4. Infection and SIRS, Antibiotics
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Transcript of 4. Infection and SIRS, Antibiotics
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Graeme MacLaren MBBS FCICM FRACP FCCPDirector, Cardiothoracic ICU
Assistant Professor of SurgeryNational University Health System, Singapore
Infection, Wounds, and SIRS in surgery
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Prcis
Natural barriers to infection Effects of surgery SIRS and sepsis Prevention
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Barriers to Infection Part of innate immunity Skin
Stronger in hands and feet Sebaceous secretions lower pH
Mucous membranes Ciliary function Mucous barrier Proteolytic enzymes eg. lysozyme Acid milieu in stomach
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Barriers to Infection Commensal enteric bacteria
Important for immune development Occupy binding sites for pathogens Provide mucobacterial barrier Anaerobic bacteria
present in greatest quantity in gastrointestinal tract diverse prevent invasion by Gram negative aerobes
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Immune defense Innate immunity
Basic polypeptides Complement Natural killer cells
Humoral defense (B-cell immunity)
Cellular defense (T-cell immunity)
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Breakdown of host defense Patient factors
Chronic illness Diabetes End-stage renal failure
Immunosuppression Steroid use Immunosuppressant therapy, eg. cyclosporin
Malnutrition malignancy
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Breakdown of host defense Surgery
Bypasses host defenses via controlled trauma SIRS May alter anatomy or blood supply permanently Perioperative antibiotics kill commensal enteric flora Associated medical devices
central venous lines urinary catheters mechanical ventilation nasogastric tubes
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Bypass of host defensesNasogastric tube:
Impairs sinus drainage, potentiating sinusitis
Endotracheal tube:(only pilot balloon visible)
Impairs coughing, ciliary function, increases % of pneumonia
Pulmonary artery catheter (central venous catheter):
Provides portal of entry into bloodstream
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Definitions Systemic inflammatory response syndrome (SIRS)
Common response to surgery Diagnosed when >1 of the following are present:
Body temperature 38 Heart rate > 90 bpm Respiratory rate >20 or PaCO2
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Definitions Sepsis is defined as
SIRS due to infection Severe sepsis is
sepsis with organ dysfunction, hypoperfusion, or hypotension
Septic shock is severe sepsis with arterial hypotension despite adequate
fluid resuscitation
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SIRS Common pathophysiological response to a host of
triggers, eg. surgery, infection, trauma, pancreatitis, burns, cardiopulmonary bypass
Mediated by a host of cytokines, including IL-6 Adrenomedullin sCD14 sELAM-1 MIP-1
Extracellular phospholipase A2 C-reactive protein
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Manifestations of infection Local
Pain Erythema Swelling Warmth
Systemic Fever or hypothermia Tachycardia Tachypnoea Vasodilation and hypotension
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Types of wounds1. Clean - no viscus, no sterile breach2. Clean contaminated - controlled entry into viscus3. Contaminated eg. emergency bowel resection,
perforated appendix4. Dirty - heavy contamination / long duration
Antibiotics used for prophylaxis in allAntibiotics used for treatment in 3. and 4.
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Common post-surgical infections Pneumonia
Ventilator-associated or not Exact definition difficult, no gold standard Presence of SIRS, worsening pulmonary infiltrates, productive
sputum consistent, but not 100% specific More common in patients with
Prolonged ventilation Upper abdominal surgery Major thoracic surgery Thoracoabdominal trauma Poor post-operative analgesia
Common cause of death; needs aggressive treatment with appropriate anti-microbials (including anti-pseudomonal + anti-staph)
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Common post-surgical infections Urinary tract infection (UTI)
Not especially common, except after urological surgery. Important to distinguish between asymptomatic catheter-
associated bacteriuria (CA-ASB) and genuine UTI. Catheter-associated UTI is: Presence of signs of symptoms compatible with UTI No other identified source of infection >10x3 cfu/ml of bacteriaCA-ASB is: >10x5 cfu/ml of bacteria No symptoms of UTI (IDSA guidelines, 2010)
Note that pyuria not useful in discriminating between them
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Common post-surgical infections Vascular catheter-associated infection
Most common with central venous catheters (CVC), also seen with arterial lines and IV cannulae. Most important determinants is efficacy of sterility of insertion and how long they are left in
No evidence that routinely changing CVCs is of benefit, unless they appear infected or the patient has SIRS with no obvious cause
All peripheral cannulae should be changed every 48-72 hours
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Common post-surgical infections Surgical site infection (SSI)
Superficial vs Deep Superficial easily diagnosed
often respond to appropriate wound care and may not require systemic antibiotics unless surrounding cellulitis, artificial material used during surgery, or SIRS present
Deep is harder to diagnose. May just manifest as SIRS without obvious focus May require imaging (eg CT scan) or surgery (eg. repeat
laparotomy) to diagnose, depending on the site of surgery Treatment always involves re-operating AND systemic
antibiotics
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Treatment of SSI Incise and drain pus Antibiotics (depends on the type of surgery) Debride devitalized tissue Remove foreign bodies
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Prevention of SSI: Asepsis Topical anti-septics, eg. chlorhexidine Thorough washing and gloving Sterile drapes Meticulous surgical technique Hair removal: often unnecessary. Clip, dont shave
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Prevention of SSI: Antibiotics Prophylactic antibiotics before skin incision shown to
reduce SSI significantly Use antibiotics appropriate to the site of surgery, eg.
cephazolin for skin organisms; ampicillin, gentamicin, metronidazole for bowel surgery.
Limit to intra-operative dosing, or
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Prevention of SSI: Other measures Maintain good control of blood sugar (eg. 4-8 mmol/L,
though ideal levels controversial, extremes should definitely be avoided)
Perioperative normothermia Other measures are controversial, including
Supplemental oxygen to decrease infection Skin stapling vs suturing Leucocyte filters on allogeneic blood products
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Example A 57 year old with a 20 year history of poorly
controlled diabetes undergoes a right hemicolectomy for an adenocarcinoma of the colon. He has been recovering well post-operatively. On POD 7, you are called to see him as he feels unwell and the nurse reports fever. Vital signs are: Temp 39 Heart rate 135 BP 80/40 Respiratory rate 22
What do you do?
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Suggested approach Resuscitate: A, B, C Notify seniors Blood cultures Other septic workup, eg. MSU, sputum, if possible Brief targeted history, eg. symptomatology Comprehensive physical examination CXR Start appropriate antibiotics Further investigations as directed by assessment, eg CT
abdomen Likely differentials: SSI, Hospital-acquired pneumonia Much less likely but worth considering: UTI, IV infection,
DVT/PE (extremely unlikely, but life-threatening), pseudomembranous colitis, epidural site infection, etc
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The end
Slide Number 1PrcisBarriers to InfectionBarriers to InfectionImmune defenseBreakdown of host defenseBreakdown of host defenseBypass of host defensesDefinitionsDefinitionsSIRSManifestations of infectionTypes of woundsCommon post-surgical infectionsCommon post-surgical infectionsCommon post-surgical infectionsCommon post-surgical infectionsTreatment of SSIPrevention of SSI: AsepsisPrevention of SSI: AntibioticsPrevention of SSI: Other measuresExampleSuggested approachThe end