Modulation of NMDA receptors-does it affect anesthesia?

Abstract EN

Background : N-methyl-D-aspartate (NMDA) receptors activation is considered one of the mechanisms involved in postoperative pain and hypersensitivity.

Aim : This study evaluated the influence of perioperative magnesium administration upon anesthesia and postoperative pain management amongst patients undergoing lower abdominal surgery.

Subjects and Methods : Sixty ASA I-II patients, were randomly divided into one of two groups.

Patients in magnesium group received i.v loading dose of magnesium sulphate 60 mg.kg-1 followed by infusion of 1g.h-1 before anesthesia induction.

The infusion was documented at the completion of surgery.

The control group received a volume of normal saline.

After surgery all patients were treated with patient-controlled i.v analgesia (PCA) which was programmed to deliver 1 mg of morphine on demand in the first postoperative day.

The two groups were comparable with respect to their characteristics.

Results : Patients in the magnesium group received significantly lower endtidal isoflurane con-centrations [1.0 (0.3) vs 1.5 (0.4)%, respectively; P< 0.001] during anesthesia.

They also showed a reduced heart rate response to laryngeal mask insertion, skin incision and removal of laryngeal mask.

Cortisol level decreased significantly at 8h postoperative in magnesium group compared with control group, while epinephrine level decreased significantly intraoperative in magnesium group compared with control one.

There was no significant difference in norepinephrine level between the studied groups.

The magnesium group consumed less PCA morphine during the first postoperative day [15.3 (5.4) vs 22.2 (6.2) mg, respectively; P = 0.005].

Pain intensity and medication side effects were similar in both groups.

Conclusion : The results suggest that perioperative magnesium administration during anesthesia reduces the intraoperative use of inhalation anesthetic, decreases hemodynamic responses, attenuates release of stress hormones, and reduces postoperative morphine consumption.