Effects of Magnesium on Individuals Undergoing Coronary Artery Bypass Graft Surgery (POINT)

The purpose of this study is to examine the effects of supplemental magnesium on the neurocognitive function of individuals undergoing coronary artery bypass graft (CABG) surgery.

BACKGROUND: Approximately 400,000 individuals undergo heart operations each year and cognitive impairment occurs frequently following surgery. An increasing number of these individuals are elderly and are particularly susceptible to cognitive dysfunction following surgery. Cognitive impairment is most notable in the early stages following heart surgery, but it may persist in some individuals. While many people think cognitive impairment is subtle, transient, or subclinical, perioperative decline is associated with 5-year cognitive deterioration and reduced quality of life. Multiple strategies, both clinical and pharmacological, have been proposed to reduce the central nervous system dysfunction associated with heart surgery. However, most strategies have been unsuccessful, met with limited success, or are unrealistic from a cost or risk-benefit ratio for the majority of people. This study will examine the effectiveness of supplemental magnesium at preventing the cognitive decline associated with heart surgery. DESIGN NARRATIVE: This study will examine the effect of supplemental magnesium on the neurocognitive function of individuals undergoing CABG surgery. The two hypotheses to be tested include the following: 1) therapeutic levels of magnesium reduce post-operative neurocognitive dysfunction after heart surgery; and 2) therapeutic magnesium levels protect quality of life through reduced cognitive dysfunction after heart surgery. This double-blind study will enroll 400 individuals and randomly assign them to either the treatment group, which will receive 100 mg/kg of magnesium, or to the control group. Anesthesia management will be standardized to minimize any impact that anesthesia may have on neurologic or neuropsychologic outcome. Neurocognitive testing will be conducted prior to surgery, and 6 weeks and 1 year following surgery.

To characterize cognitive function over time, while minimizing potential redundancy in the cognitive measures, a factor analysis was performed on the cognitive test scores from baseline. We chose a four-factor solution, which represents 4 cognitive domains: verbal memory, abstraction and visuo-spatial orientation (executive function), visual memory and attention and concentration. To quantify overall cognitive function, a baseline cognitive index was first calculated as the mean of the 4 preoperative domain scores. The cognitive index score has a mean of zero and standard deviation of 0.5. Thus, any positive score is above the mean, any negative score is below the mean, and a score of 0.5 represents 1 SD above the mean. A continuous change score was then calculated by subtracting the baseline from the 6-week cognitive index. Negative scores indicate decline and positive scores indicate improvement.

Inclusion Criteria: Coronary heart disease Exclusion Criteria: Early dementia History of psychiatric illness

Mathew JP, White WD, Schinderle DB, Podgoreanu MV, Berger M, Milano CA, Laskowitz DT, Stafford-Smith M, Blumenthal JA, Newman MF; Neurologic Outcome Research Group (NORG) of The Duke Heart Center. Intraoperative magnesium administration does not improve neurocognitive function after cardiac surgery. Stroke. 2013 Dec;44(12):3407-13. doi: 10.1161/STROKEAHA.113.002703. Epub 2013 Oct 8.