Comparison the effect of magnesium sulfate with pregabalin on prevention of remifentanil – induced hyperalgesia in patients undergoing rhinoplasty. A randomized clinical trial

Deliberate hypotension is one of the methods used to reduce hemorrhage and improve surgical field quality, particularly in head and neck surgeries. Remifentanil is among the drugs use to reach this goal. However, one of the complications of this drug is post-operative hyperalgesia, for which an enormous number of drugs has been thoroughly have been studied. In the present study, 105 patients who undergoing rhinoplasty will be categorized into three equal groups to compare the effects of magnesium sulfate and pregabalin in reducing hyperalgesia induced by remifentanil.

In the present double-blind clinical trial, which will be carried out in a parallel way, a total of 105 patients who candidate for rhinoplasty will be enrolled in the study. Eligible patients will be categorized into three equal A, B and C groups by simple randomization table.

This is a randomized, double blinded clinical trial , single center.For blindness, all of the drugs solution( Magnesium sulfate and normal saline) of this study will be prepared in 50 ml syringes that are equal in shape and pregabalin like placebo capsule will be made by only person who aware of study's groups .Anesthesiologist, patients, all person who will collaborated in the study will not aware of patients groups.

A total of 105 patients in the ASA class 1 who candidate for rhinoplasty will be enrolled in the study. Exclusion criteria include history of the heart disease, pulmonary disease, liver disease, kidney disease, neurological and psychological diseases, history of the allergy to drugs such as pregabalin, magnesium sulfate, remifentanil, history of alcohol and narcotics abuse, patients who suffering from chronic pain, those who used any pain killer drugs 72 hours prior to anesthesia.

Patients in the group A will receive 300 mg pregabalin one hour before entering operation room while the other two groups will be received placebo capsule.Patients in the group B will receive 30 mg magnesium sulfate at induction of anesthesia and then during anesthesia will receive infusion 10 mg/kg/hr of the magnesium sulfate, whereas patients in the groups A and C will receive 50 cc saline solution as a infusion in the same time period during anesthesia .

Postoperative Pain severity according to NRS ( numerical rating scale) will be recorded and will be compared.

All eligible patients will be randomized according to simple randomization table into three equal groups A, B, C.

For blindness, All of the drugs solution( Magnesium Sulfate and normal saline) of this study will be prepared in 50 ml syringes that are equal in shape and placebo of the pregabalin in the pregabalin like capsule, by only person who aware of study's groups. Anesthesiologist, patients and all persons who will collaborated in this study, will not aware of patients groups.