Surgical Infection and Use of Antibiotics

Question 1

SSI

Answer 1

Surgical site infection = infections that directly result from surgical procedures.

Infection occurs within 30 days of the surgical procedure or within 1 year if associated with surgical implant.

Question 2

Surgical site infections are broadly divided into: (2)

Answer 2

Incisional (actual site of incision)
* Superficial (skin and subcutaneous tissue)
* Deep (deep soft tissue layers [muscle, fascia])

Organ/space (infection of an anatomic part that was manipulated)

Question 3

Clinical signs of SSIs (6+)

Answer 3

• Redness (rubor)
• Swelling (tumor)
• Pain (calor)
• Heat (dolor)
• Serous discharge
• Wound dehiscence
• Fever, weakness, anorexia

Question 4

Surgical wounds are classified by degree of contamination in order to..?

Answer 4

help predict the likelihood of infection

Infection rate for all types of surgical wounds approximately 5%.

Question 5

Classification of surgical wound degree of contamination.

Answer 5

Four categories:
1) clean
2) clean-contaminated
3) contaminated
4) dirty

Question 6

What amount of bacteria equals a full on bacterial infection?

Answer 6

Having more than 10^5 (100,000) bacteria per gram of tissue.

Question 7

Describe clean surgical wounds.

Answer 7

e.g. elective neuter/spay

Infection rate 0% – 6%.

Antibiotics are usually not warranted.

• Prophylactic antibiotics appear to be indicated in some clean procedures (e.g. orthopedic implants).
• Given at induction (30 to 60 minutes prior to incision).
• Discontinued within 24 hours of the procedure (at the end of surgery).

Most likely postoperative infection occur with severe trauma with multiple fractures, traumatic procedures, orthopedic surgery.

Question 8

Describe Clean-contaminated wounds.

Answer 8

Minor break in aseptic technique during surgery.

Infection rate 4.5% – 9.3%

• Antimicrobial prophylaxis indicated.
• Choice of antibiotic based on anticipated flora.

Most likely postoperative infection in clean-contaminated fractures of the pelvis and long bones.

Question 9

Describe Contaminated wounds

Answer 9

Not infected initially, but have the potential.

Infection rate 5.8% – 28.6%.

• Antimicrobial prophylaxis indicated.
• Choice of antibiotic based on anticipated flora, then modified according
  to culture and sensitivity results.

Most likely postoperative infection – contaminated fractures of the pelvis
and long bones; contaminated urogenital procedures.

• Delicate debridement, copious lavage, antibiotic therapy → clean wound aka infection resolved or at least under control?
• Inadequate therapy → dirty wound aka infection present

Question 10

Describe Dirty wounds

Answer 10

Gross infection present at the time of surgical intervention.

(e.g. Traumatic wounds with retained devitalized tissue, foreign bodies,
fecal contamination).

• Antibiotic therapy, later modified according to culture and sensitivity
  results.
• Copious lavage, debridement required.

Question 11

Antibiotics used in conjunction with surgeries fall into one of two groups:

Answer 11

prophylactic antibiotics (name is a misnomer)
therapeutic antibiotics

Question 12

Classifications of surgical infections:
(not the same as classifi. of surgical wounds!)

Answer 12

Surgical infections can occur:
1) With primary surgical disease

2) As a complication of a surgical procedure not commonly associated with infection

3) As a complication of a support procedure e.g. phlebitis from i.v. catheter

4) With prosthetic implants

Question 13

Describe primary surgical disease

Answer 13

Nonsterile source of bacterial infection (skin, GI tract, urinary tract)

Subject only to surgical treatment not surgical prevention.

AB based on expected bacterial flora – then modified if necessary.
(osteomyelitis secondary to open fracture, pyometra, prostatic abscessation)

Question 14

Into which category would pyometra surgery belong?

Answer 14

clean-contaminated

(but if its ruptured with poss. peritonitis then contaminated)

Question 15

Contaminated means…

Answer 15

that there is bacteria present, NOT that there is infection present.

However, wherever there is contamination, there is a high chance of the development of infection.

Question 16

What factors contribute to development of surgical infection? (4)

Answer 16

• Number and virulence of the bacteria
• Competence of host defenses
• Amount of tissue damage
• Amount of dead space resulting from the procedure

All surgical procedures cause some bacterial contamination!

Question 17

Describe complications of a support procedure

Answer 17

Debilitated, traumatized, immunocompromised patients.

Intravenous catheters
* Cephalic catheters should be changed every 48 to 72 hours.
* Jugular catheters changed every 7 to 10 days.

Urinary catheters
* Common source of infection after 2-3 days

Prolonged endotracheal intubation (foreign body, disrupted cough reflex).

Question 18

Describe prosthetic implants and surgical infections.

Answer 18

Implants – foreign substances used to support, rebuild or mimic function of
an anatomic structure.

Foreign material in contaminated/infected wounds increases chance for chronic infection.

• Biofilm = colony of microorganisms, within a matrix of extracellular polymeric substance that they produce (biofilm microorganisms usually resistant to AB).
• AB treatment seldom successful until implant removed (systemic ABs can’t reach an implant that isn’t vascularized).

Aseptic technique & AB prophylaxis reduce infection; implant rejection rare.

(nonabsorbable suture, polypropylene mesh, TTA)

Question 19

Prevention of surgical infections

Answer 19

Is the primary objective of aseptic surgery.

Factors to be considered
* Age
* Physical condition
* Nutritional status
* Diagnostic procedures
* Concurrent metabolic disorders
* Nature of the wound
* Operating room practices
* Characteristics of bacterial contaminants

Question 20

Host factors to influence potential for surgical infection/complication: age

Answer 20

• Patients older than 10 years – possible inability to mount an appropriate immune response.
• Patients younger than 1 year – possible underdeveloped immune system.

Question 21

Host factors to influence potential for surgical infection/complication: physical condition, nutritional status

Answer 21

Increased risk of surgical infection:
* Patients with protein-calorie malnutrition
* Overweight
* Hypoproteinemia

Question 22

Host factors to influence potential for surgical infection/complication:
diagnostic procedures,
concurrent metabolic disorders

Answer 22

Increased risk of infection:
* Diagnostic procedures (catheterizations, centeses)
* Immunosuppressive therapy
* Previous antibiotic therapy

• Long periods of hospitalization
• Remote infections
• Concurrent debilitating disorders (Cushing’s, DM, protein-losing enteropathy)

Question 23

Host factors to influence potential for surgical infection/complication: nature of the wound

Answer 23

Allowing bacterial proliferation and inhibiting normal response:
* Presence of necrotic tissue
* Hematoma

• Serum pockets (seroma)
• Local infection
• Foreign bodies
• Dead space

Question 24

Other factors to influence potential for surgical infection/complication: operating room practice

Answer 24

• Aseptic technique (also drugs [propofol])
• Duration of surgery (teaching hospitals!)
• Risk of infection doubling approximately every 70 minutes
• Duration of anesthesia
• Preparation times should be minimized
• Perioperative warming if necessary
• Proper atraumatic tissue handling

Question 25

Other factors to influence potential for surgical infection/complication: characteristics of bacterial
contaminants

Answer 25

Nosocomial infections – caused by environmentally resistant bacteria
during hospitalization/surgery.

Risk factors:
* Overuse of antibiotics
* Indwelling catheters
* Diagnostic procedures
* Advanced age
* Chronic debilitating disease

Prevention – control of the hospital
environment, rational AB use.

Question 26

Surgical prophylactic antibiotic use is acceptable in what cases? (2)

Answer 26

• Significant risk of infection
• Infection would be catastrophic

Question 27

Surgical therapeutic antibiotic use is should be

Answer 27

Ideally based on culture and susceptibility results. However, delay might be problematic.

Question 28

Prophylactically used antibiotics must be present at the site at the time of

Answer 28

potential contamination

Not a substitute for proper aseptic technique!

Question 29

Prophylactic use of antibiotics:
Cefazolin (cefuroxime)

Answer 29

No adverse effects on platelet aggregation, bleeding time, platelet size or count, prothrombin or activated partial thromboplastin time.

• Given 30 – 60 min i.v. before incision and discontinued within 24 h (ideally at the end of the procedure).

Question 30

Therapeutic use of antibiotics should be

Answer 30

Based on clinical judgement, knowledge of the antibiotic’s mechanism of action, microbiologic factors.

Ideal drug is the least toxic, kills bacteria at the site of infection and does not negatively influence the host’s immune system.

Generally instituted before surgery and continued 2-3 days after apparent resolution of infection.

Question 31

Therapeutic use of antibiotics Indicated in patients with:

Answer 31

• Overwhelming systemic infection
• When infection is present at the surgical site or in a body cavity
• With any contaminated or dirty surgical procedure

Question 32

With most surgical infections, antibiotic
therapy needs adjunctive therapy such as (4)

Answer 32

drainage of accumulations,
debridement,
continued lavage,
removal of foreign bodies or implants

Question 33

Use of ABs for:
clean wounds?
clean-contaminated?
contaminated?
dirty?

prophy- or therapeutic?

Answer 33

ABs not used in clean surgeries except for some very minor exceptions (ortho implants).