Introduction

Urinary tract infections (UTIs) and surgical site infections (SSIs) are common concerns for postoperative morbidity after urogynecologic surgery. Of note, 7% to 33% of women will report a postoperative UTI, ^, and 0.6% to 1.3% of women will experience an SSI after urogynecologic surgery. ^, These postoperative infections are associated with increased healthcare costs, antibiotic resistance, and morbidity and mortality for patients. A recent study found that SSIs account for 31% of all healthcare-associated infections among hospitalized patients. Postoperative infections are used as a quality metric and tracked by regulatory bodies, such as The Joint Commission, the Centers for Medicare and Medicaid Services, and the National Surgical Quality Improvement Program.

Surgical operations are categorized on the basis of inherent infection risks: clean, clean-contaminated, contaminated, and dirty or infected. Any surgery that passes through or into the vagina is classified as a clean-contaminated surgery as the inherent vaginal microbiota are known to increase the risk of postoperative infections. To decrease the risk of infections after surgery, best practices recommend preoperative antiseptic cleaning of the vaginal surgical field. ^,

For abdominal surgery, several studies have demonstrated that that chlorhexidine gluconate (CHG) antisepsis results in fewer postoperative infections than povidone-iodine (iodine) for abdominal hysterectomies and cesarean deliveries, with 44% and 22% lower odds for those surgical procedures, respectively. ^, The prolonged antiseptic effect of CHG is theorized to contribute to decreased infection rates. Iodine has been reported to be effective for 2 hours, whereas CHG’s duration of action has been reported to last for 6 to 48 hours, depending on the alcohol concentration used. Therefore, CHG is the preferred antiseptic of choice before abdominal surgical procedures. ^,

For vaginal surgery, iodine is currently the only Food and Drug Administration–approved antiseptic agent. Because of this, some institutions limit or restrict the use of CHG in the vagina. However, some have found CHG to be a safe and effective vaginal antiseptic, and the American College of Obstetricians and Gynecologists lists either CHG or iodine as an acceptable preoperative vaginal antiseptic agent.

This study aimed to evaluate the comparative effectiveness of 2 preoperative vaginal antiseptic solutions (CHG and povidone-iodine) before urogynecologic surgery. As UTI is the most common infection after urogynecologic surgery, our primary objective was to compare the rates of symptomatic UTI between the 2 antiseptic agents within the first 2 weeks after surgery. We hypothesized that CHG would be noninferior to iodine concerning the prevalence of UTI within the first weeks after surgery.

Materials and Methods

We obtained institutional review board approval (Human Research Review Committee #19-039) to perform a single-masked, noninferiority, randomized controlled trial (RCT) to compare the effectiveness of CHG vs iodine for presurgical vaginal antiseptic cleaning before any urogynecologic surgery involving vaginal preparation, and we registered the trial on ClinicalTrials.gov (NCT04048356). We recruited participants scheduled for urogynecologic surgery in the University of New Mexico Health System between August 2019 and January 2021.

The inclusion criteria included English- or Spanish-speaking female participants aged ≥18 years undergoing urogynecologic surgical procedures who could provide informed consent. We excluded women that were pregnant or incarcerated and those without telephone access, those unable to return for follow-up, those having surgical procedures without the concurrent need for vaginal antisepsis (such as cases of sacral neuromodulation), or those with a known allergy to either chlorhexidine or iodine.

Patients received perioperative care that included a physical examination and any necessary diagnostic studies needed for their preoperative workup. Informed consent was obtained before enrollment. All patients received standard perioperative antibiotic prophylaxis, including intravenous antibiotics within 30 minutes of the surgical start time if indicated for the procedure.

Participants were randomly assigned to receive a standardized aqueous preoperative scrub with either 10% iodine or 2% CHG, which was conducted in a standardized fashion as described by Al-Niaimi et al. Randomization was performed after enrollment but before surgery. A blocked randomization schema was used to determine the allocation, and randomization was performed by research staff not in the operating room and communicated to surgical staff through secure digital software.

Participants were masked as they were not informed regarding which intervention they received while being anesthetized before their procedure. It was not feasible to mask the surgeon, as the 2 antiseptic preparations look distinctly different after application. Outcomes assessors were masked to the allocation as the allocation was not included in the medical record.

The primary outcome was the rate of symptomatic UTIs within 2 weeks after surgery. The secondary outcomes included vaginal irritation based on a 5-point Likert scale on postoperative day 1; symptomatic, culture-proven UTI within 2 weeks after surgery (defined as ≥10,000 colony-forming units); SSIs within 2 weeks after surgery; and any symptomatic UTI up to 6 weeks after surgery.

We conducted a sample size calculation based on a noninferiority study design and a between-group difference of ≤10% (or 50% overall UTI rate relative difference) using a baseline postoperative UTI estimate of 20% based on the range found in the urogynecologic literature. ^, This demonstrated that we would need 58 participants per group (CHG vs iodine) to detect noninferiority for our primary outcome with an alpha of 0.05 and with 80% power. Assuming a dropout rate of 20%, we anticipated enrolling at least 146 participants but planned to continue to recruit participants until we reached our primary endpoint of 2 week follow-up for 116 participants or 58 participants in each group. We later increased the anticipated enrollment numbers to allow up to 200 participants because of COVID-19 surgical rescheduling and cancellations to reach power for our primary outcome.

We evaluated between- and within-group differences using the Fisher exact test for categorical variables and t tests for continuous variables. Intention-to-treat analyses were performed for primary and secondary outcomes. Next, we performed per-protocol analyses to determine if treatment received significantly altered the results. An inferiority margin of relative risk (RR) of 1.50 was selected. Our null hypothesis was that CHG was not noninferior to iodine; in this case, the upper limit of the 95% confidence interval (CI) would exceed 1.50. As the test was single sided, our expected 95% CI would be single bounded, with the lower limit extending to negative infinity. The reason for this selection was to amplify our examination of the upper limit of the 95% CI. For other analyses, a threshold of P <.05 was selected to denote statistical significance. Statistical analyses were conducted using the JMP software (version 9.0.0; SAS Institute Inc, Cary, NC). The study followed the Consolidated Standards of Reporting Trials (CONSORT) guidelines for reporting randomized trials.

Results

A total of 158 participants met the eligibility criteria and were subsequently enrolled in the study from August 2019 to January 2021. Figure 1 reports the disposition of participants according to the CONSORT guidelines. Of note, 3 participants were initially offered participation; however, on review, the participants were noted to have an allergy to one of the antiseptic agents and therefore were excluded from the study before enrollment. Moreover, 2 participants had surgical delays because of medical issues, and an additional 19 participants were enrolled but never had surgery because of operating room closure during the COVID-19 pandemic; these 21 participants were removed from the study before randomization. The remaining 137 participants were randomized; 65 and 72 participants were allocated to iodine and CHG, respectively. In addition, 119 participants completed the primary outcome at 2 weeks follow-up for symptomatic UTI, and 18 participants were lost to follow-up. However, 1 protocol deviation occurred, and the participant received iodine instead of CHG and was analyzed on the basis of intention to treat.

Flow diagram of the study participants

Rockefeller et al. Vaginal chlorhexidine and iodine in urogynecologic surgery. Am J Obstet Gynecol 2022 .

Baseline demographic characteristics and pertinent medical and surgical histories of the study participants are shown in Table 1 . There was no statistically significant difference between the groups in any baseline characteristics. Surgical details are described in the Appendix ; there was no statistically significant difference between the iodine and CHG groups in surgery type (hysterectomy, P =.88; apical suspension, P =.99; midurethral sling, P =.28), perioperative antibiotics ( P =.99), operative time (123±105 vs 120±115 minutes; P =0.49), or Foley catheter use intraoperatively (93% vs 93%; P >.99) or at discharge (23% vs 17%; P =.35). Additional surgical classifications can be found in the Appendix .

Table 1

Demographic characteristics

Characteristic	Povidone-iodine	Chlorhexidine gluconate	P value
Patients, n	58	61	—
Age (y), mean±SD	57±12	58±13	.54
Ethnicity			.10
African American	2 (3)	0 (0)
White	20 (34)	30 (49)
Latino or Hispanic	25 (43)	26 (42)
American Indian	12 (21)	5 (8)
Other	4 (7)	2 (3)
Assisted living or nursing facility	0 (0)	1 (2)	.51
Health insurance			.98
Private	24 (41)	30 (49)
Medicaid of Medicare	26 (45)	32 (52)
VA Healthcare	4 (7)	5 (8)
Self-pay	0 (0)	1 (2)
Other or unknown	9 (16)	9 (15)
Menopausal	39 (67)	42 (69)	.99
Hormone replacement
Vaginal estrogen	11 (19)	17 (28)	.35
Hormonal birth control pills	4 (7)	2 (3)	.63
Overactive bladder medications	4 (7)	6 (10)	.80
Overactive bladder procedures	5 (7)	7 (11)	.83
Recurrent UTI	9 (16)	17 (28)	.15
Current prophylactic antibiotics for recurrent UTI	2 (3)	4 (7)	.63
Diabetes mellitus	7 (13)	9 (15)	.87
Tobacco smoking	4 (7)	8 (13)	.41
Previous hysterectomy	24 (41)	19 (31)	.33
Previous prolapse surgery	6 (10)	8 (13)	.85

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