Surgical Site Infections (2)

8/9/2019 Surgical Site Infections (2)

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D R B AS H IR U A M IN U

Surgical site infections



outline

y Introduction

y Definition

y Historical perspective

y

Epidemiology y pathogenesis

y aetiology

y Classification

y

Clinical featuresy Management

y conclusion



introduction

y Surgical site infections continue to be a majorchallenge

y in spite of various advances in science

y It is responsible for significant increase in mortality ,morbidity &hospital stay

y This means more expenditure



definitions

y Infection occurring at site of operation or surgicaltract within thirty days of surgery or one year ff

implant surgerys



Historical perspective

y Edwin smith(circa 1600 bc), ebers papyrus(circa1534)

y Hippocrates (460ad-377bc)

y Galen laudable pus theory



14th century at the time of ambrose pare(1510-1590)

y Koch (1843-1910) recognized septic foci as result of microbial growth

y Semmelweis(1818-1865) reduction in puerperalsepsis



y Pasteur revolutionarized concept of wound infection

y Lister(1827-1912) used carbolic acid

y Antoine depagne(1862-1925) reintroduced

debridment & delayed closure

y Alexander fleming(1881-1955)of penicillin



y Halsted introduced rubber gloves to his scrub nurse who allergic to materials used in sterilizinginstruments

y His student J. bloodgood made it routine use



epidemiology

y frequency of SSI difficult to monitor

y A survey by WHO infections varying from 3-21%, with wound infections accounting for 5-34% of the

total.y The 2002 report (NINSS) Oct 97 and Sept 2001,

shows rates of 10% costing1 billion pounds annually.



y 75% of deaths in surgical patients is related to SSI

y Actual estimates difficult to make here due to paucity of data



pathogenesis

y With incision on skin 5 critical initiators of inflammatory response are activated

y Coagulation proteins

y platelets

y part of the hemostatic mechanism

y herald the onset of inflammation.

y

Mast cells ,complement proteins





y bradykinin is produced from protein precursors.

y The net effect of 5 factors is vasodilation andincreased blood flow



y products from 5 initiators result in nonspecificchemoattractant signals,

y mast cells produce specific chemokine signals that

"draw" specific neutrophil, monocyte, etc



y The point is that tissue injury initiates mobilizationof phagocytes into the wound before contaminationoccurs



aetiology

y All surgical wounds are contaminated

y most cases, infection does not develop because hostdefenses are efficient

y A complex interplay between host, microbial, andsurgical factors

y ultimately determines prevention or establishmentinfection.

y Factors that affect surgical wound healing areclassified below





microbiology

y Microbial factors are;

y the dose of inoculum,

y virulence,

y Microenvironment

y impaired host defenses

y patient's own endogenous flora



y The traditional microbial concentration is bacterialcounts higher than 10,000 organisms per gram of tissue (or in the case of burned sites, organisms per

cm2

of wound).



y largest inoculum is structure ordinarily heavily colonized eg bowel.

y distal small intestine and colon have large concn of

bacteria with 103 - 104 bacteria/mL of distal small bowel content,

y 105 - 106 bacteria/mL in the right colon, and 1010 -1012 bacteria/g of stool in the rectosigmoid colon.



y Large amts also present in stomach of older patients with hypo- or achlorhydria.

y Significant concn in biliary tract when patients are

over 70 years of agey or have obstructive jaundice etc



y Procedures in female genital tract will encounter 106

- 107 bacteria/mL.

y Procedures in oropharynx, lung, or urinary tract

have significant contaminantsy Notably, SSIs are generally consequence of intra

operative contamination



y The most bacteria responsible for SSIs Staphylococcus aureus.

y The emergence of resistant strains considerably

increased burden of morbidity and mortality



y skin and mucosal surfaces ; gram-positive cocci(notably staphylococci)

y G-ve aerobes and anaerobic bacteria contaminateskin in the groin/perineal areas.

y Contaminants in GIT surgery are bowel flora

y which include g-ve bacilli (eg, E coli ), g+s,enterococci



y G+ particularly staph & strep are main exogenousflora in SSIs.

y Sources of such pathogens include ;

y surgical/hospital personnely intra operative circumstances, instruments,

operating room air.



y Methicillin resistant Staphylococcus aureus (MRSA)

y MRSA colonize skin ,body of individual withoutcausing sickness,

y this way, it can be passed on to other individuals



y Systemic factors include;

y age, malnutrition, hypovolemia, poor tissueperfusion

y obesity, diabetes, steroids,y Immuno suppressants.



y Wound characteristics include;

y nonviable tissue in wound; hematoma;

y foreign material, including drains and sutures;

y dead space; poor skin prep +shaving

y and preexistent sepsis (local or distant).



y Operative chrxs include poor surgical technique;

y lengthy operation (>2 h);

y intraoperative contamination, eg theater staff and

instrumentsy inadequate theater ventilation;



y prolonged preop stay

y hypothermia.

y The type of procedure is a risk factor.







Vacuum-assisted wound closure



classification

y Various classifications

y traditional developed in wake of uv light study of 1964

y Primarily to provide clinical estimate of inoculum of bacteria

y does not take into cognisance factors like;

y virulence, host defences, microenvironment of the wound



y Clean Wounds

y does not enter into a colonized viscus or lumen

y eg elective inguinal hernia repair

y SSI risk is minimal

y common pathogen is Staphylococcus aureus

y SSI rates is 2% or less



y Clean-Contaminated Wounds

y enters colonized viscus or cavity under elective

y contaminants are endogenous bacteria

y Eg sigmoid colectomy wounds contain E coli and Bacteroides fragilis



y Elective intestinal resection, pulmonary resection,gynecologic procedures, and head-neck cancer op inoropharynx are examples

y Infection rates in the range of 4% to 10%



y Contaminated Wounds

y gross contamination present in absence of obviousinfection.

y eg laparotomy for penetrating injury +intestinalspillage

y contaminants bacteria introduced by gross soilage

y Infection rates greater than 10%



y Dirty Wounds

y active infection is already present

y Abdominal exploration for acute bacterial peritonitis

and intra-abdominal abscess are examplesy Pathogens those of active infection

y Unusual pathogens are seen

y

Esp if infection occurred in hospital or nursing homesetting



y US CDC developed the NNIS Risk Index system

y member hospitals report cumulative data.

y A risk index developed to include ;

y traditional wound classification system definedabove and additional variables.

y This simplified risk index has a range from 0 to 3points.

y A point is added to the patient's risk index for eachof the following 3 variables:



y This simplified risk index has a range from 0 to 3points.

y A point is added to the patient's risk index for each

of the following 3 variables



y 1 point - the patient had operation classified as eithercontaminated or dirty.

1 point - the patient has an ASA preoperativeassessment score of 3, 4, or 5

1 point - the duration of operation exceeds the 75th

percentile



y standard T point (75% percentile) determined fromNNIS database

y the T point defined as length of time in hours that

represents the 75th percentile of procedures



y Table 1. Ph ysical Status Classification f or Surgical Patients

y Class I A patient in normal health

y Class II A patient with mild systemic diseaseresulting in no functional limitations

y Class III A patient with severe systemic disease thatlimits activity, but is not incapacitating



y Class IV A patient with severe systemic disease thatis a constant threat to life

y Class V A moribund patient not likely to survive 24

hours

O i T i (h )



Operation T Point (hrs)s

y Operation T Point (hrs)y Coronary artery bypass graft 5y Bile duct, liver, or pancreatic surgery 4y Craniotomy 4y Head and neck surgery 4y Colonic surgery 3y Joint prosthesis surgery 3y Vascular surgery 3y Abdominal or vaginal hysterectomy 2y Ventricular shunt 2

y Herniorrhaphy 2y Appendectomy 1y Limb amputation 1y Cesarean section 1



y newer definitions of superficial incisional SSI, deepincisional SSI, and organ space SSI

y This methodology, + NNIS Risk Index, allows

recognition of SSI rates + classification of severity.y Reporting of data stratified by risk and severity



S fi i l I i i l SSI



Superficial Incisional SSI

y Occurs within 30 days after the operation;

y Involves only the skin or subcutaneous tissue; and

y At least 1 of the following:



Purulent drainage (culture documentation not required)

Organisms isolated from fluid/tissue of superficial incision

At least 1 sign of inflammation (eg, pain or tenderness,induration, erythema, local warmth of the wound)



y Deep Incisional SSIy Occurs within 30 days of operation or within 1 year if an

implant is present;

y Involves deep soft tissues (eg, fascia and/or muscle) of the incision; and




y Purulent drainage from deep incision minus organ/spaceinvolvement

Fascial dehiscence or fascia separated by the surgeon

Deep abscess identified by during reoperation,histopathology, radiologically

Surgeon declares deep incisional infection is present.





Wound is deliberately opened by the surgeon

Surgeon or attending physician declares the wound infected.

Organ/Space SSI



Organ/Space SSI

y Organ/Space SSI

y Occurs within 30 days of operation or within 1 year if animplant is present;

y Involves structures not opened or manipulated operation




y Purulent drainage from a drain placed by a stab wound

y Organisms isolated from organ/space by aseptic culturing technique

y

Identification of abscess in the organ/space by direct examination,during reoperation, or by histopathologic or radiologic examination

y Diagnosis of organ/space SSI by surgeon



w ound grading Southampton system

0 ± normal healing

1 ± normal healing with mild bruising/erythema

2 ±

Erythema + other signs of inflammation3- Clear or heamoserous discharge

4- Pus

5-Deep or severe wound infection with or without

tissue breakdown



ASEPSIS wound score

y A dditional treatment Antibiotic for wound infection 10Drainage of pus under LA 5Debridement of wound under GA 10

Serous discharge Daily 0-5Erythema Daily 0-5Purulent exudation Daily 0-10Separation of deep tissues Daily 0-10Isolation of bacteria 10

Stay greater than 14 days 5



Clinical features

y Most have been mentioned along line

y Local features which vary depending on stage, type

y Erythema , swelling, discharge, gaping wound,

dehiscencey Systemic symtoms; fever, weight loss from increased

catabolic loss



Major w ound infectiondefined as a wound that either discharge significantquantity of pus spontaneously or secondary procedure to drain it +/- systemic signs

Minor w ound infectionsthis may discharge pus or infected serous fluid butnot excessive s



Systemic manifestations

y Sepsis is the systemic manifestation of adocumented infection

y SIRS is the body systemic response to an infected wound

y MODS is the effect that the infection has on the whole body

y MSOF is the end stage of uncontrolled MODS



management

y Detailed history y Thorough physical examinationy Relevant investigations

Gram stain

Culture (both aerobic and anaerobic)Sensitivity testing Antigen and antibody testingDetecting of RNA and DNA sequencingPCR



y Staining methods;Gram stain

y Staining for fungal elements

y Culture techniques

y Fungal cultures can be requested



y Isolation of single colonies allows further growthand identification of the specific organism.

y Sensitivity testing then follows mainly for aerobic

organisms.y Newer techniques ELISA, radioimmunoassay



y Detection of antibody in host sera

y Detection of RNA or DNA sequences by Northern,Southern, or Western blotting, respectively

y Polymerase chain reaction (PCR)y FBC, FBS, U/E,SERUM PROTEINS



y Imaging Studies

y Ultrasound can be applied to the infected woundarea to assess whether any collection needs drainage.

y MRI, CT SCAN

TREATMENT



TREATMENT

Local-Drainage

-DebridementSystemic

-resuscitation-appropriate antibiotics



prevention

yPrinciples

ySpecific 1- removal of source of infection

2 - block transfer

3 - increase patient resistance

General 1- Infrastructure

theatre design

2 - Administrative policiesantibiotic policies



y patients to shower and scrub the surgical site withantiseptic soap

y dont shave or clipp evening before operation.

y Nicks and scrapes result in colonizationy Depilatory agents recommended

y occasionally result in a hypersensitivity



y The presence of open skin wounds or infection of thehands or arms of the surgeon makes postponementof the operation desirable.

y

If the patient has any preexisting infection, SSI will be more likely.



y Prevention in the OR begins with the skinpreparation

y The site is cleansed with chlorhexidine or

povidone iodine.y Isopropyl alcohol has excellent antiseptic qualities

but is undesirable because of its flammability



y Povidone iodine should be allowed to dry before theincision

y use of caps, gowns, masks, and sterile surgical

gloves.y Double gloving prevents blood "strike through" onto

the surgeon's hands



y Avoid blood ,fluid breakthrough especially onsurgeon's forearms

y Avoid wet drapes

y replace soaked gown &drapes.y Wide areas of skin prep around surgical site reduces

risk of breakthrough



y Gas sterilization of instruments after thoroughcleansing of any particulate matter

y Bowel prep

y Achieving hemostasis at the surgical site isimportant



y process of controlling bleeding may itself increaseinfection.

y HB in soft tissues or wound space Is potent stimulus

to microbial multiplicationy exuberant use of electro cautery leaves necrotic

tissue



y Prophylactic antibioticsReduces incidence of post-op wound infections

Directed against likely bacteria

Given 30-60mins before operation

Repeated if operation >4hours



± Incision should destroy as little tissue as possible(incisionmade through entire skin layer)

- Tissue plane divided with few passes of the knife always

beginning a new pass in the depths of the wound ± Ensure bleeding has stopped before closing wound



Avoid wound edge desication

Proper wound edge apposition

Use of few sutures

Surgical Site Infections (2)

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