Abstract
OBJECTIVE
Surgical site infection (SSI) is a complication linked to increased costs and length of hospital stay. Prevention of SSI is important to reduce its burden on individual patients and the healthcare system. The authors aimed to assess the efficacy of preoperative chlorhexidine gluconate (CHG) showers on SSI rates following cranial surgery.
METHODS
In November 2013, a preoperative CHG shower protocol was implemented at the authors’ institution. A total of 3126 surgical procedures were analyzed, encompassing a time frame from April 2012 to April 2016. Cohorts before and after implementation of the CHG shower protocol were evaluated for differences in SSI rates.
RESULTS
The overall SSI rate was 0.6%. No significant differences (p = 0.11) were observed between the rate of SSI of the 892 patients in the preimplementation cohort (0.2%) and that of the 2234 patients in the postimplementation cohort (0.8%). Following multivariable analysis, implementation of preoperative CHG showers was not associated with decreased SSI (adjusted OR 2.96, 95% CI 0.67–13.1; p = 0.15).
CONCLUSIONS
This is the largest study, according to sample size, to examine the association between CHG showers and SSI following craniotomy. CHG showers did not significantly alter the risk of SSI after a cranial procedure.
Keywords: surgical site infection, chlorhexidine, craniotomy, antisepsis, preoperative showers
Surgical site infection (SSI) ranks among the most common hospital-acquired infections across all surgical procedures.1 SSIs are associated with increased morbidity and mortality, as well as increased length of stay and increased readmission and reoperation rates.1,2 Financial costs alone have been estimated to be upwards of $10 billion annually.2,3 As a result, lowering the number of SSIs after surgical procedures is of great importance for a variety of stakeholders in the healthcare system.
Microorganisms from native skin flora cause the majority of SSIs.4 As such, interventions that reduce the number of microbes present on skin preoperatively may be helpful to reduce the SSI rate. One such intervention is the use of chlorhexidine gluconate (CHG) liquid soap when showering on the days prior to surgery. CHG is an antiseptic with broad-spectrum antimicrobial activity.5 Notably, CHG has been associated with decreased SSI rates after various neurosurgical and nonneurosurgical procedures, ostensibly by reducing native skin microflora.5–8 One study compared SSI in patients who underwent total joint replacement before and after implementation of a skin antisepsis protocol that used 2% CHG cloths and found a reduction in SSIs after CHG cloths were used.8 Furthermore, a previous study examined the implementation of a CHG shower protocol prior to spine surgery and found a significant reduction in SSI rates.5
On the contrary, other evidence suggests that CHG cleansing may have limited utility in preventing SSIs. A Cochrane review of randomized controlled trials scrutinized the effect of CHG antiseptic preparation on SSI rates after surgery.9 This review concluded that the relative risk of SSI following CHG use was comparable to placebo. Furthermore, a meta-analysis illustrated that preoperative CHG bathing did not significantly reduce the risk of SSI compared with soap, placebo, or no shower.10 However, none of the aforementioned trials focused on cranial surgery specifically, and thus the efficacy of CHG in preventing SSI after craniotomy is unknown.
In November 2013, as part of a University of California Health system–wide quality improvement mandate aimed at reducing SSIs after surgery, our institution implemented an antiseptic protocol utilizing preoperative CHG showers. This uniform policy change permits the assessment of SSI in the preimplementation and postimplementation periods.
Methods
This study conformed to STROBE guidelines. All data were anonymized. Because this study was considered a quality improvement initiative, institutional review board approval and patient consent were not required. Data were collected from April 2012 to April 2016. A preoperative shower protocol utilizing CHG was implemented at our institution in November 2013 as part of a quality improvement initiative.
The handout for the CHG shower protocol is shown in Fig. 1.11,12 Patients were instructed to shower with CHG liquid soap a minimum of 3 times before surgery. For each shower, patients were instructed to wash in warm water and apply CHG to all areas of the body except for the eyes, nose, ear canals, and mouth. Patients were then asked to lather and massage their body without water before rinsing with warm water. No specific interval for a prerinse pause was provided. Patients were then instructed to dry themselves with a clean towel. Once dry, patients were asked to abstain from applying lotions and powders.
FIG. 1.
University of California Health protocol for preoperative CHG showering. Reprinted from Chan et al: Neurosurgery 85(6):817–826, 2019.5 Image credit: 2013–2016 University of California, Office of the President (PI: Torriani). Developing standardized operative bundles to decrease surgical site infections (SSI). All rights reserved. Copyright UC Health. Published with permission.
Infection Classification and Outcome Monitoring
The SSI rate and absolute number of SSIs per quarter were identified in accordance with the SSI event identification guidelines of the National Healthcare Safety Network (https://www.cdc.gov/nhsn/pdfs/pscmanual/9pscssicurrent.pdf). The National Healthcare Safety Network also provides information on the surgeons involved in each case and their level of training. Surgeon and resident involvement were logged in the electronic medical record by an in-room circulating nurse at the outset of each surgery. The Department of Hospital Epidemiology and Infection Control at our institution reviewed the records of patients who underwent cranial surgery, as identified by the ICD-9 procedure codes. All surgical procedures occurred at a single facility within our institution, and consecutive patients who fit the inclusion criteria were included. Transsphenoidal procedures were excluded due to the absence of a scalp incision. Wound revisions and incision drainage cases were also excluded. Procedures that were not classified as clean (e.g., clean-contaminated, dirty, infected) were excluded.
During the 90-day surveillance window following the procedure, we used our electronic surveillance system to identify patient records associated with any of the following: 1) positive culture result for tissue, bodily fluid, wound, or blood; 2) return to surgery for incision and debridement; or 3) ICD-9 diagnosis codes suggestive of SSI (996.6, 996.69, 998.51, and 998.58). Patient records meeting any of the abovementioned criteria were then reviewed by an infection preventionist not associated with the present study. SSIs were classified as either superficial or deep. Superficial SSIs were defined as infections that occurred within 30 days of surgery and involved only the skin and subcutaneous tissue, and deep SSIs were defined as infections that occurred within 30 days of surgery and involved deeper layers (e.g., fascial and muscle layers).
Statistical Analysis
Descriptive statistics were used to summarize group characteristics. Quarterly SSI rates and group variables were compared between the preimplementation and postimplementation periods using unpaired t-tests. Quarterly SSI rates and numbers were also stratified by craniotomy region (frontal, parietal, temporal, pterional, retrosigmoid, occipital) and analyzed separately. Means, standard errors, and percentages were reported where appropriate. A multivariable logistic regression model was fit for SSI after controlling for covariates of interest. Covariates included any baseline factor that reached p < 0.05 on univariate analysis. Post hoc power analyses were conducted. Effect sizes were calculated for t-tests using Cohen’s D formula, while the phi coefficient was used to calculate the effect size for chi-square tests. Statistical analyses were conducted using IBM SPSS (version 25, IBM Corp.); p values were 2-tailed, with an alpha value of 0.05 considered statistically significant.
Results
A total of 3126 cranial procedures were performed between April 2012 and April 2016. Eight hundred ninety-two (28.5%) of these procedures occurred before implementation of the CHG shower protocol, and 2234 (71.5%) procedures occurred after protocol implementation. Demographic and procedural characteristics are listed in Table 1. Comparisons were made between the 20 patients with SSI and the 3106 patients without infection. The overall mean SSI rate was 0.6%, with no significant univariate differences between the preimplementation (0.2%) and postimplementation (0.8%) groups (p = 0.11). A greater proportion of patients with infection had resident involvement (p = 0.04) and more than two surgeons (p = 0.03). Additionally, infection was associated with use of postoperative CSF drainage (p < 0.001) and CSF leak (p = 0.001), either as an indication for index surgery or as a postoperative complication. Infection was associated with fewer surgical drain placements (p = 0.04).
TABLE 1.
Patient and surgical characteristics of the overall cohort and patients with and those without SSI
| Characteristic | Overall Cohort (n = 3126) | w/o Infection (n = 3106) | w/ Infection (n = 20) | p Value |
|---|---|---|---|---|
| Age, yrs | 51.40 ± 0.29 | 51.40 ± 0.29 | 50.70 ± 3.43 | 0.84 |
| Male sex | 1554 (49.7) | 1546 (49.8) | 8 (40.0) | 0.52 |
| BMI, kg/m2 | 27.59 ± 0.12 | 27.59 ± 0.12 | 28.47 ± 1.60 | 0.59 |
| Length of stay, days | 5.91 ± 0.13 | 5.92 ± 0.13 | 4.45 ± 0.78 | 0.08 |
| Preop period, days | 1.19 ± 0.05 | 1.19 ± 0.05 | 0.90 ± 0.49 | 0.56 |
| Postop period, days | 4.72 ± 0.11 | 4.73 ± 0.11 | 3.55 ± 0.41 | 0.12 |
| Hypertension | 867 (27.7) | 863 (27.8) | 4 (20.0) | 0.60 |
| Diabetes mellitus | 284 (9.1) | 283 (9.1) | 1 (5.0) | 0.81 |
| History of non-CNS malignancy | 332 (10.6) | 331 (10.7) | 1 (5.0) | 0.65 |
| History of chemotherapy | 355 (11.4) | 353 (11.4) | 2 (10.0) | >0.99 |
| History of radiation therapy | 461 (14.7) | 458 (14.7) | 3 (15.0) | >0.99 |
| ASA score >II | 1420 (45.4) | 1410 (45.4) | 10 (50.0) | 0.85 |
| Smoker | 483 (15.6) | 479 (15.4) | 4 (20.0) | 0.80 |
| Prior cranial procedure | 1060 (33.9) | 1056 (34.0) | 4 (20.0) | 0.28 |
| Surgical pathology | ||||
| Tumor | 1883 (60.2) | 1866 (57.6) | 17 (85.0) | 0.38 |
| Vascular | 392 (12.5) | 392 (12.6) | 0 (0.0) | |
| Functional | 371 (11.9) | 369 (11.9) | 2 (10.0) | |
| Epilepsy | 237 (7.6) | 236 (7.6) | 1 (5.0) | |
| Hematoma | 100 (3.2) | 100 (3.2) | 0 (0.0) | |
| Repair | 72 (2.3) | 72 (2.3) | 0 (0.0) | |
| Other | 71 (2.3) | 71 (2.3) | 0 (0.0) | |
| Preop CHG shower | 2234 (71.5) | 2216 (71.3) | 18 (90.0) | 0.11 |
| Preop steroids | 549 (17.6) | 547 (17.7) | 2 (10.0) | 0.55 |
| Intraop steroids | 2547 (81.5) | 2529 (81.4) | 18 (90.0) | 0.49 |
| Postop steroids | 2531 (81.0) | 2514 (80.9) | 17 (85.0) | >0.99 |
| Intraop antibiotics | 3062 (98.0) | 3042 (97.9) | 20 (100) | >0.99 |
| Postop antibiotics | 2721 (87.0) | 2701 (87.0) | 20 (100) | 0.09 |
| Resident involvement | 2241 (71.7) | 2222 (71.5) | 19 (95.0) | 0.04 |
| >2 surgeons | 955 (30.6) | 944 (30.4) | 11 (55.0) | 0.03 |
| Site of craniotomy | ||||
| Frontal | 1118 (38.0) | 1110 (38.0) | 8 (40.0) | 0.057 |
| Parietal | 575 (18.4) | 572 (18.4) | 3 (15.0) | |
| Temporal | 665 (21.3) | 663 (21.3) | 2 (10.0) | |
| Pterional | 119 (3.8) | 117 (3.8) | 2 (10.0) | |
| Retrosigmoid | 115 (3.7) | 112 (3.6) | 3 (15.0) | |
| Occipital | 464 (14.8) | 462 (14.9) | 2 (10.0) | |
| Implants | 2770 (88.6) | 2750 (88.5) | 20 (100.0) | 0.21 |
| Sealant | 2385 (76.3) | 2367 (76.2) | 18 (90.0) | 0.24 |
| Drains | 1269 (40.6) | 1266 (40.8) | 3 (15.0) | 0.04 |
| CSF drains | 553 (17.7) | 539 (17.4) | 14 (70.0) | <0.001 |
| Op time, mins | 235.72 ± 2.13 | 235.46 ± 2.13 | 276.90 ± 22.80 | 0.08 |
| Estimated blood loss, ml | 203.47 ± 6.20 | 203.69 ± 6.24 | 182.00 ± 27.12 | 0.45 |
| CSF leak | 62 (2.0) | 59 (1.9) | 3 (15.0) | 0.001 |
Values are shown as mean ± SD or number (%). Boldface type indicates statistical significance (p < 0.05).
Table 2 compares the patient and surgical characteristics of the preimplementation cohort with those of the postimplementation cohort. Univariate analyses found significant differences (p < 0.05) between groups with respect to diabetes mellitus, American Society of Anesthesiologists (ASA) score, resident involvement, postoperative antibiotics, number of surgeons, surgical drains, and operative time. After adjustment for these covariates, implementation of the CHG protocol was not associated with SSI (adjusted OR 2.96, 95% CI 0.67–13.08; p = 0.15). The multivariable analysis results are presented in Table 3. Of note, use of surgical drains was the sole factor associated with a significant reduction in SSI (adjusted OR 0.24, 95% CI 0.07–0.84; p = 0.03).
TABLE 2.
Patient and surgical characteristics of the pre- and postimplementation CHG shower cohorts
| Characteristic | Preimplementation (n = 892) | Postimplementation (n = 2234) | p Value |
|---|---|---|---|
| Age, yrs | 51.75 ± 0.52 | 51.26 ± 0.34 | 0.43 |
| Male sex | 466 (52.2) | 1088 (48.7) | 0.08 |
| BMI, kg/m2 | 27.38 ± 0.23 | 27.67 ± 0.14 | 0.26 |
| Length of stay, days | 6.01 ± 0.23 | 5.87 ± 0.16 | 0.61 |
| Preop period, days | 1.19 ± 0.08 | 1.19 ± 0.06 | 0.99 |
| Postop period, days | 4.82 ± 0.20 | 4.68 ± 0.13 | 0.55 |
| Hypertension | 256 (28.7) | 611 (27.4) | 0.47 |
| Diabetes mellitus | 103 (11.5) | 181 (8.3) | 0.003 |
| History of non-CNS malignancy | 107 (12.0) | 225 (10.1) | 0.13 |
| History of chemotherapy | 114 (12.8) | 241 (10.8) | 0.13 |
| History of radiation therapy | 145 (16.3) | 316 (14.1) | 0.15 |
| ASA score >II | 439 (49.2) | 981 (43.9) | 0.008 |
| Smoker | 153 (17.2) | 330 (14.8) | 0.11 |
| Prior cranial procedure | 311 (34.9) | 749 (33.5) | 0.50 |
| Surgical pathology | |||
| Tumor | 557 (62.4) | 1326 (59.4) | 0.07 |
| Vascular | 89 (10.0) | 303 (13.6) | |
| Functional | 119 (13.3) | 252 (11.3) | |
| Epilepsy | 58 (6.5) | 179 (8.0) | |
| Hematoma | 28 (3.1) | 72 (3.2) | |
| Repair | 21 (2.4) | 51 (2.3) | |
| Other | 20 (2.2) | 51 (2.3) | |
| Preop steroids | 139 (15.6) | 412 (18.4) | 0.07 |
| Intraop steroids | 712 (79.8) | 1835 (82.1) | 0.15 |
| Postop steroids | 709 (79.5) | 1882 (81.6) | 0.20 |
| Intraop antibiotics | 871 (97.6) | 2191 (98.1) | 0.53 |
| Postop antibiotics | 797 (89.3) | 1924 (86.1) | 0.02 |
| Resident involvement | 607 (68.0) | 1634 (73.1) | 0.01 |
| >2 surgeons | 213 (23.9) | 742 (33.2) | <0.001 |
| Site of craniotomy | |||
| Frontal | 342 (38.3) | 846 (37.6) | 0.10 |
| Parietal | 161 (18.0) | 414 (18.5) | |
| Temporal | 208 (23.3) | 457 (20.5) | |
| Pterional | 29 (3.3) | 90 (4.0) | |
| Retrosigmoid | 39 (4.4) | 76 (3.4) | |
| Occipital | 113 (12.7) | 351 (15.7) | |
| Implants | 805 (90.2) | 1965 (88.0) | 0.08 |
| Sealant | 682 (76.5) | 1703 (76.2) | 0.93 |
| Drains | 406 (45.5) | 38.6 (38.6) | 0.001 |
| CSF drains | 159 (17.8) | 394 (17.6) | 0.94 |
| Op time, mins | 243.79 ± 4.29 | 232.50 ± 2.42 | 0.02 |
| Estimated blood loss, ml | 203.55 ± 9.53 | 203.43 ± 7.79 | 0.99 |
| CSF leak | 21 (2.4) | 41 (1.8) | 0.43 |
Values are shown as mean ± SD or number (%). Boldface type indicates statistical significance (p < 0.05).
TABLE 3.
ORs and 95% CIs from binary multivariate logistic regression analysis of SSI
| Variable | OR | 95% CI | p Value |
|---|---|---|---|
| Preop CHG shower | 2.96 | 0.67–13.1 | 0.15 |
| Diabetes mellitus | 0.49 | 0.06–3.76 | 0.49 |
| ASA score >II | 1.36 | 0.56–3.34 | 0.50 |
| Resident involvement | 6.79 | 0.90–51.5 | 0.06 |
| No. of surgeons | 1.72 | 0.66–4.48 | 0.27 |
| Drains | 0.24 | 0.07–0.84 | 0.03 |
| Op time | 1.002 | 0.99–1.01 | 0.19 |
Boldface type indicates statistical significance (p < 0.05).
Cultured Microorganisms Associated With SSI
The cultured microorganisms associated with SSIs in the preimplementation and postimplementation cohorts are shown in Table 4. There were no significant differences in the proportions of resistant microorganisms (2/2 [100.0%] SSI isolates were resistant in the preimplementation cohort vs 3/18 [16.7%] isolates in the postimplementation cohort) (Yates’ χ2 = 2.963; p = 0.09).
TABLE 4.
Causative microorganisms of SSIs in the pre- and postimplementation CHG shower cohorts
| Preimplementation, 2/892 patients w/ SSI (0.2%) |
| Resistant Propionibacterium acnes (1) |
| Methicillin-resistant Staphylococcus epidermidis & Enterobacter aerogenes (1)* |
| Postimplementation, 18/2234 patients w/ SSI (0.8%) |
| Methicillin-sensitive S. aureus (6) |
| Methicillin-resistant S. aureus (2) |
| Pseudomonas aeruginosa (2) |
| Methicillin-sensitive S. epidermidis & P. acnes (1)* |
| Methicillin-resistant S. epidermidis & P. acnes (1) |
| E. aerogenes (1) |
| Rhizopus species (1) |
| P. acnes (1)* |
| Salmonella group D (1) |
| Proteus mirabilis (1) |
| Unknown (1) |
The number of patients is shown in parentheses.
Patient underwent skull base surgery.
Discussion
This is the largest study, in terms of sample size, to examine the association between preoperative CHG showers and SSI following craniotomy. On both univariate and multivariable analyses, implementation of the preoperative CHG showering protocol was not associated with decreased SSI following craniotomy. In predictor analyses, the only identified risk factor of SSI development following craniotomy was the absence of surgical drains.
Some discussion about preoperative factors associated with SSI development is worthwhile. Placement of surgical drains was the sole risk factor that remained significant in our multivariable analysis and was associated with significantly reduced odds of SSI. These data suggest that retained postoperative subgaleal fluid may play an important role in the development of postoperative SSI. Within cranial neurosurgery, surgical drains have not demonstrated a consistent association with SSI.13–15 However, some studies do implicate prolonged drainage (≥ 72 hours) with increased SSI rates.16,17 Interestingly, we did not find a significant association between SSI development and diabetes mellitus, ASA score, operative time, number of surgeons, and resident involvement following cranial surgery. Diabetes mellitus is a relatively well-known risk factor for SSI following multiple procedure types, as well as for craniotomies specifically.18–20 Similarly, some evidence demonstrates that an ASA score > II is related to increased rates of SSI.21–23 Other studies have demonstrated an association between increased operative time and development of SSI.23–25 With respect to personnel within the operating room, involvement of residents does not seem to have a consistent association with SSIs, and there seems to be a dearth of data on the total number of surgeons and specifically the number of surgeons during craniotomy.26,27 In our series, patients with more than two surgeons often underwent skull base surgery, which accounted for 3 (15%) of our SSIs. These cases were likely correlated with increased surgical times, as well as factors unique to skull base surgery such as crossing of the paranasal sinuses.
The evidence relating preoperative CHG showers to the development of postoperative SSI is inconsistent. In 1987, a randomized controlled trial found that, over a 2-year period, preoperative CHG showers significantly decreased infection following elective surgery (9.1% infection rate) compared with placebo (11.7%) or soap (12.8%).28 In 1983, a separate crossover study involving general, gynecological, orthopedic, and urological surgery patients found that, over a 60-week period, CHG bathing (5.4% SSI rate) was not associated with a notable decrease in SSI compared with preoperative bathing with unmedicated soap (4.9%).29 More recent evidence has continued to show inconsistent results, with studies showing both decreased30 and even increased SSI31 when preoperative CHG showers were used.
A limited number of studies have included CHG showers in analyses of infection specifically following cranial surgery. In an examination of the use of a standardized protocol to reduce shunt infection, the Hydrocephalus Clinical Research Network found that preoperative hair washing with CHG shampoo was significantly associated with a decreased infection rate (3.4% of 477 patients vs 7.4% of 620 patients; p = 0.004).32 Furthermore, no differences in bacterial meningitis rates were observed in a retrospective examination of a staphylococcal decolonization regimen that involved a daily body bath with 4% CHG and intranasal application of 10% betadine ointment (622 elective craniotomies performed before regimen implementation vs 727 elective craniotomies performed after implementation). Interestingly, there was a significantly reduced risk of aseptic meningitis.33
Additional studies on the effects of CHG have been performed in the presence of screening protocols for nasal Staphylococcus aureus. S. aureus is the most common cause of SSI, with mupirocin administration to the nares and CHG to the skin being the cornerstone of decolonization protocols.34 A study that compared the use of a screening protocol, which administered mupirocin to 63 patients with S. aureus who underwent deep brain stimulation, with 119 control patients found a significant decrease in SSI in the screening group (1.6% vs 10.9%, respectively; p = 0.04).35 A prospective, randomized controlled trial with 84 patients who underwent head and neck surgery—of which 42 patients underwent a preoperative 5-day regimen of CHG skin rinses and received intranasal mupirocin, and the other patients did not undergo a decolonization regimen—found a trend toward decreased SSI after decolonization, but significance was not reached (p = 0.079).36 These results suggest that prophylaxis against methicillin-resistant S. aureus may warrant further consideration.
Although there was no significant association between SSI and preoperative CHG showers in patients who underwent craniotomy, an investigation by Chan et al. on the effect of this CHG protocol on SSI after spine surgery found a decrease in the odds of SSI.5 This suggests differences in the utility of CHG between patients undergoing cranial and spinal procedures. Both the study by Chan et al. (investigating spine surgery) and the present study (in unadjusted analyses) revealed that an increased number of surgeons was a risk factor for SSI, but the studies did not identify any other identifiable risk factors.5 The higher proportion of patients in our SSI cohort who underwent cranial surgery that involved more than two surgeons may reflect longer, more complex operations with skull base approaches that required assistance from otolaryngology.37
A study by Guzel et al. cultured skin flora samples from 100 patients before 50 cranial and 50 spinal procedures and found similar percentages of patients with coagulase-negative staphylococci and S. aureus before and after 3-minute cleaning with a CHG antiseptic.38 This suggests that there should be no differences between CHG application to the scalp versus the spine; however, differences in application of CHG to the scalp may be indicated, particularly given the presence of hair. This may partially explain the lack of effect seen in the present study. Moreover, the proximity of the nares may be crucial in patients with S. aureus, considering that 40% of the observed SSIs involved S. aureus bacteria. Indeed, this notion is further supported by evidence suggesting the benefits of intranasal mupirocin in decolonization regimens for patients undergoing craniotomy.35,36,38
Study Limitations
This study is not without several important limitations. First, due to its retrospective nature, this study is inherently limited by the ongoing evolution of surgical practice. Over time, shaving the scalp has been eliminated, and instead clippers are used to remove hair. Subgaleal drains are increasingly used postoperatively, povidone-iodine is used to rinse tissues after the dura mater is closed,39 and antibiotic powder (e.g., vancomycin powder) is applied to the subgaleal space prior to closure, in addition to personnel changes and procedure types that cannot be fully taken into account. On the other hand, at our institution, most patients received preoperative intravenous antibiotics, most commonly cefazolin. To ensure antibiotic administration, we incorporated perioperative antibiotic administration into the operative timeout required before each procedure’s incision. Moreover, there were no other concurrent quality improvement protocols regarding cranial SSI in the study period.
Furthermore, whether this particular protocol is the most optimal with respect to CHG dose and concentration, shower frequency, and shower duration has not been fully delineated.40 Second, this study did not compare CHG with other potential preoperative antiseptics, and thus analysis of multiple antiseptics is beyond this study’s capabilities. Third, stringent criteria were used to determine each SSI (i.e., SSI definitions of the National Healthcare Safety Network), possibly leading to a lower rate of infection of 0.6% compared with reports of 1.6%–9% in the literature.23,41,42 Our SSI rate may not account for patients whose admissions for SSI were outside the University of California, San Francisco system. Indeed, these may not have been captured by the data provided to us by the National Healthcare Safety Network. This is especially important considering the possibility of indolent infection occurring outside the 30-day postoperative period (i.e., the window used to define SSI in our series). However, we do not believe that this impacted our results to a significant extent, given that an analysis of 93,920 nonemergency craniotomies by Buchanan et al. found only an additional 682 (0.74%) readmissions for SSI within 30 to 90 days following surgery.18 Moreover, our study did not include other infections such as meningitis that may have been affected by CHG antiseptics.
Additionally, rates of compliance with the protocol were not ascertainable; thus, compliance bias may affect our results.43,44 Of note, when intraoperative imaging guidance was planned, several practitioners requested the placement of scalp-based fiducial markers for registration of imaging to physical space, but others did not. Imaging studies with fiducials were typically completed the evening before surgery. Patients with fiducials in place were specifically instructed not to remove the fiducials or wash their hair the night before surgery. We did not control for the placement of fiducials in this analysis. In a similar fashion, although the placement of drains was accounted for, the length of time that these drains were in place was unavailable and therefore not adjusted for in our analysis. Typically, however, drains are removed on postoperative day 1 at our institution. Importantly, in other unpublished analyses of our surgical drain protocol, we have not found a correlation between length of drain placement and development of SSI.
This study had relatively low power (45%) to detect differences between patients with and those without infection based solely on preoperative CHG showering. The effect size between patients with and those without infection was also small (0.07). Yet, based on a similar paper by Abode-Iyamah et al. that assessed the use of vancomycin powder,19 the effect size can be expected to be small in the context of low SSI rates. To reach 80% statistical power with our current effect size, the overall patient cohort would need to more than double, to a total of 7895 patients.
Conclusions
This is the largest study to examine the association between preoperative CHG showering and SSI following craniotomy. CHG showering was not associated with decreased SSI following cranial surgery, even after we adjusted for potential confounding variables. In multivariable-adjusted analyses, use of surgical drains was the sole factor associated with reduced SSI. Further prospective studies are needed to better define any potential impact CHG showering may or may not have on SSI rates following cranial surgery.
Acknowledgments
We would like to acknowledge Drs. Anette Molinaro and Yalan Zhang for their assistance with the statistical analysis of this study.
Disclosures
Dr. Chan receives support for non-study-related research from Orthofix Medical, Inc. Dr. Mummaneni is a consultant for DePuy Synthes, Globus, and Stryker; has direct stock ownership in Spinicity/ISD; receives support for non-study-related research from AO Spine, ISSG, and NREF; receives royalties from DePuy Synthes, Thieme Publishers, and Springer Publishers; and has grants from AO Spine and ISSG. Dr. Chang receives funding from the National Institutes of Health (grants R01-DC012379, R00-NS065120, and DP2-OD00862) and the Esther A. and Joseph Klingenstein Fund. Dr. Larson received honoraria from Medtronic, grants from Voyager Therapeutics, and nonfinancial support from MRI Interventions. Dr. Starr is a consultant for Medtronic and Boston Scientific and receives research support from Medtronic. Dr. McDermott is a consultant for Stryker.
ABBREVIATIONS
- ASA
American Society of Anesthesiologists
- CHG
chlorhexidine gluconate
- SSI
surgical site infection
Footnotes
Supplemental Information
Current Affiliations
Dr. Lawton: Department of Neurosurgery, Barrow Neurological Institute, Phoenix, AZ.
Dr. McDermott: Miami Neuroscience Institute, Miami, FL.
References
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