Antibiotic Prophylaxis

See also SSI

Principles

1.  Target tissue concentration
- need highest concentration at time of incision and until closure.
- IV administration <1 hr before incision, often at induction (~30-60m prior to incision is best)
- if oral, ensure timing is accurate for type.
- there is still small benefit if dose given interoperatively, but none afterwards.

2.  Cover long procedures adequately
- if <2hrs, single dose adequate
- additional doses beyond wound closure = no evidence of benefit.
Antibiotics with short half-lives (<2hrs, eg cefazolin, cefoxitin) re-dosed every 3-4hrs if prolonged
- final dose may still be given just prior to wound closure.

3. When to use prophylaxis
Usually indicated in clean-contaminated and contaminated operations.
- nb, where operation is 'dirty', antibiotics are being used for treatment, not prevention.
- clean-contaminated biliary surgery when high risk only (eg >70yrs, diabetics, recent instrumentation in biliary tract); vast majority of lap choles = no benefit.
Any procedure with high rate of bacteraemia in at-risk pts (eg heart valves)
Clean surgery is controversial
- indicated in all foreign body implants when infective complication serious.
- in breast, hernia, RCTs show some evidence for benefit, but confounded by high risk of infection in control group.
- can argue for use in high-risk pts undergoing relatively clean surgery (eg gastric)
- or where stress / work delay / reoperation risk would justify it.

4. Administer correctly
If not administered correctly may be harmful instead of beneficial.
- do not use prolonged cover for drains, catheters etc.
- prolongation leads to C dif and increased later noscomial infections, as well as drug resistance.

Choice of Antibiotic

1. Safety


2. Appropriately narrow spectrum
- never a quinolone or 3rd gen cefalosporin

3. Cover Staph aureus
- always cover staph for clean / highrisk celan-contaiminated surgery of biliary / upper GI.
- 1st gen cef good choice / clindamycin when history of anaphylaxis to penicillins
- vanc where institutional MRSA >20% of all SSIs, god-forbid.

4. Cover most likely microbes to infect at site.
See below.


Example Regimen

Appendicectomy (anaerobes, coliforms):
- cefotetan or ce
ftriaxone and metronidazole.
- nb not actually prophylaxis; cipro if really needed due to allergy.

Biliary
- coliforms, enterococci, anaerobes in obstruction
- coamoxyclav or cephazolin or ceftriaxone.

Cardiovascular (staph):
- cefamandole or teicoplanin.

Colorectal (anaerobes, coliforms):
- cefotetan or coamoxyclav or cefuroxime and metron
idazole.

Gastric malignancy (coliforms, anaerobes):
- coamoxyclav or cephazolin and metronid
azole.

Gynaecological (coliforms, anaerobes, streptococci):
- cefotetan or coamox
yclav.

Orthopaedic hip (staph, coliforms):
- cephazolin or cefamandole or teicoplanin.

Orthopaedic amputation (clostridia, staph, strep):
- coamoxyclav or flucloxacillin +/- me
tronidazole.

Transplant (coliforms, pseudomonads, staphylococci):
- ciprofloxacin, ceftazidime.

Trauma
Multiple studies unequivocally prove that 24hrs with 2nd gen cef is all that is required for penetrating abdo trauma.
- even when shock and colonic injury.

Urological (coliforms):
- coamoxyclav, gentamicin.

References
Integrated basic surgical sciences.
Barie et al. Surg Clin N Am, 85(2005):1115-35.