Surgical Site Infections

ASSOCIATE PROFESSOR SABAHATTİN DESTEK  | GENERAL SURGERY SPECIALIST 

A surgical site infection (SSI) is an infection that develops in the incision site, organ or cavity following an operation. These infections would not have developed if the patient had not undergone surgery and are therefore necessarily associated with health care. The process of postoperative HAIs involves many patient- and hospital-related elements. It can cause many additional problems and even death. From a scientific point of view, its importance was explained in the 19th century by Semmelweis, who used antiseptics and showed that hand washing before delivery reduced puerperal fever and surgical infection rates, and reduced the mortality rate due to puerperal sepsis from 12% to 2%. Available data has determined that surgical wound infections are responsible for over two million hospital-acquired infections in hospitalized patients in the United States.

Surgical wound infections are classified as follows:

• Superficial incisional infection: Affects only the skin and subcutaneous tissues. One of the following criteria must be met: purulent discharge from the wound, microorganism isolated on culture, at least one symptom of infection and diagnosis by the surgeon. These infections account for more than 50% of all surgical infections.

• Deep incisional infections: Involve deeper tissues, including muscles and fascial planes. One of the following criteria must be met: purulent discharge from the wound, dehiscence or reopening of the deep incision by the surgeon after infection was suspected, evidence of abscess formation or other surgeon diagnosis of deep infection.

• Organ/cavity infection: May involve any organ other than the surgical incision site but must be related to the surgical procedure. One of the following criteria must be met: purulent discharge from a drain placed in the organ, microorganism isolated from the organ, abscess or other infection involving the organ.

For a wound to be classified as a surgical site infection, it must occur within 30 days of surgery (one year for organ/cavity infections with an implant in situ), involve only skin, subcutaneous tissues, deep layers or organs, have abscess fluid or microorganisms identified at the wound site.

If the surgeon opens the surgical site to clean the wound, this is considered a surgical wound infection. If there is only a suture abscess, the wound is not considered to be infected. The majority of surgical wound infections are due to the body’s own microorganism flora, usually found in mucous membranes, skin or hollow internal organs.

CAUSES:

Causes of postoperative wound infection vary according to geographic region, surgical specialty and the wide range of procedures performed. Risk factors can be divided into patient, surgical procedure and hospital factors. 

Patient-related risk factors include advanced age, malnutrition, dehydration and blood loss, obesity, steroid use, diabetes, use of immunosuppressive agents, smoking and concomitant infection at another site. 

Risk factors related to the surgical procedure include hematoma formation, use of foreign objects such as drains, leaving dead space, prior infection, time to clean the surgical field, preoperative shaving, poor skin preparation, long surgery, poor surgical technique, loss of body temperature, long stay in the operating room and long hospitalization.

Looking at the operating room environment, the operating room layout and surgical materials should be arranged to ensure a clean and sterile surgical procedure. Ventilation, positive pressurization and filtration are very important in operating rooms. The day before surgery, the operating room environment should be washed with disinfectants to reduce the ambient flora. Hair cleaning in patients should be done with a razor just before surgery. It has been shown that proper hand brushing technique for the surgeon and the use of double gloves reduce infection rates.

The type of surgical procedure is also an important risk factor. According to surgical procedures, wounds are also classified as clean, clean-contaminated, contaminated and dirty-infected. 

• Clean wounds: A procedure in which no inflammation is encountered during the operation and sterility is maintained. Here, the digestive, urogenital and respiratory tracts are not entered. Inguinal hernia, thyroid and eye surgeries are included in this group.

• Clean contaminated wounds: These are procedures where the digestive, urogenital and respiratory tracts are entered in a controlled manner but without contamination. Surgeries such as gallbladder surgery, spleen surgery fall into this group.

• Contaminated wounds: A procedure where asepsis is not followed or an incision is made through acutely inflamed tissue (not purulent). They also include traumatic wounds (less than 24 hours old) or if there is significant transmission from the digestive, urogenital and respiratory tracts. Appendectomy, abdominal gunshot surgeries fall into this group.

• Dirty/infected wounds: A procedure performed on hollow internal organs with holes or an incision into acutely inflamed (purulent) tissue. Also included are traumatic wounds (older than 24 hours) with necrotic tissue or caused by a contaminated mechanism (contact with fecal material). Such as surgery for perforation of the stomach or large intestine.

EPIDEMIOLOGY (INCIDENCE):

In 2018, the morbidity from surgical site infections (SSIs) in the US was 157,500, with an estimated mortality of 8,205. CAIs were associated with 11% of deaths in intensive care units. For each HAI that develops in patients, an average of 11 days of additional hospitalization and an annual burden of 3.2 billion dollars to the system. 

According to 2017 data, the overall HAI rate in our country is 0.72%. It is generally accepted that 70% of healthcare-associated infections are preventable. HAIs bring with them increased workload and cost, and these developing infections also contribute to the increase in antibiotic resistance.

SOURCES OF DEVELOPMENT:

The first step in the development of CAE is microbial transmission, which can come from endogenous (intracorporeal) or exogenous (extracorporeal) sources.

Endogenous flora includes the patient’s skin, mucous membranes and hollow organs. The most common endogenous causative organisms are S. aureus, coagulase negative staphylococci, Enterococcus and Escherichia coli. However, the occurrence of infection is highly dependent on the surgery performed. S. aureus and coagulase-negative staphylococci are the most common agents in cardiac, breast, ophthalmic, orthopedic and vascular surgeries, while gram-negative bacilli and anaerobes are more common in abdominal surgeries.

Exogenous transmission of microorganisms from the operating room to patients can occur, including the air in the operating room, operating room equipment and instruments, materials used and personnel. The most common exogenous organisms are staphylococci and streptococci. The number and resistance of the microorganism are also important risk factors. There is an increase in the proportion of potent microorganisms detected from post-operative wound infections, such as MRSA, due to the unconscious use of antibiotics. In the United States, the incidence of MRSA-associated CAE increased from 12% in 2000 to 23% in 2005.

PROCESS OF INFECTION DEVELOPMENT:

The typical time window for the onset of CAE symptoms is 3-7 days after the procedure, and by definition these symptoms must occur within 30 days (or one year in cases with implants) after surgery. 

Patients with metabolic syndrome, especially diabetics, smokers, the elderly and the immunocompromised are at higher risk. People who have had difficult/long or contaminated surgery are at higher risk. Most patients complain of gradual onset of pain and discharge and may feel generally unwell.

Clinical signs of surgical site infections include erythema, localized pain, unexplained persistent fever, discharge from the wound (often purulent), wound dehiscence and problems with wound healing. The presence of wound blisters, gray or black tissue increases the risk of wound infection.

DIAGNOSIS and DIAGNOSIS:

Diagnosis depends on clinical examination. Microbiologic samples should be taken to identify the causative microorganisms. Ultrasound or CT/MRI imaging is useful if deep infection is suspected.

Various systems and procedures for preoperative risk assessment for CAI can predict the likelihood of developing infection based on risk factors, but they are not always successful.

There is one life-threatening condition that should be excluded in the diagnosis of surgical site infections. Necrotizing fasciitis is a rapidly spreading infection. If necrotizing fasciitis is diagnosed clinically, the patient should be operated on immediately. Effective antibiotics as well as removal of the skin fascia and other dead tissue in the operating room are essential for treatment.

TREATMENT and MANEGEMENT

Many general recipes and guidelines are available to prevent surgical site infections. These include preoperative skin preparation, use of films on the skin, sterility rules of the operating room, perioperative and postoperative prophylactic antibiotics and dressings. 

For prophylaxis before clean and clean contaminated surgeries, a safe, narrow-spectrum antibiotic should be used to cover the expected microorganisms and given to the patient 30 to 60 minutes before surgery. In contaminated and dirty surgeries, antibiotics should be given for treatment instead of prophylaxis. In addition, foreign bodies (mesh, implants, metal structures) should be removed to prevent prolonged infection. For successful treatment of infection, early surgical intervention should be performed.

PROGNOSIS and OUTLOOK:

Many models have been created to help predict prognosis and identify high-risk patients to prevent surgical site infections. These models have been used successfully in colorectal cancer patients. Factors such as type of surgery, urgency, dirty-infected wound, presence of surgical drain, surgeon’s experience, prolonged operation time, inappropriate conditions of the operating room have been identified as obvious risk factors for prolonged hospital stay.

Complications of surgical wound infection can be classified as local and systemic. Local complications include delayed and non-healing of the wound, cellulitis, abscess formation, osteomyelitis, as well as further wound disruption. Systemic complications include bacteremia with the possibility of distant hematogenous spread and sepsis.

PATIENT and PATIENT CONSIDERATIONS:

When surgery is planned, it is important to optimize patients for surgery. This optimization is done to reduce the overall complication rate rather than focusing only on wound infections.

The patient may be asked to lose weight with a healthy diet and regular exercise, change some medications such as steroid drugs, antidiabetic drugs. It is very important to quit smoking before surgery, to eat a good protein-based diet, and to protect against infectious diseases such as influenza.

In the preoperative evaluation of the patient, the patient must be evaluated by anesthesiologists. During surgery, all operating room personnel are responsible for maintaining sterility and ensuring that the operating room time, temperature and available instruments are sterile. When building operating rooms, the size of the operating room and airflow are very important. Post-operative ward doctors, nurses, dieticians, physiotherapists and assistants will all influence recovery and therefore post-operative wound infection rates.

SOURCES:

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