Intrathecal Magnesium Prolongs Fentanyl Analgesia: A Prospective, Randomized, Controlled Trial

Abstract

Magnesium occurs naturally in the spinal cord and blocks the NMDA glutamate channel. In animal studies, intrathecal magnesium sulfate improves spinal morphine analgesia. For patients receiving spinal analgesia for labor, the addition of magnesium sulfate to the opioid fentanyl prolonged analgesia with no increase of side effects.

Effects of adjunct intrathecal magnesium sulfate to bupivacaine for spinal anesthesia: a randomized, double-blind trial in patients undergoing lower extremity surgery

“…Consistent with published results [3,7], we found that the mean duration of spinal anesthesia was prolonged with the addition of IT MgSO 4 , but this difference was not statistically significant. The absence of a statistically significant difference may simply indicate that IT MgSO 4 actually does not prolong the duration of spinal anesthesia, or it may be due to the limited statistical power of the study.…”

“…Similar reductions in analgesic requirements have been reported in other orthopedic and non-orthopedic populations [7,9,12,15,16]. This effect is in contrast to that reported in a number of other studies [3,8]. Taken together, these results seem to indicate that in order for total analgesic consumption to be reduced, higher doses of MgSO 4 are required, similar to the dose used in our study (100 mg) and that of Arcioni et al [9].…”

“…Both animal and human studies have shown that the addition of intrathecal (IT) magnesium sulfate (MgSO 4 ) prolongs spinal anesthesia and reduces the incidence of side effects observed when local anesthesia are used in high doses or combined with opioid analgesia [1,2]. MgSO 4 produces anti-nociception and potentiation of opioid activity, presumably by its action as a voltagegated N-methyl-D-asparate (NMDA) receptor agonist [3].…”

Could adding magnesium as adjuvant to ropivacaine in caudal anaesthesia improve postoperative pain control?

“…It was demonstrated that the ineffectiveness of magnesium in intravenous applications may be due to its inability to form effective cerebrospinal fluid concentrations because of inadequate penetration through the blood-brain barrier [13]. For this object, Buvanendran et al [20] used magnesium intrathecally and demonstrated that 50 mg intrathecal use of magnesium prolonged analgesia in adults. In the light of these data, we thought that we could get the same effect through epidural caudal use of magnesium.…”

“…Based on these studies, we used magnesium epidurally and did not detect any neurological deficit in the patients in the postoperative period. Buvanendran et al in the first randomized clinical study in literature, took as a reference 188 lg of intrathecal magnesium potentializing morphine antinociception for postoperative pain by taking a rat model that they used in their previous study [20,21]. The differences between rats and humans in cerebral fluid amount and body weight were taken into account.…”