Effect of Neuromuscular Blockade on Operating Conditions and Overall Satisfaction During Spinal Surgery

The investigators aim to investigate operating conditions, postoperative recovery and overall satisfaction of surgeons between deep neuromuscular blockade (NMB) group and restricted NMB group during spinal surgery under general anesthesia. The investigators hypothesize that this study can present good surgical conditions, postoperative recovery outcomes and overall satisfaction of surgeons in deep NMB group, thereby proving the advantages of deep NMB as well as flaws of restricted NMB in spine surgeries.

* Group treatment (Arms): group treated with restricted neuromuscular blockade (NMB) (Group RB); group treated with deep NMB (Group DB) → randomized allocation (subjects: motor-evoked potential \[MEP\] not monitored surgeries) * Inclusion criteria: American Society of Anesthesiologists (ASA) physical status I-II adults, aged 18-75 years, scheduled for elective spinal surgery (cervical or lumbar surgeries which have lesions no more than 3 spinal levels and not monitored by MEP) of duration \>1 hour and prone position under total intravenous anesthesia (TIVA). * Exclusion criteria: Pregnancy, the receipt of medication known to interfere with neuromuscular blockade, diseases affecting neuromuscular transmission, and the history of hypersensitivity on rocuronium or sugammadex. The patients who will have hemodynamic instability, mean blood pressure increase or fall of \> 30% from baseline (lasting for more than 5min), and blood loss \> 1 L during surgery, and MEP monitored surgeries. * Outcome Measures * Primary outcome: Mean value of peak inspiratory pressure recorded every 15 minutes. * Secondary outcomes: 1. The number of body movements (including cough or any diaphragm movement). 2. The degree of bleeding of each patient scaled by surgeons (Intraoperative scale for assessment of operating condition of surgical field: 0 - No bleeding, 1 - Slight bleeding - no suctioning of blood required, 2 - Slight bleeding - occasional suctioning required but not threatened the operative field, 3 - Slight-bleeding - frequent suctioning of blood was required that threatens the operative field a few seconds after suctioning, 4 - Moderate bleeding - frequent suctioning of blood was required which threatens the operative field directly after suctioning, 5 - Sever bleeding - continuous suctioning of blood was required which severely threatened the operative field make the surgery not possible). 3. The muscle tone of each patient scaled by surgeons (1: muscle tone is good, suitable for surgery; 2: muscle tone is moderate, but do not affect the operation; 3: muscle tone is hard, making the operation difficult.). * Three time-points of assessment of the muscle tone: ① At the placement of back muscle retractor for opening the operating site after the skin and subcutaneous incision, ② At the screw insertion through the pedicle of spine during surgery, ③ At the other period (overall muscle tone). 4. Mean value of pressure of back muscle retractor placed in the operating site (recorded every 15 minutes): measured by the pressure probe placed between the retractor and the back muscle. 5. Overall satisfaction of surgeons for the surgical condition will be assessed by the surgeons who perform surgery using numerical rating scale (NRS; 1-10) after surgery. 6. Recovery profiles including eye opening time, extubation time and sedation score (the Observer's Assessment of Alertness/ Sedation (OAA/S) score; awake, 5 to unresponsive, 1) every 10 min for 1 hour at postanesthesia care unit (PACU). 7. Postoperative adverse events