Surgical Site Infection(SSI)

Team A-khoula HospitalAhmed Azmy

Key points:

Definition

Classifications

Incidence and

outcome

Sources of infection

Microbiology

Diagnostic workup

Prevention

Treatment

DEFINITION &

CLASSIFICATIONS

In 1992, US (CDC) revised its definition of 'wound infection', creating the definition 'surgical site infection' (SSI) to prevent confusion between the infection of a surgical incision and the infection of a traumatic wound(Horan et al., 1992).

SSI occurs at the site of surgery within 30 days of an operation or within 1 year of an operation if a foreign body is implanted as part of the surgery.

DEFINITION

CLASSIFICATIONS OF SSIs

I. Classification Based On The Depth Of Infection Penetrating Into The Wound:

1.INCISIONAL SSIs

a) Superficial incisional

b) Deep incisional

2.ORGAN/SPACE SSIs

*HORAN ET AL.,1992

II. Classification Of Deep Periprosthetic Infections (Tsukayama et al., 2003):

III. Classification Of Infections Associated With Fracture-Fixation Devices:

ACCORDING TO THE ROUTE OF INFECTION:

1)Perioperative

2)Contiguous

3)Hematogenous

ACCORDING TO THE ONSET OF SYMPTOMS AFTER

IMPLANTATION:

1)Early infection (< 2 weeks)

2)Delayed infection(2 wks – 10 wks)

3)Late infection (> 10 wks)

IV. Classification Of Postoperative Spinal Infections:

1) SUPERFICIAL INFECTIONS: Do not penetrate below the lumbar fascia.

2) DEEP INFECTIONS: Extend below the lumbar fascia and can present as diskitis, osteomyelitis, and epidural abscess.

INCIDENCE &

OUTCOME OF SSIs

The 3rd most frequently reported nosocomial infection.

22% of all HAIs are SSIs.

Prolong total hospital stay.

Double rehospitalisation rates.

The case fatality was the 2nd highest in orthopedic

surgery.

In europe, the total cost of all SSIs has been estimated

to range between 1.5 and 19 billion euros.

INCIDENCE AND OUTCOME OF SSIs

In PJI: TKR infection rates from 0.68% to 1.60%. THR infection rates from 0.67% to 2.4%.

*National Health Care Safety Network (NHSN),2009

In spine surgery: <1% after decompressive procedures. >10% after instrumented fusions.

INCIDENCE AND OUTCOME OF SSIS (CONT.)

In trauma surgery: Incidence is generally higher.

SOURCES OF SSIs

SOURCES OF SSIS

I. EXOGENOUS SOURCES II. ENDOGENOUS SOURCES

1. Air current deposition of contaminated particulates.

2. Direct contact of micro-organisms from contaminated hands, instruments or implants.

1. Hematogenous seeding from a pre-existing infection at a remote site .

2. Bacteria released into the wound when non-sterile body sites are entered.

3. Patient's own skin flora .

MICROBIOLOGY &

PATHOGENESIS

MICROBIOLOGY OF SSIs

I. BACTERIA

II. FUNGI

1. Commensal bacteria: May cause infection if the natural host is compromised eg, cutaneous coagulase negative staphylococci.

2. Pathogenic bacteria:a) Gram +ve: staphylococci are

the most common cause of prosthetic joint infections.

b) Gram –ve: eg., pseudomonas species

c) Anaerobes: eg., bacteriodes & clostridium species

Candida albicain

RECENT ADVANCES IN MICROBIOLOGY OF SSIs

“…(Dowd, Sun et al., 2008) have used advanced, next-generation, molecular methods such as bacterial Tag-Encoded FLX Amplicon Pyrosequencing (bTEFAP) to evaluate the microbial ecology of SSIs. In contrast, the results suggest that anaerobic rod shaped bacteria predominate in biofilms “

[4] Determinants Of

Infection

Inoculum of the bacteria

Wound Microenvironment

Virulence of the bacterial

contaminant

Host Defenses Integrity

PATHOGENESIS OF SSIs

Role of microbial biofilms (cont.):

Biofilms are surrounded by an extracellular matrix that might physically restrict the diffusion of antimicrobial agents.

Nutrient and oxygen depletion within the biofilm cause some bacteria to enter a non-growing (i.e. stationary) state in which they are less susceptible to growth-dependent antimicrobial killing.

DIAGNOSTIC WORKUP

Biological studies

Imaging

studies

Clinical presentation

Histopathological studies

Microbiologi

cal studies

DIAGNOSTIC WORK-UP

I.CLINICAL PRESENTATION :

•Spreading erythema of the skin around the incision line• Local pain• Local oedema• Heat• Pyrexia• Increased exudate /suppuration• Abscess formation• Lymphangitis• Cellulitis• Loss of function of a limb• Septacaemia

II.Microbiological studies:

Obtain ≥3 intraoperative tissue biopsies for microbiology and histology.

No swabs of sinus tracts or wounds.

Stop antibiotics >2-3 weeks before.

cytological test– sensitivity: - Leukocytes >1,700/mm³: 94% - Neutrophils >65%: 97%

New diagnostic methods as PCR.

WHEN? in whom the diagnosis of prosthetic joint–associated infection has not been established preoperatively.

HOW? by an intraoperative frozen section to look for evidence of acute inflammation.

+VE TEST: Varies (≥1 to ≥10 neutrophils / HPF).

III.HISTOPATHOLOGICAL STUDIES:

IV.IMAGING STUDIES:

Imaging plays an inferior role in early infection.Useful in delayed and late infections to assess the extent of infection.

INCLUDES:

1. Plain x-rays2. Ultrasonography3. Contrast arthrography4. Nuclear medicine5. Computed Tomography (CT)6. Magnetic Resonance Imaging (MRI)

RECENT ADVANCES IN IMAGING STUDIES

Fluorodeoxyglucose - positron emission tomography (FDG-PET):-Best criterion to conclude infection in patients with suspected periprosthetic infection Negative PET scan has 100 % sensitivity Positive PET can not differentiate between wear and infection*Delank et al., 2006

V.Biological Work-Up:

(CRP, ESR, WBCS COUNT) determination is recommended but is

not specific.

The diagnostic accuracy for prosthetic joint infection was best for

INTERLEUKIN-6 (Elie et al., 2010).

PROCALCITONIN levels (>0.5 ng/ml) were VERY SPECIFIC

(98%) but had a LOW SENSITIVITY (33%)(González et al.,

2011).

RISK FACTORS &

RECENT TRENDS IN PREVENTION OF SSIs

RISK FACTORS OF SSISI. PATIENT-RELATED RISK FACTORS:

1. Age2. Diabetes Mellitus / Perioperative Hyperglycemia 3. Obesity4. Tobacco Use5. Malnutrition6. Nasal Colonization With Staph Aureus 7. Pre-existing Remote Body Site Infection8. Compromised Immune System9. Peri-Operative Transfusions 10. Prolonged Preoperative Hospital Stay

II. PROCEDURE-RELATED RISK FACTORS:1. Operative Wound Class 2. Patient Skin Preparation In The Operating Room 3. Preoperative Shaving 4. Perioperative Hypoxia5. The Duration Of Surgery6. Surgical Technique7. A Postoperative Hematoma8. Surgical drains 9. Suboptimal Timing Of Antibiotic Prophylaxis10.Traffic in the Operating Room

RECENT TRENDS IN PREVENTION OF SSIs

I. PREOPERATIVE PREPARATION

1) PREOPERATIVE SHOWERING (CORE):Using chlorhexidine cut the risk for a SSI in half, compared with washing with 10% povidone-iodine.

1) HAIR REMOVAL (CORE):performed only when necessary via the use of electric clippers on the day of surgery.

1) NASAL DECOLONIZATION:with CHG and intranasal mupirocin.

1) STAFF THEATRE WEAR: wearing non-sterile theatre wear minimize the risk of SSI.

 A. PREOPERATIVE PERIOD (core):

Evaluate patients for pre-existing medical conditions. Assessment of the patient’s susceptibility and risk factors for infection.

B. INTRAOPERATIVE PERIOD:

1) SKIN ANTISEPSIS (CORE):with antiseptic that contains a combination of CHG or iodine with alcohol.

2) SURGICAL HAND ANTISEPSIS:alcohol-based rubs is as effective as aqueous solutions.

II. THE PERIOPERATIVE SETTING

3)ANTIMICROBIAL PROPHYLAXIS (CORE):

Choice of antimicrobial agent:Cephalosporin (cefazolin, cefuroxime) If β lactam allergy, use clindamycin or vancomycin

Timing of administration:Start up to 60 min before incision: cefazolin, cefuroxime, clindamycinStart up to 120 min before incision: vancomycinInfusion completed 10 min before tourniquet inflation

Dosing:Cefazolin. 1-2 g (2 g for patient weighing >86 kg)Cefuroxime, 1.5 gVancomycin and clindamycin dosing based on patient mass Duration:Single preoperative doseRedose for prolonged procedure or significant blood loss discontinue within 24 h after wound closure

*prokuski et al., 2008

4) MAINTAINING PATIENT HOMEOSTASIS:

a) Warming (core): Forced air warming for patients with a body temperature <36°C. b) Oxygenation: Using higher oxygen concentrations

c) Blood Transfusions (Hill et al., 2003):triple the risk of nosocomial infection compared with no transfusion. c) Perioperative Blood Glucose Control (core): should be maintained < 200 mg/dl for the first 48 hours after surgery.

c) Wound Irrigation & Intracavity Lavage: By betadine, Antibiotics & DetergentsUse pulsatile lavage

5) GOOD SURGICAL TECHNIQUE & WOUND CLOSURE

6) OTHER INTRAOPERATIVE FACTORS:a) Air Quality: laminar airflow Temperature should be maintained between (18 to 25 ºC) and

humidity between (40 to 60%).

b) Gloving: a second pair of surgical gloves provides a protective barrier to

both the patient and surgeon.

c) Minimize OR traffic.

d) Gowns and Drapes: should be resistant to tears, punctures, and abrasions.

e) Sterility Assurance

III.THE POSTOPERATIVE PERIOD (core)

The sterile dressing should remain in place for 24-48 hours postoperatively.

Silver-containing hydrofiber® (SCH) dressing (AQUACEL® silver [AG] dressing provides an excellent choice because:

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1) DIRECT METHOD: direct observation for SSI by a surgeon or a trained nurse

2) INDIRECT METHOD: combination of the following: review of microbiology reports, surgeon and/or patient surveys, and screening for readmission of surgical patients.

Follow-up phone calls to patients

Outpatient culture reports

Outpatient reports of antibiotic usage data

Readmission data to hospital or to another

hospital

TREATMENT OF SSIs

I. GENERAL TREATMENT OF SSIs:

1. Wound Assessment.

2. Incision & Drainage.

3. Systemic Antibiotic Therapy.

II. TREATMENT OF SPECIAL CASES IN SSIs:

1. Treatment Of Prosthetic Joint Infections.

2. Treatment Of Postoperative Spinal Infections.

3. Treatment Of Infections Associated With

Fracture Fixation-devices.

I. GENERAL TREATMENT OF SSIs

1. Wound assessment:

Helps:

To promote normal wound healing.

Identify risk factors as obesity, DM.

Identify early signs of infection.

2. Incision And Drainage:

Superficial incisional SSI can usually be treated without debridement, with oral antibiotics.

Suspected deep or organ/space SSI, fever (temperature>38.5◦C), or tachycardia (heart rate, 110 beats/min) generally require antibiotics in addition to opening of the suture line.

Most surgical wounds that are re-opened are left to heal by secondary intention.

Not Indicated: For uncomplicated SSIs

Indicated: If there is systemic evidence of Toxicity or cellulitis that extends >2 cm beyond the incision.

The Choice Of Antibiotic: Is defined by the operation performed through the incision and the likely infecting organism.

3. Systemic Antibiotic Therapy:

TREATMENT OF MRSA SSI:

Vancomycin, the reference standard MRSA treatment.

Teicoplanin, twice as active as vancomycin against S. aureus.

TREATMENT ALTERNATIVES IN MRSA SSI :

Doxycycline and Clindamycin are recommended for the outpatient treatment of non severe SSI.

Linezolid or Daptomycin are recommended in outpatients with moderately severe infections and for hospitalised patients with severe SSIs.

Tigecycline, Linezolid And Vancomycin are the most active agents against Gram-positive bacteria across Europe.

3. Systemic Antibiotic Therapy (continued):

II. TREATMENT OF SPECIAL CASES IN SSIs

1. TREATMENT OF PROSTHETIC JOINT INFECTIONS:

GOALS:

Eradicate infection.prevent its recurrence.preserve mechanical joint function.

PRINCIPLES OF TREATMENT:

Appropriate Surgical Strategy

Suitable Antibiotic Therapy.

2. Treatment Of Postoperative Infection Of The Spine:

GOALS:

Eradicate the germ.

Obtain wound closure.

Maintain spinal/vertebral

stability.

Obtain union of any grafts.

3. ttt Of Postoperative Infection Of The Spine(continued):

Most superficial and deep infections require aggressive excision of tissue associated with initial intravenous antibiotic therapy.

The duration of initial parenteral antibiotic treatment is usually 15 days. Then propose oral antibiotics.

3. Treatment Of Infections Associated With Fracture-Fixation Devices:

GOALS:

Consolidation of the fracture.

Prevention of chronic osteomyelitis.

i. SURGICAL THERAPY:

If the implant is stable, debridement with retention of the device combined with long-term antibiotic treatment.

If resistant or difficult-to-treat microorganisms are causing the infection complete hardware removal and external fixation is preferable.

ii. ANTIMICROBIAL THERAPY:

Duration is 3 months in cases of device retention and 6 weeks after removal of the infected fixation device. IV treatment should be administered for the first 2−4 wks, followed by oral therapy.