Effect of epidural magnesium on the incidence of chronic postoperative pain after video-assisted thoracic surgery.

Objective: The aim of this study was to determine whether the epidural administration of magnesium during the perioperative period decreased the incidence of chronic postoperative pain (CPOP) at 3 months after video-assisted thoracic surgery.

Design: Prospective, randomized, and blinded.

Setting: A university hospital.

Participants: Patients.

Interventions: Before the induction of anesthesia, the patients were assigned randomly to receive normal saline, 5 mL, (group C, n = 72) or magnesium sulfate, 100 mg (group M, n = 72), epidurally. At the end of surgery, group C received a continuous infusion of a mixture of 0.2% ropivacaine, 226 mL, and fentanyl, 1,200 μg, through a patient-controlled epidural analgesia pump for 48 hours. In group M, magnesium sulfate, 500 mg, was added to the infusion.

Measurements And Main Results: The incidence and severity of CPOP were assessed by a telephone survey 3 months after surgery. Patients were asked whether they experienced pain and to rank the severity of the pain using a 3-point scale (1, mild; 2, moderate; 3, severe). The incidences of CPOP were 42.4% in group C and 49.1% in group M. The severities of pain in the patients with CPOP were 1.0 (1-2) in group C and 1.0 (1-2) in group M. The incidence and severity of CPOP did not differ between the 2 groups.

Conclusions: The epidural administration of magnesium from before the induction of anesthesia to 48 hours postoperatively did not decrease significantly the incidence or severity of CPOP in patients undergoing video-assisted thoracic surgery.