnoid hemorrhage (n=2), intracerebral hemorrhage (n=2), hydrocephalus (n=1), and subdural hematoma (n=1) were studied. Mean (±SD)Mg values are presented (table). Baseline Mg was higher in CSF. Although plasma Mg increased, CSF Mg was unchanged. Conclusions: Although the CSF to plasma Mg gradient is maintained in patients with intracranial hypertension, intravenous infusion of 5g MgSO4 does not further increase CSF Mg. This suggests systemic infusion of MgSO4 may not be an effective route of administration for neuroprotection.