(1)Objectives: Lidocaine, is the first amino amide-type of local anesthetics, and have analgesic, antihyperalgesic, and antiinflammatory effects. These properties are mediated by a variety of mechanisms, including sodium channel blockade, as well as inhibition of G protein– coupled receptors and N- methyl- D- aspartate receptors. Inhibition of Postoperative Pain by Continuous Low- Dose intravenous Infusion of Lidocaine is devoid of side effects and can be used to decrease the severity of postoperative pain, therefore this study aims to reducing the need for potent morphinomimetic drugs in the postoperative period to reduce pain after surgery will be performed. Also, lidocaine can reduce side effects such as nausea and vomiting, postoperative shivering and be effective in reducing intraoperative bleeding.
(2) Design: A total of 60 adult patients aged 16 to 40 years will be randomly admitted to the chamran hospital requiring bimaxillary orthognathic surgery had studied. The following parameters such as: Individual patient information , medical history, the patient's hemodynamic values before- during and after surgery, duration of operation, the amount of blood loss during operation and blood products transfusion, the use of drugs or narcotics for pain relief , postoperative nausea and vomiting and postoperative shivering will be recorded.
(3) Setting and conduct: The patients were randomly divided to receive either lidocaine (group I) or saline (group II) is allocated, while anesthesiologist, nurses and patients are unaware of the content of injection (Medications prepared by other nurses and are randomly coded)
(4) Participants including major eligibility criteria: Patients with no history of systemic disease and without taking any analgesic medications criteria that were willing to cooperate in this study were enrolled; and Exclusion criteria included known allergy to the study drugs; Serious adverse drug reaction to amide local anaesthetics; hepatic and renal dysfunction ; patients with heart block including second or third degree (without pacemaker) ; Severe sinoatrial block (without pacemaker) ; Use of opioid or analgesics 3 days before the study; Acute Porphyria; Accelerated idioventricular rhythm ; Bradycardia ; and Patients who did not sign the informed consent.
(5) Intervention: Patients in the first group will be received an intravenous "Lidocaine" 1 mg / kg body weight bolus for 5 min followed by 2 mg / kg / hr dissolved in saline via pump infusion and the second group will receive " placebo" as same bolus volume of "normal salin" in a 5-minute intravenous infusion and is continued until the en of operation.
(6) main outcome measures: During surgery the patient's heart rate, blood pressure and blood oxygen saturation is recorded at specified intervals and at the end of the operation will take analgesics were recorded. After surgery the patients were monitored for up to 4 hours in the recovery room and pain intensity (VAS) is measured by a person who was unaware of group members every half hour, also duration of operation, the amount of blood loss during operation and blood products transfusion, the use of drugs or narcotics for pain relief , postoperative nausea and vomiting and postoperative shivering will be recorded.
In the surgical ward for 12 hours, if the drug is administered by a nurse for pain relief will be recorded. And then any post-operative complications will be asked in the questionnaire .