What is Postoperative Wound Infections?
Surgical site infections, or infections that happen where surgery took place, are the main types of hospital-acquired infections for surgical patients. There was a time when these infections were very common after surgeries, and they often led to severe outcomes like limb removal or even death. However, once healthcare professionals started understanding the importance of cleanliness to prevent infection and started using antiseptic techniques, patient outcomes improved considerably.
Post-surgery infections continue to play a significant role in patient health issues and death rates after surgery, causing over 2 million hospital-acquired infections every year in the United States. The Centers for Disease Control and Prevention (CDC) categorize surgical site infections into different types such as infections that are skin-deep, infections that go deeper into the incision, or infections that affect the organs or spaces in the body. Infections related to the surgical site are those that happen within 30 days after surgery or within 1 year after a medical device has been implanted.
Superficial Incisional Infections are infections that only affect the skin and tissue just below the skin. They make up over half of all surgical site infections. Diagnosing these infections can happen in several ways: if there’s pus coming from the surgical site, if a microorganism is found at the surgical site, if the surgeon identifies it as an infection, or if the surgeon purposely opens the wound and there are signs of infection such as swelling, redness, or localized pain or warmth.
Deep Incisional Infections are those that affect soft tissues deeper than just below the skin, like muscles and fascial planes (layers of tissue that stabilize and enclose muscles). This can be diagnosed if there’s pus from the surgical site, if the wound comes apart on its own, if the surgeon reopens a deep incision suspecting infection or if the wound spontaneously comes apart, along with a positive wound culture and at least one sign of infection such as fever or localized pain or tenderness. A CT scan showing an abscess or infection in deep tissues can also be used to diagnose this.
Organ/Space Infections affect organs or anatomical spaces beyond the incision site but deeper than the muscles. This can be diagnosed if there’s pus from a drain placed in the organ, space, or cavity, if an isolated organism is found in the involved organ, cavity, or related abscess, if a CT scan shows an abscess or infection in the organ, cavity, or anatomical space. However, a wound does not count as infected if it’s only a stitch abscess, localized skin inflammation, or an infected superficial stab puncture.
Most surgical wound infections come from the body’s own flora, which are microorganisms typically found on mucous membranes, skin, or hollow organs. Generally, the higher the concentration of these microorganisms, the greater the risk of wound infection. For example, when there are more than 10,000 microorganisms per gram of tissue, the likelihood of a wound infection goes up.
What Causes Postoperative Wound Infections?
Various factors can cause infections after a surgery. These can include direct exposure, transmission through the air, or contamination by resident microbes – bacteria or microorganisms normally found in and on our bodies. The chances of getting an infection can also vary depending on the type of surgery, the manner in which it is performed, and even where you live – with certain places having higher or lower rates of specific infections.
Not everyone is equally at risk either. Older patients, those malnourished, obese, using certain medicines like steroids, having uncontrolled diabetes, immune system problems, and even smokers, have a greater chance of wound infection. Other risk factors include traumas, the location of the surgery, a long stay in the hospital before the operation, poor skin cleanliness before the surgery, and existing infections elsewhere in the body.
Surgeons will often try to minimize any risk before the surgery. This could include encouraging quitting smoking, losing weight, making sure blood-clotting is normal, and controlling blood sugar levels.
There are also factors within the surgery itself that could increase the risk of an infection. These include a build-up of fluid such as blood or clear, watery fluid; contamination of the surgical site, instruments, or personnel; use of drains; presence of foreign material in the surgical site; not keeping the body warm enough; improper hair removal; not enough use of preventative antibiotics; not enough skin preparation; quick surgical preoperative scrub; a long surgery; poor ventilation in the operation room; history of prior infection; long inpatient stay before or after surgery and bad surgical practices (like not keeping tissue hydrated, causing direct injury, placing too much stress on the tissue, causing excessive tissue damage).
It’s vital for the surgical team to stick to the preoperative checklist to keep surgical site infection rates low and the operation room well-ventilated. The room should have effective air filtration and a fast air exchange rate.
Preoperatively, patients can reduce their skin bacteria by a chlorhexidine shower the night before and/or the day of the surgery. In terms of hair removal, it’s typically done right before surgery unless it might lead to more skin injuries. Sterile items such as stethoscopes, transfer slides, keyboards, and the like, should also be cleaned regularly to prevent bacterial contamination.
In order to categorize the procedure, the World Health Organization uses a checklist to help prevent complications and improve safety and outcomes, including the prevention of surgical site infections.
The four procedures are clean, clean-contaminated, contaminated, and dirty or infected:
1. Clean: Sterility is maintained. The gastrointestinal, urogenital, and respiratory tracts are not accessed.
2. Clean-contaminated: The procedure involves entry into the gastrointestinal, urogenital, or respiratory tract in a controlled way with no existing contamination.
3. Contaminated: Sterile technique is breached, or there is spillage from the gastrointestinal tract, the cutting through acutely inflamed (but not purulent – meaning pus-filled) tissue. It includes open traumatic wounds that are 12 to 24 hours old.
4. Dirty or infected: The procedure involves performing on perforated organs or cutting through acutely inflamed and purulent tissue. This category also includes open traumatic wounds older than 24 hours with dying tissue or fecal contamination.
Risk Factors and Frequency for Postoperative Wound Infections
Surgical site infections occur in about 0.5% to 3% of all surgery patients. Gathering data about these infections is challenging due to the increasing number of surgeries performed as outpatient procedures. To counter this, the NHSN has begun to collect data on infections after surgeries performed in outpatient clinics. However, these infections often become noticeable after the patient has left the clinic or hospital, and might not be recorded in the hospital file. Therefore, any data reported should be understood in this context.
Despite efforts to prevent them, infections that occur at the surgical site still have a significant effect on patient health and survival rates. They account for 20% of all infections caught in healthcare settings. If you get an infection at the site of your surgery, you are more likely to need intensive care and your risk of dying is 2 to 11 times as high. You’re also five times as likely to be readmitted to the hospital. Surgical site infections are the most common reason why patients need to unexpectedly return to the hospital after surgery.
In 2018, there were 157,500 surgical site infections reported in the U.S., resulting in about 8,205 deaths. Out of all the deaths in intensive care units, 11% were linked to surgical site infections. Having a surgical site infection typically means you will spend an extra 10 to 11 days in the hospital and it will cost more than $20,000. Because of this, surgical site infections put an additional $3.3 billion burden on the U.S. healthcare system each year.
The chance of getting an infection at the site of your surgery is correlated with how contaminated the surgical wound was at the time of the surgery.
- Clean wounds have an infection rate of about 2.1 per 1,000 surgeries.
- Clean-contaminated wounds have an infection rate of about 3.3 per 1,000 surgeries.
- Contaminated wounds have an infection rate of about 6.4 per 1,000 surgeries.
- Dirty or infected wounds have an infection rate of about 7.1 per 1,000 surgeries.
Signs and Symptoms of Postoperative Wound Infections
Symptoms of surgical site infections, or infections that occur after surgery in the part where the surgery took place, typically appear within 3 to 7 days after a procedure. However, these symptoms must occur within 30 or 90 days of the surgery, depending on the type of surgery that was performed. The specifics of when symptoms can occur depend on the kind of surgery.
Surgeries that require monitoring for infection for up to 90 days after the procedure include breast surgery, heart surgery, bypass grafts for coronary arteries, craniotomy (brain surgery), spinal fusion, fracture reduction, hernia repair, hip and knee replacement, pacemaker surgery, peripheral vascular bypass surgery, and ventricular shunt placement.
Surgeries that are technically complex, lengthy, contaminated, or emergency procedures have a higher risk of resulting in an infection. Patients with these superficial or deep surgical site infections often experience gradual pain around the site of surgery and a general feeling of discomfort or tiredness. They might also notice a discharge from the surgery site or find that their bandages are frequently saturated. Those with organ/space infections may experience localized or widespread pain and general symptoms like fever, chills, night sweats, tiredness, and discomfort. The physical check-up might find redness around the surgery site, discharge, wounds splitting open, or healing delay. Pain on touch may be localized or spread out.
It is always best to examine a patient with a potential surgical site infection in person. But, when an in-person examination isn’t possible, it’s important to visually inspect the affected area. Using medical photography to review wounds can improve diagnostic accuracy and prevent overtreatment in instances where face-to-face consultations are not possible.
During the physical examination, all dressings must be removed and the wound examined for any signs of blisters, tension, swelling, unusual tenderness, excessive redness, pus-filled bumps, blackish-gray tissue, and signs of insufficient blood supply (ischemia) or tissue death (necrosis). A touch test should be performed using a sterile technique. Any wounds present must be carefully examined with a sterile cotton swab to check for dead space, deep closure integrity, pockets of fluid, and tissue deterioration. If there is any discharge, good or bad, it should be collected and sent for further analysis to help identify the bacteria or other organisms causing the infection and thus guide treatment options.
Testing for Postoperative Wound Infections
The diagnosis of an infection at the site of a surgery, also known as a surgical site infection, is primarily based on clinical signs. However, it’s useful to conduct wound cultures to identify the bacteria or other pathogens causing the infection and to help decide the best antibiotic treatment.
If a deep infection is suspected, imaging techniques like ultrasound, CT scans, or MRIs can help. There are also specific tools used to predict the chance of getting an infection based on different risk factors. Some widely recognized models include the National Nosocomial Infection Surveillance System, the Australian Clinical Risk Index, and the European System for Cardiac Operative Risk Evaluation. While these tools can be useful, they may not take all factors into account or apply to specific surgeries. As a result, more specialized scoring systems have been introduced.
Patients with a superficial infection (in the outer layer of skin) usually don’t show signs of infection that affect the whole body. However, some people may have a fever or increased white blood cell count. In these cases, imaging techniques are usually not necessary. For patients with a deeper infection, a fever and a high white blood cell count are more likely. Depending on the situation, testing may show increased levels of proteins that our body produces to fight off infections, like procalcitonin and C-reactive protein. However, these tests are not essential to make a diagnosis. In particular, diagnosing an infection that is deep within a wound can be tricky, especially in people with obesity. This is where imaging techniques can be useful in determining the exact location and extent of the infection. Abscesses (pockets of pus) can then be drained and cultured (tested) to guide antibiotic treatment, which can improve patient outcomes.
When organs or areas around the surgical site are infected, patients usually show general signs and symptoms of infection, even if the wound itself looks fine. Diagnosing this type of infection usually requires imaging, which may reveal a fluid collection or an abscess in or near the surgical site. As with deep skin infections, draining these pockets of infection can help with treatment.
Necrotizing soft tissue infections are a specific type of severe infection that pose a significant danger to the patient’s life and increases the chances of other health problems. People with these types of infections usually become critically ill within a couple of days after surgery and may show signs of systemic infection. The area around the wound may be unusually painful compared to normal post-surgery pain. There may also be other signs like darkening or reddening skin, swelling, crackling under the skin when touched, bruising, reduced blood supply, blistering, or outright tissue death. Drainage from the incision may also be excessive. Test results may show unusually high or low white blood cell counts.
Necrotizing soft tissue infections can affect any part of the body, including the fascia (connective tissue) and muscles, and can spread rapidly along these tissues. Imaging can help confirm a diagnosis but should not delay surgical treatment, which involves removing infected or dead tissues. Fournier’s gangrene is a typical example of a post-operative necrotizing soft tissue infection and is considered a surgical emergency.
Treatment Options for Postoperative Wound Infections
To prevent infections after surgery, doctors follow a detailed strategy that includes assessing and managing any chronic health problems, advising patients to stop smoking, and ensuring optimal cleanliness. A 2017 guideline called the “CDC and Health Infection Control Practice Advisory Committee Guideline for the Prevention of Surgical Site Infections” is a popular reference for this strategy.
A study from Japan found that by incorporating a thorough pre-surgery oral hygiene routine, the number of infections after surgery was significantly reduced. Methods included professional dental cleaning, denture care, improved general dental care, and any necessary dental procedures before the surgery.
The routine use of tubes to help drain wounds (or surgical drains) is generally discouraged due to questions about their effectiveness and impact on patient recovery. If used, it’s important these are taken out promptly. Preventive measures such as antibiotic irrigation, applying antibiotic or antiseptic creams, using antibiotic-impregnated stitches, and using antiseptic dressings have shown some promise but they need more research.
The use of a procedure called prophylactic negative pressure therapy is suggested for specific high-risk surgical cases and contaminated wounds. Despite its proven effectiveness in high-risk surgeries, the results can vary due to different levels of wound contamination and the characteristics of each patient and wound.
Depending on factors like the specific surgery, type of infection, the patient’s characteristics and the presence of any implanted materials like stents or mesh, the treatment can vary. This could include removing the implanted material, taking samples for lab analysis, and administering antibiotics.
Vacuum-assisted wound therapy, where a device is used to apply pressure to the wound to promote healing and prevent infection, has been used successfully in many types of surgery. The use of such therapy requires specialist oversight, and it may require frequent removal of dead tissue. In certain cases, it might be necessary to drain fluid buildup or remove infected implants and prosthetics.
Some special cases might need other interventions, such as infections involving mesh used in hernia repairs may need draining, antibiotics, wound cleaning, and possible removal of the mesh. For infections involving orthopedic hardware, treatments could include cleaning the bone, long-term antibiotics and possible removal of the hardware.
Newer technologies such as absorbable meshes that promote tissue growth may be helpful in treating patients who have trouble with wound healing, especially those with diabetes. Hyperbaric oxygen therapy, which involves breathing pure oxygen in a pressurized room or chamber, also shows promising results for treating complex, non-healing wounds after surgery.
What else can Postoperative Wound Infections be?
Usually, it’s pretty easy to tell if an infection is present after surgery because it’s visible at the site of the incision. However, if someone starts to feel unwell after a surgical procedure, it’s important to consider other potential post-surgery problems like an infection, fluid leaking out of the surgical site, or ongoing bleeding. That said, it’s always necessary to keep in mind that the symptoms might not be linked to the surgery or the surgical wound at all. For example, the patient could have an infection in the skin (cellulitis) unrelated to the surgical site or could even be having an allergic reaction to antibiotics or other substances. Also, sometimes a patient might get an infection after surgery that’s not directly related to the operation, for example:
- A urinary tract infection
- Pneumonia
- A blockage in a lung artery (pulmonary embolus)
What to expect with Postoperative Wound Infections
Spotting and promptly treating all surgical wounds is essential for the best outcome or prognosis. Nonetheless, the best strategy is to strictly follow a prevention plan. Various models or ways have been created across different surgery specialties to help identify patients at high risk and prevent surgical site infections. As an example, a research study focused on patients with colorectal cancer discovered that factors like the patient’s physical state, tumor characteristics, and type of surgery can reliably predict the risk of surgical site infections.
Moreover, factors related to the surgery like the type of procedure, whether the surgery was an emergency, the wound’s class (if it was infected or dirty), use of surgical drains, the surgeon’s experience, a long operation time, and certain factors after the surgery like extended hospital stays and the need for blood transfusions during surgery were identified as independent risk factors for surgical site infections.
Possible Complications When Diagnosed with Postoperative Wound Infections
Complications from surgical wound infections can appear in two main ways – locally (at the site of the wound) or systemically (throughout the whole body). Local complications may involve delayed wound healing, which can potentially lead on to long-term wounds and harm to the tissue around the wound. Additional local complications could include additional infections, formation of pus-filled abscesses, and osteomyelitis, a type of bone infection.
Systemic complications, on the other hand, involve bacteremia, a condition where bacteria enters the bloodstream. This can potentially lead to the spread of infection to different parts of the body and may cause sepsis, a serious condition where the body’s response to infection causes injury to its own tissues and organs. In severe infection cases, organs might fail, or existing health conditions could get worse.
List of Potential Complications:
- Delayed wound healing
- Chronic wounds
- Local tissue damage
- Additional infections
- Abscess formation
- Osteomyelitis (bone infection)
- Bacteremia (bacteria in the bloodstream)
- Distant spread of infection
- Sepsis
- Organ failure
- Worsening of existing health conditions
Recovery from Postoperative Wound Infections
Taking good care of a surgical wound is crucial during any hospital or rehabilitation stay. The wound might even be the main reason a patient needs professional medical care. For the patient’s overall health and, in some cases, for their survival, it’s really important that the wound heals well. The methods for caring for wounds are always improving and becoming more specialized. When it comes to caring for a surgical wound, it’s necessary to properly assess the wound in a timely manner and decide on the best steps to take for treatment. This ensures the best possible healing results for the patient.
Preventing Postoperative Wound Infections
Some factors that can be controlled or changed, like a person’s weight, how well they manage their diabetes, and whether they smoke, can help reduce the risk of infection after surgery. For surgeries that are planned ahead of time, doctors often educate and advise patients on certain actions to take before their surgery. It’s common for patients to be encouraged to lose weight, stick to their medication plans, and maintain a healthy lifestyle.
Quitting smoking is another critical step in improving a patient’s risk factors. If possible, it can be helpful to include the patient’s family in these discussions. The advice given and the procedures followed can vary depending on the patient’s existing health conditions and the type of surgery they are undergoing. For example, a patient preparing for a spinal surgery might be advised to keep their HbA1c (a measure of blood sugar control) levels below 8%, take certain medications called α-blockers if they are a male over 60, ensure their serum albumin (a protein in blood) levels are above 3.5 g/dL, undergo heart stress tests, and emphasize the importance of quitting smoking.
