This prospective, randomized, double-blind and placebo controlled study was performed after approval from ethic committee of Wenzhou people’s hospital, number: 2016003. The protocol for this clinical trial was registered at CHICTR.ORG.CN (ChiCTR-IPR-16008814).
During preoperative visit, all patients were provided informed consents and educated about the symptoms of CRBD (characterized as a burning sensation with an urge to void or as discomfort in the suprapubic area) and numerical rating scale (NRS) Severity of CRBD was recorded using an NRS ranging from 0 (no discomfort) to 100 (most severe discomfort).
From July to December 2019, male patients with an ASA physical status Ⅰ to Ⅲ, who were scheduled to transurethral resection prostate were included. Patients were excluded if they were unable communicate, refused join the study, had a history of severity heart disease, lung disease, psychiatric disease, chronic pain or long-term administration of analgesics.
All patients had no premedicated, standard monitoring consisted of ECG, non-invasive arterial pressure (NIBP), and pulse oximetry (SpO2). Anesthesia was induced with 0.05mg kg-1 midazolam, 4μg﹒kg-1fentanyl, 1.5mg kg-1 propofol and 0.6mg kg-1 rocuronium. Intraoperative maintenance anesthesia relied on intravenous anesthesia; remifentanil infusion was maintained at 0.2μg kg-1 min-1; intraoperative propofol infusion rate was adjusted to maintain BIS value within 40-60; rocuronium was intermittently injected. 16/18 Foley urinary catheter was inserted and 5 ml sterile normal saline was injected into the balloon at the end of operation. After the surgery, 0.5mg atropine and 1mg neostigmine were administered to antagonize residual muscle relaxation. These patients were transferred to PACU after the endotracheal catheter was removed. PCIA analgesia was postoperatively applied. the analgesic was 100μg sufentanil added to 100ml normal saline, the background infusion was 1ml per hour, the predetermined time was 8min and the volume of each press was 2ml.
After reporting CRBD, patients were randomly assigned to one of two groups (control or oxycodone) with the help of a computer generated random number table. The assignments were concealed in opaque envelopes and opened immediately before induction by a nurse who was blinded to this study and was responsible for preparing the study drugs. All medications were administered in identical 2 ml syringes. patients were randomized into two groups using sealed envelopes by an anaesthesiologist responsible for the randomization. The group controlled received same volume normal saline, whereas the oxycodone group intravenous inject oxycodone 0.03mg kg-1 (product batch number: AW259, Mundipharma, Britain).
The primary outcome was defined as the reduction in the severity of CRBD assessed by NRS . Secondary outcomes were sufentanil consumption, during of PACU, incidences of agitation and requiring treatment of hypertension, heart rates (HRs), mean arterial pressure (MAP), and adverse effects included PONV, over sedation. All these outcomes were assessed at 0, 5min 1/2 h, and 2 h after administration of the study drug by blinded assessors. Times of duration of PACU were recorded.VAS scores were used to assess pain in these patients: 0 point, no pain; 10 points, unbearable pain. The Ramsay Sedation Scale was measured . Patients with a sedation scale score of at least 4 were considered over sedation. The patients with severe vomiting received intravenous injection of 4mg ondansetron. Analgesic doses and anti-hypertension received by the two groups of patients within 6 hours after the operation were recorded. Agitation was defined as a Richmond Agitatione Sedation Scale (RASS) score  of +3 or +4 during the PACU stay. If the patients’ blood pressure higher 30% than baseline at the ward or more than 180mmHg mustbe used anti-hypertension agents.
The calculation of the sample size was based on our previous study, 60% of patients complain of CRBD postoperatively .The severity of CRBD (NRS) of 10 patients was 80 at the time of reporting CRBD. Assuming that the severity of CRBD reduced from 80 to 50 (decrease of 30) after therapy with oxycodone. We calculated that 33 patients would be needed in each group to achieve statistical significance (α=0.05 and β=0.20). Considering a 20% dropout rate, 80 patients per group were included.
All data were analyzed with SPSS16.0 software package (SPSS, Inc., Chicago, IL, USA). NRS, HR and MAP over time between the groups were analyzed by repeated measures analysis of variance (ANOVA) and then t-test was used to compare values at each time point. Rescue analgesic was analyzed by t-test Analyses of categorical variables (incidence of side effects) were performed by χ2 or Fisher’s exact-tests. Data were analyzed according to the intention-to-treat principle. P<0.05 indicated statistically significant differences.