Graeme MacLaren MBBS FCICM FRACP FCCPDirector, Cardiothoracic ICU

Assistant Professor of SurgeryNational University Health System, Singapore

Infection, Wounds, and SIRS in surgery

Prcis

Natural barriers to infection Effects of surgery SIRS and sepsis Prevention

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

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

Immune defense Innate immunity

Basic polypeptides Complement Natural killer cells

Humoral defense (B-cell immunity)

Cellular defense (T-cell immunity)

Breakdown of host defense Patient factors

Chronic illness Diabetes End-stage renal failure

Immunosuppression Steroid use Immunosuppressant therapy, eg. cyclosporin

Malnutrition malignancy

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

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

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

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

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

Manifestations of infection Local

Pain Erythema Swelling Warmth

Systemic Fever or hypothermia Tachycardia Tachypnoea Vasodilation and hypotension

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.

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)

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

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

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

Treatment of SSI Incise and drain pus Antibiotics (depends on the type of surgery) Debride devitalized tissue Remove foreign bodies

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

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

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

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?

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

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