Letter to the Editor. The efficacy of local vancomycin for reducing surgical site infections after cranioplasty

Ravi Sharma MBBS, Manoj Phalak MCh and Varidh Katiyar MBBS
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  • All India Institute of Medical Sciences, New Delhi, India
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TO THE EDITOR: We read with keen interest the article by Abode-Iyamah et al.2 regarding the use of vancomycin powder (VP) to prevent surgical site infection (SSI) in patients undergoing first-time cranioplasty (Abode-Iyamah KO, Chiang HY, Winslow N, et al: Risk factors for surgical site infections and assessment of vancomycin powder as a preventive measure in patients undergoing first-time cranioplasty. J Neurosurg [epub ahead of print May 12, 2017. DOI: 10.3171/2016.12.JNS161967]). We commend the authors for undertaking an evaluation of the risk factors for SSI following cranioplasty and its prevention by the application of topical vancomycin. However, there are some concerns with this article that merit discussion. In their study, for the definition of SSI, the authors took into consideration any infection occurring a year after surgery. The reason the authors cited for this was the placement of implants in cranioplasties, and no further justification was provided.

The authors mentioned that according to their protocol, individuals with penicillin allergy received intravenous (IV) vancomycin as antibiotic prophylaxis. It would have been interesting to know how many patients in the 2 patient groups had penicillin allergy and received IV vancomycin. It could be a cause of bias in their study and should have been mentioned. Further, there was no evaluation for vancomycin allergy in the patients. We suspect that vancomycin allergy may play a role in altering the efficacy of VP.

It is mentioned that during the initial craniectomy, dural substitute was placed over the native dura without watertight dural closure. The choice of the material used was dural repair or DuraMatrix (Stryker), per senior surgeon preference. There was no additional treatment of this layer during the cranioplasty procedure. It has not been determined whether the specific implant used makes any difference in the rates of infection and efficacy of VP.

Since the study was retrospective, the criterion determining who received VP and who did not is unclear. There may have been some differences in the patients belonging to the 2 groups with regard to surgeon preference or doubt about intraoperative contamination or something else. The reason for using VP in the treatment group should have been studied to eliminate possible biases by the authors.

The dosage of the VP was not decided by any standardized method; 500–2000 mg was applied based on subjective assessment of the wound size, and no steps were taken to measure the local vancomycin concentration attained. Moreover, the lack of watertight closure during the initial dural repair and placement of the drain in the space where the VP was applied makes one wonder whether an adequate antimicrobial concentration was maintained for a sufficient duration or whether it was washed away with the drain output. These 2 issues may have led to highly variable local vancomycin concentrations, leading to erroneous results and conclusions. In this regard, it is worth mentioning the methodology of Abdullah et al.1 wherein they used a single dose of 1 g of vancomycin in every patient and also measured the local concentration of the drug, though the wound size was not taken into account to calculate the dose. Although multiple craniotomies before cranioplasty were found to be associated with SSI, this variable was excluded from the multivariate analysis without mention of any reason for doing so.

Shibahashi et al.3 have reported that operative time is a major determinant of SSI after cranioplasty. However, Abode-Iyamah et al. found this variable to be non-significant in the univariate analysis. Furthermore, diabetes, which is expected to be an important factor, lost its significance in the multivariate analysis. These observations suggest that the power of their study was too small to detect the impact of VP on decreasing an already low SSI rate. The study power seemed to have been further decreased by nonstandard dosing and the placement of subgaleal drains.

It is very commendable that the authors themselves noted many of these drawbacks of their study, but because of these drawbacks the study fails to contribute to the topic of interest. A prospective study taking into account all of the above factors as well as those already included in the study will be more informative regarding the usefulness of topical vancomycin in reducing SSIs following cranioplasty.

Disclosures

The authors report no conflict of interest.

References

  • 1

    Abdullah KG, Attiah MA, Olsen AS, Richardson A, Lucas TH: Reducing surgical site infections following craniotomy: examination of the use of topical vancomycin. J Neurosurg 123:16001604, 2015

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  • 2

    Abode-Iyamah KO, Chiang HY, Winslow N, Park B, Zanaty M, Dlouhy BJ, : Risk factors for surgical site infections and assessment of vancomycin powder as a preventive measure in patients undergoing first-time cranioplasty. J Neurosurg [epub ahead of print May 12, 2017, DOI: 10.3171/2016.12.JNS161967]

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  • 3

    Shibahashi K, Hoda H, Takasu Y, Hanakawa K, Ide T, Hamabe Y: Cranioplasty outcomes and analysis of the factors influencing surgical site infection: a retrospective review of more than 10 years of institutional experience. World Neurosurg 101:2025, 2017

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  • 1 University of Iowa Carver College of Medicine, Iowa City, IA;
  • 2 University of Iowa Hospitals and Clinics, Iowa City, IA; and
  • 3 University of Iowa College of Public Health, Iowa City, IA
Keywords:

Response

We thank the editor for the opportunity to address the concerns raised by Sharma et al. in response to our published paper “Risk factors for surgical site infections and assessment of vancomycin powder as a preventive measure in patients undergoing first-time cranioplasty.” The authors raised some concerns needing further clarification, which we believe will be beneficial to all readers. With regard to the duration of monitoring for SSI, the National Healthcare Safety Network’s definition of SSI changed from “infection that occurs within one year of procedures that involved implantation” to “infection that occurs within 90 days, with or without implantation.”2,3 We used the prior definition since the definition was changed during our study period. In addition, given that many infections after primary cranioplasty have a delayed onset and that infections associated with implants can have significant adverse effects, we believe that patients should be followed up for 1 year so that all SSIs related to cranioplasty implants are identified.

Our institutional protocol specifies that patients with penicillin allergy receive IV vancomycin as antibiotic prophylaxis. We identified patients who were allergic to penicillin based on their reported medication allergy history. In general, we do not test patients for antibiotic allergies before surgical interventions. While vancomycin can cause adverse effects, such as red man syndrome, such reactions should not affect the antibiotic’s efficacy in preventing infection and should not affect our study results. In addition, we did not identify adverse reactions related to VP or IV vancomycin.

In general, we used Durepair (Medtronic Inc.) or DuraMatrix (Stryker Inc.) for dural substitute/duraplasty after the initial craniectomy. We did not administer additional treatments to this layer during the cranioplasty. If the dura mater was torn during the dissection for the cranioplasty, it was reapproximated with 4-0 Nurolon sutures. We agree that no prior study has evaluated the efficacy of these materials and VP, but this issue could not be addressed in our retrospective study.

As stated in our paper, we began using VP as a departmental quality improvement initiative based on the results in spine procedures.4,5,7 Initially, neurosurgeons adopted this intervention slowly, and they determined who should and should not receive VP based on their own preferences rather than on written criteria. Most surgeons in our department eventually began using VP, and it is now used commonly. Because the use of VP during cranial procedures had not been reported on previously, the dose of VP initially varied in part because wound size varied and in part because some surgeons were concerned about toxicity (for example, seroma). However, our paper and that of Abdullah et al. have shown that VP can be safely used even in a setting in which watertight closure was not established during the initial craniectomy.1 We recommended that surgeons place a drain when VP is applied to surgical incisions made during spinal and cranial operations because VP creates an osmotic gradient that could increase the risk of seroma. In addition, Abdullah et al. noted that they placed drains in patients who received topical VP. However, it is unclear how Abdullah et al. obtained the concentration after craniotomy, probably from the drain at the time intervals they mentioned.1

In our multivariable analysis, neither operation duration nor diabetes, the risk factors that have been identified in previous studies, was significantly associated with SSI. In Shibahashi et al.’s study,6 the mean surgical duration was 132 minutes for patients with SSI and 76 minutes for those without SSI (p < 0.001). In our study, the mean operative duration was 132.7 minutes for patients with SSI and 142.1 minutes for those without SSI (p = 0.57), times comparable to the operative duration for patients with SSI in Shibahashi et al.’s study. Diabetes was more prevalent in patients with SSIs than in those without SSIs in our study (26.7% vs 9.1%, p = 0.05 on bivariable analysis). However, after adjusting for other risk factors in the multivariable analysis, diabetes was no longer significant. The power of a statistical test is mainly affected by the distribution of the variables of interest (that is, risk factors for SSI) in the study population, the magnitude of the effect of interest (that is, odds ratio), and the sample size. The narrower the variable distribution, the bigger the effect size, and the larger sample size can result in higher power. In addition, the statistical significance in a multivariable analysis is further affected by other variables included in the multivariable model. Our study could have been underpowered to detect a significant association for operative duration or diabetes with SSI; however, those were not the main factors of interest in our study. Nonetheless, we agree that both operation duration and diabetes are important modifiable risk factors that should be addressed by surgeons. Interventions that can control blood glucose levels and surgical techniques that can shorten the procedure duration should be implemented to lower the risk of infection after cranioplasty.

We appreciate the authors’ interest in our paper. Most of their concerns should have been addressed in the original paper. While a retrospective observational study can be affected by bias, such studies provide important information and a foundation for further studies. Future prospective studies could add to our knowledge regarding the efficacy of interventions to prevent SSI in patients undergoing cranioplasty.

References

  • 1

    Abdullah KG, Attiah MA, Olsen AS, Richardson A, Lucas TH: Reducing surgical site infections following craniotomy: examination of the use of topical vancomycin. J Neurosurg 123:16001604, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Centers for Disease Control and Prevention: The National Healthcare Safety Network (NHSN) Manual: Procedure-associated Module: Division Surgical Site Infection (SSI). (http://www.cdc.gov/nhsn/pdfs/pscmanual/9pscssicurrent.pdf) [Accessed November 3, 2017]

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  • 3

    Horan TC, Gaynes RP, Martone WJ, Jarvis WR, Emori TG: CDC definitions of nosocomial surgical site infections, 1992: a modification of CDC definitions of surgical wound infections. Infect Control Hosp Epidemiol 13:606608, 1992

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    • Export Citation
  • 4

    Khan NR, Thompson CJ, DeCuypere M, Angotti JM, Kalobwe E, Muhlbauer MS, : A meta-analysis of spinal surgical site infection and vancomycin powder. J Neurosurg Spine 21:974983, 2014

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    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    O’Neill KR, Smith JG, Abtahi AM, Archer KR, Spengler DM, McGirt MJ, : Reduced surgical site infections in patients undergoing posterior spinal stabilization of traumatic injuries using vancomycin powder. Spine J 11:641646, 2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Shibahashi K, Hoda H, Takasu Y, Hanakawa K, Ide T, Hamabe Y: Cranioplasty outcomes and analysis of factors influencing surgical site infection: a retrospective review of more than 10 years of institutional experience. World Neurosurg 101:2025, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Sweet FA, Roh M, Sliva C: Intrawound application of vancomycin for prophylaxis in instrumented thoracolumbar fusions: efficacy, drug levels, and patient outcomes. Spine (Phila Pa 1976) 36:20842088, 2011

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    • PubMed
    • Search Google Scholar
    • Export Citation

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Contributor Notes

INCLUDE WHEN CITING Published online February 16, 2018; DOI: 10.3171/2017.7.JNS171589.

Disclosures The authors report no conflict of interest.

  • 1

    Abdullah KG, Attiah MA, Olsen AS, Richardson A, Lucas TH: Reducing surgical site infections following craniotomy: examination of the use of topical vancomycin. J Neurosurg 123:16001604, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Abode-Iyamah KO, Chiang HY, Winslow N, Park B, Zanaty M, Dlouhy BJ, : Risk factors for surgical site infections and assessment of vancomycin powder as a preventive measure in patients undergoing first-time cranioplasty. J Neurosurg [epub ahead of print May 12, 2017, DOI: 10.3171/2016.12.JNS161967]

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Shibahashi K, Hoda H, Takasu Y, Hanakawa K, Ide T, Hamabe Y: Cranioplasty outcomes and analysis of the factors influencing surgical site infection: a retrospective review of more than 10 years of institutional experience. World Neurosurg 101:2025, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 1

    Abdullah KG, Attiah MA, Olsen AS, Richardson A, Lucas TH: Reducing surgical site infections following craniotomy: examination of the use of topical vancomycin. J Neurosurg 123:16001604, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Centers for Disease Control and Prevention: The National Healthcare Safety Network (NHSN) Manual: Procedure-associated Module: Division Surgical Site Infection (SSI). (http://www.cdc.gov/nhsn/pdfs/pscmanual/9pscssicurrent.pdf) [Accessed November 3, 2017]

    • Export Citation
  • 3

    Horan TC, Gaynes RP, Martone WJ, Jarvis WR, Emori TG: CDC definitions of nosocomial surgical site infections, 1992: a modification of CDC definitions of surgical wound infections. Infect Control Hosp Epidemiol 13:606608, 1992

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Khan NR, Thompson CJ, DeCuypere M, Angotti JM, Kalobwe E, Muhlbauer MS, : A meta-analysis of spinal surgical site infection and vancomycin powder. J Neurosurg Spine 21:974983, 2014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    O’Neill KR, Smith JG, Abtahi AM, Archer KR, Spengler DM, McGirt MJ, : Reduced surgical site infections in patients undergoing posterior spinal stabilization of traumatic injuries using vancomycin powder. Spine J 11:641646, 2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Shibahashi K, Hoda H, Takasu Y, Hanakawa K, Ide T, Hamabe Y: Cranioplasty outcomes and analysis of factors influencing surgical site infection: a retrospective review of more than 10 years of institutional experience. World Neurosurg 101:2025, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Sweet FA, Roh M, Sliva C: Intrawound application of vancomycin for prophylaxis in instrumented thoracolumbar fusions: efficacy, drug levels, and patient outcomes. Spine (Phila Pa 1976) 36:20842088, 2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

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