Infection in Surgical Patients
August, 2006Mike Joutovsky, PGY3
Department of SurgerySt. Barnabas Hospital
Defense Barriers
Physical Chemical Immunologic
Host defense
Barrier Microbial flora Humoral Cellular cytokine
Microbial flora
Humoral defenses
Immunoglobulin Complement
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
Immunoglobulin
Complement system
Series of serum proteins that may became activated via either classic or alternative pathway
Cellular defense
Macrophage PMN leucocytes cytokines
Surgical Site Infection ( SSI )
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
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
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
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.
Causes Table 1. Pathogens
Commonly Associated with Wound Infections and Frequency of Occurrence*Pathogen Frequency (%) *NNIS System (CDC, 1996)
Staphylococcus aureus
20
Coagulase-negative staphylococci
14
enterococci 12
Escherichia coli
8
Pseudomonas 8
enterobacter 7
Proteus Mirabilis
3
Klebsiella pn. 3
Bact. fragilis 2
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
The type of procedure is a risk factor too
Antimicrobial agents
Prophylaxis Empiric therapy Directed therapy
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
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.
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.
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
Intraoperative re-dosing
Operation is prolong If massive blood loss occurs The patient is obese
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
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
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
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
Tertiary Peritonitis
recurrent intra-abdominal infection after initial surgical and antimicrobial therapy of secondary bacterial peritonitis.
Nosocomial Pneumonia 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
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
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
Other Specific Site Infection
Parotitis Sinusitis Pseudomembranous colitis