INFECTION AND SEPSIS

1. INFECTION AND SEPSIS • Surrounded by pathogens • Infection is the exception • Protective from infection • Physical barriers • Chemical barriers • Immunological function

2. Physical and ChemicalBarriers to Infection • Skin • stronger in hands and feet • sebaceous secretions lower pH • Mucous membranes • ciliary function • mucous barrier • acid mileu in stomach

3. Barriers breached in Surgery

4. Barriers Breached in Trauma

5. Immune Defense • Humoral defense • antibodies • complement • Cellular defense • Cytokines • potential for deleterious effects Interaction of mechanisms

6. Breakdown of Host Defense • Physical, chemical and immunological breakdown -act synergistically e.g. patient with • diabetes • immunosuppresion • surgery • Potential for deleterious effects

7. Fourniers Gangrene

8. 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

9. Breakdown of Host Defense- GIT Flora Transmigration of bacteria • Lack of feeding • Overuse of antibiotics • Absence of bile • Protein malnutrition • Immune deficiency

10. ICU patient fed enteraly To preserve GIT integrity

11. 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

12. 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

13. 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

14. Wound Closure Wounds • Closure by • primary intention • secondary intention • Timing of closure • delayed primary closure • secondary closure

15. Closure by Secondary Intention

16. 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

17. 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

18. 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

19. Enterocutaneous Fistula

20. 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

21. Common Post Surgical Infections • Urinary Tract Infection • catheters • dehydration • Remove catheters early • Ensure hydration • Antimicrobial therapy

22. 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

23. Less Common Post Surgical Infections • Necrotising soft tissue infection • Parotitis • Sinusitis • Tonsillitis

24. Treatment of Infection General principles • incise and drain pus • antibiotics as needed • debride dead tissue • remove foreign bodies

25. 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

26. 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

27. 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

28. Multiple System Organ Failure AKA - Gram neg. bacterial sepsis • 30% mortality • Healthy and compromised host • 3-13 cases per 1000 admissions • Nosocomial

30. Multiple System Organ Failure Factors • Host compromise • Elderly, disability • Malnutrition • Antimicrobial therapy • Major surgery • Cavity manipulation • Immunosuppression e.g. steroids

31. MSOF • Fever • Acidosis, hypoxemia • Disordered oxygen and substrate use • Hyperglycaemia • Decreased systemic vascular resistance • Elevated cardiac output • Hypotension

32. MSOF • Evidence for LPS - endotoxin • LPS • O antigen - specific for each organism • core LPS • membrane lipid A

33. 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

34. 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

35. Problem A 23 year old man had a perforated appendix. Three days post op this was his temperature chart. What is your interpretation.

36. Problem What is your choice for antibiotic prophylaxis for • colorectal surgery • biliary surgery • upper GI surgery

37. 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?