Surgical Prophylaxis and Antimicrobial Selection

Surgical Prophylaxis

• Antibiotics administered before contamination of sterile tissues or fluids are considered prophylactic, aiming to prevent infection.
• Skin flora (including S. Aureus and coagulase-negative staphylococci, e.g., Staphylococcus epidermidis) are predominant organisms causing Surgical Site Infections (SSIs) after clean procedures.
• In clean-contaminated procedures (e.g., abdominal, heart, kidney, and liver transplantations), gram-negative rods and enterococci, alongside skin flora, are the primary organisms.

Antimicrobial Selection

• Prophylactic antimicrobial choice depends on surgical procedure, pathogen likelihood, antimicrobial safety, efficacy, current evidence, and cost.
• Gram-positive coverage (e.g., S. aureus, S. epidermidis) is usually included in surgical prophylaxis.
• Parenteral antibiotic administration is preferred for reliable tissue concentration.
• First-generation cephalosporins (e.g., cefazolin) are the preferred choice for clean procedures.
• Broad-spectrum coverage (e.g., cefoxitin, or cefotetan) may be needed for anaerobic or gram-negative coverage cases.
• Vancomycin can be considered if methicillin-resistant S. aureus (MRSA) risk is high.
• Clindamycin can be an alternative to cefazolin for certain cases.

Types of Surgical Operations

• Surgical operations are classified as clean, clean-contaminated, contaminated, or dirty.

• Antimicrobial prophylaxis is suitable for clean, clean-contaminated, and contaminated procedures.

• Non-prophylactic antibiotics are used for treatment in operations with existing infections.

• Table 1 (in the provided text) outlines classification, surgical site infection risk, and antibiotic indication.

• Clean: Uninfected wounds with no inflammation in closed procedures

• Clean-Contaminated: Wounds involving organs (e.g., biliary tract) under controlled conditions

• Contaminated: Open wounds or wounds with gross spillage from the gastrointestinal tract

• Dirty: Wounds with obvious preexisting infection (e.g., abscess, pus)

Principles of Antimicrobial Prophylaxis

• Intravenous (IV) administration is preferred for reliable serum/tissue concentration over intramuscular.
• Oral antibiotics can be used adjunctively in some cases (e.g., bowel operations) to reduce microbial counts in the bowel.
• Oral agents are not typically a replacement for IV agents.

Timing of First Dose

• A single dose of antimicrobial is ideal 30 minutes to 1 hour before incision, providing sustained levels in the blood and wound.
• For fluoroquinolones and vancomycin, administration may occur up to 2 hours before incision to avoid complications.

Dosing and Redosing

• Maintaining antibiotic concentrations above the minimum inhibitory concentration (MIC) is crucial for the duration of the surgery.
• Redosing is required when the duration of surgery exceeds the drug's half-life to maintain needed antimicrobial concentrations.
• Clinicians should have necessary extra doses for longer-than-expected surgeries.

Duration

• Antimicrobial prophylaxis beyond wound closure or 24 hrs (48 hrs for cardiac surgery) is generally unnecessary.
• Preventing the unnecessary use of antibiotics beyond needed time frames is promoted.

Combination Antimicrobial Therapy

• Using combinations of antimicrobials broadens the spectrum of coverage to tackle mixed infections, optimize effectiveness, and prevent resistant organisms.
• Effective in cases of various infections (intra-abdominal, female pelvic).
• Increased spectrum of activity is beneficial for nosocomial infections.

Thromboprophylaxis

• Deep vein thrombosis (DVT) is frequent in major surgery, particularly in patients older than 40.
• Postoperative increases in platelets, and venous trauma contribute to DVT risk.
• Thromboprophylaxis (prevention of DVT) is given to reduce the occurrence of DVT and associated risks.
• Mechanical devices (e.g., thromboembolic deterrent stockings) and drugs (e.g., heparin, LMWH) are used for prophylaxis.

Regimen

• National guidelines exist for VTE prophylaxis, which involve assessing risk factors and using anticoagulants (e.g., heparin, enoxaparin, fondaparinux) preoperatively and during the initial stages of the postoperative phase.

• Various factors like surgery type and the patient's medical history are considered to manage the risk of VTE.

Table 2

• The table provides likely pathogens and recommended prophylaxis regimens for common surgical procedures (e.g., gastroduodenal, biliary tract procedures) in the table. High-risk patients, specific to each procedure, are highlighted in the comments section.