Mechanical bowel preparation is regarded as an efficient method to improve surgical visualization and bowel handling during a variety of surgical procedures.1–5 In contrast to laparotomy in which bowel may be retracted and packed to improve surgical visualization, this cannot be achieved at laparoscopy and an empty bowel may improve visualization, particularly when working in the deep pelvis in a confined space such as the posterior pelvic compartment.
Historically, preoperative mechanical bowel preparation is used for many surgical specialties with presumed improvement of surgical view, bowel handling, and lower complication risk.6–10 The most commonly used mechanical bowel preparation is a hyperosmotic laxative,1 and the routine use of these preparations preoperatively has been investigated in colorectal2,3 and urologic surgery.4 Collectively, these studies report that mechanical bowel preparation has no benefit to the surgical view, decreasing surgical difficulty during open surgery or decreasing anastomotic leakage or wound infection when bowel surgery is performed.5 These preoperative preparations are noted to contribute to increased patient discomfort1,11–14 as evidenced from two large, randomized, controlled trials of 2,697 patients2,3 reporting that mechanical bowel preparation does not reduce anastomotic complication or wound complication in colorectal or urologic surgery.8 Current clinical guidelines reflect this research, recommending that mechanical bowel preparation should not be routinely used before open colorectal surgery;15–17 however, mechanical bowel preparation is recommended for laparoscopic colorectal surgery to facilitate manipulation of the bowel.18
There are limited data assessing the effect of bowel preparation before gynecologic laparoscopy, with none assessing the surgical field visualization in the deep posterior compartment. This single-blind randomized study aims to estimate the role of three common preoperative diet regimens with or without mechanical bowel preparation for women having laparoscopic benign gynecologic surgery describing surgical visualization and bowel handling, the evaluation of patient discomfort and electrolyte changes, and bowel function after surgical procedures involving the posterior pelvic compartment.
MATERIALS AND METHODS
Ethics approval for this study was granted by South Eastern Sydney Illawarra Area Health Service Northern Hospital Network Human Research Ethics Committee (HREC Reference No. 08/096) and written informed consent was obtained from all patients. This randomized, single-blind, clinical trial was conducted in a tertiary teaching hospital and all patients undergoing laparoscopic surgery for benign gynecologic pathology likely involving the posterior pelvic compartment were invited to participate. Patients were approached a minimum of 5 days before surgery and were given verbal and written information pertaining to the study.
Inclusion criteria were women aged 18–80 years, fluent in spoken and written English, capable of completing questions relating to pain, and able to understand the implications of their involvement in the study. As per National Health and Medical Research Council guidelines, participants only could be enrolled in a single research study. Exclusion criteria included known or suspected pregnancy or malignancy, women who may become distressed because of the involvement in the study, or intercurrent illness or conditions that, according to the research team, may have interfered with the results of the study.
Those who agreed to participate each signed a consent form and were randomized into one of the three groups: fasting alone; minimal residue diet; or minimal residue diet with mechanical bowel preparation with oral sodium picosulphate. Women in the fasting only group had a normal diet before surgery, with patients scheduled for morning surgery fasted from midnight and those scheduled for afternoon surgery fasted from 6:00 AM. Women in the minimal residue diet group were restricted to a liquid diet 2 days before surgery and clear fluids only on the day before surgery. They fasted as per the fasting only group. The minimal residue diet with mechanical bowel preparation group followed the same diet as the minimal residue diet group and had one sachet of sodium picosulphate (PicoPrep) on the day before surgery no later than 3:00 PM. A second sachet of sodium picosulphate was used 4–6 hours after the first sachet.
Randomization was by computer-generated sequence in balanced blocks of 21, with concealment achieved by telephone allocation by a third-party research assistant not involved in patient recruitment or data collection. Participants were notified of their randomization group and given a dietary instruction sheet with suggested menu according to their allocated group. This included electrolyte drinks for the minimal residue diet and the minimal residue diet plus mechanical bowel preparation group. They were contacted immediately before surgery to ensure that they were complying with their group allocation. Participants who did not comply with the assigned diet were excluded from the study.
Demographic data collected included age, body mass index (calculated as weight (kg)/[height (m)]2), tobacco use, type and number of past surgeries, and the indication for the present surgery. Baseline symptomatology scores were obtained at the time of recruitment before any dietary instruction for headache, nausea and vomiting, sensation of thirst, weakness, tiredness, anxiety, and overall level of discomfort. These were obtained using a visual analog scale and a 5-point verbal descriptor scale. Validated questionnaires were used to assess baseline colorectal function, including the COREFO,19 consisting of six multi-item scales for incontinence, social effects, frequency, stool-related aspects, abdominal pain, and need for medication to aid evacuation. This questionnaire was repeated at 1 week and 1 month postsurgery. Baseline blood samples from each participant were obtained to assess hemoglobin, hematocrit, sodium, potassium, chloride, bicarbonate, creatinine, and urea before the commencement of presurgical diet.
On the day of surgery before commencing the procedure, participants were again scored according to symptomatology, reassessing symptoms as at baseline, and a second set of blood samples were drawn before intravenous fluids were commenced in preparation for anesthesia. Differences in serologic investigations between the three groups were assessed as absolute value of the difference and categorically by a change from the laboratory normal range to an abnormal range. Laparoscopic surgery was performed using high-pressure entry with Veress needle with an initial pressure of 20 mm Hg for primary trocar entry, followed by 15 mm Hg for secondary port placement and the subsequent surgical procedure, with the patient positioned at 30 deg of Trendelenburg tilt. The operating surgeon remained outside the room until the patient had been appropriately prepared and draped to prevent unblinding from the observation of bowel seepage that may occur after mechanical bowel preparation. Intraoperative data were collected from the primary surgeon, who was blinded to the randomization group, regarding the surgical field visualization at the beginning of the case and the bowel handling, with visual analog scale and verbal descriptor scale recorded at the end of the case. Data of the primary laparoscopic procedure, intraoperative time, and complications were recorded. Surgical procedures were performed by both trainees and consultants in gynecologic surgery at the Royal Hospital for Women or the Prince of Wales Private Hospital.
One day after surgery, participants completed another symptomatology score using visual analog scale and verbal descriptor scale. On discharge, participants were contacted by telephone at 1 week and 1 month after surgery to complete the bowel function questionnaire.
An a priori power calculation was obtained using the Stat Calc program from the Centers for Disease Control and Prevention20 following the published works of Muzii11 and Olivera.1 These data reported an adequate surgical field in 80% of patients having bowel preparation, achieving 80% power at the 0.05 significance level and finding a clinically significant difference of 20% in the intraoperative surgical view (a visual analog scale score change of 1.6 of 10); 246 patients were required for the study, with each arm having a minimum number of 82 patients. Data were recorded and analyzed using SPSS data editor 18.0 for Windows. Levene test was used to assess equality of variance of the data. When appropriate and according to the distribution of the data, Student t test was used for the comparative evaluation of paired data, analysis of variance assessment was used for demographic comparison, the Kruskal-Wallis test was used for continuous data, and the χ2 test was used for categorical data. Post hoc analysis for multiple comparisons was undertaken by the Bonferroni test when variance was equal and by Dunn test when unequal variance was demonstrated. Fisher exact test was used for small samples. Statistical significance was set at a P<.05. At the completion of the study, a third-party research assistant audited the database for transcription errors.
Between December 2008 and May 2011, 597 women were eligible to participate in the study; 308 consenting patients were randomized, with 86 patients in the fasting alone group, 84 in the minimal residue diet group, and 87 in the minimal residue with mechanical bowel preparation group. Figure 1 demonstrates patient disposition through the study. The completed database was audited for transcription error, and all critical data fields and 10% of random data fields were audited; this resulted in an error rate less than 1%.
Surgical data from the study are reported in Table 1. The overall complication rate was low at 1.6%, with no difference between the three groups (P=.2). One participant from the fasting only group had a blood transfusion after laparoscopic myomectomy. One patient from the minimal residue diet plus mechanical bowel preparation group required transfusion after total laparoscopic hysterectomy, a second patient required this after myomectomy, and a third patient in this group required readmission for a vaginal vault hematoma after total laparoscopic hysterectomy. There were no complications in the minimal residue diet group only, and there was no bowel complication from any group during the study.
The result of intraoperative surgical view and bowel handling between the three groups by visual analog scale is demonstrated in Figure 2. Minimal residue diet plus mechanical bowel preparation provides a better surgical view compared with the fasting only group or the minimal residue diet group (P<.01). The minimal residue diet plus mechanical bowel preparation group also had significantly better bowel handling than the two other groups (P=.04). However, when the surgical view and bowel handling were assessed by verbal descriptor scale and were categorized as excellent, good, medium, sufficient, or poor, there was no statistically significant differences between the three groups (P=.2 and P=.3, respectively). The overall quality of surgical view in all groups was good, with more than 80% of participants across all three groups scoring “good” or “excellent” for surgical view. More than 95% of all participants in all three groups scored “sufficient” or better for both parameters of surgical view and bowel handling. Of note, there were patients who scored “poor” for bowel handling across all three groups, with no significant differences (P=.8).
When a pair-wise comparison was made between two groups, the minimal residue diet plus mechanical bowel preparation compared with the fasting only group provided better surgical view (P<.01) but no improvement in bowel handling (P=.07). The mechanical bowel preparation group also provided a better surgical view than the minimal residue diet group (P=.03), but not in bowel handling (P=.1). When compared with the fasting only group, the minimal residue diet group showed no difference in surgical view (P=.6) or bowel handling (P>.99).
There were significant changes in the absolute difference in urea, potassium, chloride, and bicarbonate among the three groups. The absolute differences in hemoglobin, hematocrit, sodium, and creatinine were not significantly different between the three groups. A significant categorical difference was demonstrated for urea only. These results are displayed in Table 2.
Patient symptomatology at baseline was not different between the three groups. After the assigned preoperative diet regime, the symptomatology visual analog scale scores from baseline were significantly different between the three groups. The symptomatic changes in headache, thirst, weakness, and tiredness were greatest in the minimal residue diet plus mechanical bowel preparation group, and were the least in the fasting only group. This is displayed in Figure 3. The difference in scores for anxiety was an exception in that there was no difference between the three groups (P=.7). When using the verbal descriptor scale, participants reported a significant difference in headache (P<.01), weakness (P<.01), tiredness (P=.03), and overall discomfort (P<.01) after the preoperative diet regime; the symptoms were most severe in the minimal residue plus mechanical bowel preparation group and least severe in the fasting only group. Nausea (P=.07), thirst (P=.1), and anxiety (P=.2) were not different between the groups. Pair-wise analysis between the fasting only group and the minimal residue plus mechanical bowel preparation group showed significantly greater symptomatic visual analog scale change in the mechanical bowel preparation group for all symptoms (headache, P<.01; thirst, P<.01; weakness, P<.01; tiredness, P<0.01; overall discomfort, P<0.01) but no significant difference in anxiety (P=.7). When the fasting only group was compared with the minimal residue diet group, a significantly greater symptomatic visual analog scale change in the minimal residue diet group was seen in all symptoms (headache, P<.01; thirst, P=.04; weakness, P<.01; tiredness, P<.01; overall discomfort, P<.01) but, again, there was no significant difference in anxiety (P=.6). Pair-wise comparison between minimal residue diet group and mechanical bowel preparation group demonstrated no difference in symptoms, with the exception of worse headache scores after mechanical bowel preparation when compared with the minimal residue diet group (P=.03).
Bowel function assessment using COREFO questionnaire demonstrated that there was no difference in the change of bowel function between the three groups. This included aspects of fecal incontinence, social effect, frequency, stool-related aspects, and need for medication.
Fifty-one participants (17%) withdrew or were excluded because of protocol violation after randomization. Twenty-eight withdrew after randomization, and the reasons for withdrawal included dissatisfaction with their group allocation, pregnancy, cancellation, or delay in scheduled surgery beyond the study closure date. Twenty-three participants were excluded from the study because of a protocol violation (incorrect diet regimen was followed) or patients had surgery performed by a different surgical team than that scheduled. A sensitivity analysis of patients who withdrew or were excluded showed an even distribution between the three groups (P=.8).
For laparoscopic gynecologic surgery, three previous randomized studies11,21,22 have evaluated the use of preoperative mechanical bowel preparation and the effect on surgical and patient outcomes. Table 3 summarizes the findings of these studies and included our study for comparative purposes. Only one of these studies included a control group, and two limited study patients to adnexal surgery, in which the surgical view may be enhanced by mobilizing pathology laterally or to the anterior compartment where bowel handling is not an issue. Given the current guidelines in colorectal surgery for using mechanical bowel preparation at laparoscopy and the absence of evidence for gynecologic laparoscopy involving the deep posterior compartment (such as hysterectomy or excision of moderate to severe endometriosis in which removal of the cervix or dissection of cul-de-sac is required), this study adds valuable new information indicating mechanical bowel preparation is of limited value during laparoscopy, even in the deep pelvis, which may be considered in future surgical guidelines for laparoscopy.
Having three arms in this single-blind study, we demonstrated that there is no advantage to using a diet preparation without mechanical bowel preparation compared with fasting alone, with this group having no improvement in visual field or bowel handing but significantly worse preoperative symptoms such as thirst and headache. We demonstrated a statistically significant difference in the visual field when comparing fasting alone with diet and mechanical bowel preparation using a visual analog scale; however, with a difference of 1 point on a 10-point scale, the clinical significance is questionable. A Likert scale comparison did not demonstrate a difference in any of the groups regarding bowel handling or visual field, and the good or excellent rating of more than 80% across the three groups supports an adequate field in the absence of mechanical bowel preparation in the deep pelvis. Of note is that a poor visual field and poor bowel handing were equally reported in all three groups. Patients who underwent mechanical bowel preparation had the worst preoperative symptoms, and previous work reports that adequate hydration preoperatively improves outcomes and patient satisfaction.23–25
Electrolytes and serologic assessments were not significantly altered after minimal residue diet with or without mechanical bowel preparation, which is in keeping with results from previous work.26,27 In this study, extensive information regarding diet, fluid, and electrolyte replacement before surgery may have contributed to this positive result and always should be utilized. These positive findings are reassuring; however, women in our study were young and could be expected to tolerate the effects of mechanical bowel preparation better than elderly patients or those with multiple medical comorbidities. When mechanical bowel preparation is used in an older population such as those in their sixth decade and beyond, studies report significantly reduced total body water loss that may affect circulatory function, especially those with cardiac, renal, or hepatic disease.28 Therefore, it is imperative that the benefits outweigh the risk, and because a substantial benefit has not been demonstrated at laparoscopic or open surgery in the index study or previously, deleterious outcomes in an older population may be expected to be greater.
There was no bowel-related complication in any group in this study, nor was there any conversion from laparoscopy to laparotomy for any reason. We do acknowledge that this study is not adequately powered to detect a difference in bowel injury or conversion to laparotomy, and this was not an outcome of the study. The reported risk of bowel injury during gynecologic laparoscopic surgery ranges between 0.08% and 0.33%,29 and a study to demonstrate a 50% reduction in bowel injury requires a sample size of approximately 25,000 patients.30 Because the bowel is not commonly opened primarily during gynecologic surgery, we must rely on data from colleagues with colorectal experience, whose work does not support the use of mechanical bowel preparation to reduce anastomotic leak.5–10 Because bowel leakage is an unlikely scenario for gynecologic laparoscopy, the issue of vision, the capacity to complete the scheduled surgery, and bowel handling are pertinent, and we have shown no substantial advantage in mechanical bowel preparation for this purpose.
For the original power calculation used during for this study, previous published data were used with limited information regarding data spread. We demonstrated that there was a statistical difference in visual field between the groups; however, because all groups had such high scores on the visual analog scale and the verbal descriptor scale, there is no substantive clinical difference in outcomes for surgery.
Using the COREFO questionnaire across three timeframes, this study demonstrated that having different preoperative diet regimes did not significantly alter postoperative bowel function of participants. This highlights that there are perioperative factors other than usage of mechanical bowel preparation or preoperative diet regime that contribute to postoperative bowel function. These may include factors such as opioid use, analgesia, and operative anatomical issues, including parasympathetic neuropraxia, postoperative diet, and mobilization,31–33 which apply to all abdominal surgery and not just gynecologic surgery.
An important methodologic issue from our study was that 17% of patients withdrew or were excluded because of a protocol violation. The most common reason for withdrawal was dissatisfaction with group allocation, with women in the mechanical bowel preparation group withdrawing because of anticipated discomfort with the preparation; this has been noted in previous studies.1,14–16 However, an equal number withdrew because they were not allocated to mechanical bowel preparation, which likely reflects a general perception of safety linked with the “cleansing of the bowel,” which contradicts the available evidence.3,34–36
In conclusion, minimal residue diet plus mechanical bowel preparation improves surgical view and bowel handling, but the benefit is small and of little clinical significance. Given the significant symptoms and discomfort caused for patients undertaking minimal residue diet with or without mechanical bowel preparation, fasting only without any preoperative diet or bowel preparation is the preferable alternative, even in advanced laparoscopic gynecologic surgery.
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