Surgical Prophylaxis Flashcards
Where do the bacteria reside in the skin?
On the superficial layer: easy to wash off
In the deeper skin layers: resident bacteria (difficult to remove)
What are some Preventative measures for patient preparation to avoid post-surgical infections?
- Treat pre-existing infections
- Shower with antispectic (chlorhexidine) the night before surgery
- Skin-pre: hair clipping (not shaving; Betadine, alcohol, chlorhexidine; skin prepped in concentric circles
- abx prophylaxis prn
- mupiricin topical for S. aureus carriers
What are the 4 principles of antibiotic prophylaxis/
- Use agent that reduces SSIs for the particular type of surgery
- Agent must be safe, inexpensive and BACTERICIDAL with spectrum that covers most probably contaminants.
- Time infusion so that bactericidal concentration of drug is established in serum/tissues by the time skin is incised
- Maintain therapeutic levels until at most a few hrs after incision closed.
When is the best timing for prophylactic abx?
Within 60 minutes before the surgical infusion
Fluoroquinolones, aminoglycosides and vancomycin require prolonged infusion times: within 2 hours of incision.
Risk Factors for Surgical Infection
- microbial concentration and virulence
- injury to wound tissues
- foreign material
- resistance to peri-op abx
- general and local host immunity
- periop abx
Surgical wound classification
Class I: Clean
Class II: Clean-contaminated
Class III: contaminated
Class IV: Dirty infected
What is the gold standard abx used and why?
Cephalosporins (especially cefazolin)
- effective against many G+ and G-
- safe
- acceptable PK
- cost efficient
- may need additional coverage in some surgeries
What is the first line choice? If serious penicillin allergy?
How about in distal GI tract?
- Cefazolin
- Clindamycin or vancomycin if serious pencillin allergy
-Distal GIT: add metronidazole to cover anaerobics including B. fragilis
When is vanco chosen instead of first line?
Why is it not first line in the first place?
- MRSA/MRSE present in post-op infections
- known MRSA colonization or high risk for MRSA based on surveillance data (nursing home, recent hospitalization, Hemodialysis)
- severe penicillin allergy
-vanco is less effective in preventing SSIs due to MSSA
What kind of PK does cephalosporins exhibit? What does this mean in terms of dosing?
Time-dependent PK
Therefore, you must maintain levels >MIC for duration of operation. If duration exceeds 2 times the half life, an additional dose should be given ex. 2 hours for cefazolin
How long should prophylaxis last? Should there be prophylaxes post-wound closure?
- less than 24 hours
- There’s a few cases where it’s warranted, but majority of the time it’s not needed
What is the most common organism causing SSIs?
Where does the source of these organisms come from?
- S. aureus
- Colonization in nares
What is Mupirocin? Used for Structure discription MoA how long does it take to work?
-Used to kill S. aureus in known carriers of it
-Unique structure: hort fatty acid side chain linked to monic acid by ester linkage
-Inhibits isoleucyl-tRNA synthetase -> elongation of protein chains
Bacteriostatic/bactericidal at concentrations after 24-3h
What is the spectrum of activity for mupirocin?
What is it not active against?
S. aurues (including MRSA)
S. epidermidis
S. pyogenes
Not active against:
- normal skin flora
- enterobacteraciae or enterococcus
PK of Mupirocin:
Absorption
- Not absorbed from skin very well
- if absorbed, it is rapidly metabolized or protein bound
