Surgical site infection (SSI)
A surgical site infection (SSI) is a bacterial infection that occurs at the site of a surgical operation, resulting from the incision made during the procedure. These infections can vary in severity, leading to complications that range from mild discomfort to life-threatening conditions. They are a significant concern in both low-income and high-income countries, with an estimated 160,000 to 300,000 cases occurring annually in the United States alone. SSIs can extend hospital stays and contribute to rising healthcare costs, underscoring the need for effective prevention measures in surgical settings.
Infections can be classified into three categories: superficial incisional infections affecting the skin, deep incisional infections involving underlying muscle and tissue, and organ or space infections that impact internal organs. While bacteria causing SSIs are commonly found on the skin or in the environment, factors such as pre-existing health conditions, the type of surgery, and surgical duration can increase the risk of infection. Symptoms typically include fever, swelling, and pus formation, with treatment often requiring antibiotics and sometimes surgical intervention to drain the infected area. Patients can reduce their risk of SSI by communicating any health issues to their healthcare providers and following post-operative care instructions.
Surgical site infection (SSI)
A surgical site infection (SSI) is a bacterial infection that results from the skin opening made for surgery. Surgical site infections can cause problems externally and internally and range in severity from mild to life threatening. While they are more likely to be a problem in poorer nations, surgical site infections can happen anywhere surgery is done. They contribute to long-term illness, additional hospitalization, and antibiotic resistance. Preventing surgical site infection is a priority in hospitals around the world.
Overview
One of the skin’s most important functions is to serve as a barrier against organisms that cause infections. Any type of break in the skin presents the possibility of an infection. The cut in a skin made for surgery can present a greater risk because it is more than a superficial opening in the skin surface. Surgical incisions are made not only in the skin’s surface but also in organs and tissue beneath the skin.
A surgical site infection generally presents within thirty days of the surgery. According to the Hospital Improvement and Innovation Network (HIIN) in 2018, SSIs affect between 160,000 and 300,000 US patients annually. About 2 to 5 percent of people who have inpatient surgery in the United States will develop an SSI. This is considerably less than the estimated 11 percent who contract them in lower-income countries, but is still enough to result in an average of 9.7 additional hospital days per patient with an SSI and add $3.5 billion to $10 billion in medical costs annually in the United States alone. HIIN estimated in 2018 that efforts at 1,500 US hospitals to reduce SSIs had saved $16 million in a single year.
The three main types of SSIs are classified by where they develop. A superficial incisional infection occurs on the skin’s surface near the cut made by the physician. A deep incisional infection involves the muscles and tissues beneath the skin’s surface. An organ or space surgical site infection involves the organs underneath the skin, muscles, and tissue. It can also involve the spaces between organs.
Surgical infections come from bacteria. Streptococcus, Pseudomonas, and Staphylococcus bacteria are most likely to cause an infection. These are very common bacteria found on surfaces and in fluids. A person can develop an infection from bacteria that was already on or in their body prior to the surgery, from airborne bacteria, or from coming in contact with a person or surface that is contaminated.
Bacteria can get into a wound in a number of ways. In planned surgery, the room, instruments, or operating room personnel can be inadvertently contaminated with bacteria despite precautions such as disinfecting the room, washing, and wearing protective garments. The area to be operated upon will also be cleaned with an antiseptic solution. Improper cleaning or an inactive solution can allow bacteria to remain. Bacteria can also be present on body hair near the incision; this is one of the reasons surgical sites are shaved.
An infection can occur if the surgery involves an internal organ such as the bowels or bladder, where bacteria may already be present. If these organs are cut accidentally or as part of the surgical procedure, bacteria can be released, resulting in what is known as a contaminated wound.
Not all surgeries are planned. In some cases, emergency surgical procedures are done quickly without time for the usual cleanliness precautions. Bacteria on the skin can then enter the wound and cause an infection. These are called dirty wounds because it is known before the surgery that bacteria are almost certainly present.
Wounds that involve operating on an internal organ are known as clean-contaminated wounds. This is because although the external incision appears clean, the possibility of contamination from inside the organ exists. A clean wound is one that has no obvious source of contamination and does not involve cutting into an internal organ.
Some conditions can make a person more likely to suffer an infection. These include comorbid conditions, or other health problems, including being overweight; being elderly; smoking; having a condition that affects immunity; having abdominal surgery; having emergency surgery; or having surgery that takes longer than two hours.
Symptoms, treatments, and prevention
A person with an SSI will likely experience a fever, along with pain, tenderness, swelling, and warmth near the infection. If the infection is directly at the site of the incision, the area may also be red. An infected wound may not heal properly or it may take longer to heal than expected. Although all of these things seem to be negative, they are actually signs of the body attempting to take care of itself.
Most infections will have some degree of pus. When something foreign, such as bacteria, invades the body, the immune system is activated to take care of it. White blood cells are released to fight the infection. Pus in an accumulation of dead white blood cells that have attacked the bacteria. This is why pus forms at the site of infection. It can be white or yellow in color, and it usually smells bad. The amount and composition of pus can tell physicians about the nature of the infection that caused it. The pus can be tested to determine what type of bacteria is present and help decide the best way to treat it. This helps ensure the antibiotics used are effective and minimizes the chances of the bacteria developing antibiotic resistance.
Sometimes an SSI is superficial, limited to the skin surface near the surgical wound. Other times the infection is deeper and pus accumulates inside the body. This can force the wound open or prevent it from healing. This happens in deeper incisions, such as those that penetrate the muscle and tissue beneath the skin. Sometimes the accumulation of pus is deep within the body and forms an abscess, which is an area of infected tissue. This can cause a more serious health risk.
SSIs are treated with antibiotics. These can be administered topically if the infection is on the skin surface, but will usually also be administered orally or, in some cases, by injection or intravenously. Deep incision infections and abscesses require antibiotics that are taken orally or administered by injection or intravenously. Treating these wounds may also require the surgeon to reopen the wound to drain the infection or to place a tube to allow the infection to drain out over time.
Patients can take some steps to avoid infections. Patients should make sure physicians are aware of other health conditions, such as diabetes or heart disease, that make infection more likely. Patients may be instructed to avoid shaving the area to be operated on beforehand, to help avoid causing small infections that can spread during surgery (medical personnel take care of any necessary shaving immediately before the procedure). Avoid touching the wound after surgery except as directed by a physician.
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