Infection in Surgical Patients

1. Infection in Surgical Patients August, 2006 Mike Joutovsky, PGY3 Department of Surgery St. Barnabas Hospital

7. Defense Barriers • Physical • Chemical • Immunologic

8. Host defense • Barrier • Microbial flora • Humoral • Cellular • cytokine

9. Microbial flora

10. Humoral defenses • Immunoglobulin • Complement

11. Immunoglobulin • All Ig classes (IgM, G, A, E, D and igG subclasses are composed of one type (M,G,A,E,D) of heavy (H) and one type of light (L) protein. • Each L chain is linked to an H chain, and H chains are interlinked. • H chain activate complement or bind to receptors of either macrophages or PMN leucocytes • The amino terminus of the H and L chains together forms antigen-binding site

12. Immunoglobulin

13. Complement system • Series of serum proteins that may became activated via either classic or alternative pathway

15. Cellular defense • Macrophage • PMN leucocytes • cytokines

16. Surgical Site Infection ( SSI )

17. Clinical criteria ( CDC ) • A purulent exudate draining from the surgical site • A positive fluid culture obtained from a surgical site that was closed primarily • The surgeon’s diagnosis of infection • A surgical site that requires reopening

18. FACTS • One out of every 24 patients who have inpatient surgery in the United States has a postoperative SSI • The cost of SSIs are substantial: an increased total cost of more than 300% • SSIs increase the post operative length of hospital stay by 10-14 days

19. Definition • SSI is a difficult term to define accurately because it has a wide spectrum of possible clinical features • “It’s hard to define, but I know it when I see it.” • SSI are classified into three categories, depending of which anatomic areas are affected

21. Definitions of SSI • Superficial incisional SSI: Infection involves only skin and subcutaneous tissue of incision. • Deep incisional SSI: Infection involves deep tissues, such as fascial and muscle layers. This also includes infection involving both superficial and deep incision sites and organ/space SSI draining through incision. • Organ/space SSI: Infection involves any part of the anatomy in organs and spaces other than the incision, which was opened or manipulated during operation.

22. Causes • Table 1. Pathogens Commonly Associated with Wound Infections and Frequency of Occurrence*Pathogen Frequency (%)*NNIS System (CDC, 1996)

23. Risk factors • Decreased host resistance can be due to systemic factors affecting the patient's healing response, local wound characteristics, or operative characteristics. • Systemic factors include age, malnutrition, hypovolemia, poor tissue perfusion, obesity, diabetes, steroids, and other immunosuppressants. • Wound characteristics include nonviable tissue in wound; hematoma; foreign material, including drains and sutures; dead space; poor skin preparation, including shaving; and preexistent sepsis (local or distant). • Operative characteristics include poor surgical technique; lengthy operation (>2 h); intraoperative contamination, including infected theater staff and instruments and inadequate theater ventilation; prolonged preoperative stay in the hospital; and hypothermia

24. The type of procedure is a risk factor too

25. Antimicrobial agents • Prophylaxis • Empiric therapy • Directed therapy

26. Classes of Antimicrobial Agents • Penicillins, Cephalosporins, carbapenems inhibit cell wall synthesis, resulting in bacteriolysis • Tetracyclins, chloramphenicol, and macrolides inhibit bacterial ribosomal activities and thus overall protein synthesis • Vanco inhibits assembly of peptido glycan polymers • Quinolones inhibit bacterial DNA synthesis

27. Prophylactic Antibiotics • General agreement exists that prophylactic antibiotics are indicated for clean-contaminated and contaminated wounds • Antibiotics for dirty wounds are part of the treatment because infection is established already. • Clean procedures might be an issue of debate. No doubt exists regarding the use of prophylactic antibiotics in clean procedures in which prosthetic devices are inserted because infection in these cases would be disastrous for the patient.

28. Systemic preventive antibiotics should be used in the following cases • A high risk of infection is associated with the procedure (eg, colon resection). • Consequences of infection are unusually severe (eg, total joint replacement). • The patient has a high NNIS risk index.

29. The antibiotic should be administered preoperatively but as close to the time of the incision as is clinically practical. Antibiotics should be administered before induction of anesthesia in most situations. • The antibiotic selected should have activity against the pathogens likely to be encountered in the procedure. • Postoperative administration of preventive systemic antibiotics beyond 24 hours has not been demonstrated to reduce the risk of SSIs

30. Intraoperative re-dosing • Operation is prolong • If massive blood loss occurs • The patient is obese

31. Colorectal Surgery • Recommended oral prophylaxis consist of Neomycin plus erythromycin or Neomycin plus Flagyl, along with administration of mechanical bowel preparation • Intravenous cefoxitin or cefazolin preoperatively and continued 2 doses or 24 hrs postoperatively

32. Intraabdominal Infection • Usually polymicrobial • There is synergism between aerobic and anaerobic organisms • Peritonitis vs abscesses formation • Abscesses • Determined by gravity and the physiologic drainage basins of the abdomen • Subphrenic space, pelvic space, subhepatic space, paracolic gutter, lesser sac, subfascial area

33. Primary Peritonitis • Microorganisms lodge in the peritoneal cavity without a fundamental intraabd. Process • Previously occurred in miliary TB, but now commonly occurs in ascites • Most common organism in ascties is S. pneumoniae

34. Secondary peritonitis • Usually begins with perforation of the GI tract • From inflammatory or neoplastic process • One major factor in determining severity is the size of the bacterial inoculum • Perforated appendix has 106 to 107 bacteria per g • Sigmoid colon has 1010 to 1011 bacteria per g • Anaerobes exceed aerobes 1,000-fold • Adjuvant factors are also important • Food, fiber, exfoliated cells, blood, dead tissue • Bacteria that are eliminated are either phagocytized or removed into the lymphatic system

35. Tertiary Peritonitis • recurrent intra-abdominal infection after initial surgical and antimicrobial therapy of secondary bacterial peritonitis.

36. Comes from atelectasis, aspiration, and contamination from ventilation Most common bacteria Pseudomonas, Klebsiella, Staph, E. coli, Proteus, Enterobacter, Pneumococcus, Serratia, group A Strep, H. flu Host defenses Glottis Cilia Mucus Secretory IgA and IgG Surfactant Transferrin Alveolar macrophages Nosocomial Pneumonia

37. Urinary Tract Infections • Foley catheterization is usually the culprit • Host defenses • Urine flow, antireflux, epithelium, mucus, IgA, urethral length • Common organisms • E. coli, Klebsiella, Pseudomonas, Proteus, Enterobacter, Enterococcus, Serratia, Citrobacter, Staph epidermidis

38. Catheter and Prosthetic Device Infection • The trauma of the catheter placement, the foreign body itself, and the contaminating bacteria lead to an inflammatory response • Eradication cannot be achieved because of the persistence of the foreign body • Intimal vein disruption and clot formation also lead to bacterial proliferation • Removal should never be delayed nor should antimicrobial agents be withheld

39. Other Specific Site Infection • Parotitis • Sinusitis • Pseudomembranous colitis