1.3 Surgical infection, indication of antibiotic use, antibiotic prophylaxis

Question 1

What are surgical infectious diseases?

Answer 1

• skin and soft tissue infections (abscess, carbuncle, ulcer, decubitus, diabetic foot)
• osteomyelitis, intrabdominal infections
• secondary peritonitis due to: appendicitis, cholecystitis, cholangitis, liver abscesses, acute pancreatitis, duodenal perforation, large bowel perforation

Question 2

What are the infectious complications of surgical interventions?

Answer 2

surgical infection refers to postoperative infections associated with the surgical site

• wound infection
• respiratory tract infection
• intravascular devices
• postoperative peritonitis + abscess

Question 3

What is the pathogenesis of surgical infections?

Answer 3

• dead phagocytic cells, fibrins, opsonins, dead/living microorganisms and bacterial products form a compound referred to as “pus”
• the purulent environment is hypoxic and acidic, thus inhibiting normal cellular and enzymatic functions

Question 4

What are the sources of surgical infections?

Answer 4

• colonizing flora
• normal flora:
  - gram (+) on the skin
  - mainly gram (-) in the GI tract
  - aerobes in esophagus, large bowel and sexual organs
• external flora
  - toxin mediated damage
  - microbial attachment

Question 5

Wound infection rate of different types of surgical procedures

Answer 5

• clean procedure: 1.5-4.2%
• contaminated procedure: <10%
• clean-contaminated procedure: 10-20%
• dirty/infected procedure: 20-40%

Question 6

What are the risk factors that increase incidence of surgical infections?

Answer 6

• hematoma in the wound (blood enables bacterial growth)
• necrotic tissue, foreign body (provides portal of entry), obesity, contamination
• advanced age, shock, DM, alcoholism, malnutrition
• cancer chemotherapy, immunosuppression, remote site infection

Question 7

How are SSI’s classified?

Answer 7

Surgical site infections (SSI) are divided into categories based on the level of penetration. The extent of bacterial invasion into the surrounding soft tissues and/or systemic dissemination determine the need for antibiotics per os or i.v.

Question 8

Characteristics of superficial/incisional SSI

Answer 8

• involves the skin and subcutaneous tissue
• treated with oral antibiotics covering gram (+) organisms

Question 9

Characteristics of subcutaneous abscess

Answer 9

• requires incision and drainage
• can ocur in any setting where there is a wound

Question 10

Characteristics of deep incisional SSI

Answer 10

• extends into the muscle and fascia
• requires re-opening of the wound and debridement of necrosis
• antibiotics must be administered to prevent systemic infection and sepsis

Question 11

How can surgical infections be prevented?

Answer 11

• removal of body hair
• sterile skin preparation using iodine solution or chlorhexidine
• sterile barriers and draping fields
• short operation time
• maintaining normothermia during the procedure
• glycemic control
• appropriate surgical technique: making the wound as small as possible and reducing dead space in the wound by using layered closure and closed caution drainage; suturing so that tissue perfusion and oxygenation is maintained
• appropriate conditions in the OR (laminar flow ventilation, aseptic technique)

Question 12

What is the systemic antibiotic prophylaxis for normal flora/wild species?

Answer 12

usually empircal treatment is sufficient: effective against the presumable causative organism and is a broad spectrum agent

Question 13

What is the systemic antibiotic prophylaxis for nosocomial flora/resistant species?

Answer 13

required definitive therapy: effective against the cultured organism and has a narrower spectrum (ie. clostridium difficile)

Question 14

Characteristics of combined therapy in systemic antibiotic prophylaxis

Answer 14

widens the spectrum and increases the effect and increases the effect

Question 15

Characteristics of monotherapy in systemic antibiotic prophylaxis

Answer 15

narrower spectrum, cheaper, fewer side effects, lower environmental harm

Question 16

What are the multi-/pan-resistant pathogens?

Answer 16

gram (+): MRSA (methicilin resistant S. aureus), VRE (vancomycin resistant enterococci)
gram (–): ESBL (extended spectrum beta-lactamase), pseudomonas aeruginosa, acinetobacter spp.

Question 17

Why is antibiotic prophylaxis important?

Answer 17

antibiotic prophylaxis has shown to reduce the rate of SSIs by 80%, which decreases ICU time, hospitalization time, costs, risk of readmission and mortality

Question 18

Dosage and administration of antibiotic prophylaxis

Answer 18

• initial antibiotics are administered 1 hour prior to the incision to ensure adequate serum and tissue levels
• longer procedures require re-dosing depending on the pharmocokinetics of the drug
• cephalosporins are the first-line agents if there are no allergies or any contamination prior to the surgery – second agents are sometimes required (ie. perforation in the GI tract requires extensive gram (-) coverage)
• when treating an existing infection, the prophylactic is only given until the specific agent has been cultured and demonstrated

Postoperative therapy
- usually prophylaxis is onle continue for less than 24 hours after surgery
- longer than 24 hour infusions can result in bacterial resistance and increases risk of clostridium difficile infection, without any positive effects on SSI rates
- cardiac surgery may require longer infusions (48 hours)

Question 19

Guidlines for preoperative management of surgical patients with regard to SSI

Answer 19

• prophylactic antibiotic delivery within 60 minutes prior to incision
• prophylactic antibiotics consistent with approved guidelines
• cessation of prophylaxis withing 24 hours postoperative
• appropriate hair removal
• glucose control in cardiac surgery
• normothermia in colorectal surgery

Question 20

Differential diagnosis of postoperative fever

Answer 20

• wind: pneumonia, atelectasis (deper breathing, coughing) in the first 24-48 hours
• water: UTI after post-op day 3
• wound: wound infections after post-op day 5
• walking: can help reduce DVT and PE, which usually occurs at day 7-10
• wonder drugs: could begin at the time medications/transfusions are introduced