1. Antibiotic prophylaxis
E.Mehrtash
Intern at QUMS
Surgery journal of (OXFORD) 2011

2. Surgical site infection
Surgical site infection (SSI) is infection arising in a wound created by a surgical procedure:
Bone
Joint
Tissue
Cavities
Prostheses
SSI is diagnosed if infection occurs within 30 days of surgery (or within 1 year when an implant is affected).

3. Surgical site infection
SSI is classified according to the tissues involved:
Superficial incisional - infection involving only skin or subcutaneous tissue at the incision site.
Deep incisional - infection involving deep soft tissues (e.g. fascial and muscle layers) of the incision.
Organ space - infection involving any part of the anatomy other than the incision that was opened or manipulated during the operation.
SSI is a common postoperative complication, affecting nearly 5% of patients overall and accounting for 14% of healthcareassociated infections.

4. The rationale behind antibiotic prophylaxis
The aim of antibiotic prophylaxis in surgery is to prevent SSI whilst minimizing the collateral damage that occurs with all antibiotic use.
The targets of antibiotics are skin/mucosal colonizing and contaminating organisms at the operative site:
Operations above the waist should targeting Gram-positive bacteria (staphylococci and streptococci).
Operations below the waist should targeting Gram-positive and Gram- negative bacteria (e.g. Escherichia coli).
For trauma with open wounds and in oral or abdominal operations, anaerobic cover must be considered.

5. Cont…
Antibiotic prophylaxis should not be used to prevent postoperative complications which are unrelated to the wound or surgical site.
Use of prophylactic antibiotics is not a replacement for optimal patient preparation, good surgical technique and theatre environment.

6. Who is at risk of SSI and who needs prophylaxis?
Wound environment
Low haemoglobin.
Presence of necrotic tissue or foreign bodies.
Dead space.
Patient colonization by MRSA.
Lancefield group A/C/G streptococci or other resistant organisms.
Patient characteristics including host defence
Extremes of age
Presence of shock/hypoxia/hypothermia
Glycaemic control
Chronic illness
Immunosuppressive agents
Nutritional state
Obesity
Coexisting infection

7. Who is at risk of SSI and who needs prophylaxis?
Pathogen exposure
Virulence of organisms
Size of inoculum
Operation factors
length of scrub
Skin asepsis
Preoperative shaving and skin preparation
Length of operation
Theatre ventilation
Equipment sterilization
Foreign material at surgical site
Surgical drains
Surgical technique (haemostasis, trauma, closure)

8. Classes of operation
Four classes of operation exist, with an increasing rate of bacterial contamination and subsequent risk of SSI:
Clean
an operation in which no inflammation is encountered
The respiratory, alimentary and genitourinary tracts are not entered.
There is no break in aseptic operating theatre technique.
Primary wound closure is undertaken
Clean-contaminated
an operation in which the respiratory, alimentary or genitourinary tract is entered but there is no significant spillage (e.g. appendicectomy).

9. Classes of operation Contaminated
an operation in which acute inflammation (without pus) is encountered or where there is visible contamination of the wound.
For example, gross spillage from a hollow viscus during the operation or open/compound operations operated on within 4 hours.
Operations in which there is a major break in aseptic technique also fall into this category
Dirty
operations in the presence of pus or devitalized tissue
previously perforated hollow viscus, or open/compound injuries more than 4 hours old.

10. Indications
Antibiotic prophylaxis should be administered to patients who are undergoing the following types of operation:
clean surgery involving prosthesis or implant placement (e.g. joint replacement)
clean-contaminated surgery
contaminated surgery.
Prophylaxis should not be used for dirty surgery as in this circumstance a treatment course of antibiotics should be prescribed.

11. Factors determining what antibiotics to use
Spectrum of cover
Penicillin allergy
MRSA carriage

12. dose, timing, route of administration and duration
the dose used for prophylaxis should be the same as that used for treatment
first dose does not require adjustment in renal impairment
Timing
Prophylaxis should be started in almost all circumstances at or less than 30 minutes prior to the first skin incision.
Route of administration
Generally, the intravenous (IV) route should be used
some antibiotics do reach equivalent tissue concentration when given orally (e.g. fluoroquinolones).

13. Cont…
In some types of surgery alternative routes are used either alone or combined with IV prophylaxis:
topical administration for grommet insertion
impregnated cement for cemented joint replacements in addition to IV prophylaxis
intracameral prophylaxis in cataract surgery
intraventricular antibiotics during ventriculoperitoneal shunt neurosurgery in addition to IV antibiotics
some surgeons use gentamicin-impregnated collagen fleeces or implants in, for example, abdominoperineal resection and cardiac surgery.

14. Cont…
Duration
For many types of surgery, a single dose of antibiotic is adequate
An additional dose of prophylactic antibiotic is needed if:
The operation lasts more than 4 hours and the antibiotic used has a pharmacokinetic profile similar to cefazolin
There is intraoperative blood loss greater then 1500 ml (25 ml/kg in children)
The operation is prolonged beyond the half-life of the antibiotic used.
For arthroplasty, and other operations inserting foreign material, 24 hours of prophylaxis is generally recommended

16. Specific consideration
Co-morbidities that may impact on antibiotic choice include:
long QT syndrome (macrolides and quinolones can cause further QT prolongation)
epilepsy (quinolones lower the seizure threshold)
glucose-6-phosphate dehydrogenase deficiency (nitrofurantoin, quinolones and sulphonamides)
myasthenia gravis (many antibiotics can worsen symptoms)
acute intermittent porphyria (multiple antibiotics can precipitate crises

17. Special groups
Meticillin-sensitive S. aureus (MSSA)-colonized patients:
Patients known to be nasal or skin carriers of MSSA who are undergoing surgery with a high risk of major morbidity should receive pre- or perioperative decolonization therapy as for MRSA.
Paediatrics
appropriate choice and dose adjustment depending on the age and weight

18. Special groups Patients undergoing splenectomy: encapsulated organisms
Patients should receive pneumococcal, meningococcal, Haemophilus influenzae type b (Hib) and influenza vaccinations(at least 2 weeks prior to surgery).
All high-risk patients should be offered lifelong prophylactic antibiotics
(<16 or >50 years old or those with an inadequate serological response to pneumococcal vaccination, history of invasive pneumococcal disease, underlying haematological malignancy)

19. Special groups immunocompromised patients:
human immunodeficiency virus and immunosuppressive drugs:
These patients should receive the same prophylaxis as immunocompetent patients, but extra vigilance for the development of SSI is needed.
Patients at risk of infective endocarditis:
can occur following bacteraemia in patients with predisposing cardiac lesions
Patients with intercurrent infection:
Those with pre-existing infection that is being treated should still receive antibiotic prophylaxis and then return to the preoperative regimen.
UTI

20. Special groups Obese patients
Physiological changes in obesity affect the distribution, protein binding, metabolism and clearance of antimicrobials.
Tissue distribution :
hydrophilic antibiotics (b-lactams, aminoglycosides, glycopeptides)
lipophilic drugs (fluoroquinolones, macrolides, lincosamides, tetracyclines, tigecycline)
Antimicrobial agents with a narrow therapeutic window (e.g. aminoglycosides) are often dosed according to weight
Some data support giving a higher induction dose of b- lactams and vancomycin in obese patients