Postoperative Infection

Overview

Postoperative infections are healthcare-associated infections that develop as a complication of surgical procedures. They represent a significant challenge in modern healthcare, affecting patient outcomes, extending hospital stays, increasing healthcare costs, and potentially leading to serious complications or death if not properly managed.

The Centers for Disease Control and Prevention (CDC) classifies surgical site infections into three categories: superficial incisional SSI affecting only the skin and subcutaneous tissue; deep incisional SSI involving deep soft tissues like fascia and muscle; and organ/space SSI affecting organs or spaces other than the incision that were opened or manipulated during surgery.

These infections typically develop within 30 days of surgery, or within 90 days if an implant is left in place. The risk varies significantly depending on the type of surgery, with clean procedures having infection rates of 1-5%, clean-contaminated procedures 3-11%, contaminated procedures 10-17%, and dirty-infected procedures 15-30%.

The economic burden of postoperative infections is substantial, with each infection adding an average of $13,000-25,000 to healthcare costs and extending hospital stays by 7-11 days. More importantly, these infections can lead to reoperation, permanent disability, or death, making prevention and early recognition crucial for optimal patient outcomes.

Symptoms

The symptoms of postoperative infections vary depending on the location, depth, and severity of the infection. Early recognition of these symptoms is crucial for prompt treatment and prevention of complications.

Local Signs at the Surgical Site

• Skin swelling - edema and inflammation around the incision
• Abnormal appearing skin - redness, warmth, and changes in skin color
• Increased tenderness or pain at the surgical site
• Purulent drainage from the incision
• Wound dehiscence (separation of wound edges)
• Delayed wound healing
• Induration (hardening of tissues)
• Heat emanating from the wound area

Systemic Signs and Symptoms

• Fever - often the first systemic sign of infection
• Chills and rigors
• Malaise and general feeling of illness
• Fatigue and weakness
• Loss of appetite
• Nausea and vomiting
• Elevated heart rate (tachycardia)
• Elevated respiratory rate

Site-Specific Symptoms

• Sharp abdominal pain - severe pain following abdominal surgery
• Jaw swelling - localized swelling after oral or maxillofacial surgery
• Skin on leg or foot looks infected - signs of infection in extremity surgeries
• Difficulty breathing (respiratory surgeries)
• Urinary symptoms (genitourinary procedures)
• Neurological symptoms (neurosurgery)
• Joint pain and stiffness (orthopedic procedures)

Superficial Incisional SSI Symptoms

• Redness extending from the incision edges
• Warmth and tenderness along the incision
• Purulent discharge from the superficial incision
• Pain or tenderness at the incision site
• Swelling limited to superficial tissues

Deep Incisional SSI Symptoms

• Fever greater than 38°C (100.4°F)
• Spontaneous dehiscence of deep tissues
• Abscess formation in deep tissues
• Severe localized pain
• Diagnosis of deep SSI by surgeon or attending physician

Organ/Space SSI Symptoms

• Symptoms specific to the organ system involved
• Abscess formation in organ spaces
• Systemic signs of sepsis
• Organ dysfunction or failure
• Positive cultures from organ/space sites

Complications and Warning Signs

• Spreading cellulitis beyond the surgical site
• Necrotizing fasciitis (rapidly spreading deep infection)
• Sepsis and septic shock
• Organ failure
• Persistent high fever despite treatment
• Rapid deterioration in clinical condition
• Mental status changes
• Hypotension or shock

Time Course of Symptom Development

• Early (1-3 days): Local pain, mild swelling, low-grade fever
• Intermediate (3-7 days): Increased drainage, redness, systemic symptoms
• Late (7-30 days): Deep tissue involvement, abscess formation
• Delayed (>30 days): Usually associated with implants or foreign bodies

Causes

Postoperative infections result from bacterial contamination of the surgical site, which can occur through multiple pathways during the perioperative period. Understanding these causes helps in developing effective prevention strategies.

Microbial Causes

Common Bacterial Pathogens

• Staphylococcus aureus: Most common cause, includes MRSA (methicillin-resistant)
• Coagulase-negative staphylococci: Common in implant-related infections
• Enterococcus species: Often seen in abdominal and genitourinary surgeries
• Escherichia coli: Common in colorectal and genitourinary procedures
• Pseudomonas aeruginosa: Associated with contaminated equipment or solutions
• Enterobacter species: Increasingly antibiotic-resistant organisms
• Streptococcus species: Group A and B streptococci

Anaerobic Bacteria

• Bacteroides fragilis (abdominal surgeries)
• Clostridium species (especially in contaminated wounds)
• Peptostreptococcus species
• Fusobacterium species

Fungal Pathogens (Less Common)

• Candida species
• Aspergillus species
• Other opportunistic fungi in immunocompromised patients

Sources of Contamination

Endogenous Sources

• Patient's own flora: Skin, mucous membranes, gastrointestinal tract
• Nasal carriage: S. aureus colonization
• Bowel flora: During gastrointestinal procedures
• Remote infections: Bacteremia from distant infection sites
• Preexisting conditions: Diabetes, immunosuppression

Exogenous Sources

• Operating room environment: Air, surfaces, equipment
• Surgical team: Healthcare workers' skin, respiratory droplets
• Surgical instruments: Inadequately sterilized equipment
• Implants and foreign materials: Prosthetic devices, sutures
• Contaminated solutions: Irrigation fluids, medications

Mechanisms of Infection Development

Bacterial Adherence and Biofilm Formation

• Initial bacterial attachment to tissues or foreign materials
• Biofilm development providing protection from antibiotics
• Persistent bacterial reservoirs
• Resistance to host immune responses

Tissue Damage and Compromise

• Surgical trauma disrupting normal tissue defenses
• Ischemia and necrosis providing bacterial growth medium
• Hematoma and seroma formation
• Foreign body reactions

Procedural Factors Contributing to Infection

• Inadequate skin preparation: Insufficient antisepsis
• Breaks in sterile technique: Contamination during surgery
• Prolonged operative time: Increased exposure to contamination
• Excessive tissue damage: Rough handling, extensive dissection
• Poor hemostasis: Blood and clot accumulation
• Inadequate antibiotic prophylaxis: Wrong timing, dose, or selection
• Hypothermia: Impaired immune function and wound healing
• Hyperglycemia: Impaired neutrophil function

Environmental Factors

• Operating room ventilation and air quality
• Traffic in and out of operating room
• Overcrowding of healthcare facilities
• Inadequate cleaning and disinfection protocols
• Cross-contamination between patients

Risk Factors

Multiple patient-related, procedure-related, and environmental factors contribute to the risk of developing postoperative infections. Understanding these risk factors helps identify high-risk patients and implement targeted prevention strategies.

Patient-Related Risk Factors

Medical Comorbidities

• Diabetes mellitus: 2-3 fold increased risk
  • Impaired neutrophil function
  • Poor wound healing
  • Increased susceptibility to infection
  • Risk increases with poor glycemic control
• Obesity (BMI >30): Significant risk factor
  • Increased technical difficulty
  • Poor tissue perfusion
  • Increased operative time
  • Wound tension and healing problems
• Malnutrition: Albumin <3.5 g/dL associated with increased risk
• Chronic kidney disease: Impaired immune function
• Liver disease: Decreased protein synthesis and immune dysfunction
• Cardiovascular disease: Poor tissue perfusion
• Chronic obstructive pulmonary disease: Respiratory complications

Immunocompromising Conditions

• Cancer and chemotherapy: Neutropenia and immune suppression
• Corticosteroid use: >10mg prednisone daily for >2 weeks
• Immunosuppressive medications: Transplant patients, autoimmune diseases
• HIV/AIDS: Severely compromised immune system
• Radiation therapy: Local tissue damage and immune effects
• Advanced age: Declining immune function (>65 years)

Lifestyle and Social Factors

• Smoking: 2-6 fold increased risk
  • Impaired wound healing
  • Decreased tissue oxygenation
  • Increased respiratory complications
• Alcohol abuse: Immune dysfunction and poor nutrition
• Drug abuse: Increased infection risk and poor compliance
• Poor hygiene: Increased bacterial colonization
• Recent hospitalization: Exposure to resistant organisms

Procedure-Related Risk Factors

Surgical Factors

• Wound classification:
  • Clean: 1-5% infection rate
  • Clean-contaminated: 3-11% infection rate
  • Contaminated: 10-17% infection rate
  • Dirty-infected: 15-30% infection rate
• Duration of surgery: >2 hours significantly increases risk
• Emergency vs. elective: Emergency procedures have higher infection rates
• Complexity of procedure: More extensive surgeries carry higher risk
• Minimally invasive vs. open: Open procedures generally higher risk

Perioperative Factors

• Inadequate antibiotic prophylaxis: Wrong drug, timing, or duration
• Hair removal method: Shaving increases risk vs. clipping
• Skin preparation: Inadequate antisepsis
• Hypothermia: Core temperature <36°C
• Hyperglycemia: Perioperative glucose >180 mg/dL
• Blood transfusion: Immunomodulatory effects
• Hypoxemia: Tissue oxygen levels <60 mmHg

Technical Factors

• Breaks in sterile technique
• Inadequate hemostasis
• Excessive tissue trauma
• Foreign body placement (implants, mesh)
• Wound closure under tension
• Poor tissue approximation

Healthcare System Factors

• Hospital characteristics:
  • High patient volume and turnover
  • Teaching vs. non-teaching hospitals
  • Infection control practices
  • Antimicrobial stewardship programs
• Surgeon experience: Learning curve effects
• Operating room factors: Ventilation, traffic, contamination
• Nursing and support staff: Experience and adherence to protocols

Postoperative Risk Factors

• Prolonged hospitalization: Exposure to resistant organisms
• ICU stay: Multiple invasive devices and procedures
• Inadequate wound care: Poor technique or compliance
• Premature suture/staple removal: Wound dehiscence
• Poor pain control: Limiting mobility and coughing
• Urinary catheter use: Risk of urinary tract infection
• Central line use: Risk of bloodstream infection

Diagnosis

The diagnosis of postoperative infections is based on clinical criteria, laboratory findings, and sometimes imaging studies. Early accurate diagnosis is crucial for timely treatment and prevention of complications.

Clinical Diagnosis Criteria

CDC Surveillance Definitions

Superficial Incisional SSI (within 30 days of procedure):

• Infection involves only skin and subcutaneous tissue of incision, AND
• At least one of the following:
  • Purulent drainage from superficial incision
  • Organisms isolated from aseptically obtained culture
  • Signs/symptoms of infection AND superficial incision deliberately opened
  • Diagnosis of superficial SSI by surgeon or attending physician

Deep Incisional SSI (within 30-90 days depending on implant):

• Infection involves deep soft tissues AND
• At least one of the following:
  • Purulent drainage from deep incision
  • Spontaneous dehiscence or deliberately opened with signs of infection
  • Abscess found on examination, reoperation, or imaging
  • Diagnosis of deep SSI by surgeon or attending physician

Organ/Space SSI (within 30-90 days depending on implant):

• Infection involves organs or spaces opened or manipulated during surgery AND
• At least one of the following:
  • Purulent drainage from drain placed in organ/space
  • Organisms isolated from aseptically obtained culture
  • Abscess found on examination, reoperation, or imaging
  • Diagnosis of organ/space SSI by surgeon or attending physician

Physical Examination

• Inspection: Redness, swelling, drainage, dehiscence
• Palpation: Tenderness, warmth, induration, fluctuance
• Measurement: Size of erythema, wound dimensions
• Documentation: Photography for objective monitoring
• Systemic assessment: Vital signs, general appearance

Laboratory Studies

Microbiological Studies

• Wound culture:
  • Tissue biopsy preferred over swab cultures
  • Quantitative cultures >10^5 organisms/gram tissue
  • Include anaerobic cultures for appropriate specimens
  • Susceptibility testing for antibiotic selection
• Blood cultures: For patients with systemic signs of infection
• Fluid cultures: Aspirated fluid from collections or drains
• Gram stain: Rapid preliminary information about organisms

Laboratory Markers of Infection

• White blood cell count: Elevated WBC >11,000/μL
• C-reactive protein (CRP): Elevated >10 mg/L
• Erythrocyte sedimentation rate (ESR): Elevated but non-specific
• Procalcitonin: Elevated in bacterial infections >0.5 ng/mL
• Lactate: Elevated in severe infections and sepsis

Imaging Studies

Ultrasound

• First-line imaging for fluid collections
• Real-time guidance for drainage procedures
• Assessment of deep tissue involvement
• No radiation exposure

Computed Tomography (CT)

• Excellent visualization of deep abdominal infections
• Detection of abscesses and collections
• Guidance for percutaneous drainage
• Assessment of complications

Magnetic Resonance Imaging (MRI)

• Superior soft tissue contrast
• Useful for spine and joint infections
• No radiation exposure
• May require contrast enhancement

Nuclear Medicine

• Indium-111 labeled WBC scan: Localizes infection
• Gallium-67 scan: Inflammatory process imaging
• PET scan: Metabolic activity assessment
• Useful when anatomical imaging is inconclusive

Differential Diagnosis

• Non-infectious complications:
  • Hematoma or seroma formation
  • Wound dehiscence without infection
  • Foreign body reaction
  • Allergic reaction to sutures or dressings
• Other inflammatory conditions:
  • Drug reactions
  • Autoimmune conditions
  • Radiation effects
  • Chemical irritation
• Remote infections: UTI, pneumonia, thrombophlebitis

Risk Assessment and Scoring Systems

• NNIS Risk Index: ASA score, wound class, operation duration
• SENIC Score: Multiple risk factors assessment
• SEPSIS-3 Criteria: For systemic infection assessment
• qSOFA Score: Quick sepsis assessment tool

Treatment Options

Treatment of postoperative infections requires a comprehensive approach that includes antimicrobial therapy, surgical management when necessary, and supportive care. The specific treatment strategy depends on the type, severity, and location of the infection.

Antimicrobial Therapy

Empirical Antibiotic Selection

Initial antibiotic choice should be based on:

• Likely pathogens: Based on surgical site and type of procedure
• Local resistance patterns: Hospital and unit-specific antibiograms
• Severity of infection: Mild, moderate, or severe presentation
• Patient factors: Allergies, renal function, other comorbidities

Common Empirical Regimens

• Mild superficial infections:
  • Cephalexin 500mg PO QID
  • Clindamycin 300-450mg PO TID (if penicillin allergic)
  • Trimethoprim-sulfamethoxazole (for MRSA coverage)
• Moderate infections:
  • Cefazolin 1-2g IV Q8H
  • Ampicillin-sulbactam 3g IV Q6H
  • Vancomycin 15-20mg/kg IV Q12H (if MRSA suspected)
• Severe or organ/space infections:
  • Piperacillin-tazobactam 4.5g IV Q6H
  • Meropenem 1g IV Q8H
  • Vancomycin plus cefepime or ceftazidime

Targeted Therapy

Once culture results are available:

• De-escalation: Narrow spectrum based on sensitivities
• MRSA infections: Vancomycin, linezolid, daptomycin, or ceftaroline
• Enterococcal infections: Ampicillin (sensitive) or vancomycin (VRE)
• Gram-negative infections: Beta-lactams, fluoroquinolones, or carbapenems
• Anaerobic infections: Metronidazole, clindamycin, or beta-lactam combinations

Surgical Management

Indications for Surgical Intervention

• Abscess formation requiring drainage
• Necrotizing soft tissue infection
• Infected implants or foreign bodies
• Fascial dehiscence with deep infection
• Failure to respond to antimicrobial therapy
• Hemodynamic instability due to infection

Surgical Procedures

• Incision and drainage:
  • Bedside drainage for superficial collections
  • Operating room drainage for complex cases
  • Placement of drains when appropriate
• Debridement:
  • Removal of necrotic and infected tissue
  • Sharp debridement preferred
  • May require multiple procedures
• Wound revision:
  • Excision of infected wound edges
  • Primary closure vs. delayed closure
  • Vacuum-assisted closure (VAC) therapy
• Hardware removal:
  • Infected orthopedic implants
  • Mesh infections in hernia repairs
  • Vascular graft infections

Wound Care Management

Wound Assessment and Cleaning

• Daily assessment: Size, depth, drainage, surrounding tissue
• Cleaning: Normal saline irrigation
• Debridement: Remove devitalized tissue and debris
• Drainage management: Monitor output and character

Dressing Selection

• Dry gauze: For wounds with minimal drainage
• Hydrocolloid dressings: For granulating wounds
• Alginate dressings: For heavily draining wounds
• Antimicrobial dressings: Silver or iodine-containing
• Negative pressure therapy: VAC for complex wounds

Supportive Care

Nutritional Support

• Adequate protein intake (1.2-2.0 g/kg/day)
• Vitamin C and zinc supplementation
• Correction of nutritional deficiencies
• Enteral nutrition preferred over parenteral

Metabolic Management

• Glycemic control: Target glucose <180 mg/dL
• Fluid and electrolyte balance: Adequate hydration
• Pain management: Adequate analgesia
• Temperature control: Fever management

Treatment Duration

• Superficial SSI: 5-7 days of antibiotics
• Deep SSI: 7-14 days depending on response
• Organ/space SSI: 14-21 days or longer
• Bacteremia: 2-4 weeks depending on organism
• Osteomyelitis: 6-12 weeks of therapy

Monitoring and Follow-up

• Clinical response assessment at 48-72 hours
• Laboratory markers trending (WBC, CRP)
• Wound healing progress
• Antibiotic side effects monitoring
• Long-term functional outcomes

Treatment of Complications

• Sepsis: Aggressive fluid resuscitation, vasopressors
• Organ failure: Supportive care, ICU management
• Antibiotic resistance: Infectious disease consultation
• Persistent infection: Surgical re-exploration

Prevention

Prevention of postoperative infections requires a comprehensive, multidisciplinary approach involving preoperative optimization, intraoperative best practices, and postoperative care. Evidence-based prevention strategies can reduce infection rates by 25-50%.

Preoperative Prevention Measures

Patient Optimization

• Glycemic control:
  • Target HbA1c <7% for elective surgery
  • Perioperative glucose control <180 mg/dL
  • Consider endocrinology consultation for poorly controlled diabetes
• Smoking cessation:
  • Stop smoking ≥4 weeks before surgery
  • Nicotine replacement therapy support
  • Counseling and behavioral interventions
• Nutritional optimization:
  • Correct malnutrition (albumin ≥3.5 g/dL)
  • Protein supplementation if needed
  • Consider delaying elective surgery for severe malnutrition
• Weight optimization: Consider weight loss for severely obese patients

Preoperative Screening and Treatment

• MRSA screening:
  • Nasal PCR or culture for high-risk patients
  • Decolonization with mupirocin and chlorhexidine
  • 5-day treatment course before surgery
• Remote infection treatment:
  • Identify and treat active infections
  • Postpone elective surgery until resolved
  • UTI, dental infections, skin infections
• Immunization status: Update vaccinations as appropriate

Preoperative Skin Preparation

• Patient bathing:
  • Chlorhexidine soap night before and morning of surgery
  • Alternative: povidone-iodine if chlorhexidine allergy
  • Focus on surgical site area
• Hair removal:
  • Avoid shaving (increases infection risk)
  • Use electric clippers if hair removal necessary
  • Remove hair as close to surgery time as possible
• Antiseptic preparation:
  • Alcohol-based chlorhexidine preferred
  • Povidone-iodine alternative
  • Allow adequate contact time for antiseptic action

Intraoperative Prevention Strategies

Antibiotic Prophylaxis

• Timing: Within 60 minutes before incision (120 minutes for vancomycin)
• Selection: Based on procedure type and likely pathogens
• Dosing: Weight-based dosing for obese patients
• Duration: Single dose or ≤24 hours postoperatively
• Redosing: If procedure >2 half-lives of antibiotic

Environmental Controls

• Operating room ventilation:
  • Positive pressure with ≥15 air changes per hour
  • HEPA filtration for orthopedic implant procedures
  • Limit OR traffic during procedures
• Sterilization and disinfection:
  • Proper instrument sterilization protocols
  • Environmental surface disinfection
  • Flash sterilization only when absolutely necessary

Surgical Technique

• Sterile technique:
  • Proper hand hygiene and gloving
  • Sterile draping and equipment handling
  • Change gloves if contaminated
• Tissue handling:
  • Gentle tissue manipulation
  • Adequate hemostasis
  • Remove devitalized tissue
  • Minimize electrocautery damage
• Wound closure:
  • Avoid excessive tension
  • Proper tissue approximation
  • Minimize foreign material

Perioperative Care

• Normothermia:
  • Maintain core temperature ≥36°C
  • Forced-air warming devices
  • Warm irrigation fluids
• Oxygenation:
  • FiO2 ≥80% during surgery and early recovery
  • Maintain adequate tissue perfusion
  • Avoid hyperoxia in cardiac procedures
• Fluid management:
  • Goal-directed fluid therapy
  • Avoid fluid overload
  • Maintain adequate perfusion pressure

Postoperative Prevention

Wound Care

• Incision protection:
  • Sterile dressing for 24-48 hours
  • Keep incision clean and dry
  • Avoid unnecessary dressing changes
• Hand hygiene:
  • Healthcare workers before wound contact
  • Patient and family education
  • Alcohol-based hand sanitizer availability

Early Mobilization and Care

• Early ambulation to prevent complications
• Respiratory exercises to prevent pneumonia
• Remove urinary catheters as soon as possible
• Remove central lines when no longer needed

Quality Improvement and Surveillance

• Infection surveillance:
  • Active surveillance for SSI
  • Standardized definitions and reporting
  • Risk-adjusted infection rates
• Antibiotic stewardship:
  • Appropriate antibiotic selection and duration
  • Minimize antibiotic resistance
  • Regular review of prophylaxis protocols
• Feedback and education:
  • Regular infection rate reporting to surgeons
  • Continuing education on prevention strategies
  • Implementation of evidence-based bundles

When to See a Doctor

Seek immediate emergency care for:

• High fever >101.5°F (38.6°C) with chills
• Severe, worsening pain at the surgical site
• Rapid spreading redness or red streaking from incision
• Signs of sepsis: confusion, rapid breathing, rapid heart rate
• Wound dehiscence with visible deep tissues or organs
• Profuse or foul-smelling drainage from surgical site
• Difficulty breathing or chest pain after surgery
• Signs of shock: dizziness, low blood pressure, rapid pulse

Contact your surgeon urgently for:

• Any fever above 100.4°F (38°C) after surgery
• Increasing skin swelling around incision
• Abnormal appearing skin with redness or warmth
• Purulent or bloody drainage from surgical site
• Opening of surgical incision
• Persistent or worsening sharp abdominal pain
• New onset nausea, vomiting, or inability to eat
• Any concerns about wound healing or appearance

Schedule follow-up appointment for:

• Routine post-operative wound check as scheduled
• Suture or staple removal
• Mild drainage or delayed wound healing
• Questions about activity restrictions or wound care
• Medication side effects or concerns

Preventive measures to discuss with your healthcare team:

• Proper wound care techniques and supplies
• Signs and symptoms to watch for
• Activity restrictions and guidelines
• Medication compliance and completion
• Follow-up appointment scheduling
• When to resume normal activities

High-risk patients should be especially vigilant if they have:

• Diabetes mellitus or poor glucose control
• Immunocompromising conditions or medications
• History of previous surgical site infections
• Obesity or nutritional deficiencies
• Chronic medical conditions affecting wound healing

Related Conditions

• Cellulitis
• Necrotizing Fasciitis
• Sepsis
• Wound Dehiscence
• Abscess
• Osteomyelitis
• Prosthetic Joint Infection
• Healthcare-Associated Infection

References

1. Berríos-Torres SI, Umscheid CA, Bratzler DW, et al. Centers for Disease Control and Prevention Guideline for the Prevention of Surgical Site Infection, 2017. JAMA Surg. 2017;152(8):784-791.
2. Ban KA, Minei JP, Laronga C, et al. American College of Surgeons and Surgical Infection Society: Surgical Site Infection Guidelines, 2016 Update. J Am Coll Surg. 2017;224(1):59-74.
3. World Health Organization. Global Guidelines for the Prevention of Surgical Site Infection. 2nd ed. Geneva: World Health Organization; 2018.
4. Allegranzi B, Bischoff P, de Jonge S, et al. New WHO recommendations on preoperative measures for surgical site infection prevention: an evidence-based global perspective. Lancet Infect Dis. 2016;16(12):e276-e287.
5. Korol E, Johnston K, Waser N, et al. A systematic review of risk factors associated with surgical site infections among surgical patients. PLoS One. 2013;8(12):e83743.