Definition

During surgical procedures, postoperative wounds are created through incisions made in the skin using a scalpel. When not properly tended to, these wounds have the potential to become infected, presenting a range of complications and, in severe instances, even resulting in mortality. Postoperative wound infections, categorized as nosocomial infections, stem from healthcare facilities and hospital services.

Causes

Postoperative wound infections primarily originate from bacterial sources. Staphylococcus, Streptococcus, and Pseudomonas species are the most frequently encountered bacteria responsible for such infections. These pathogens can enter postoperative wounds through multiple pathways, including contact with contaminated hands of caregivers, exposure to surgical instruments used during the procedure, interaction with airborne bacteria, or the dissemination of existing bacterial reservoirs within the patient's body to the postoperative wound site.

Postoperative wounds are classified into four categories based on wound cleanliness, risk of infection, and wound location:

• Class I: This category refers to clean wounds. These wounds exhibit no signs of infection or inflammation. Examples of clean wounds include injuries involving the eyes, skin, and circulatory system.
• Class II: Clean-contaminated wounds. Despite lacking signs of infection, these wounds carry a high risk of infection due to their location. For instance, postoperative wounds within the digestive tract are highly susceptible to infection.
• Class III: Contaminated wounds. These postoperative wounds have been in contact with external objects, leading to a significantly elevated risk of infection, and are considered to be contaminated. Examples of these wounds include gunshot wounds that contaminate the skin surrounding the surgical site.
• Class IV: Dirty or contaminated wounds. Postoperative wounds in this category are considered heavily contaminated. This includes wounds exposed to fecal materials.

Risk factor

Risk factors for postoperative wound infections can be categorized into patient-related and procedure-related risk factors. Patient-related risk factors include advanced age, malnutrition, hypovolemia (insufficient blood volume), obesity, use of corticosteroid medications, diabetes mellitus, immunosuppressive drug therapy, smoking, and the presence of concurrent infections in other parts of the body.

Procedure-related risk factors for postoperative wound infections are:

• Hematoma formation that leads to the accumulation of blood near the surgical site
• Utilization of devices such as drains that are used to drain fluids
• Presence of dead space resulting from tissue loss during surgery
• Prolonged duration of preoperative hand washing (surgical scrub)
• Preoperative shaving of the patient's hair
• Extended duration of the surgical procedure
• Contamination of the operating room environment
• Prolonged hospitalization

Symptoms

An infected wound typically presents symptoms such as redness, delayed wound healing, fever, pain, warmth, and swelling. A postoperative wound infection can be classified based on the following criteria:

• Onset of infection is within 30 days following surgery (for procedures involving implanted objects, infections may occur up to 1 year post-surgery)
• Involvement of the skin, subcutaneous tissue, deep connective tissue, or distant organs
• Presence of pus discharge or isolation of pathogens from the wound site

Postoperative wound infections are classified as follows:

• Superficial incisional infections. This type of infection is characterized by pus discharge from the postoperative wound. Pus can be cultured to identify the causative pathogens.
• Deep incisional infections. Similar to superficial incisional infections, it is also characterized by pus discharge but may involve more extensive tissue layers. Manifestations may include spontaneous wound opening or deliberate reopening by the surgeon, which can be done to drain pus.
• Organ/space infections. This infection results in pus discharge from drainage tubes that remove fluid from the affected organ/space. Pus accumulation may occur within abscesses surrounded by necrotic or infected tissue.

Diagnosis

The diagnosis of postoperative wound infection is typically established based on information on patient symptoms, medical history, and physical examination findings. Additionally, the doctor may collect a pus sample from the wound for laboratory analysis. This pus sample is cultured to identify the causative pathogens and assess their antibiotic susceptibility. In cases where the infection extends deeper, imaging procedures such as ultrasound, computed tomography (CT) scans, or magnetic resonance imaging (MRI) may be requested by doctors.

Management

Most cases of postoperative wound infections could be effectively managed with antibiotics. However, the doctor may opt for additional surgical interventions or procedures in certain situations. One common approach is debridement, which involves reopening the postoperative wound to clean it in the operating room thoroughly. Additionally, if surgical implants or foreign objects are implicated in the infection, the doctor may consider removing them, as bacteria can colonize them. However, such decisions are carefully weighed, considering the potential benefits and risks for the patient. 

Complications

Complications arising from postoperative wound infections can be categorized into local and systemic complications. Local complications encompass prolonged wound healing, non-healing wounds, cellulitis, abscess formation, osteomyelitis, and wound dehiscence (re-opening of the wound). Meanwhile, systemic complications that could affect the entire body may include bacteremia (presence of bacteria in the bloodstream), the spread of infection to distant organs, and sepsis (characterized by an excessive immune response triggered by infection).

Prevention

Prevention of postoperative wound infections involves measures implemented both before and after surgery. Preoperative measures to reduce infection risk include:

• Showering with an antiseptic cleanser provided by your healthcare provider before surgery
• Avoiding shaving, as it can irritate the skin and increase the risk of skin infections
• Ceasing smoking before surgery, as smokers are at higher risk of postoperative wound infections. While quitting smoking can be challenging, consulting a healthcare provider for a cessation plan can be beneficial

After the surgery, you can take the following steps:

• Maintain the sterile wound dressing applied by the surgeon for up to 48 hours post-surgery
• Take preventative antibiotics (if prescribed) by your doctors
• Ensure understanding of proper wound care procedures, consult with the doctor or nurse to clarify any questions about wound care
• Always wash hands with soap and running water before touching the wound, and ensure your caregivers do the same
• Remain actively involved during hospitalization. You could monitor the frequency of wound dressing changes, cleanliness of the surroundings, adherence to proper hand hygiene, and glove usage by healthcare providers when handling the wound.
• Remain actively involved during hospitalization. You could monitor the frequency of wound dressing changes, cleanliness of the surroundings, adherence to proper hand hygiene, and glove usage by healthcare providers when handling the wound.

When to see a doctor?

If you notice any signs or symptoms of infection following surgery, it's crucial to seek immediate medical attention at the nearest emergency room. Signs and symptoms of postoperative wound infection may include:

• Increasing pain at the wound site
• Redness or swelling around the wound area
• Blood or pus discharge from the wound
• Increased drainage from the wound, with changes in consistency or color (e.g., thickening, brown, green, or yellow discharge)
• Foul odor 
• Wound enlargement, deepening, excessive dryness, or darkening
• Fever persisting at or above 37.5 degrees Celsius for more than 4 hours

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