Preventing Postoperative Infections: An Evidence-Based Approach

Nutrition

More has been reported about the relationship between infection and nutrition in the general surgery and critical care literature than in the spine literature, although a relationship between malnutrition and SSI has been shown in spine surgery as well.

A study by Klein and coworkers followed three groups of patients and analyzed infections and other complications against markers of nutritional status. Patients were deemed nutritionally replete if they had a serum albumin of at least 3.5 g/dL and an absolute lymphocyte count (a stable immune marker) of at least 1500 cells/mm . Patients falling below either or both of these cutoffs were considered malnourished. Two of 85 nutritionally replete patients suffered complications, compared with 11 of 29 who were malnourished, a difference that is even more dramatic considering the disparate sizes of the groups. Of note, the researchers found that 40% of patients older than 60 years were malnourished. They found similar results among patients who were operated on for spondylodiscitis, as well as for spinal cord injury.

Considering the aforementioned results, one reasonable nutrition assessment and management approach would be to check serum albumin and absolute lymphocyte counts preoperatively, especially in older patients. If abnormal, elective surgery should be deferred until a nutrition consult is obtained and the patient is nutritionally replete.

Antiseptic Shower

Some have advocated the use of antiseptic showers, either with povidone-iodine (Betadine) or with chlorhexidine gluconate (CHG). A study of 700 surgical patients demonstrated a reduction of bacterial skin colonization with either soap, by a factor of 1.3-fold with iodine and ninefold with CHG. Similar results have been found elsewhere. Showering with regular bath soap has a positive effect as well, likely caused by the mechanical cleansing of skin. As of their 2017 guidelines, the Centers for Disease Control and Prevention (CDC) recommends a soap or antiseptic shower at least the night before the surgery.

Mupirocin Nasal Ointment

Staphylococcus aureus is the leading cause of SSIs in clean surgical procedures, including spinal operations. An association has been noted between nasal carriage of S. aureus in patients and the occurrence of SSIs. About 30% to 35% of people in the United States are nasal carriers of S. aureus at any given time. A short course of treatment with mupirocin (Bactroban) ointment has been shown to eliminate S. aureus in many of these carriers, who can be identified by nasal testing. Alternatively, nasal povidone-iodine can be applied 2 hours before the operation. This is an option for patients unable to receive the full course of mupirocin treatment and those allergic to the same.

The literature has not uniformly shown that mupirocin reduces the risk of SSI per se. ^{, ,} However, when all nosocomial S. aureus infections (not just SSIs) among patients with nasal S. aureus were considered, one study did show a statistically significant decrease in incidence with the use of mupirocin ointment.

A subsequent randomized controlled trial (RCT) published in the New England Journal of Medicine assessed patients being admitted to the hospital for nasal S. aureus carriage. Patients testing positive were treated with nasal mupirocin ointment twice daily and CHG baths daily for 5 days, resulting in a significantly lower overall S. aureus infection rate and a lower rate of deep SSI when compared with the controls.

At this point, there is sufficient evidence to advocate the routine testing of patients for nasal S. aureus carrier status before elective surgical interventions and treatment of carriers with nasal mupirocin or povidone-iodine.

Hair Removal

Removing hair by shaving with a razor has been compared with the use of electric clippers in three RCTs. These trials focused on clean operations (general and cardiac procedures), and their results were pooled in a Cochrane review. This yielded a total of 3193 patients, divided nearly evenly between shaving (1627) and clipping (1566). The infection rate was 2.8% for the former group and 1.4% for the latter, yielding a relative risk of 2.02, which surpassed statistical significance.

In addition to this strong evidence against shaving, two other points can be made. First, there is no good evidence to show that hair removal lowers the infection rate. The step may be omitted entirely. Second, depilatory creams have been associated with a lower infection rate than shaving in several trials ; providing another alternative to razors. Razors should only be used for hair removal with the clear understanding that their use has been associated with higher infection rates in several large, well-designed trials.

Skin Preparation

The rationale for preparing the skin before incision is twofold. First, the mechanical scrubbing of the skin removes dirt, as well as some bacteria and dead skin cells. Second, the prep solution should have an intrinsic bactericidal or bacteriostatic effect.

Commonly employed agents contain alcohol (isopropyl or ethyl), CHG, or iodine/iodophors. Alcohol has excellent activity against bacteria and good activity against mycobacteria, fungi, and viruses. However, it cannot be used alone because it has essentially no residual activity once allowed to evaporate. Before evaporation it is flammable, which makes it incompatible with electrocautery.

CHG has good to excellent activity against bacteria and viruses. It is fair at eliminating fungi and has little activity against mycobacteria. Its residual activity is excellent; however, it can cause keratitis and ototoxicity, with serious consequences.

Given the clinical limitations of other preparations, CHG and iodophor solutions are most commonly used as surgical skin preps. CHG has been shown to reduce bacterial skin colonization to a greater degree than iodophors (see the prior section). No evidence yet demonstrates a lower SSI rate when using CHG in spine procedures, although using both CHG and iodine may have a positive effect. ^, In a large RCT, CHG was shown to reduce the line infection rate when compared with iodophor prep in the placement of central venous catheters.

More recently, two single-step skin prep solutions have become more popular: DuraPrep (3M, St. Paul, MN), a combination of iodine povacrylex and isopropyl alcohol, and ChloraPrep (CareFusion, San Diego, CA), which contains CHG and isopropyl alcohol. Both meet the Association of periOperative Registered Nurses (AORN) and CDC guidelines for reduction of SSI, but there is insufficient evidence to recommend one over the other. It is worth noting that the package insert for Chloraprep advises against its use for lumbar puncture or in contact with the meninges, so this must be taken into account when deciding.