Role of Magnesium Sulfate in Postoperative Analgesia

The Benefits of Magnesium

It has long been known that magnesium could be beneficial in treating seizures, irregular heartbeats, and chronic pain. As an antagonist, it could stop the action of the N-methyl-D-aspartate receptor, and as calcium channel blocker, magnesium has pain-relieving effects by blocking the channel that causes hypersensitivity to pain and preventing the receiver of pain stimuli from sending signals to the brain.

Magnesium can also help protect against the harmful effects of glutamate, which causes harmful behaviors and nerve injuries.

Limited information is available on how magnesium affects pain in humans. Some research has shown an inverse relationship between the severity of pain and serum magnesium concentration. Magnesium supplementation is more effective than placebo in decreasing pain and relieving premenstrual mood changes and depression in women with premenstrual syndrome.

Magnesium supplementation was associated with lower postoperative analgesic requirements than fentanyl. In a study, patients received magnesium through their veins before surgery, and then the pain medication they needed afterward was measured. It was found that people who got magnesium required less pain medication than those who did not. Magnesium also seemed to help with how well they felt after surgery and how well they slept.

In this present study, an assessment was made of the effect of magnesium on analgesic requirements, pain, comfort, and quality of sleep in the postoperative period.

The Study on Magnesium for Postoperative Analgesia

In this randomized, double-blind study, 42 patients undergoing abdominal hysterectomy with general anesthesia were assigned equally into two groups. The treatment group received 15 milliliters (ml) of 20% magnesium sulfate (MgSO4), while the control group had 15 ml saline before the start of surgery and 2.5 ml of the same solution per hour for the next 20 hours.

Patients received 7.5 milligrams of midazolam orally as a preoperative premedication an hour before surgery. After induction of general anesthesia, patients received intravenously either MgSO4 or saline.

Postoperative morphine requirement was assessed for 48 hours using a patient-controlled device. Maximum expiratory flow (peak flow), pain at rest and during peak flow, and discomfort were evaluated using the visual analog scale up to the 48th postoperative hour and one week and one month after surgery. Insomnia was assessed after the first and second postoperative nights.

The Results

Compared to control subjects, magnesium-treated patients consumed 30% less morphine during the first 48 hours, which was most pronounced during the first six hours. They experienced less discomfort during the first and second postoperative days. The magnesium-treated group revealed no change in postoperative sleeping patterns compared to preoperative patterns. Control group patients showed an increase in insomnia during the first and second postoperative nights compared to preoperative values. Moreover, no major adverse effects were found owing to magnesium.

The Conclusion

The supplementation of magnesium sulfate before and during surgery is associated with a smaller analgesic requirement, less discomfort, and better quality of sleep in the postoperative period and without adverse effects. Magnesium could be of interest as an adjuvant to postoperative analgesia.

Reference

Role of Magnesium Sulfate in Postoperative Analgesia