This study constituted a prospective, randomized, double blind, placebo-controlled trial. All patients were enrolled and signed informed consent from February 1, 2022 to January 20, 2023. The protocol of this study was registered at the Thai Clinical Trials Registry (TCTR20221017001) on 17/10/2022 after receiving approval by the Institutional Review Board of Medical Ethics
Participants
Eighty male patients aged 20 to 70 years, were scheduled for complex fusion lumbar spinal surgery at least two levels under general anesthesia with American Society of Anesthesiologists physical status I and II. Patients with a history of previous urological surgery, cardiovascular disease, end stage renal disease, bladder outflow obstruction, overactive bladder and psychiatric disorder were excluded.
Randomization and Blinding
All participants were randomly assigned to either the lidocaine group (group L) or the normal saline group (group C) by a block of four computer generated random number tables. The concealed envelopes were disclosed before the patient entered the operation theater and medication was prepared by an uninvolved first anesthesiologist. Anesthetic induction, maintenance and extubating were performed by a second anesthesiologist blinded in the study. A third blinded anesthesiologist recorded all outcomes and complications.
Procedures
Anesthetic premedication was not allowed all patients. Noninvasive blood pressure, electrocardiography, pulse oximetry and capnography were completed before inducing anesthesia. Intravenous anesthetic administration was performed by propofol, cisatracurium and fentanyl. Mechanical ventilation was maintained to control the end tidal carbon dioxide tension between 35 and 40 mmHg. A 50% oxygen in air mixture and sevoflurane were performed for anesthetic maintenance. After adequate depth of anesthesia, a foley catheter ≥20 Fr was achieved; the balloon was inflated with 10 ml sterile water and fixed to the thigh with plaster. The dosage of lidocaine was demonstrated based on a related study [17]. In group L, 1.5 mg/kg of intravenous lidocaine was injected before inducing anesthesia. Consequently, two mg/kg/h of lidocaine was infused during the anesthetic period. In group C, patients established 0.9%NaCl at the identical bolus volume and continuous infusion rate as group L. All medications in both groups were discontinued and the muscle relaxant was reversed at the end of anesthesia. Patients were extubated after fulfilling extubating criteria and transferred to the postanesthesia care unit (PACU). Patient controlled analgesia (PCA) morphine (1mg/ml) was administered with PCA dose 1 mg each with lock out interval 10 min on arrival at the PACU. Consequently, the Foley catheter was removed after 24 h postoperatively.
Outcomes
The primary outcome was incidence of moderate to severe CRBD in the PACU between group comparison. The secondary outcomes were postoperative pain and opioid requirement during the first 24-hour postoperative period, mild and moderate to severe CRBD at 1, 2, 6 and 24 hours postoperative periods, intra-operative opioids, patient satisfaction, the adverse effects of lidocaine and surgical complications. The severity of CRBD was recorded as follows: none (patients did not complain of CRBD when asked); mild (informed by patients separately when questioned); moderate (described by patients autonomously, i.e., without being requested, and not along with any behavioral reply) or severe (defined by patients autonomously accompanied by behavioral replies such as waving limbs, strong voiced response and efforts to pull out the catheter) (1, 7, 18). Verbal numerical rating scale (VNRS, 0 = no pain and 10 = worst pain imaginable) was also assessed when appraising CRBD at 0, 1, 2, 6 and 24 hours after surgery. Patient satisfaction was evaluated at 6 hours postoperative periods by global perceived effects on a seven-point scale (GPES) defined using the question: how would you estimate your satisfaction with this medication for preventing CRBD? grade: 1 = very dissatisfied, 2 = somewhat dissatisfied, 3 = slightly dissatisfied, 4 = neither satisfied nor dissatisfied, 5 = slightly satisfied, 6 = somewhat satisfied and 7 = very satisfied) (19, 20). Patient satisfaction was also evaluated in a subanalysis according to the grade of patient satisfaction (grades 1, 2 and 3, dissatisfied patients’ group; grade 4, neither satisfied nor dissatisfied patients’ group; grades 5, 6 and 7, satisfied patients’ group).
In addition, the adverse effects of lidocaine were evaluated during the 24-hour postoperative period. Surgical complications were also recorded until discharge.
Sample Size Calculation and Statistical Analysis
The sample size was intended based on the related study of Kim D et al. (17). The probability of significantly alleviated pain from control was 0.667, whereas the probability of significantly diminished pain from lidocaine was 0.258. The power of study was set at 80%, and the required number of participants was at least 30 per group. All analyses were accomplished using Stata IC15 (Stata Corp, 2017, College Station, TX, USA). Continuous data were presented as mean and standard deviation (SD) for sufficiently normally distributed variables. For nominal variables, absolute and relative frequencies were demonstrated for each group. Chi-square test and independent t-test were used to compare the differences between groups in categorical and continuous variables, respectively. A P values <0.05 was considered statistically significant.