BEST PRACTICES FOR PREVENTING SURGICAL SITE INFECTIONS

Surgical procedures, while often life-saving or life-enhancing, carry an inherent risk of infection. Postoperative infections can significantly impact patient recovery, prolong hospital stays, increase healthcare costs, and in severe cases, lead to serious morbidity or mortality. A thorough understanding of their causes, types, diagnosis, and management is crucial for healthcare professionals involved in surgical care.

This guide provides a structured overview of key aspects related to infections occurring after surgery.

Factors Contributing to Infection After a Surgical Procedure

Numerous factors, acting individually or in concert, can increase a patient’s susceptibility to postoperative infection. These can broadly be categorized into patient-related, procedure-related, and environment-related factors:

• • • Patient-Related Factors:
      • Age: Both very young and elderly patients are at higher risk due to immature or compromised immune systems.
      • Nutritional Status: Malnutrition (protein deficiency, vitamin/mineral deficiencies) impairs wound healing and immune function. Obesity is also a significant risk factor, affecting tissue perfusion and increasing tension on incisions.
      • Comorbidities: Chronic conditions like diabetes mellitus (impaired neutrophil function, poor vascular supply), peripheral vascular disease, chronic kidney disease, liver disease, and chronic lung disease compromise immune response and tissue viability.
      • Immunosuppression: Conditions like HIV/AIDS, receipt of chemotherapy, long-term corticosteroid use, or organ transplantation significantly reduce the body’s ability to fight infection.
      • Smoking: Reduces tissue oxygenation, impairs collagen synthesis, and compromises immune cell function.
      • Pre-existing Infections: Active infections elsewhere in the body (e.g., UTI, pneumonia, distant skin infection) can seed the surgical site hematogenously.
      • Colonization: Presence of pathogenic bacteria on the skin (e.g., Staphylococcus aureus in the nares) or mucous membranes increases the risk of contamination.
      • Length of Hospital Stay Before Surgery: Prolonged hospitalization before surgery increases exposure to hospital flora.
      • Skin Preparation: Inadequate or inappropriate antiseptic skin preparation before surgery leaves bacteria on the skin surface.
      • Foreign Bodies/Implants: Presence of prosthetic material (mesh, implants, sutures) provides a surface for bacteria to adhere and form biofilms, making eradication difficult.
    • Procedure-Related Factors:
      • Classification of Wound: The inherent risk of infection varies significantly based on the level of contamination during surgery (Clean, Clean-Contaminated, Contaminated, Dirty).
      • Duration of Surgery: Longer procedures are associated with increased risk due to prolonged exposure of tissues to the environment, increased desiccation, and potential for breaks in technique.
      • Intraoperative Contamination: Breaches in sterile technique, spills of bowel contents or infected material, or inadequate wound irrigation.
      • Amount of Tissue Trauma/Necrosis: Extensive tissue handling, poor hemostasis leading to hematoma or seroma formation, and devitalized tissue provide a fertile ground for bacterial growth.
      • Blood Loss and Transfusion: Significant blood loss can impair tissue perfusion; transfusions may have immunomodulatory effects.
      • Surgical Technique: Meticulous technique, minimizing dead space, gentle tissue handling, and appropriate closure reduce infection risk.
      • Sterilization Issues: Improper sterilization of instruments or drapes, though rare, can directly introduce pathogens.
    • Environment-Related Factors:
      • Operating Room Air Quality: Inadequate ventilation or filtration can introduce airborne contaminants.
      • Sterilization and Disinfection Protocols: Adherence to strict protocols for instruments, surfaces, and equipment.
      • Healthcare Worker Practices: Hand hygiene compliance, proper use of personal protective equipment (PPE), and control of surgical traffic in the OR.
      • Hospital Cleanliness: Overall environmental hygiene within the hospital.

Types of Surgical Infections

Infections occurring after surgery can manifest in various locations. The most common and directly related are Surgical Site Infections (SSIs), but other infections are also frequent postoperative complications.

• • • Surgical Site Infections (SSIs): Infections occurring at the operative site within 30 days of surgery or within one year if an implant is left in place.
      • Superficial Incisional SSI: Involves only the skin and subcutaneous tissue of the incision. Characterized by pain, tenderness, localized swelling, redness, heat, or purulent discharge with or without fever.
      • Deep Incisional SSI: Involves fascial and muscle layers at the incision site. May present with fever, pain, or evidence of infection extending below the subcutaneous tissue; often diagnosed by spontaneous dehiscence or deliberate opening of the incision revealing infection, or visualization during examination.
      • Organ/Space SSI: Involves any part of the anatomy (organs or spaces) deeper than the fascial layer that was manipulated during surgery. Examples include intra-abdominal abscess after bowel surgery, mediastinitis after cardiac surgery, or joint infection after orthopedic surgery. Often presents with fever, pain related to the affected area, and systemic signs of infection.
    • Other Common Postoperative Infections:
      • Urinary Tract Infection (UTI): Especially common in patients with indwelling urinary catheters.
      • Pneumonia: Often develops in patients with decreased mobility, impaired cough reflex, or prolonged mechanical ventilation (Ventilator-Associated Pneumonia – VAP).
      • Central Line-Associated Bloodstream Infection (CLABSI): Infection associated with central venous catheters.
      • Intra-abdominal Abscess: A localized collection of pus within the abdominal or pelvic cavity (often considered a type of organ/space SSI, but frequently discussed separately due to its complexity).
      • Clostridioides difficile Infection (CDI): Colitis caused by the bacterium Clostridioides difficile, often following antibiotic use (including surgical prophylaxis).
      • Distant Infections: Exacerbation of pre-existing infections at sites unrelated to the surgery.

Principles of Prophylactic Antibiotic Use

Surgical antibiotic prophylaxis aims to prevent SSIs by reducing bacterial contamination at the surgical site during the perioperative period. It does not replace meticulous surgical technique or sterile practices. Key principles include:

• • • Indication: Prophylaxis is indicated for procedures with a significant risk of SSI (e.g., procedures involving prosthetic material, contaminated wounds, procedures where consequences of infection are severe) and where the likely pathogens are known. It is generally not indicated for routine clean surgical procedures (e.g., uncomplicated hernia repair).
    • Timing: The antibiotic should be administered intravenously before the surgical incision to ensure adequate tissue concentration when contamination is most likely to occur. The optimal timing is typically within 60 minutes prior to incision. For certain antibiotics (like vancomycin or fluoroquinolones) requiring longer infusion times, administration may start up to 120 minutes prior.
    • Selection: The chosen antibiotic should target the most likely pathogens for the specific surgical site and procedure. For example, skin surgery typically targets Staphylococcus aureus and Streptococcus species, while bowel surgery requires coverage for enteric gram-negative rods and anaerobes. Hospital-specific antibiograms and guidelines should be considered.
    • Dosing: An appropriate dose based on patient weight and renal/hepatic function is crucial to achieve adequate tissue levels. Obese patients often require higher doses.
    • Duration: Prophylactic antibiotics should be continued for the shortest possible time to be effective. For most procedures, a single dose is sufficient. Continuing antibiotics for more than 24 hours post-surgery generally does not improve outcomes and increases the risk of resistance and side effects (like C. difficile infection). Re-dosing during surgery may be necessary for prolonged procedures (typically >2-4 hours) or significant blood loss.
    • Route of Administration: Intravenous administration is preferred to ensure rapid and reliable tissue concentration.

Diagnostic Features and Indicated Treatment for Common Skin Infections (Post-Surgical)

The most common post-surgical skin infection is superficial incisional SSI.

• • • Diagnostic Features:
      • Timing: Typically appears 4-7 days post-surgery, though onset can vary.
      • Local Signs: Erythema (redness) spreading from the incision edge, increased warmth, tenderness or pain disproportionate to the expected recovery, induration (firmness), and swelling.
      • Purulent Discharge: Pus draining from the incision or when the suture line is opened. This is the most definitive sign.
      • Systemic Signs: Fever may or may not be present, depending on the severity and extent of infection. Leukocytosis (elevated white blood cell count) may be seen on lab tests.
    • Treatment:
      • Wound Management: The cornerstone of treatment is often opening the incision to allow for drainage of pus and debridement of any non-viable tissue. This reduces bacterial load and improves antibiotic penetration.
      • Wound Care: Once opened, the wound requires regular cleaning (e.g., saline irrigation) and packing to promote healing by secondary intention.
      • Antibiotics:
        • For localized infection with minimal systemic symptoms after drainage: Local wound care may suffice.
        • For spreading cellulitis, significant induration, or systemic signs (fever): Systemic antibiotics are indicated. The choice depends on the likely pathogen (commonly Staphylococcus aureus and Streptococcus pyogenes). Initial empirical therapy should cover these, considering local prevalence of MRSA (Methicillin-Resistant Staphylococcus aureus). Culture of any purulent drainage is essential to guide definitive therapy.
      • Pain Management: Adequate analgesia is important during wound care.

Clinical Features and Treatment of Anaerobic and Synergistic Gangrene

These are severe, rapidly progressive soft tissue infections requiring urgent management.

• • • Anaerobic Gangrene (Gas Gangrene): Most commonly caused by Clostridium perfringens, often in contaminated wounds or areas with poor blood supply.
      • Clinical Features: Rapid onset (within hours to days of contamination), excruciating pain at the site (often out of proportion to initial physical findings), rapidly spreading edema and skin discoloration (bronze, then dusky, potentially with bullae), palpate crepitus (subcutaneous gas bubbles), foul-smelling serosanguinous (serum and blood) discharge, and marked systemic toxicity (fever, tachycardia, hypotension, shock, altered mental status, often surprisingly quickly).
      • Treatment: Medical emergency. Requires immediate, aggressive surgical debridement to remove all infected and necrotic tissue. High-dose IV antibiotics (often penicillin plus clindamycin) are crucial; clindamycin inhibits bacterial toxin production. Supportive care for shock and multi-organ failure is critical. Hyperbaric oxygen therapy may be used as an adjunct, though its definitive role is debated and it must not delay surgery or antibiotics.
    • Synergistic Gangrene (e.g., Necrotizing Fasciitis, Meleney’s Gangrene, Fournier’s Gangrene): Polymicrobial infection involving a mix of aerobic and anaerobic bacteria; often affects subcutaneous tissue and fascia.
      • Clinical Features: Initial pain and local inflammation (may mimic cellulitis) often progress more slowly than gas gangrene initially (days), but then accelerate. Severe pain is characteristic. Skin changes progress from erythema to dusky patches, bullae, and frank necrosis. Crepitus may be present but is less common than in gas gangrene. The infection spreads along fascial planes, leading to undermining of skin edges. Systemic signs (fever, sepsis, organ dysfunction) develop as the infection progresses. Fournier’s gangrene is a specific variant affecting the perineum and genitalia, often linked to local infections or trauma in this area.
      • Treatment: Also a surgical emergency. Extensive and repeated surgical debridement is paramount to remove all necrotic tissue until viable bleeding tissue is encountered. Broad-spectrum IV antibiotics covering both aerobes (Gram-positive, Gram-negative) and anaerobes are essential, guided by culture results. Combination therapy (e.g., carbapenem, piperacillin-tazobactam, or combination of metronidazole or clindamycin with agents targeting Gram-positives like vancomycin and Gram-negatives like a cephalosporin or fluoroquinolone) is often necessary. Supportive care for sepsis is critical.

Diagnostic Evaluation for an Intra-abdominal Abscess

An intra-abdominal abscess is a walled-off collection of pus within the peritoneal cavity or retroperitoneum. It is a serious complication, often following abdominal surgery, trauma, or inflammatory conditions.

• • • Clinical Suspicion: High index of suspicion in a patient with persistent or recurrent fever (>4-5 days post-op), unexplained leukocytosis, abdominal pain (localized or diffuse), ileus (lack of bowel function), or signs of sepsis after abdominal surgery or abdominal trauma. The location of pain may suggest the location of the abscess (e.g., right upper quadrant pain suggesting subphrenic or hepatic abscess).
    • Laboratory Tests: Complete Blood Count (CBC) typically shows leukocytosis (high white blood cell count) with a left shift (increase in immature neutrophils). Inflammatory markers like C-reactive protein (CRP) and Erythrocyte Sedimentation Rate (ESR) are usually elevated. Blood cultures may be positive, especially if the abscess is causing sepsis.
    • Imaging Studies (Primary Diagnostic Tools):
      • Computed Tomography (CT) Scan with IV and/or Oral Contrast: This is the modality of choice for diagnosing intra-abdominal abscesses. CT provides detailed anatomical information, accurately locates the abscess, defines its size and extent, identifies associated findings (like fluid collections, gas, or underlying pathology), and helps plan drainage.
      • Ultrasound (US): Useful for identifying collections in certain locations (e.g., pelvis, flank, subphrenic space) and for guiding percutaneous drainage. It is less sensitive for detecting deep or scattered smaller collections, collections obscured by bowel gas, or defining the full extent of complex abscesses.
      • Magnetic Resonance Imaging (MRI): Can be used in specific situations, such as when CT contrast is contraindicated, or for evaluating complex pelvic pathology.
    • Aspiration and Culture: If an abscess is identified, image-guided percutaneous aspiration is often performed. This serves both diagnostic and therapeutic purposes. The aspirated fluid is sent for Gram stain, culture, and sensitivity testing to identify the causative organisms and guide antibiotic therapy.

Causes of Postoperative Fever and Discussion of Diagnostic Steps for Evaluation

Postoperative fever, defined as a body temperature exceeding 38°C (100.4°F) following a surgical procedure, is a common clinical occurrence. While often transient and benign, it can also signal potentially serious complications. Prompt and systematic evaluation is crucial for identifying the underlying cause and initiating appropriate management.

Common Causes of Postoperative Fever

The timing of fever onset post-surgery can provide valuable clues regarding its etiology. A common mnemonic used to categorize postoperative fever causes is the “5 Ws”:

1. Wind (Pulmonary Complications):
   • Timing: Typically occurs within the first 24-48 hours post-operation.
   • Causes: Atelectasis (most common cause of early fever), aspiration pneumonia, hospital-acquired pneumonia, pulmonary embolism (PE).
   • Mechanism: Decreased lung expansion due to pain, anesthesia, or immobility leads to collapse of alveoli (atelectasis), which can predispose to infection.
2. Water (Urinary Tract Infection – UTI):
   • Timing: Usually occurs after 3-5 days post-operation.
   • Causes: Catheter-associated UTI (most common), urinary stasis.
   • Mechanism: Urinary catheters introduce bacteria into the urinary tract and impair natural clearance mechanisms.
3. Wound (Surgical Site Infection – SSI):
   • Timing: Typically occurs after 5-7 days post-operation, though early infections (within 48 hours) are possible, especially with Streptococcus pyogenes or Clostridium perfringens.
   • Causes: Bacterial contamination of the surgical incision or deeper surgical space.
   • Mechanism: Breakdown of sterile technique or compromised wound healing allows bacterial proliferation.
4. Wonder Drugs (Drug Fever):
   • Timing: Variable, can occur any time after starting the offending medication. Often a diagnosis of exclusion.
   • Causes: Reaction to administered medications (e.g., antibiotics, heparin, blood products).
   • Mechanism: An immunological reaction causing hypothalamic temperature dysregulation. Fever often resolves with discontinuation of the drug.
5. Walk (Deep Vein Thrombosis – DVT) / Whopper (Abscess/Other Infections):
   • Timing: Typically occurs after 7-10 days post-operation, but can be earlier or later.
   • Causes: DVT, superficial thrombophlebitis, intra-abdominal abscess, line infection (central or peripheral), Clostridium difficile infection, sinusitis (nasogastric tube related).
   • Mechanism: Venous stasis and hypercoagulability post-surgery predispose to clot formation (DVT), which can cause low-grade fever. Abscesses and other infections are localized collections of pus.

Other Causes:

• Transfusion Reaction: Can cause fever immediately during or shortly after blood product administration.
• Anesthesia-related: Malignant Hyperthermia (a rare, life-threatening cause of very early fever with muscle rigidity).
• Underlying Medical Conditions: Pre-existing infections, inflammatory conditions (e.g., gout flare).

Diagnostic Steps for Evaluation of Postoperative Fever

A systematic approach guided by the potential causes and their typical timing is essential.

Step 1: Initial Assessment & Data Gathering

• Confirm Fever: Accurately measure the patient’s temperature and document the time of onset.
• Review Patient History:
  • Preoperative status: Comorbidities, baseline temperature, presence of pre-existing infections.
  • Type of Surgery: Clean vs. contaminated wound, duration, complexity.
  • Anesthesia utilized.
  • Medications administered (pre-, intra-, and post-operatively).
  • Transfusion history.
  • Presence of drains, catheters (urinary, IV lines, central lines), tubes (NG tube).
  • Immunization status (e.g., influenza, pneumococcal).

Step 2: Focused Clinical Evaluation (History and Physical Examination)

• Detailed History:
  • Timing of fever onset in relation to surgery.
  • Associated symptoms: Cough, shortness of breath, chest pain, dysuria, frequency, flank pain, abdominal pain, nausea, vomiting, diarrhea, wound pain, redness, swelling, leg pain, swelling, calf tenderness.
• Thorough Physical Examination:
  • General Appearance: Alertness, signs of distress, hydration status.
  • Vital Signs: Temperature trend, heart rate, respiratory rate, blood pressure, oxygen saturation.
  • Respiratory System: Auscultate lung sounds (rales, rhonchi, diminished breath sounds), assess for increased work of breathing.
  • Cardiovascular System: Listen for murmurs, assess pulses.
  • Abdomen: Palpate for tenderness, distension, masses. Assess bowel sounds. Inspect surgical incision.
  • Extremities: Inspect for redness, swelling, warmth, tenderness (suggestive of DVT or cellulitis). Homan’s sign is unreliable.
  • Surgical Site: Inspect the incision for erythema, warmth, tenderness, induration, drainage (color, consistency, odor). Palpate gently around the wound.
  • Drain/Catheter Sites: Inspect insertion sites for erythema, warmth, tenderness, purulence.
  • Genitourinary: Palpate
  • Other Potential Sites: Examine nasal passages (NG tube), pharynx, skin folds.

Step 3: Targeted Investigations (Based on Clinical Suspicion and Routine Practice)

• Laboratory Studies:
  • Complete Blood Count (CBC): Evaluate white blood cell count (WBC) and differential (neutrophils, left shift suggestive of bacterial infection). Note that WBC can be elevated post-surgery even without infection.
  • Inflammatory Markers: C-reactive protein (CRP), Erythrocyte Sedimentation Rate (ESR) – non-specific but trends can be helpful.
  • Electrolytes and Renal Function: Assess for dehydration or kidney impairment.
  • Liver Function Tests (LFTs): Can be altered in systemic infection or drug-induced injury.
• Cultures: Obtain cultures from sites suggested by the clinical assessment.
  • Blood Cultures: Obtain at least two sets from different peripheral sites (or one from a peripheral site and one from a central line if present) to rule out bacteremia or line infection.
  • Urine Culture: If patient has a catheter or develops dysuria/frequency. Obtain a clean catch or specimen from the catheter sampling port.
  • Wound Culture: If there is drainage or clinical signs of infection. Obtain a specimen from the deepest part of the wound after cleaning the surface.
  • Sputum Culture: If patient has cough, productive sputum, or pulmonary symptoms.
  • Other Cultures: Based on suspicion (e.g., stool for C. difficile toxin if diarrhea is present).
• Imaging Studies:
  • Chest X-ray (CXR): Essential for evaluating pulmonary causes (atelectasis, pneumonia, pleural effusion).
  • Ultrasound: Doppler ultrasound of extremities if DVT is suspected. Ultrasound can also help identify fluid collections or abscesses in some locations (e.g., superficial wound, pelvis).
  • Computed Tomography (CT) Scan: Useful for evaluating deeper infections (intra-abdominal or pelvic abscesses), PE (CT angiography), or complex pneumonias.
  • Other Imaging: As clinically indicated (e.g., MRI, nuclear medicine scans).

Step 4: Revisit the “5 Ws” and Other Causes Systematically

• Based on the timing of the fever and the results of the initial evaluation, systematically work through the potential causes.
• Is there evidence of Wind-related issues on CXR or exam?
• Is there evidence of Water-related issues on urinalysis or urine culture?
• Is the Wound showing signs of infection?
• Review medication list – could it be a Wonder Drug?
• Are there signs of Walk-related issues (leg swelling, pain) or a deeper collection (Whopper)?

Step 5: Consider Less Common Causes and Consult Specialists

• If the initial workup is negative or inconclusive, broaden the differential to include less common causes.
• Consider consultation with Infectious Disease, Surgery, or other specialists as appropriate.

Step 6: Re-evaluate and Monitor

• Monitor the patient’s temperature trend, vital signs, and clinical status closely.
• Review culture results as they become available.
• Repeat lab work or imaging if the patient’s condition changes or initial studies were inconclusive.
• Assess response to empiric antibiotics (if started).

Conclusion

Postoperative fever requires diligent evaluation. By utilizing a structured approach, clinicians can effectively assess the patient, identify the most probable causes based on timing and clinical findings, and initiate targeted investigations and management to address potentially life-threatening complications. Collaboration among the surgical, anesthesia, nursing, and consulting teams is vital for optimal patient outcomes.