The present study was registered at http://www.chictr.org/cn/ (ChiCTR-IOR-15006977) and was approved (B2015-114R) by the Ethics Committee of Zhongshan Hospital, Fudan University, China. Between August 2015 and August 2017, we enrolled 124 consecutive patients, 25–65 years of age and ASA I–II, who were scheduled for elective surgery under general Anesthesia. Written informed consent was obtained from all patients before randomization. Exclusion criteria were a history of allergy to rocuronium, succinylcholine, propofol and remifentanil, gastro-esophageal reflux, a known predisposition to malignant hyperthermia, neuromuscular disease and medications that could influence neuromuscular function, body mass index more than 35 kg/m2, anticipated difficult intubation, history of throat diseases, patients with a contraindication to the use of succinylcholine were also excluded.
Patients were randomly assigned into two groups by the program of SPSS16.0 software, the rocuronium group (Group R, n=62) and succinylcholine group (Group S, n=62). No preoperative sedatives or analgesics were administered. The monitoring of each patient included electrocardiogram, oxygen saturation, noninvasive blood pressure, capnography and BIS (BIS; A-2000TM SP, Aspect Medical System, Norwood, MA, USA). A train-of- four (TOF) mode was used to stimulate the ulnar nerve at the wrist. A brief period of initial TOF-Watch calibration
was performed after informing the patient of the initiation of nerve stimulation. The output current was kept at 40-50 mA (delivered at 2 Hz every 12 s). In group R, the TOF counts at 60s after rocuronium injection and the time to loss of TOF were recorded. A 18G cannula was inserted into a vein in the forearm and lactated Ringer’s solution was started before induction of Anesthesia. Two three-way stopcocks were used in our study, one is connected with the syringe pump of remifentanil, and the another one was attached to the first one to allow for injection of other agents during induction. All patients received 100% oxygen for 3 min through an anesthesia facemask before any drugs injection. The pain on injection during rocuronium and propofol administration was graded by using a four-point scale (none, mild, moderate and severe). A Glidescope video laryngoscopy (blade size 3) was used in all patients during tracheal intubation.
The positive pressure ventilation was not performed before the endotracheal tube was inserted. After preoxygenation, a bolus of 1 mg kg-1 lidocaine was given, then anesthesia was induced with intravenous remifentanil 2μg kg-1 given over 30s and propofol 2mg kg-1 (administered within 5s). After loss of consciousness (judged by loss of eyelash reflex and response upon calling out the patient’s name), the rocuronium (0.6 mg kg-1, administered within 5s) and succinylcholine (1.5mg kg-1, administered within 5s) was given in group R and group S, respectively. Tracheal intubation was performed 60s after rocuronium and succinylcholine injection. After intubation, anesthesia was maintained with 0.7-1.0 MAC of sevoflurane and remifentanil infusion and additional boluses of rocuronium 10mg and fentanyl 50μg were given if necessary. The patient’s mean blood pressure (MAP) and heart rate (HR) were recorded before induction of anesthesia, immediately, 1min and 3min after tracheal intubation. To prevent the anesthesiologist who performed the tracheal intubation and evaluated the intubating conditions from noting the muscle fasciculations induced by succinylcholine, she was called to enter the operating room 50s after administration of the rocuronium or succinylcholine.
The intubating conditions of each patient was graded as excellent, good, or poor, which were depending on the guidelines for Good Clinical Research Practice in Pharmacodynamic Studies of Neuromuscular Blocking Agents(Table.1). Both excellent or good intubating conditions were regarded as clinically acceptable, and the poor intubating conditions were regard as clinically unacceptable.
All patients were interviewed at the time of entrance to the PACU and 2h, 12h, 24h, 48h postoperatively to assess postoperative sore throat, hoarseness and myalgia. As showed in Table.2, these complications were evaluated by the criteria reported by Thomas et al, any score ≥1was defined as sore throat or hoarseness or myalgia. The hemodynamic events (hypotension/ hypertension, tachycardia/ bradycardia) during the induction and intubation were also assessed.
The primary endpoint of our study was the incidence of sore throat in two groups. Given the reported incidence of sore throat is about 68%(24h after operation) in patient using bolus succinylcholine, we assumed that with the same intubating conditions, more than 15% difference (down to 53%) was of clinical significance. With a 0.05 level of significance and 80% power, it was calculated that 59 patients were required in each group. Therefore, we included 62 patients per group to compensate for dropouts. Statistical analyses were performed using SPSS16.0 (SPSS, Chicago, IL, USA). Patient characteristic data and continuous data were expressed as mean±(SD). Student’s t test was used to analyze continuous data. Categorical data were expressed as percentages and numbers and were compared using Chi-square or Fisher’s exact test. A P value of <0.05 was considered as statistically significant.