Objective
The objective of this study was to compare the backfill standard voiding trial (SVT) that relies on the assessment of voided volume to subjective patients’ evaluation of their voiding based on the assessment of the force of stream (FOS) after an outpatient midurethral sling surgery.
Study Design
This double-blinded randomized trial included patients undergoing an outpatient midurethral sling surgery without any other concomitant surgery. Participants were randomized to either the SVT group or to the FOS group. The primary outcome was the rate of catheterization any time up to 6 weeks after surgery. Both groups underwent the same backfill voiding trial protocol postoperatively. Measurements of the voided amount, postvoid residual, and the response to the FOS visual analog scale were collected. The criteria for passing the voiding trial in the SVT group was voiding at least two-thirds of the instilled amount; while the criteria for passing the trial in the FOS group was assessment of FOS at least 50% of the baseline, regardless of the voided volume. Participants were interviewed preoperatively and 2-4 days, 7-9 days, and 6 weeks postoperatively. All postoperative interviews included assessments of pain, tolerance of physical activity, urinary FOS, as well as satisfaction with the surgery. Validated questionnaires (Incontinence Severity Index and Urinary Distress Inventory, short form) before the surgery and 6 weeks after were used to evaluate urinary symptoms.
Results
A total of 108 patients were enrolled and randomized, and 6-week follow-up data were available for 102 participants (FOS 50, SVT 52). The 2 groups were similar with respect to demographic characteristics and urinary symptoms. The incidence of catheterization was also similar between the groups (FOS 13 [26%], SVT 13 [25.5%]; P = .95). Amount voided had a moderate correlation with FOS assessment (Spearman rho 0.5; P < .001). There was no significant difference in mean catheter days, pain scores, Incontinence Severity Index, and Urinary Distress Inventory, short form scores between the 2 groups. Of the patients who were discharged home without a catheter in either group none required catheter reinsertion within 6 weeks after the surgery.
Conclusion
Patient’s subjective assessment of the urinary FOS correlated well with the measured voided amount and no difference in catheterization days was noted between the subjective and objective assessment of voiding. Thus subjective evaluation of the FOS is a reliable and safe method to use after outpatient midurethral surgery.
Midurethral sling (MUS) surgeries are among the most common procedures performed in the United States. MUS are less invasive than the Burch colposuspension and the autologous rectus fascia sling procedures and as such are associated with less blood loss and shorter recovery time without compromising the efficacy of treatment. Despite numerous advantages of these surgeries, 25-35% of patients are discharged home with indwelling catheters.
The challenge for surgeons performing antiincontinence procedures is to avoid postoperative urinary retention and minimize the need for postoperative catheterization and its associated risks. In addition to being the leading cause of hospital-acquired urinary tract infections (UTIs), indwelling catheters are also a source of discomfort, embarrassment, and inconvenience, particularly if patients desire to return to work or daily activities immediately. Additionally, many women are distressed by the idea of going home with a catheter. Elkadry et al evaluated how patients perceive surgical outcomes and found that 9% of women believed that being discharged with a catheter was a surgical complication and 15% named “catheter” as the worst aspect of their surgery.
After antiincontinence surgery, an assessment of voiding function (voiding trial) is often performed to determine who can be safely discharged without a catheter. A commonly described voiding trial technique is the backfill-assisted voiding trial, which involves filling the bladder with 300 mL of sterile fluid via the catheter while in the recovery room, removing the catheter, and allowing the patient to void. The patient is discharged with an indwelling catheter if the voided amount is less than two-thirds the infused volume. When utilizing this protocol, approximately 35% of patients require catheterization after a sling. This backfill-assisted voiding trial technique has been shown to be more efficient than the alternative of simply removing the catheter, waiting for a patient to void after parenteral or oral hydration, and then measuring a postvoid residual (PVR). Despite being widely used in multiple randomized trials, the precise requirements for volume voided or PVR volumes have not been critically evaluated, particularly for outpatient minimally invasive sling surgeries.
An alternative method of voiding evaluation, which utilizes a visual analog scale (VAS) ascertaining the urinary force of stream (FOS) after surgery relative to the force prior to surgery has been reported. This method specifies the criteria for discharge without a catheter as a subjective report by the patient of her FOS that is >50% of her baseline FOS using a VAS ( Figure 1 ). In this study, 94.6% of patients were discharged home without a catheter and with no incidence of acute voiding dysfunction necessitating recatheterization. While subjective patient evaluation of voiding appears to be safe, it is not known how patient’s subjective perception of voiding correlates with the measured voided volume or the PVR volume. The objective of this study was to compare the backfill standard voiding trial (SVT) to the FOS voiding trial in a double-blind randomized controlled trial and to determine if subjective patient evaluation is a safe method to determine the need for indwelling catheterization after an outpatient sling surgery. Our hypothesis was that the rate of catheterization would be significantly lower when using the FOS technique as compared to the backfill voiding trial.
Materials and Methods
In this double-blinded randomized trial, patients undergoing an outpatient MUS surgery for female stress urinary incontinence were eligible for participation. Participants were excluded if the surgery involved any concomitant urinary tract or pelvic reconstructive procedure or if the procedure, in itself, necessitated postoperative catheterization, as in the event of a cystotomy. Participants with a history of neurologic conditions affecting the urinary tract system, pelvic organ prolapse beyond the hymen during straining (any compartment), or previous antiincontinence procedure were also excluded. Eligible patients were recruited preoperatively and all participants signed an institutional review board–approved research informed consent form. All participants received a single prophylactic dose of intravenous antibiotics at the time of the procedure. All participants underwent the same standardized postoperative protocol in the recovery room that included backfilling the bladder with 300 mL of normal saline solution through the transurethral catheter, removing the catheter, and allowing the participant to void within 30 minutes. PVR was measured using bedside ultrasound. All participants were asked to assess their voiding using FOS VAS, by comparing the postoperative FOS with the preoperative FOS on a scale of 0-120%, given that preoperative FOS is 100% ( Figure 1 ). Participants were randomly assigned using a 1:1 allocation ratio to 2 different criteria for catheter management. Participants randomized into the SVT group were discharged with a catheter if the voided amount was <200 mL and the PVR was greater than one third of the total amount. The participants in the FOS group were discharged with the catheter if they reported the FOS to be <50% of their baseline FOS, regardless of the voided amount and the PVR ( Figure 2 ).
Treatment allocation was made by a computer-generated random numbers table using randomly permuted blocks of varying sizes of 4, 6, and 8 known only to research nurses not involved in patient recruitment or data collection. Randomization was stratified by surgeon (8 surgeons). Group allocation was revealed after surgery in the recovery nursing unit by opening an opaque envelope with specific instructions regarding the postoperative voiding assessment. The patient as well as all study investigators, the surgeon, and the research coordinator remained masked to treatment assignment throughout the study and data analysis.
The primary outcome of the study was the rate of catheterization within 6 weeks after the surgery. We hypothesized that the rate of catheterization within a 6-week period after surgery would be lower in the FOS group than in the SVT group. Secondary outcomes were the rate of UTI, efficacy of the procedure as measured by validated questionnaires, patient’s postoperative pain, and activity level as well as satisfaction with the surgery.
Participants completed a series of questionnaires at 4 time points: preoperatively and 2-4 days, 7-9 days, and 6 weeks postoperatively. The questionnaires were administered in a telephone interview by a masked investigator or a research assistant. Preoperative and 6-week postoperative interviews included validated questionnaires that evaluate urinary incontinence (Incontinence Severity Index [ISI] and Urinary Distress Inventory, short form [UDI-6]). The preoperative interview also included questions regarding patient’s expectations. The questionnaire asked that the patient rate how important it is to have “Good control of pain immediately after the surgery,” “Minimal pain within 1 week of the surgery,” “Going home without a bladder catheter,” and “Returning to my daily activities (other than work) within a few days of the surgery,” and “Returning to work within the time frame that is acceptable.” The responses were ranked as “Not important,” “slightly important,” “moderately important,” and “greatly important.” Data regarding medical comorbidities were collected from the medical record using the Charlson Comorbidity Index. All postoperative interviews included assessments of pain using a pain scale that addressed general pain and pain specifically generalized to the genital urinary area, voiding (using FOS scale), and tolerance of physical activity. Satisfaction with the surgery was assessed at the 3 postoperative interviews with the question: “How satisfied are you with the surgery?” Possible responses were: “very satisfied,” “somewhat satisfied,” “somewhat dissatisfied,” or “very dissatisfied.” Incidence of UTI was determined by reviewing the electronic medical record and by asking the subjects at the time of postoperative interview if they had called a physician or had been seen for any reason by a medical provider and the patient reported that she was seen and/or treated for a UTI. Presence of UTI was considered positive even if she was treated based on symptoms, in the absence of a positive culture. During each interview specific symptoms of voiding dysfunction and UTI were assessed, and if positive the subjects were prompted to contact their physician and the results were followed up by the research staff.
A sample size of 51 participants per group provided 80% power to detect a 10% difference in the rate of catheterization between the 2 methods, provided that the incidence of catheterization rate is 35% based on the previous studies. Assuming a 5% loss to follow-up, the total sample size required was 108 (54 per group). All statistical analyses were performed using the intention-to-treat principal. Descriptive statistics were used to report the primary and secondary outcomes including the rates and 95% confidence intervals (CIs). Categorical variables were described with frequencies and percentages. The primary outcome (rate of postoperative catheterization) was determined using Pearson χ 2 test, as were other categorical variables. Continuous variables were compared using Student t tests. Software (JMP, version 10; SAS Institute, Cary, NC) was used to conduct statistical analysis.
Results
This trial was approved by the Institutional Review Board (11-082) and registered on clinicaltrials.gov (NCT01343784). In all, 108 participants were recruited for this randomized trial (53 in SVT group and 55 in FOS). The data for the assessment in the recovery room were not recorded for 2 and 6 participants in SVT and FOS group, respectively. All data for 102 participants (50 in SVT group and 52 in FOS) were complete at the 6-week follow-up ( Figure 3 ). Recruitment for this study occurred in multiple different locations in our health system across northeast Ohio. Due to limited study personnel, we relied on surgeons to identify patients who met study criteria and a study nurse contacted the patient to verify criteria and obtain consent. This did not allow us to obtain an accurate screening and exclusion denominator. Overall, the randomization was successful; with similar baseline participant characteristics in both groups ( Table 1 ). The overall catheterization rate was not significantly different between the 2 voiding trial interventions (SVT 13 [26.0%], FOS 13 [25%], difference 1%; 95% CI, –15.6% to +17.7%; P = .95) ( Table 2 ). Mean number of catheterization days was 3.4 (±2.1) for the FOS group, and 2.4 (±1.1) for the SVT group ( P = .14); 2-4 days after surgery 5 (10.2%) participants in the FOS group and 6 (11.3%) in the SVT group had a catheter in place ( Table 2 ). The mean voided volume, and PVR and FOS values were likewise not statistically different between the groups. Voided amount had a moderate correlation with FOS (Spearman rho 0.5; P < .001).
| Patient characteristics a | FOS (n = 53) | SVT (n = 55) | P value |
|---|---|---|---|
| Age, y | 55.44 (35.8–78.11) | 57.21 (35.0–76.07) | .97 |
| White race | 47 (92.2%) | 49 (96.1%) | .34 |
| Parity | 2 (0–7) | 2 (0–5) | .57 |
| BMI, kg/m 2 | 28.9 (18.78–51.9) | 30.0 (18.8–47.36) | .95 |
| CCI b | 2 (0–7) 0.90 (0–0.98) | 0 (0–5) 0.90 (0.21–0.98) | .99 .58 |
| Urinary urgency symptoms preoperatively | 26 (52%) | 34 (64.2%) | .57 |
| Urinary frequency | 22 (44%) | 28 (53%) | .37 |
| Nocturia | 16 (32%) | 21(40%) | .42 |
| Anticholinergic medication use preoperatively | 5 (10%) | 2 (3.8%) | .21 |
| Retropubic/transobturator sling | 29/24 | 30/25 | .15 |
| ISI score | 6 (0–12) | 6 (0–12) | .83 |
| UDI-6 score | 85.0 (33.3–100) | 83.3 (16.7–100) | .44 |
a Continuous data presented as median (range), Student t test, and categorical data presented as number (%), Wilcoxon signed rank test
b Predicts 10-y mortality for patient who may have range of comorbid conditions, total of 22 conditions, score is age-adjusted and 10-y survival calculated.
| Finding | FOS (n = 52) | SVT (n = 50) | P value |
|---|---|---|---|
| Perioperative evaluation a | |||
| Amount voided, mL | 200 (0–400) | 275 (0–500) | .16 |
| Postvoid residual, mL | 107.5 (0–544) | 66 (0–600) | .53 |
| FOS, b % | 70 (0–110) | 85 (0–120) | .40 |
| Discharged with catheter | 13 (26%) | 13 (25.5%) | .95 |
| Postoperative evaluation: day 2–4 a | |||
| General pain (0–10) | 2 (0–7) | 1 (0–9) | .65 |
| Urethral and vaginal pain (0–10) | 1.9 (0.28) 2 (0–7) | 2.2 (0.27) 2 (0–8) | .38 |
| Urinary urgency | 11 (22.5%) | 10 (19.2%) | .69 |
| Narcotic medication use | 24 (49.0%) | 18 (34.0%) | .12 |
| Nonnarcotic medication use | 25 (51.0%) | 27 (51.0%) | .99 |
| Presence of catheter | 5 (10.2%) | 6 (11.32%) | .86 |
| FOS, % | 100 (50–110) | 100 (20–120) | .85 |
| Very/somewhat satisfied with surgery | 32 (65%)/15 (31%) | 38 (72%)/13 (25%) | .78 |
| Postoperative evaluation: day 7–9 a | |||
| General pain (0–10) | 0 (0–5) | 0 (0–6) | .34 |
| Urethral and vaginal pain (0–10) | 1 (0–7) | 0 (0–9) | .62 |
| Urinary urgency | 13 (26%) | 10 (19.3%) | .41 |
| Urinary urgency | 13 (26%) | 10 (19.3%) | .41 |
| Narcotic medication use | 6 (11.8%) | 7 (13.5%) | .80 |
| Nonnarcotic medication use | 14 (27.5%) | 13 (24.1%) | .53 |
| Presence of catheter | 0 | 0 | |
| FOS | 100 (50–120) | 100 (50–120) | .66 |
| Very/somewhat satisfied with surgery | 36 (72%)/13 (26%) | 42 (79%)/10 (19%) | |
| Postoperative evaluation: week 6 a | |||
| General pain (0–10) | 0 (0–5) | 0 (0–7) | .26 |
| Urethral and vaginal pain (0–10) | 0 (0–1) | 0 (0–4) | .13 |
| Urinary urgency | 23 (48.9%) | 15 (30.6%) | .07 |
| Narcotic medication use | 1 (2.1%) | 0 (0%) | .20 |
| Nonnarcotic medication use | 6 (12.8%) | 4 (8.2%) | .46 |
| Presence of catheter | 0 | 0 | |
| FOS | 100 (40–120) | 100 (75–120) | .56 |
| Very/somewhat satisfied with surgery | 34 (72%)/10 (21%) | 38 (78%)/7 (14%) | .65 |
| ISI score | 0 (0–8) | 0 (0–8) | .08 |
| UDI-6 | 33.3 (0–100) | 19.4 (0–100) | .13 |
a Continuous data presented as median (range), Student t test; and categorical data presented as number (%), Wilcoxon signed rank test
b Determined using visual analog scale where 100% corresponds to FOS at baseline, score ranges from 0% (unable to void) to 120% (20% better than at baseline).
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