Surgical infection is a clinical disorder that manifests when the virulence factors of a microorganism introduced during surgical procedures overcome the innate and adaptive immune responses of the host.
Types of surgical infections
- Ventilator-associated pneumonia
- Catheter-associated urinary tract infections
- Central line-associated infections
- Surgical site infections (develop within 30 days of the procedure or within 90 days after a prosthetic material is implanted):
- Superficial: skin and superficial soft-tissue infections around incision sites
- Deep: infection involving fascia or deep spaces (e.g., abdominal or pelvic abscess)
- Patient factors:
- Diabetes mellitus
- Peripheral vascular disease
- Prior radiation to the area
- Extremes of age
- Corticosteroid therapy
- Treatment-related factors:
- Long-term catheter use
- Poor disinfection and sterile techniques for invasive procedures or catheter care
- Emergent procedures
- Absent or inadequate antibiotic prophylaxis
- Prolonged hospitalization
- Prolonged operative time
Etiology and Pathophysiology
Several factors make patients who have undergone surgery particularly susceptible to nosocomial infections:
- Incisions made during surgical procedures can serve as a direct site of entry.
- Surgical illness creates a state of immunosuppression.
- Periods of mechanical ventilation during and after surgery:
- Risk for pneumonia
- Increased aspiration risk
Presence of bacteria may or may not be associated with clinically significant infection.
- Colonization: Bacteria are present but do not stimulate an immune response with corresponding signs and symptoms of local or systemic disease.
- Infection: Proliferation of microorganisms in tissues, organs, or cavities stimulates an immune response that leads to local and/or systemic disease.
- Sepsis: life-threatening organ dysfunction caused by excessive and disproportionate host response to infections
Pathogenesis of infection
- Once microbes enter, host defenses (i.e., tissue barriers, iron-sequestering lactoferrin and transferrin, fibrinogen) act to control and/or eliminate pathogens:
- In the peritoneal cavity, a diaphragm motion extracts the microorganism-containing peritoneal fluid from the abdominal cavity into the lymphatic circulation.
- Macrophages, low levels of complement (C) proteins, and immunoglobulins are embedded in the vast majority of tissues to aid in host defense.
- Macrophages secrete cytokines (tumor necrosis factor (TNF)-α; IL-1β, 6, and 8; and interferon (IFN)-γ) to recruit and activate inflammatory cells.
- Potential outcomes:
- The microorganism is eradicated.
- Containment in the parenchyma (i.e., abscess)
- Localized infection, displaying local symptoms (i.e., cellulitis)
- Systemic infection (bacteremia or fungemia) with associated symptoms (i.e., fever, tachycardia)
Timeline of infection
- Early postoperative (1‒3 days):
- Always consider a preexisting community-acquired infection.
- Early surgical site infection:
- Group A Streptococcus
- Clostridium perfringens
- Pneumonia: peak incidence at postoperative day 2
- Urinary tract infection: should be considered in any patient with a catheter in place
- Late postoperative (> 3 days):
- Surgical site infection is the most common cause.
- Catheter-related infections
- Antibiotic-associated infections: C. difficile
Signs of systemic inflammation (SIRS):
- Temperature > 38ºC (100.4ºF) or < 35ºC (95ºF)
- HR > 90/min
- RR > 20/min or PaCO2 < 35 mm Hg
- WBC > 12,000 (leukocytosis) or < 4,000 (leukopenia)
Specific findings related to surgical infections:
- Tenderness at or around the surgical wound
- Redness (erythema) of the surgical incision
- Purulent drainage from the surgical wound
- Rebound tenderness
Signs of shock:
- Altered mental status
Quick sepsis-related organ failure assessment (qSOFA):
- Identifies patients at the greatest risk of poor outcomes outside of an ICU
- Based on 3 parameters:
- RR ≥ 22/min
- Altered mentation
- Systolic BP ≤ 100 mm Hg
- WBC > 10,000
- ↑ Serum creatinine
- ↑ BUN
- ↑ CRP, erythrocyte sedimentation rate
- Lactic acid
- Urine culture
- Sputum culture
- Gram staining and culture of wound or collection
- Blood cultures
- 1st-line imaging modality in the majority of cases
- Chest: assess for infiltrates or consolidation if > concern for pneumonia
- Abdomen: upright to assess for free air
- 2nd-line imaging modality in the majority of cases if the patient is stable
- More sensitive than X-ray for detecting consolidation, infiltrates, and effusion
- Abdominal CT identifies free air, free fluid, and bowel inflammation.
- Soft-tissue infections can be identified with stranding, or if gas in the tissue is concerning for a necrotizing infection.
- Rarely the 1st-line modality except in children and pregnant individuals
- Magnetic resonance cholangiopancreatography to image the biliary system
Prevention of surgical infections depends largely on sterile technique, hand hygiene, and the administration of prophylactic antibiotics.
- The WHO’s 5 steps of hand hygiene:
- Before touching a patient
- Before a clean/aseptic procedure
- After the risk of body-fluid exposure
- After touching a patient
- After touching a patient’s surroundings
- Soap and water, or alcohol-based disinfectants are both acceptable (exception: for C. difficile, where soap and water must be used, as alcohol does not kill bacterial spores).
Preoperative MRSA screening
- Can reduce MRSA transmission in wards
- Contact precautions are initiated for patients with known MRSA infections or colonization:
- Gown, mask, and gloves upon entering the patient’s room
- Hand hygiene
- Positive results are followed by decolonization therapy and antibiotic prophylaxis prior to the procedure.
A term used to describe steps taken by the surgical team before and during a surgical procedure to prevent the development of postoperative infections, which includes:
- Before every procedure, using an aqueous antiseptic surgical solution chosen by the institution
- At least 3 minutes of washing time
- Sterile gowns
- Surgical cap
- Face shield
- Prepping of the surgical site:
- Chlorhexidine prep
- Properly sterilized or single-use surgical instruments
- Antibiotic coverage to further prevent the proliferation of commensal microorganisms
- Selection depends on:
- Procedure to be performed
- Expected pathogens
- Local patterns of resistance
- Disease severity
- Age of the patient
- Organ dysfunction
- Institutional guidelines
- Single doses are used as they are as effective as multidose courses.
- Attention must be paid to the timing of administration so that adequate serum concentrations are achieved prior to the start of the surgical procedure.
- Cardiac, vascular, and orthopedic cases:
- Cefazolin or cefuroxime
- GI procedures:
- Neomycin and erythromycin
- Cefazolin with metronidazole
- Gynecological procedures:
- Cefazolin, cefoxitin, cefotetan, or cefuroxime
The management of surgical infections is described using the term “source control,” which implies the combination of surgical management (if indicated) with the administration of antibiotics.
- Avoid antibiotics in self-limiting infections to avoid the development of resistance.
- Identification and sensitivities of organisms guide antibiotic selection.
- Empiric therapy can be started based on clinical suspicion, but should be narrowed to fit sensitivities of the identified organisms.
- Each antibiotic has specific dosing and time intervals based on its pharmacokinetics.
- Be aware of potential side effects and monitor accordingly.
|S. pyogenes (group A β-hemolytic Streptococcus)||Clarithromycin|
- Most often needs to be drained
- Technique depends on the type of abscess:
- Incision and drainage for superficial skin/soft-tissue abscess
- Percutaneous needle aspiration with/without catheter placement:
- Abdominal/pelvic or deep soft-tissue abscesses
- Ultrasound or CT guidance is used.
- Open surgery: may be needed if percutaneous drainage is not feasible
Necrotizing fasciitis and diabetic foot infections:
- Urgent surgical debridement of all necrotic tissue
- Often require repeated/serial debridements
- Gossain, S., Hawkey, P.M. (2018). Infections and antibiotics. In Garden, O.J., et al. (Eds.), Principles and Practice of Surgery. pp. 48–59. https://www.clinicalkey.com/#!/content/3-s2.0-B9780702068591000042
- Quick, C.R.G., et al. (2020). Immunity, inflammation and infection. In Quick, C.R.G., et al. (Eds.), Essential surgery: Problems, Diagnosis and Management. pp. 31–49. https://www.clinicalkey.com/#!/content/3-s2.0-B9780702076312000031
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