ABSTRACT
Background: Neuropsychological dysfunction is a major complication of thoracic aortic surgery with hypothermic circulatory arrest [HCA]. Magnesium has been shown to have neuroprotectant effect in acute stroke and in short term neurological dysfunction after cardiopulmonary bypass. We sought to study the effect of magnesium on the neuropsychological function after HCA for aortic arch surgery using retrograde cerebral perfusion [RCP]
Methods: Forty patients scheduled for elective thoracic aortic surgery including the arch using HCA with RCP were randomly assigned to two equal groups. The magnesium group received magnesium sulfate to increase plasma magnesium level between 1.5 to 2 folds throughout the operation and for 24 hours, while the placebo group received normal saline over the same period as a control. The patients' neurocognitive state was assessed by cognitive P300 visual evoked potentials and the revised Wechsler Adult Intelligence Scale done the day before the operation and 2 weeks postoperatively. P300 was assessed as area under the curve [AUC] between 280 and 600 ms and center of this area [Ct [time], Cv [voltage]]. The ratio of these parameters acquired by target [TG] and non-target [NTG] stimulus [TG/NTG], was calculated to assess concentration on TG stimulus and defined as concentration index [CI: CI[AUC], CI[Ct], and CI[Cv]]
Results: There were no stroke, seizure, or hospital mortality in either group. Preoperatively, in the magnesium group, AUC and Cv acquired by TG stimulus in both Cz and Fz leads were significantly altered postoperatively [P value <0.05]. In the placebo group, no significant postoperative change was observed in all leads on TG stimulus. Postoperative CI [Ct] in the placebo group, were significantly impaired in all leads. The revised Wechsler Adult Intelligence Scale shows significant decline between baseline and postoperative scores in three subtests [digit span P value <0.05, arithmetic, and picture completion P value <0.01] for magnesium group and four [digit span, arithmetic, picture completion, and picture arrangement P value <0.01] for placebo group. Statistical difference between groups in test score changes was found in one subtest [picture arrangement P value <0.05]
Conclusion: Magnesium administration in patients undergoing aortic arch surgery with hypothermic circulatory arrest using retrograde cerebral perfusion did not affect the neurocognitive outcome assessed by cognitive P300 visual evoked potentials and the revised Wechsler Adult Intelligence Scale, further work is needed to prove any protective value for magnesium in this context