Journal of Anesthesiology and Pain

Background: Blood loss is one of the most critical problems in major surgery. Spinal surgery usually associated with considerable blood loss and allogenic transfusions. Controlled hypotension is one of efficient methods for decreasing operative blood loss. The objective of this study was evaluation of the efficacy of magnesium sulfate in comparison with remifentanil for induction of relative hypotension in posterior fusion of spine surgery. 
Methods: In this double blind randomized clinical trial, 40 patients with ASA I & II physical status candidate for lumbar posterior spinal fusion surgery were enrolled and assigned in two groups (remifentanil and magnesium sulfate) randomly. After the induction of anesthesia and giving the prone position, relative controlled hypotension was induced for one group with 0.15 µg/kg remifentanil infusions and in second group with 50 mg/kg loading dose and then 15 mg/kg/hr magnesium sulfate infusion. All other aspects of anesthesia and surgery were similar in two groups. The target MAP range used in this study was 60-70 mmhg. In the course of surgery the hemodynamic variables, volume of blood loss, urine output, fluid intake and surgeon's satisfaction were recorded. Data was analyzed with SPSS version 13 software and P- value less than 0.05 was considered meaningful.   
Results: Twenty patients in Mg group and 19 patients in remifentanil group were studied. There was no statistical difference between two groups according to the hemodynamic variables, volume of blood loss, urine output, fluid intake and surgeon's satisfaction (p > 0.05). The target mean arterial pressure was achieved in 75% of Mg and 58% of remifentanil groups. Although, the frequency of TNG consumption was higher (42.1%) in remifentanil group than magnesium sulfate (25%), but this difference wasn't statistically significant (p= 0.320).
Conclusions: Our finding showed that in patients undergoing lumbar posterior spinal fusion surgery, remifentanil and magnesium sulfate has the same hypotensive effect and the volume of blood loss without any significant side effects.