Author: Micheal Vlessides
Anesthesiology News
Intravenous administration of magnesium sulfate seems to improve neuropsychological outcomes in patients undergoing brain surgery, according to the results of a new study. The investigation also found that patients treated with magnesium sulfate exhibited improvements with respect to the presence of gliosis/edema as much as six months after surgery.
“Magnesium sulfate has gained interest in recent years as a potential protector of brain function,” commented Isabel Gracia, MD, a senior specialist in anesthesiology at Hospital ClÍnic de Barcelona, in Spain. “Its favorable safety profile, together with the fact that it is not expensive, makes it attractive as a protective agent. What’s more, results of previous studies have been promising.”
Each participant underwent an IV infusion upon their arrival to the OR, which was maintained for 24 hours. Individuals in the study group received 4 g of magnesium sulfate in 100 mL of saline over 20 minutes, followed by 20 g in 24 hours. All patients underwent total IV anesthesia with propofol and remifentanil via a target-controlled infusion system.
“A comprehensive battery of neuropsychological tests was performed before surgery and after one, six and 12 months,” Dr. Gracia said.
For purposes of the trial, mild cognitive impairment was considered a decline of 1.0 to 1.5 SDs from baseline; moderate impairment a decline of 1.5 to 2.0 SDs; and severe impairment a decline of more than 2.0 SDs. Both controls and treatment patients were stratified according to the type of surgery, for either brain tumor or epilepsy.
In a presentation at the 2019 annual meeting of the American Society of Anesthesiologists (abstract BOC02), Dr. Gracia reported that 51 patients were included in the final analysis. Of these, 25 were included in the magnesium group (seven underwent surgery for epilepsy, 18 for brain tumor) and 26 in the control group (nine epilepsy, 17 tumor). There were no differences in the type of malignancy among patients undergoing tumor surgery.
At six months after surgery, MRI was performed in 21 patients in the magnesium group and 23 controls. The analysis showed that 11 patients in the magnesium group (55%) demonstrated gliosis/edema, compared with 19 controls (90.5%; P=0.0144). The Table highlights these differences.
| Table. Presence of Gliosis/Edema at Six Months After Surgery | ||||
| Group | Time | Magnesium Sulfate (n=25) |
Controls (n=26) | P Value |
|---|---|---|---|---|
| Epilepsy | Basal | 0 | 0 | — |
| Postoperative | 6 (85.7%) | 9 (100%) | 0.4389 | |
| Six months | 4 (100.0%) | 7 (100.0%) | — | |
| Tumor | Basal | 11 (61.1%) | 11 (64.7%) | 1.000 |
| Postoperative | 12 (66.7%) | 14 (82.4%) | 0.444 | |
| Six months | 7 (43.8%) | 12 (85.7%) | 0.0269 | |
| All | Basal | 11 (44.0%) | 11 (42.3%) | 1.000 |
| Postoperative | 18 (72.0%) | 23 (88.5%) | 0.1737 | |
| Six months | 11 (55.0%) | 19 (90.5%) | 0.0144 | |
Contrast enhancement around the surgical cavity was evident in five magnesium sulfate patients and eight controls at six months (P=0.0416). Tumor progression at six months, on the other hand, was evident in one individual who received magnesium sulfate, and three who were controls (P=0.2940).
Neuropsychological testing assessed seven areas of cognitive ability:
- intellectual level;
- language;
- verbal memory (left hemisphere);
- visual memory (right hemisphere);
- selective attention/operative memory;
- sustained attention/visual–manual coordination; and
- spatial ability.
No differences were found between groups with respect to baseline neuropsychological test results.
“When analyzing the neuropsychological tests, we found a trend toward improvement in the magnesium sulfate group versus the control group in both epilepsy and tumor surgery,” Dr. Gracia noted. At six months after surgery, no patient experienced cognitive impairment of any sort.
“These results confirm that the administration of magnesium sulfate may become a standard of care in brain surgery,” Dr. Gracia concluded. “Nevertheless, a larger study is needed to help support these findings.”
Magnesium’s Effect on Cerebral Edema
Ehab Farag, MD, a professor of anesthesiology at the Cleveland Clinic Lerner College of Medicine, in Cleveland, noted that despite its obvious quality, the study was nonetheless limited by its size. “This is a well-done study, but it’s a small set of patients,” said Dr. Farag, who is an Anesthesiology News editorial board member. “So it’s impossible to extrapolate these findings to all neurosurgeries.”
Nevertheless, Dr. Farag recognized the potential beneficial effects of magnesium in patients undergoing brain surgery. “We know from obstetric anesthesia in preeclamptic and eclamptic women that magnesium is very helpful in decreasing cerebral edema and maintains the integrity of the blood–brain barrier, so that effect may well be translated to this subset of patients.”
Dr. Farag noted that his personal use of magnesium in these settings is largely surgeon dependent, and tempered with a healthy dose of the agent’s potential adverse effects. “My opinion is sometimes it works and sometimes it doesn’t,” he said.
“Either way, it is important to recognize that because it works like a calcium channel blocker, magnesium can also drop the blood pressure during anesthesia, and this has the potential to be more harmful to the brain than anything else. So, if you give magnesium, you have to be very careful with what you’re doing, because it’s not without risks and complications.”