Comparison Of Deep Versus Moderate Neuromuscular Blockade on Intra-Operative Blood Loss During Spinal Surgery

After applying standard monitoring of pulse oximetry, ECG, noninvasive blood pressure, general anesthesia will be induced with fentanyl 1 µg/kg and propofol 2-3 mg/kg and Rocuronium 0.6 mg/kg will be administered for muscle relaxation after loss of consciousness, under the guidance of neuromuscular blockade monitoring. Tracheal intubation will be performed at a train-of-four count of 0. After that end-tidal carbon dioxide and temperature will be continuously monitored during the procedure. Mechanical ventilation will be instituted with o2:air of 4 L/min, tidal volume of 6-8 ml/kg and respiratory rate appropriate to achieving end-tidal carbon dioxide of 30-35 mmHg. no positive end-expiratory pressure; and inspiratory/expiratory ratio 1: 2. The patient's position will then be changed from supine to prone. Ephedrine 4 mg (if mean arterial pressure \< 60 mmHg and heart rate \< 40 bpm), or atropine 0.5 to 1.0 mg (if heart rate \< 40 bpm) are used to prevent hypotension or bradycardia

Neuromuscular blockade monitoring will be established and continuously monitored after induction using the Train Of Four (TOF) at the adductor pollicis muscle on the opposite hand and wrist to radial artery cannulation. Two surface electrocardiography electrodes will be placed on cleaned skin overlying the ulnar nerve, with one electrode positioned on the ulnar side of the flexor carpi radialis tendon and the other positioned 3cm proximal to the first. The transducer is then positioned with the flat side against the thumb. Supramaximal stimuli will be applied after autonomic calibration of acceleromyograph after an initial tetanic stimulus. After confirming a train-of-four ratio of 95 to 105%, neuromuscular blockade monitoring will start. The train-of-four mode of supramaximal stimulation (0.2 ms duration, frequency 2 Hz, two s duration) will be applied at 15 s intervals, which last until the end of anaesthesia.