The Effects of Dexmedetomidine on Tourniquet Pain Associated With Lower Extremity Surgeries Under General Anesthesia in Same Day Elective Patients

The study will be a prospective, randomized, double blinded, and placebo controlled clinical trial. The subject population will consist of patients ages 18 to 80 undergoing same day, lower extremity surgery involving the use of a tourniquet with a minimal surgical time of 60 minutes. Subjects will be recruited on the day of surgery, after consultation with the primary surgeon as to the use of a tourniquet and the anticipated tourniquet time. Subjects will be approached while awaiting surgery either on E yellow or Same day Surgery in the Doctor's Office Complex. The study will be explained. The subject and family members will be given an opportunity to ask questions and if agreeable the subject will be asked to provide written consent. Standard American Society of Anesthesiologists monitors will be used including pulse oximetry, electrocardiogram, and non-invasive blood pressure monitoring. Both groups will have an infusion running.

The experimental group (n= 40) will have a Dexmedetomidine infusion at 0.5 mcg/kg/hr without a loading dose. The control group (n= 40) will have an equivalent volume of 0.9% normal saline infusing.

Induction will commence after the initiation of the infusion and will be identical for both groups: Midazolam 2mg IV, Fentanyl 1-2 micrograms/kg, Lidocaine 1mg/kg, and Propofol 1.5 to 2 mg/kg. Following induction an appropriately sized Laryngeal Mask Airway (LMA) will be placed. A second intravenous line (preferably 18Gauge or larger) will be placed in the opposite upper extremity to collect blood samples. Prior to sampling a waste of 10milliLiters will be withdrawn and later returned to the patient. Anesthesia will be maintained with isoflurane at a Minimum Alveolar Concentration of 0.8 to 1.2. Mean arterial pressures that exceeds 130mmHg or >30% above baseline or heart rate(HR)s >110 bpm will first be treated with additional doses of Fentanyl every two minutes for a total dose of 5mcg/kg. If there is no response following the total dose of Fentanyl then within two minutes further treatment with Labetalol consisting of titrated doses starting at 5mg IV. Rescue doses of Hydralazine up to 20mg are allowed to treat hypertension not responsive to Fentanyl and Labetalol

Measurements:

The following measurements will be collected. Time 0 : In Operating Room holding area Baseline MAP, Heart Rate(HR) , and Respiratory Rate (RR) will be recorded A baseline Numeric Ration Scale Pain Score determined