Study Design, Settings, and Patients
This prospective, randomized trial was approved by the Medical Ethics Committee of the First Affiliated Hospital of Gannan Medical University (LLSC-2020121002), and all patients provided informed consent for all treatments and trials. The study was conducted and reported in accordance with the Consolidating Standards of Reporting Trials (CONSORT) 2010 statement.
This study included adult patients with American Society of Anesthesiologists physical status (ASA) I/II who were scheduled to undergo elective PELD from June 2018 to March 2021. Patients with contraindications to LAI, allergies to any of the drugs planned to be administered, infection at the puncture site, or who had previous spine surgery, severe spinal stenosis, morbid cardiovascular impairments including preexisting heart block or compromised left ventricular function (defined as an ejection fraction <45%) were excluded from the study. Surgeons and anesthesiologists were aware of the study being conducted but were blind to participant allocation.
Study Protocol
Patients were assigned randomly to receive either intravenous DEX sedation throughout the surgery (Group A) or the same volume of normal saline intravenously (Group B) using a computer-generated table of random numbers. The patient’s group allocation was concealed using a sequentially numbered, sealed opaque envelope, which was opened only by a separate investigator who prepared the anesthetic solution before the surgery. The operations were performed by a single experienced surgeon (blinded to the study protocol) using the same technique. Intravenous access was secured before the patient’s arrival in the operating room.
In the operating room, standard monitoring was applied. DEX was diluted with normal saline to obtain a concentration of 4 µg·mL–1, patients received 1 µg·kg–1 of intravenous DEX for 10 min as a loading dose, followed by continuous infusion at a rate of 0.5 µg·kg–1·h–1 throughout the surgery (Group A), and patients in Group B received the same volume of normal saline. After the infusion of the loading dose, all patients received LAI in the surgical site using 10 ml of 1% lidocaine (Suicheng Industrial, China) and 10 ml of 0.75% ropivacaine (Qilu Industrial, China) by the same surgeon. Intravenous DEX or normal saline administration was stopped at the start of skin closure.
An administration-approved, noninvasive, bioimpedance-based respiratory volume monitor (RVM; ExSpiron, Respiratory Motion, Inc., Waltham, MA) was used to provide real-time respiratory data, including minute ventilation (MV), tidal volume (TV), and respiratory rate (RR). The predicted MV (MVPRED) for nonintubated patients, representing the expected MV during quiet respiration in the awake period, was calculated based on body surface area (BSA) and patient sex. The RVM collected bioimpedance traces via an electrode padset placed in the recommended positions: at the sternal notch, xiphoid, and right midaxillary line at the level of the xiphoid. The electrode padset was applied in a fashion similar to that of standard electrocardiogram electrodes.
Intraoperative hypotension (defined as a >20% decrease in systolic pressure from baseline) was treated with 5-10 mg of intravenous ephedrine; bradycardia (defined as a heart rate <45 beats min–1) was treated with 0.5 mg of intravenous atropine; and respiratory depression (an MV less than 40% of the MVPRED, sustained for a period of 1 minute or longer) was treated with endotracheal intubation for respiratory support.
Measurement Values
Data were recorded as the primary outcomes, including the SpO2, MV, VT, and RR at the following time points: T0, baseline; T1, 10 min after the start of intravenous DEX; T2, before the skin incision; T3, after the skin incision; T4, 30 min after surgery; T5, at the end of surgery; and T6, 24 hours after surgery. Venous blood samples were taken at T0, T5 and T6 to detect serum levels of interleukin-6 (IL-6), tumor necrosis factor (TNF-α) by enzyme-linked immunosorbent assay (ELISA), and malondialdehyde (MDA) and glutathione peroxidase (GSH-PX) by colorimetric methods. The patients were asked to assess their level of pain during the procedure using a visual analog scale (VAS), which ranged from 0 (no pain) to 10 (worst possible pain), from T2 to T5.
Statistical Analyses
Statistical analysis was performed using GraphPad Prism 8 (GraphPad Software, San Diego, CA, USA). Data are expressed as the mean ± standard deviation or the median (interquartile range). Data were analyzed using repeated-measures analysis of variance (ANOVA), and intergroup differences at the same time point were analyzed using a two-sample t test. A p< 0.05 was considered to indicate a statistically significant difference.