The main objective of this study was to compare the wound infiltration (peritonsillar fossa) of magnesium sulphate combined with bupivacaine, bupivacaine alone and saline solution on post-tonsillectomy pain in children. The accessory objectives were to evaluate the effect of magnesium sulphate infiltration on prevention of laryngospasm and occurrence of nausea/vomiting.

This study is a prospective; double blinded and randomized clinical trial. Seventy-five children undergoing tonsillectomy were enrolled. Patients were randomized into three groups using closed envelop technique. Group 1 (N=24) received saline solution (NaCl), group 2 (N=25) received 0.25% bupivacaine (1mg/kg) and group 3 received magnesium sulphate (5mg/kg) and 0.25% bupivacaine (1mg/kg) after tonsillectomy using three-point technique. Pain was evaluated using mCHEOPS scale. The occurrence of laryngospasm, nausea and vomiting was monitored.

The mCHEOPS scores of the group 3 were significantly lower than those of the group 2 and 1 (P<0.001). Time to first analgesic administration was longer for the group 3 than for the groups 2 and 1 (P<0.001). The mean consumption of additional analgesic drugs was lower for the group 3 than the other groups (P<0.001). There were no episodes of laryngospasm in the group 3 in comparison with the other groups. The difference of the incidence of nausea and vomiting was not statistically significant (P=0.628).

The adjunction of magnesium sulphate to bupivacaine proved to provide more efficient pain control than bupivacaine alone. However, the small number of participants and the absence of sampling at the P level of 0.005 do not allow to conclude with absolute certainty.