This randomized controlled study was conducted at the Thai-German Multidisciplinary Endoscopic Training Center, Department of Obstetrics and Gynaecology, Faculty of Medicine Siriraj Hospital between 8 May 2015 and 7 May 2016, in accordance with the ethical principles stated in the most recent version of the Declaration of Helsinki. The study protocol was ethically approved (COA number Si 245/2015) and financially supported (grant number R015831072) by the Faculty of Medicine, Siriraj Hospital, Mahidol University. The trial was also registered in the Thai Clinical Trials Registry with the identification number of TCTR20160208003.
Sample size calculation
We initially performed a pilot study on patients undergoing elective laparoscopic surgeries for benign gynecologic diseases to find out the incidence of moderate to severe PLSP, and had discovered noticeably lower incidence of shoulder pain in the DSPR group (20%) when compared with the conventional group (37.5%). With the assumed type I error of 0.05 and the study power of 80%, the sample size for each group was calculated to be at least 104 patients.
Following the CONSORT 2010 flow diagram (Figure 1), a total of 228 patients scheduled for elective gynecological laparoscopic surgeries were recruited. Only those aged 18 years old and above, with the American Society of Anesthesiologists (ASA) physical status classes I or II, who had given consent to participate in the study were eligible. Those with the following criteria including pregnancy, poorer ASA scores, drug or alcohol abuse, preoperative shoulder pain or other chronic pain syndrome, prolonged use of analgesics, allergy to sulfonamides, contraindication to non-steroidal anti-inflammatory drugs (NSAIDs) or any other drugs used in the study, intellectual or psychological disability affecting pain threshold evaluation, gynecologic malignancies, and/or uncontrolled cardiopulmonary-hepatorenal diseases were excluded from the study.
Of 228 enrolled patients, 8 were excluded due to the past history of sulfonamide allergy. After obtaining written informed consent, the remaining 220 patients were equally categorized into 2 groups including control group (n = 110) and experimental group (n = 110) using computerized randomization method. The randomization code was specified into numbers and concealed in the opaque envelopes. Each envelope was opened by the surgeon in the operating theater prior to commencing the laparoscopic surgery. All of the participants were blinded to their group allocation. During the study period, participants were further excluded from the trial if there was/were (1) unwillingness to participate, (2) no suprapubic port placement, (3) major complications such as bowel, bladder, and/or ureteric injuries, (4) massive hemorrhage (blood loss ≥1,000 milliliters) and/or the need for intra- or post-operative blood transfusion, (5) conversion to laparotomy, and/or (6) occult gynecologic malignancy.
Steps of the delayed suprapubic port removal
Both conventional and DSPR techniques were implemented at the end of each elective laparoscopic surgery utilizing one primary (10-mm umbilical) port and at least two (5-mm) ancillary, including suprapubic, ports. All laparoscopic procedures were performed under 12-mmHg carbon dioxide (CO2) insufflation pressure with a flow rate of 20 liters per minute. All patients were positioned in a Trendelenburg position without the use of shoulder rest. CO2 insufflation was discontinued at the end of the surgery. In the control (conventional) group, all ancillary ports were removed under vision, leaving only the opened umbilical cannula for passive abdominal deflation while the patient was still in Trendelenburg position. Gentle abdominal compression from periphery (360 degree) towards the umbilicus was undertaken to actively expel CO2 gas, followed by removal of the umbilical cannula. In the experimental (DSPR) group, all ancillary ports were also removed under vision except the suprapubic cannula, thus leaving both the opened umbilical cannula and the opened suprapubic cannula for passive pneumoperitoneum deflation while the patient was still in Trendelenburg position. The two-step abdominal compression was performed, primarily from periphery (360 degree) towards the umbilicus to actively evacuate CO2 prior to removal of the umbilical cannula, and secondarily from xiphoid and lateral abdominal aspects towards the pelvic cavity to further facilitate CO2 expulsion prior to removal of the suprapubic cannula (Figure 2).
Parecoxib and acetaminophen were routinely prescribed for postoperative pain control. All participants were provided with two separate doses of 40 mg intravenous parecoxib immediately at the end of the surgery and at 12 hours after the surgery. An additional 500 mg acetaminophen tablet was given every 6 hours postoperatively for 48 hours. The 2 mg intravenous morphine was also administered on request every 2 hours during the first 24 hours for breakthrough postoperative pain control.
The incidence and the severity of PLSP were evaluated during the first 24- and 48-hours post-surgery at different intervals including 0 to 6 hours, 6 to 12 hours, 12 to 24 hours, and 24 to 48 hours respectively, using the self-rating visual analogue scales (VAS). Each participant was asked to rate the level of PLSP on a 100–mm long horizontal line VAS, from 0 (no pain) to 100 (worst imaginary pain), by placing a perpendicular mark at the point that corresponded to the perceived pain level. The level of PLSP was further classified into 4 pain categories, including no pain (0–4 mm), mild pain (5–44 mm), moderate pain (45–74 mm), and severe pain (75–100 mm) [11]. In case of early hospital discharge within 48 hours postoperatively, the participants were assigned to continue rating their PLSP level at home.
Apart from PLSP assessment, other information regarding the participants’ baseline characteristics, perioperative outcomes such as ASA physical status, number of port placement, operative time, estimated blood loss, and length of hospital stay, as well as number of the participants requiring additional morphine injection were also evaluated. All statistical analyses were performed using the Statistical Packages for the Social Sciences version 18 for Windows (SPSS Inc, Chicago, IL, USA). Continuous variables were expressed in terms of mean ± standard deviation or median (IQR) whereas categorical data were presented as number and percentage. Pearson Chi-square test or Fisher’s exact test was used to compare the differences of categorical data between the control and the experimental groups, whereas independent Student’s t-test or Mann-Whitney U-test was used to compare the differences of continuous variables. The p-value of less than 0.05 was used to determine statistical significance. With the design of randomized controlled study, the authors assumed that all confounding factors and biases were already minimized with no data variability. Hence, we omitted the use of regression analysis in this study.