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F2. Magnesium as a Neuroprotectant in Cardiac Surgery: A Randomized Study
Sunil K Bhudia, Delos M Cosgrove, Richard I Naugle, Jeevanantham Rajeswaran, Buu-khanh Lam, Emily Walton, Roberta C Palumbo, Eugene H Blackstone; Cleveland, OH

Objective:
To evaluate the efficacy of magnesium as a neuroprotectant in patients undergoing CABG and/or valve surgery on cardiopulmonary bypass (CPB).
Methods:
From 2/2002 to 9/2003, 350 patients (male 77%, mean age 62±12 years, range 23-88 years) undergoing elective CABG and/or valve surgery were enrolled in a randomized, blinded, placebo-controlled study. Patients with preoperative atrial fibrillation and renal impairment were excluded. All were randomized to receive either magnesium to elevate their plasma magnesium level during CPB 1.5 to 2 times normal (magnesium group, 174 patients) or no intervention (placebo group, 176 patients). Neurological and neuropsychological assessments were performed preoperatively (both), at 24 h and 96 h post-extubation (neurological), and 3 months postoperatively (neuropsychological). Neurological scores were analyzed using ordinal longitudinal methods, and principal components analysis was performed on neuropsychological data followed by linear regression using component scores as the response variable.
Results:
Preoperative median magnesium levels were 1.63 mg/dL in both the magnesium and placebo groups. Magnesium was elevated in both groups at 3 hours (3.45 and 1.68 mg/dL, respectively), and remained elevated in the magnesium group out to 24 h (Fig.). Seven patients (2%) had postoperative stroke, 2 (1%) in the magnesium group and 5 (3%) in the placebo group (P=.4). Neurologically, patients in the magnesium group performed better than those in the placebo group (P=.002), due to a decline in cerebellar function (primitive reflexes) in the placebo group. Neuropsychological assessment at 3 months revealed little difference in performance between the groups (P>.6), but older age (P=.0006), history of stroke (P=.003), worse coronary artery disease (P=.02), and lower education level (P=.0007) were associated with worse performance.
Conclusions:
Magnesium is safe at the elevated plasma levels used during CPB in this study. Short-term neurological performance is better in patients receiving magnesium, particularly cerebellar performance, but in the long-term, other factors tend to be important in determining neuropsychologic outcome. Nevertheless, this short-term benefit could be important to patients’ recovery.

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