LC 9: SURGICAL INFECTION

KEY POINTS

A. SEPSIS

  • Life-threatening syndrome

  • Infection + dysregulated systemic host response

  • Some form of organ dysfunction
    B. SOURCE CONTROL

  • Key concept

  • Necrotic tissue is a good medium for bacterial growth and may impede level of antimicrobial agent

  • Control the source of infection by way of removing necrotic tissue, purulent material since it may impede the level of antimicrobial agent at the site of infection.
    C. PRINCIPLES OF PROPHYLACTIC ANTIBIOTIC TREATMENT

  • Select an agent for commonly found organisms at the site of surgery.

  • Initial dose within 30 minutes prior to infection (latest guideline = 2 hours).

  • Redose for long duration surgery (guideline 3 hours).

  • Should not be continued for more than 24 hours after surgery (routine prophylaxis).
    D. PRINCIPLES IN SERIOUS INFECTION ANTIBIOTIC

  • Identify likely sources of infection.

  • Select antibiotics for a particular agent.

  • Inadequate antibiotics → increased mortality (start with a broad spectrum).

  • Obtain sensitivity test (C/S) and refine treatment. If the initial test is responsive, shifting of medication (antimicrobial) is not recommended.

  • If no infection is identified after 3 days – discontinue antibiotic (AB) based on patient progress.

  • Discontinue AB after appropriate course.
    E. SSI

  • Is prevented with appropriate patient preparation, timely perioperative antibiotic administration, maintenance of perioperative normothermia and normoglycemia, and appropriate wound management.
    F. NECROTIZING STI

  • Early recognition and debridement
    G. TRANSMISSION OF HIV

  • Universal precaution (including hepatitis and others)

  • In surgery, we protect ourselves by using proper PPE, donning & doffing.

  • Applies to not only in HIV but also in any infection cases such as the recent pandemic infection, COVID-19.

  • Routine use of barriers when anticipating contact with blood or body fluids.

  • Washing of hands and other skin surfaces immediately after contact with blood or body fluids.

  • Careful handling and disposal of sharp instruments during and after use.

DEFINITIONS

  • INFECTION:

    • The presence of microorganisms in host tissue or the bloodstream. It does not mean that if you do not have symptoms, you do not have the microorganism.

  • CLASSICAL LOCAL MANIFESTATIONS:

    • Rubor: redness

    • Calor: heat

    • Dolor: pain

    • Tenderness

  • SYSTEMIC MANIFESTATIONS:

    • Elevated temperature - also a sign of inflammation

    • Elevated WBC - manifestation of infection

    • Tachycardia

    • Tachypnea

BARRIERS OF INFECTION

FIRST LINE OF DEFENSE

  1. Physical barrier:

    • Epithelial/mucosal

    • Any break in the skin or mucosa leads to the introduction of microorganisms into the body.

  2. Host barrier cells:

    • Substances secreted can limit microbial proliferation and prevent invasion.

    • Example: hair cells trap microorganisms.

  3. Resident/commensal microbes (Good bacteria):

    • The second line of defense, meaning these bacteria have already entered our body.

    • Include inflammatory responses and immunoglobulins.

RISK FACTORS OF INFECTION

  1. Injury:

    • Breakage of the first line of defense.

  2. Impaired resuscitation/definitive care:

    • Example: blood transfusion can decrease immune response.

    • Blood sugar control is critical.

  3. Host Factors (Impaired defenses):

    • Genotype (Innate immunity)

    • Older age (extremes of ages)

    • Hyperglycemia

    • Nutritional status

MEDICAL CONDITIONS KNOWN TO INCREASE RISK OF POSTOPERATIVE INFECTION

  • Extreme of age (Neonates, very old adults)

  • Malnutrition

  • Obesity (poor circulation)

  • Diabetes Mellitus

  • Prior site irradiation

  • Hypothermia

  • Hypoxemia

  • Coexisting infection remote to the surgical site

  • Corticosteroid therapy (lower immune response)

  • Recent operations, especially of chest or abdomen

  • Chronic inflammation

  • Hypocholesterolemia

OUTCOMES OF INFECTION

  • Outcomes depend on the immune system:

    1. Eradication

    2. Containment:

    • Sign of containment is an ABSCESS.

    1. Locoregional Infection:

    • If not contained, it could spread to regional nodes (e.g., infected wound on the right leg drains to the inguinal region).

    1. Systemic:

    • Septicemia.

SYSTEMIC INFLAMMATORY RESPONSE SYNDROME (SIRS)

  • Proinflammatory response to a variety of disease processes such as infection, pancreatitis, polytrauma, malignancy, and burns.

CRITERIA FOR SIRS

  • General Variables:

    • Fever (core temp >38.3°C)

    • Hypothermia (core temp <36°C)

    • Heart rate >90 bpm

    • Tachypnea

    • Altered mental status

    • Significant edema or positive fluid balance (>20 mL/kg)

    • Hyperglycemia in the absence of diabetes

  • Inflammatory Variables:

    • Leukocytosis (WBC >12,000)

    • Leukopenia (WBC <4,000)

    • Bandemia (>10% band forms)

    • Plasma C-reactive protein >2 S.D. above normal value

    • Plasma procalcitonin >2 S.D. above normal value

SIRS IS NOT EQUIVALENT TO SEPSIS

SEPSIS

  • Defined as life-threatening organ dysfunction caused by a dysregulated host response to infection.

  • Organ dysfunction is identifiable as an acute change in total SOFA score ≥2 points due to infection.

    • The baseline SOFA score can be assumed to be zero in patients without known pre-existing organ dysfunction.

    • A SOFA score ≥2 reflects an overall mortality risk of about 10% in a general hospital population with suspected infection.

SEQUENTIAL (SEPSIS-RELATED) ORGAN FAILURE ASSESSMENT SCORE (SOFA)

  • RESPIRATION: PaO2/FIO2 (kPA) ratio

  • COAGULATION: Platelet count

  • LIVER: Bilirubin

  • CIRCULATORY VASCULAR SYSTEM: Mean Arterial Pressure (MAP) and use of vasopressors

  • CNS: Glasgow Coma Scale (GCS) Score

  • RENAL: Creatinine and urine output

qSOFA (QUICK SOFA) CRITERIA

  • Respiratory rate: ≥22/min

  • Altered mentation

  • Systolic blood pressure: ≤100 mmHg

    • This criterion identifies adult patients with suspected infection likely to have poor outcomes and does not require laboratory tests and can be assessed quickly and repeatedly.

SEPTIC SHOCK

  • Definition: Septic shock is a subset of sepsis where underlying circulatory and cellular/metabolic abnormalities are profound enough to increase mortality significantly.

  • Identification of septic shock includes clinical constructs of sepsis with persisting hypotension requiring vasopressors to maintain MAP ≥65 mmHg and serum lactate level >2 mmol/L (18 mg/dL) despite adequate volume resuscitation.

    • With these criteria, hospital mortality is over 40%.

COMMON PATHOGENS

  • Gram-positive:

    • Aerobic skin commensals (Staph/Strep)

    • Enteric organisms (E. faecalis and faecium)

  • Gram-negative:

    • Bacilli: Enterobacteriaceae (E. coli, Klebsiella), Pseudomonas

  • Fungi:

    • Nosocomial infections - Candida

  • Virus:

    • Immunocompromised patients

GENERAL PRINCIPLES IN MANAGEMENT (INFECTION CONTROL)

REDUCE PRESENCE OF EXOGENOUS AND ENDOGENOUS MICROORGANISMS (PROPHYLAXIS)

  • Can be grouped into:

    • Skin preparation

    • Antimicrobial Therapy

    • Patient physiological management

    • The first step for infection control is to reduce the microbial burden.

    • Pathogens can be reduced either endogenously or exogenously.

PATHOGEN SOURCES

  • ENDOGENOUS:

    • Present in the patient, increased flora.

      • Reduce patients' flora on the skin using antiseptics.

      • Operations are not performed if there are pre-existing infections (e.g. UTI, pneumonia) until infections are treated.

  • EXOGENOUS:

    • Outside the body.

      • Surgical personnel must adhere to proper hygiene and aseptic technique.

      • The environment and ventilation of the OR must be controlled.

PROPHYLAXIS

SKIN PREPARATION

  • Full body bath or shower using soap or antiseptic agent the night before surgery.

  • Hair removal should be done at the OR using clippers.

  • Skin cleansed with alcohol-based antiseptic agent.

PREOPERATIVE ANTIMICROBIAL THERAPY

  • Should be administered based on guidelines within the correct time frame, allowing bactericidal concentration in tissues before incision.

    • Physiologic Management Intraoperative Patient:

  • Maintain euglycemia (serum glucose <200 mg/dL)

  • Maintain normothermia

  • Optimize tissue oxygenation

SOURCE CONTROL

  • Drainage of purulent materials (e.g., abscess) is crucial for antimicrobial penetration.

  • Debridement of infected or necrotic tissues must occur.

  • Removal of foreign bodies at the infection site enhances the inflammatory response.

  • Immediate intervention within the first 12 hours if feasible minimizes morbidity and mortality.

EXAMPLES IN SOURCE CONTROL

  • If an intravenous device is the source, remove after establishing another access.

PROPER USE OF MICROBIAL AGENTS

  • PROPHYLACTIC:

    • To reduce the number of microbes entering the tissue or body cavity.

  • EMPIRIC:

    • Use tailored for high infection risk or significant contamination, limiting to short courses (3-5 days).

    • E.g.

    • UTI: 3-5 days

    • Pneumonia: 7-8 days

    • Bacteremia: 7-14 days

    • Osteomyelitis, endocarditis, prosthetic infections: 6-12 weeks

PRINCIPLES IN ANTIMICROBIAL PROPHYLAXIS

FOUR PRINCIPLES GUIDE THE ADMINISTRATION OF AN ANTIMICROBIAL AGENT FOR PROPHYLAXIS

  1. Safety: Ensure it is safe and appropriate.

  2. Appropriate narrow-spectrum coverage for relevant pathogens.

  3. Little or no reliance on the agent for the therapy of infection (to limit resistance).

  4. Administration should occur within 1 hour before surgery and within a defined period thereafter, ideally a single dose or up to 48 hours for cardiac surgery.

PROPHYLACTIC ANTIBIOTIC OF CHOICE

  • First generation cephalosporin: Most common for clean, clean-contaminated surgeries, especially those associated with gram-positive cocci (Staph aureus).

  • If gram-negative coverage required:

    • Consider second generation cephalosporins or combine with metronidazole.

    • Vancomycin may be used in high MRSA incidence areas.

DURATION OF TREATMENT

  • Prophylaxis: Single dose only.

  • Empiric: Treatment lasts for 3-5 days, discontinued in the absence of local/systemic infection.

  • Therapeutic: Standard guidelines.

SURGICAL SITE INFECTION (SSI)

CLASSIFICATION

  • Incisional infections resulting from surgery:

    • Superficial incisional: Limited to skin and subcutaneous tissue occurring within 30 days.

    • Deep incisional: Involves deep tissue (e.g. fascia or muscle).

    • Organ/Space: Involves other body parts outside skin, fascia, and muscle.

DEVELOPMENT OF SSI FACTORS

  1. Degree of microbial contamination: During surgery.

  2. Duration of the procedure: Higher risk with longer procedures.

  3. Host factors: Diabetes, malnutrition, obesity, immune suppression.

RISKS FOR POSTOPERATIVE INFECTION

  • Extremes of age (neonates, older adults)

  • Malnutrition

  • Obesity

  • Diabetes mellitus

  • Prior site irradiation

  • Chronic inflammation

ORGANISMS CAUSING SSI

  • Predominantly skin flora:

    • Staphylococcus aureus 30.0%

    • Coagulase-negative staphylococci 13.7%

    • Enterococcus spp. 11.2%

    • Escherichia coli 9.6%

    • Pseudomonas aeruginosa 5.6%

    • Enterobacter spp. 4.2%

    • Klebsiella pneumoniae 3.0%

PRINCIPLES IN ANTIMICROBIAL PROPHYLAXIS (AMP)

  • Use AMP shown to reduce SSI.

  • Safe, inexpensive and bactericidal covering most probable intraoperative contaminants.

  • Administered at times ensuring bactericidal concentration achieved when skin incision is made and maintained until operation closure.

GENERAL TREATMENT APPROACHES

  • ANTIBIOTICS:

    • Choice depends on suspected pathogen, severity of infection, patient medical history.

  • SURGICAL THERAPY:

    • Significant collection of pus, tissue necrosis, or foreign bodies indicates interventions like drainage and wound care.

PREVENTION OF SSI

  • INTERVENTIONS:

    • Optimize patient health: Smoking cessation, weight management, control diabetes, address infections, review medications.

    • Reduce microbial burden through hygiene and proper surgical techniques.

    • Enforce sterile technique and environmental control in the OR.

INTRAOPERATIVE MEASURES

  1. Maintain a sterile field.

  2. Reduce surgery duration to limit exposure time.

POST-OPERATIVE CARE

  • Regular wound care, monitor signs of infection, manage pain and promote early ambulation.

  • Educate patients on proper wound care.

INTRA-ABDOMINAL INFECTIONS

GUIDELINES ON MANAGEMENT

  • Antibiotics must meet specific criteria when treating for peritonitis.

PERITONITIS CLASSIFICATIONS

  1. PRIMARY:

    • Hematogenous route or direct inoculation, common in ascites patients.

  2. SECONDARY:

    • Due to perforation or severe organ inflammation, requires source control like resection or draining necrotic tissue.

  3. TERTIARY:

    • Persistent peritonitis needing aggressive interventions.

POSTOPERATIVE NOSOCOMIAL INFECTION

  • Common types: Postoperative pneumonia (VAP), central line-associated bloodstream infection, and urinary tract infections.

SKIN & SOFT TISSUE INFECTIONS

DEFINITIONS AND INFECTIONS

  1. CELULITIS: Non-necrotizing inflammation of skin and subcutaneous tissue, typically acute.

  2. FOLLICULITIS: Infection of hair follicles, generally manageable with hygiene.

  3. FURUNCLE & CARBUNCLE: Abscess conditions requiring drainage or surgical intervention.

  4. NECROTIZING FASCIITIS: Severe condition that can lead to mortality, with swift intervention required.

KEY POINTS AND CONCLUSIONS

A. Recognize the vital importance of timely identification and intervention in infection management, including early antibiotic administration.
B. Proper surgical techniques must be adhered to in both preoperative and postoperative care to reduce risk factors associated with infection.
C. Understanding microbial dynamics and maintaining source control are essential for successful outcomes in surgical settings.
D. The adoption of global guidelines ensures best practices are followed across surgical disciplines to prevent and manage SSI.