Win The Battle Against Postoperative Infections

By Stacey Stefansky, DPM, Thanh L. Dinh, DPM, and Barry Rosenblum, DPM

Despite advances in aseptic technique and antibiotic prophylaxis, post-operative infections remain a significant complication following podiatric surgery. Postoperative infections can increase morbidity, lengthen recuperation time and compromise the success of a surgical procedure. Data collected by the Centers for Disease Control and Prevention (CDC) estimate that postoperative infections occur in 2.1 percent of all clean, uncontaminated surgical procedures.1
Studies pertaining specifically to podiatric surgery have produced comparable postoperative infection rates. Hugar, et. al., demonstrated a 1.35 percent infection rate following outpatient foot surgery.2 Miller, et. al., reported a 2.2 percent infection rate following inpatient surgery on 1,841 patients.3

What Are The Risk Factors?
Risk factors for postoperative infections can be categorized into host defenses and contamination through the surgical environment. Appropriate patient selection and adherence to proper sterile technique can potentially minimize the risk of infection.
Certain systemic conditions such as diabetes, peripheral vascular disease and malnourishment have been found to increase the risk of infection.4 Additionally, obesity and advanced age have been shown to increase the risk of postoperative infection.5

Factors influencing contamination of the surgical wound include human activity in the operating room, length of the procedure, draping technique and a break in sterile technique. Excessive movement by non-scrubbed personnel in the operating room accounts for most of the microorganisms in the air. Furthermore, it has been demonstrated that the rate of infection increases two-fold with every hour of operating time.5

Key Prevention Pointers
In addition to appropriate patient selection and maintaining sterile technique, you can prevent postoperative infections with prophylactic
antibiotics. When using prophylactic antibiotics, consider two important guidelines. First, you should direct the antibiotic against the most likely organism to cause an infection in that particular case. Secondly, you should achieve maximal antibiotic levels at the time you make the surgical incision.6
In order to adhere to these guidelines, infuse the antibiotic at least 30 minutes prior to making the surgical incision. There is no evidence that postoperative doses of antibiotic are necessary.7 If you’re going to use a tourniquet, administer the antibiotic prior to inflation of the cuff. Otherwise, inadequate antibiotic levels in the tissue will result.8
Antibiotic prophylaxis is recommended in certain situations in podiatric surgery. These situations include trauma surgery, prolonged surgery, when you’re using an implant and when you’re operating on immunocompromised patients.
There is some debate as to whether patients with damaged heart valves or diagnosed heart murmurs should be prophylaxed for podiatric surgery. In clean podiatric surgery, there is no evidence of significant bacteremia.9 However, patients undergoing incision and drainage of abscesses have been shown to develop bacteremia, primarily from manipulation of the infected skin. In this particular instance, you should use prophylaxis antibiotics.

How To Recognize Postoperative Infection Signs
Prompt diagnosis of the postoperative infection is critical to limiting the severity of complications. The signs and symptoms of a postoperative infection include erythema, edema, increased warmth and pain. These symptoms are similar to the normal inflammatory process that occurs following surgery. The key to differentiating between the two processes may be the intensity of the presenting symptoms. Be aware that the pain associated with a postoperative infection is often unresponsive to strong analgesics and narcotics.
It is also important to bear in mind that a hematoma may mimic an infection in the early postoperative period. While a hematoma displays all the same characteristics, it manifests 24 to 48 hours after surgery, compared to a postoperative infection, which most commonly occurs after day three.
When patients have severe postoperative infections, they may demonstrate systemic symptoms such as fever, chills, malaise and an elevated white blood cell count. However, be aware that these symptoms may be suppressed in diabetic patients due to an altered immune response. Saltzman, et. al., found that two-thirds of patients never mounted a fever greater than 100ºF and half of these patients did not demonstrate leukocytosis.10 Therefore, it is imperative to maintain a high index of suspicion in this particular group of patients.

Testing Essentials For Confirming Your Diagnosis
Once you have clinical suspicions of a postoperative infection, proceed to obtain laboratory testing and imaging studies in order to confirm the diagnosis. Anytime you see purulent drainage, be sure to obtain aerobic and anaerobic cultures along with a preliminary gram stain. You should take the cultures from the deepest area of the wound bed in order to prevent contamination from normal skin flora. The gram stain provides a valuable tool for making an early determination of the group of bacteria, which will facilitate selecting an appropriate antibiotic.
Blood cultures are warranted when the patient exhibits systemic symptoms of bacteremia, such as a fever of 101.6ºF or greater, chills, nausea or vomiting. Blood cultures should be drawn from several body sites over a 24-hour period as bacteremia is frequently intermittent. A complete blood count may reveal an elevated white blood cell count in addition to a “left shift,” which refers to the increased proportion of immature leukocytes in the bloodstream that are activated by the presence of infection. The more severe the infection, the greater the “left shift.”

You should order radiographs if you suspect a deep infection or gas in the tissues. The presence of gas in the tissue indicates an anaerobic infection that necessitates immediate surgical drainage. If there is evidence of bone infection, gallium-67 citrate scans have been shown to be useful in the early diagnosis of osteomyelitis. However, MRI remains the gold standard for diagnosis, as it can help you detect early edema changes in the bone marrow (suggestive of osteomyelitis) well before X-rays and bone scans. Getting an MRI is also beneficial in identifying and localizing the presence of a deep abscess.

A Guide To Common Postoperative Organisms
Staphylococcus aureus remains the most common organism isolated from postoperative infection. Miller, et. al., found S. aureus responsible for 83 percent of postoperative infections following foot and ankle surgery over a 20-year period.3 A coagulase positive organism, S. aureus infections are characterized by a creamy yellow purulent discharge.
Staphylococcus epidermidis is the second most prevalent bacteria isolated from postoperative infections. The clinical picture with S. epidermidis infection involves an intensely erythematous, edematous and painful surgical wound with a characteristic white purulent drainage. S. epidermidis is also the likely culprit when infection with hardware occurs due to the organism’s ability to adhere more readily to plastic and metals, forming a glycocalyx.11
Other bacteria implicated in postoperative infections include beta-hemolytic Streptococcus, gram negative bacilli such as Escherichia coli, Klebsiella, Proteus, Pseudomonas, Enterobacter, Serratia, and rarely, anaerobic bacteria such as Peptostreptococcus and Bacteroides fragilis.12 Infection with beta-hemolytic Streptococcus is characterized by a serous drainage with intense erythema and lymphangitis. These infections are extremely virulent and need to be treated aggressively. The gram negative infections are particularly malodorous and the anaerobic infections are commonly found in conjunction with other organisms.

Treatment Pearls You Can’t Afford To Miss
Treatment varies according to the severity of the infection as well as the overall health of the patient. Be sure to differentiate superficial skin infections from deeper infections with abcess formations. In superficial infections, the skin is warm, tender and erythematous. There is generally no joint pain or fluctuance to the area. Occasionally, you may detect lymphangitis or lymphadenopathy in addition to an elevated white count. When it comes to treating superficial infections, emphasize empiric oral antibiotics until you get the definitive culture results. It may be necessary to release a few sutures in order to promote drainage of any fluid.
With deeper infections, you’ll also notice skin that is warm, tender and erythematous. However, there is often considerably more swelling and fluctuance. In these infections, performing surgical drainage and debridement is mandatory along with using broad-spectrum intravenous antibiotics. Surgical drainage of the infection should include copious irrigation and taking deep intraoperative cultures to guide definitive antibiotic therapy. Following drainage and debridement, maintain an open wound with daily dressing changes. You may opt for secondary closure following resolution of the infection.

There is considerable debate as to whether you should remove hardware in the face of infection. As mentioned previously, Staphylococcus can adhere to an implant, creating a barrier to the normal immune response and antibiotics.13-15 However, internal fixation is vital for fracture or osteotomy stability, and may, in fact, prevent infection.16,17 Contaminated fractures with stability have been found to have a lower rate of clinical infection compared to fractures with no internal fixation.17,18 The one exception to this rule is the scenario in which chronic infection exists. In this instance, you should remove or replace the hardware.

Case Study One: When There Are Post-Op Chills, Fever And Erythema
A 60-year-old female, with a past medical history significant for insulin dependent diabetes, hypertension and Charcot joint disease, initially presented with a chronic plantar foot ulcer. The ulcer was recalcitrant to conservative therapy and surgical intervention was pursued. Postoperatively, the patient was admitted for 24-hour observation and discharged one day after the operation with oral antibiotics.
Two days after the operation, the patient complained of fever and chills. She denied any nausea or vomiting, but did state that her blood sugars were slightly elevated. On examination, you could see the incision site was well coapted with the sutures intact. There was evidence of surrounding erythema extending to the dorsum of the midfoot. The surrounding skin was macerated and there was serosanguinous drainage when pressure was exerted. There were no areas of fluctuance, crepitus, malodor or purulence. Subsequently, the patient was evaluated in the emergency department and admitted with a diagnosis of cellulitis.
The patient was admitted to the hospital for intravenous antibiotics, wound care, lab evaluation and possible surgical intervention. On hospital day number three, we removed the sutures to allow for more adequate drainage. Afterward, there was decreased erythema, edema and drainage, but the patient continued to have low grade fevers. Therefore, on hospital day number six, we made the decision to explore the wound in the operating room to see if there was any collection that could be causing the patient to continue to spike fevers.
Upon exploring the wound in the operating room, we found a small collection of purulent material at the dorsal portion of the surgical incision. We drained the purulence, irrigated the wound and packed it open. Following this procedure, the patient remained afebrile and was discharged from the hospital on home intravenous antibiotics.

Case Study Two: Resolving Post-Op Concerns After
A Metatarsal Head Resection And Achilles Tendon Lengthening
A 44-year-old male, with a past medical history significant for insulin dependent diabetes and peripheral neuropathy, came into the emergency department with fevers, chills and elevated blood sugars for two days. Additionally, he had undergone a left pan metatarsal head resection with an Achilles tendon lengthening. Following the original procedure, he had two weeks of oral antibiotics, but was not currently on any antibiotic therapy.
An examination of the left lower calf revealed a well healed surgical incision with surrounding erythema and edema in the area of the Achilles tendon lengthening. At the time of the patient’s admission, no fluctuance or wound opening was noted. We did notice an ulceration below the first metatarsal head. The ulceration was shallow with no clinical signs of infection.
The patient was admitted for intravenous antibiotics, wound evaluation and for ultrasound to rule out DVT. He was started on vancomycin and Ciprofloxacin for his history of MRSA. Over the next few days, the areas of redness and swelling improved on the calf and foot. However, on hospital day number three, a new sinus tract appeared over the healed Achilles incision site. Following a stab incision of the area at the bedside, we expressed purulent material from the site. Then we decided to explore and debride the wound in the operating room.
Upon exploring the wound, we noted copious amounts of purulent drainage coming from the area and tracking up the posterior area of the calf. We debrided the wound of all necrotic and devitalized tissue and followed with copious irrigation with pulse lavage. We packed the wound open with normal, twice-a-day saline dressing changes. This was secondarily closed one week later after all clinical signs of infection were gone. The patient was discharged with a course of intravenous antibiotics. The patient has come in several times since his discharge and all wounds have healed completely.

In Conclusion
Despite preventive measures, postoperative infections remain a threat to the success of any surgical procedure. A heightened awareness to the signs and symptoms along with aggressive treatment is the key to limiting the severity of the complications.

Dr. Rosenblum is an Assistant Clinical Professor of Surgery at Harvard Medical School and is the Director of Podiatric Residency Training at the Beth Israel Deaconess Medical Center in Boston.

Dr. Dinh is an Assistant Clinical Instructor of Surgery at Harvard Medical School and is the Assistant Director of Podiatric Residency Training at Beth Israel Deaconess Medical Center in Boston.

Dr. Stefansky is an Assistant Clinical Fellow of Surgery at Harvard Medical School and is a third-year resident at Beth Israel Deaconess Medical Center in Boston.



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Additional References

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