Background: Magnesium presents analgesic effects by blocking the non-competitive N-methyl-D-aspartate receptor in the spinal cord. The purpose of this study was to evaluate the effects of epidural magnesium on cumulative dose of ropivacaine in patients with patient-controlled epidural analgesia (PCEA) after a thoracotomy.
Methods: In a randomized, prospective, double-blind trial, we enrolled 40 patients undergoing PCEA after a thoracotomy. Control group (n = 20) received an initial dose of 0.375% ropivacaine 0.1 ml/kg, and following demand doses of 0.2% ropivacaine 2 ml with 15 min lockout interval on the patient demand. Magnesium group (n = 20) additionally received MgSO4 100 mg in the initial dose and 4 mg in the demand doses. Cumulative dose of ropivacaine, the resting and coughing visual analog scale (VAS) score were measured at 3, 6, 12, 24, and 48 hours after surgery.
Results: Magnesium group showed lower cumulative dose of ropivacaine than control group at 12, 24, and 48 hours after the surgery (P<0.05), but not at 3 and 6 hours (P < 0.05). The VAS score was not different between 2 groups (P < 0.05).
Conclusions: Epidural magnesium may be useful as an adjuvant to ropivacaine after a thoracotomy. However, because magnesium showed no beneficial effect at the early period after the surgery, more investigation about proper initial dose is required.
Keywords: Magnesium; Patient-controlled analgesia; Ropivacaine; Thoracotomy.