Intravenous Magnesium Sulfate to Deliberate Hypotension and Bleeding after Bimaxillary Orthognathic Surgery; A Randomized Double-blind Controlled Trial

Statement of the Problem: The preoperative or intraoperative administration of intravenous magnesium sulfate has been approved as an accepted medication for stabilizing hemodynamic indices during surgeries.
Intraoperative blood loss during orthognathic surgery is frequently abundant and sometimes requires blood transfusion. The present trial addressed the efficacy of intravenous magnesium sulfate on deliberating hypotension and bleeding reduction in patients undergoing bimaxillary orthognathic surgery.
This randomized double-blinded placebo controlled trial was conducted on 52 consecutive patients who underwent orthognathic surgery. The participants were randomly assigned to two groups receiving intravenous magnesium sulfate 30 mg/kg body weight bolus for 15 minutes immediately before anesthesia induction, followed by 10 mg/kg/hr dissolved in saline via pump infusion (n=26) and the second group received placebo as same bolus volume of normal saline in a 15-minute intravenous infusion which was continued until the end of operation (n=26). Both systolic and diastolic blood pressures were measured before anesthesia induction at baseline, during surgery, and at the end of the surgery. Intraoperative blood loss was also determined.
Systolic and diastolic blood pressures did not differ between the two groups at baseline. Although a downward trend of both systolic and diastolic blood pressures was seen during the operation in both groups, the decrease in blood pressures occurred with greater gradient in the group administered magnesium sulfate. Assessing difference in the trend of the changes in systolic and diastolic blood pressures between the two study groups (adjusted for gender, age, mean body mass index, and time of surgery) showed different trends in the changes of blood pressures. No differences were observed in blood loss or blood product requirement between the two groups.
The administration of intravenous magnesium sulfate can attenuate both systolic and diastolic blood pressures during orthognathic surgery with no significant effect on the volume of blood loss or need for blood transfusion.