Surgical Site Infection: Prevention, Diagnosis, and Treatment

Michael Glotzbecker, MD

Jean-Christophe Leveque, MD

PEDIATRIC SURGICAL SITE INFECTIONS

Why Do SSI After Pediatric Spinal Surgery Matter?

Prevention of surgical site infections (SSIs) after pediatric spinal surgery has received significant attention recently given the profound consequences of this complication.¹,²,³,⁴,⁵,⁶ If diagnosed with a SSI, patients may require multiple trips to the operating room, extended hospitalizations, and long-term treatment with antibiotics. Direct costs related to hospitalization associated with a pediatric SSI after posterior spinal fusion (PSF) have been estimated to range between $26 977 and $961 722.³ In addition to the direct costs to the health care system and the patient, there are significant psychological and other indirect costs the family must shoulder associated with unexpected hospital admissions, additional doctor visits, as well as missed work and school.⁷,⁸ For this reason, there is incentive for local institutions as well as multicenter collaboratives to identify and refine processes to prevent SSIs and minimize the impact when this complication is encountered.

Acute SSIs are defined as occurring within 3 months of the index procedure based on the Center for Disease Control (CDC) guidelines,⁹ while chronic/delayed SSIs occur more than 3 months after PSF. While the acute SSI rate in healthy children who are treated with PSF with adolescent idiopathic scoliosis (AIS) is relatively low, the reported SSI rate has been reported to be as high as 30% in populations with neuromuscular disease (myelodysplasia, cerebral palsy, etc.).⁴,¹⁰,¹¹,¹²,¹³,¹⁴,¹⁵,¹⁶,¹⁷,¹⁸,¹⁹,²⁰,²¹,²²,²³,²⁴ A recent multicenter study of 946 patients demonstrated the SSI rate to be 9.2% and 2.6% in neuromuscular and AIS populations, respectively.²⁵ The rate after PSF in complex patients is unacceptably high and highlights the scope of the current problem. Further, the predicted and observed readmission rate following PSF is highly variable between institutions.²⁶ The high SSI rate and high variability in rates between institutions represents a clear area to focus process improvement efforts as even a small reduction in the SSI rate in these high-risk populations could have significant social and financial impact.

What Do We Know Regarding Microbiology in SSIs?

The most common infecting organisms in acute SSIs are Staphylococcus aureus and Staphylococcus epidermis. S aureus accounts for about 60% of infections, but polymicrobial and/or gram-negative organisms are frequently found in up to 45% of neuromuscular cases.⁵,²²,²⁵,²⁷ Gram-positive anaerobic rods (Propionibacterium acnes) are asymmetrically identified in patients with AIS diagnosed with latent infections.²⁷,²⁸

We also know that the operating room may not be as “sterile” as we think. There is a known baseline contamination rate of the surgical wound and implants. In a study of 105 consecutive noninfection cases, there was a 9.5% contamination rate of spinal implants, although this rate was reduced to 2% when the implants were covered.²⁹ Similarly, a report of intraoperative wound cultures prior to closure showed a 23% contamination rate.³⁰ The correlation of this baseline bacterial contamination and SSI infection rate as well as our ability to influence it with local factors (antibiotics, irrigation) is not understood.

What Do We Know About Preoperative Risk Factors for Pediatric SSI?

There are a number of studies that have considered preoperative risk factors for SSI in pediatric patients. Some of these risk factors are not modifiable. However, factors that may be modified present an opportunity mitigation of risk through preoperative optimization.³¹ Potentially, the most important risk factor is not modifiable, as nonidiopathic diagnosis/ASA status, or the presence of a G/GJ tube carries a much higher risk of SSI.²⁰,²³,²⁴,²⁵,³²,³³

In contrast, both obesity²²,³³,³⁴ as well as malnutrition³⁵ have been identified as SSI risk factors that can be assessed and modified prior to surgical intervention. Similarly, a positive urine culture, particularly in patients with myelomeningocele is an independent risk factor for SSI in these patients with the organism cultured from the urine being the causative organism for the SSI in two-thirds of patients.³⁶,³⁷ Pretesting and decolonization in patients with myelomeningocele therefore may reduce SSI risk in these patients.

Unfortunately, the literature is relatively poor in defining preoperative risk factors. Two recent systematic reviews have assessed the literature and gave grades of recommendation for perioperative risk factors. In the first,³⁸ there was no grade A evidence for preoperative risk factors, and there was grade B evidence that underlying neuromuscular disease and urinary/bowel incontinence increase the risk of SSI. There was grade C evidence for modifiable risk factors such as malnutrition, obesity, and a positive urine culture increasing the risk of SSI. In a more recent systematic review of 167 studies,³⁹ there was grade C evidence that obesity increased the risk of infection, and there were insufficient data to make conclusions regarding any other preoperative factors including incontinence, preoperative bowel prep, or malnutrition.

What Do We Know About Intraoperative Risk Factors for Pediatric SSI?

Multiple studies have demonstrated that proper antibiotic dosing within 1 hour of skin incision is an important factor in reducing SSI risk.²²,⁴⁰,⁴¹,⁴² There is no published evidence in pediatric spinal surgery skin preparation technique; however, many have adopted the use of chlorhexidine-alcohol over povidone-iodine based
on a randomized control trial in the general surgery literature that demonstrated a reduction in both deep and superficial SSI rates.⁴³

Intraoperative factors that have been suggested to increase SSI rates include hypothermia,³⁴ operative time,³⁰,³³ implant prominence (unit rods),¹⁰,³² and instrumentation to the pelvis.¹⁴,²⁵ There are several studies that suggest that stainless steel implants have a higher risk of late infection compared to titanium implants.⁴⁴,⁴⁵,⁴⁶ The data surrounding the use of drains are conflicting, with the majority of studies demonstrating no difference. However, a few studies have suggested that there may be a benefit.²²,⁴⁷,⁴⁸

As mentioned previously, there is a baseline contamination rate of surgical wounds, and therefore, local strategies may have merit in reducing SSI risk. As summarized in two recent reviews, there is some evidence that appears to favor the use of topical vancomycin to reduce SSI rates in adults.⁴⁹,⁵⁰ There are limited data in children that support safety, but no data have proven efficacy to date. In a series of 87 consecutive patients, 500 mg of vancomycin powder was given locally to children >25 lb. There was no change in creatinine, and serum vancomycin was undetectable in the serum at days 1 and 4.⁵¹ In a recent multicenter data, the safety of vancomycin was studied in 1398 children and demonstrated a 0.07% adverse reaction rate in children as young as 7 months and as small as 7 kg.⁵² There is one study in patients with cerebral palsy that demonstrated a reduced infection risk (15.2%-3.9%) by using topical gentamicin (8-10 mg/kg) in the wound prior to closure.¹⁷ There are two adult RCTs and one systematic review that suggest the use of dilute povidone iodine can reduce SSI risk.⁵³,⁵⁴,⁵⁵ Unfortunately, there are no data to suggest its efficacy in children.

There is some evidence that a plastic surgery/multilayer closure can reduce the risk of SSI in nonidiopathic patients.⁵⁶ When comparing a standard closure to a plastic multilayer closure, one study demonstrated a 19% wound complication rate (8/42) vs 0% in the plastic multilayer closure group.

In a systematic review of intraoperative risk factors,³⁸ inappropriate perioperative antibiotic prophylaxis and increased implant prominence increase the SSI risk and first-generation stainless steel implants increase the risk of late infection compared to newer-generation titanium implants. These risk factors were grade B evidence. There is a grade C evidence that blood loss, blood transfusions, number of levels fused, extension to the sacrum/pelvis, use of drains, type of allograft, or prolonged operative time increase the risk. In a more recent review,³⁹ there is a grade B evidence that surgery duration, closure method, and the use of drains have no effect on SSI rate. There is a grade B evidence that implant prominence increases the SSI rate. There is insufficient evidence to demonstrate that vancomycin powder, povidone-iodine wash, vacuum-assisted closure dressing, dressing type, gentamicin in the bone graft, hypothermia, antibiotics for multiple days, or pelvic fixation influence SSI risks.

How Do We Get Better?

With relatively poor data, surgeons have little to guide them with regard to infection prevention strategies, and for this reason, significant variability exists between surgeons and centers.⁵⁷,⁵⁸ There is evidence in the literature that patient outcomes can be improved by just reducing variability.⁵⁹ When data are limited,³⁸,³⁹ consensus building approaches such as the Delphi method can be used to derive “Best Practices.” Best practice guidelines for infection prevention have
been published and serve as a starting point in reducing variability (Table 1).⁶ With standardization of care and implementation of infection control protocols, local institutions and national study groups can get a better handle on their infection control practices. With increased standardization, it becomes easier to understand and study variability as well as research practices that may truly have equipoise.

Table 1 Final Best Practice Guidelines: Consensus Recommendations to Prevent Surgical Site Infections in High-Risk Pediatric Spine Surgery

	Consensus (%)
	Total	Strongly Agree	Agree
1. Patients should have a chlorhexidine skin wash at home the night before surgery.^a	91	61	30
2. Patients should have preoperative urine cultures obtained and treated if positive.^a	91	26	65
3. Patients should receive a preoperative Patient Education Sheet.^a	91	48	43
4. Patients should have a preoperative nutritional assessment.^a	96	57	39
5. If removing hair, clipping is preferred to shaving.^b	100	61	39
6. Patients should receive perioperative intravenous cefazolin.^a	91	65	26
7. Patients should receive perioperative intravenous prophylaxis for gram-negative bacilli.^a	95	65	30
8. Adherence to perioperative antimicrobial regimens should be monitored (ie, agent, timing, dosing, redosing, cessation).^a	96	61	35
9. Operating room access should be limited during scoliosis surgery whenever practical.^a	96	61	35
10. Ultraviolet lights need not be used in the operating room^a	87	48	39
11. Patients should have intraoperative wound irrigation.^a	100	83	17
12. Vancomycin powder should be used in the bone graft and/or the surgical site.^b	91	48	43
13. Impervious dressings are preferred postoperatively.^b	91	56	35
14. Postoperative dressing changes should be minimized before discharge to the extent possible.^a	91	52	39
^aThese interventions reached consensus after the first round of voting. ^bThese interventions reached consensus after the second round of voting.
Reproduced with permission from Vitale MG, Riedel MD, Glotzbecker MP, et al. Building consensus: development of a Best Practice Guideline (BPG) for surgical site infection (SSI) prevention in high-risk pediatric spine surgery. J Pediatr Orthop. 2013;33(5):471-478. Ref.⁶