Magnesium added to bupivacaine prolongs the duration of analgesia after interscalene nerve block.
OBJECTIVE
Local anesthetic adjuvants have been studied previously in an attempt to prolong the duration of analgesia after peripheral nerve blockade. Magnesium has been shown to have an antinociceptive effect in animal and human pain models. We evaluated the effects of adding magnesium sulphate to long-acting local anesthetics for interscalene nerve block to prolong the duration of analgesia and improve the analgesic quality.


METHODS
We enrolled 66 patients undergoing arthroscopic rotator cuff repair. The interscalene nerve block was performed with 0.5% bupivacaine 20 mL with epinephrine (1:200,000) plus either 10% magnesium sulphate 2 mL (Magnesium Group) or normal saline 2 mL (Saline Group). The following data were recorded for 24 hr after surgery: onset times and durations of sensory and motor blocks, analgesic duration, the pain numeric rating scale (NRS), postoperative fentanyl consumption, and complications.


RESULTS
The duration of analgesia was longer in the Magnesium Group than in the Saline Group [mean and (standard deviation) 664 (188) min vs 553 (155) min, respectively; P = 0.017]. Patients in the Magnesium Group had significantly reduced pain NRS scores at 12 hr (P = 0.012), but the cumulative fentanyl consumption was similar in both groups. The onset times and durations of sensory and motor blocks were not significantly different between the two groups.


CONCLUSIONS
The addition of magnesium sulphate to a bupivacaine-epinephrine mixture for interscalene nerve block prolongs the duration of analgesia and reduces postoperative pain.
Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, #50 Irwon-dong, Gangnam-gu, Seoul 135-710, Korea.
Ae Ryoung
AR
Lee
Hye-won
HW
Yi
In Sun
IS
Chung
Justin Sangwook
JS
Ko
Hyun Joo
HJ
Ahn
Mi Sook
MS
Gwak
Duck Hwan
DH
Choi
Soo Joo
SJ
Choi
D000368:Aged; D000698:Analgesia / Q000379:methods; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000627:therapeutic use*; D001182:Arthroscopy / Q000379:methods; D002045:Bupivacaine / Q000008:administration & dosage / Q000627:therapeutic use*; D004837:Epinephrine / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008278:Magnesium Sulfate / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy*; D011446:Prospective Studies; D017006:Rotator Cuff / Q000601:surgery; D016037:Single-Blind Method; D013997:Time Factors
D000779:Anesthetics, Local; D008278:Magnesium Sulfate; D002045:Bupivacaine; D004837:Epinephrine