General anesthesia will be induced using an injection of 1-1.5 mg/kg of propofol, 1-2 mic/kg of fentanyl, and 0.5 mg/kg of atracurium,with all doses to be titrated. An endotracheal tube will be inserted after 3 minutes of mask ventilation.
Anesthesia will be maintained using isoflurane (1%) and atracurium at a dosage of 0.1mg\\kg every 20 minutes.
After endotracheal intubation, the patients will be mechanically ventilated with a 50% oxygen-air mixture, utilizing a tidal volume of 8 mL/kg based on ideal body weight at an inspiratory rate of 10-14 breaths per minute. Adjustments will be made to ensure that the end-tidal CO2 partial pressure (ETCO2) between 35 and 40 mmHg, with peak airway pressure kept below 30 mmHg.
The surgeon will start limb elevation, exsanguinating of blood and applying a double- cuffed tourniquet(zimmer A.T.S.3000) at the middle of the arm over cotton padding,with pressure ranging 200 mmHg according to the patient's blood pressure (50mmHg above systolic blood pressure).
After completion of surgical procedure,tourniquet deflation will be performed by anesthesia technician blinded to the study groups into two ways according to the randomization number received in closed envelop with the patient file and blinded from the research anesthiologist: in gradual group (G group) deflation by rate 50mmHg/ 30s untill complete release within 3 minutes .In intermittent group (I group) complete deflation will occur for 10 seconds, then reinflated for 50 seconds, repeating this cycle three times until complete release. If the surgery exceeded 2 hr, the intermittent technique for deflation will be used The researcher anesthesiologist who collects data, including hemodynamics and labs will be separated from the upper limb, tourniquet device, and the technician by surgical curtain to ensure full blinding of the deflation technique.
A bolus of lidocaine 1.5 mg\\kg will be administered 10 minutes before tourniquet inflation will be used to attenuate the increase of blood pressure after tourniquet inflation.
