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Infection and sepsis

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					INFECTION AND SEPSIS
     Surrounded by pathogens
     Infection is the exception
     Protective from infection
         Physical barriers
         Chemical barriers
         Immunological function
Physical and Chemical
Barriers to Infection
    Skin
        stronger in hands and feet
        sebaceous secretions lower pH
    Mucous membranes
        ciliary function
        mucous barrier
        acid mileu in stomach
Barriers breached in Surgery
Barriers Breached in Trauma
Immune Defense
   Humoral defense
       antibodies
       complement

   Cellular defense
   Cytokines
       potential for deleterious effects
    Interaction of mechanisms
Breakdown of Host Defense
   Physical, chemical and immunological
    breakdown -act synergistically
    e.g. patient with
           diabetes
           immunosuppresion
           surgery
   Potential for deleterious effects
Fourniers Gangrene
Commensal Microbial Flora
    Important for immune development
    Occupy binding sites for pathogens
    Provide mucobacterial barrier
    Anerobic bacteria
        present in greatest quantity in GIT
        Greatest diversity
        Prevent invasion by gram neg. aerobes
Breakdown of Host Defense
- GIT Flora
   Transmigration of bacteria
     Lack of feeding
     Overuse of antibiotics

     Absence of bile

     Protein malnutrition

     Immune deficiency
ICU patient fed enteraly
To preserve GIT integrity
Infection Manifestation
   Local signs
       pain,redness,swelling, warmth loss of
        function
   Systemic signs
       Fever, somnolence, confusion, ileus,
        hypotension
   Lab tests
       TW,-polymorphs, Cultures
   Non infective- causes may manifest as
    infection
Common Infections
Wound infection
   Initial inoculum overwhelms host defense
        Occurs at 5 - 7 days post op
   Factors
        host - immune suppression, DM, renal failure
        surgeon - technique
        environment - contamination
Common Infections
Types of Wounds
1. Clean - no viscus, no sterile breach
2. Clean contaminated - controlled entry into
   viscus
3. Contaminated - emergency bowel resection,
   perforated appendix
4. Dirty - heavy contamination / long duration
Antibiotics used
              type 2 as prophylaxis
              type 3,4 as treatment
Wound Closure
 Wounds
    Closure by
          primary intention
          secondary intention
    Timing of closure
          delayed primary closure
          secondary closure
Closure by Secondary Intention
Intraabdominal Infection
Defense
   Bacterial clearance - stomata between
    mesothelial cells under diaphragm lead to
    lymph vessels
   Phagocytosis - both resident and recruited
    phagocytes
   Sequestration - by fibrin rich inflammatory
    exudate, with omentum/viscera
Intraabdomianal Infection
   Signs of peritonitis
   Pain
       sharp in character, well localised at first
       spreads to surrounding areas
       involuntary guarding, rigidity
       absent bowel sounds
   Posture
       lying still, rapid breathing ,no movement
   General condition
       ill, septic, dehydrated, hypotension
Intraabdominal Infection
   Usually viscus perforation
       colon worse than upper GIT
   Isolates
       aerobic - E. Coli, klebsiella other
        enterobacter, strep, enterococci,
        proteus, pseudomonas
       anaerobic - bacteroides, Clostridium
   Treatment is surgical and aggressive
    antibiotic treatment
Enterocutaneous Fistula
Common Post Surgical
Infections
   Pneumonia
       Protein malnourished
       upper abdominal wounds ® poor cough
       bed bound - atelectasis
       elderly
       ventilator
   Occurs from 3 days post op
       careful clinical exam,CXR
       Routine chest physiotherapy
Common Post Surgical
Infections
   Urinary Tract Infection
         catheters
         dehydration
   Remove catheters early
   Ensure hydration
   Antimicrobial therapy
Common Post Surgical
Infections
   Catheter and prosthetic devices
         I/v canulas
         central lines
         mesh
   Skin organisms- S aureus, S epidermidis
   Aseptic technique
   Remove if infected
Less Common Post
Surgical Infections
   Necrotising soft tissue infection
   Parotitis
   Sinusitis
   Tonsillitis
Treatment of Infection
General principles
    incise and drain pus
    antibiotics as needed
    debride dead tissue
    remove foreign bodies
Antibiotic Therapy
Prophylaxis
    Short course to prevent infection
    Must be on board before contamination
    Antibiotics with activity against expected
     inoculation organisms
    Avoid extended spectrum agents
    Post op benefit not proven
    Topical antibiotics - not proven
Antibiotic Therapy
Empirical therapy
    based on clinical information
    search for source must continue
    limit duration of empirical therapy
    use known institution pattern of infection
    multi agent vs broad agent
Antibiotic Therapy
Directed therapy
    target identified pathogens
    choose suitable efficacy /minimal
     toxicity agent
    cover aerobic and anaerobic if
     likelihood exist for both
    extended spectrum as last resort
Multiple System
Organ Failure
AKA - Gram neg. bacterial sepsis
   30% mortality
   Healthy and compromised host
   3-13 cases per 1000 admissions
   Nosocomial
Multiple System Organ Failure
   Factors
       Host compromise
       Elderly, disability
       Malnutrition
       Antimicrobial therapy
       Major surgery
       Cavity manipulation
       Immunosuppression e.g. steroids
MSOF
   Fever
   Acidosis, hypoxemia
   Disordered oxygen and substrate use
   Hyperglycaemia
   Decreased systemic vascular resistance
   Elevated cardiac output
   Hypotension
MSOF
   Evidence for LPS - endotoxin
   LPS
       O antigen - specific for each organism
       core LPS
       membrane lipid A
LPS - EFFECTS
   non specific polyclonal b cell proliferation
   macrophage activation, cytokine release
   hypotension, hypoxemia
   bacterial translocation
   complement and coagulation activation
   platelet and white cell margination
LPS - Mechanism
   Direct effect of bacteria
   Indirect (mediated) effect
       trigger macrophages to release TNFa, IL-1,
        IL-6, aIFN
       TNFa, IL-1, - primary mediators but may
        be deleterious in large amounts
       aIFN- causes continued activation of
        macrophages
       Permeability defects in microcirculation
       ARDS, GUT, Hepatic, renal failure
Problem
A 23 year old man
had a perforated
appendix. Three
days post op this
was his temperature
chart. What is your
interpretation.
Problem
 What is your choice for antibiotic
 prophylaxis for
         colorectal surgery
         biliary surgery
         upper GI surgery
Problem
A 75 year old diabetic had an operation for
perforated diverticular disease. His wound
was found to be infected on the 5th POD.
What factors may have contributed to this?

				
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