Surgical Prophylaxis Quiz

Surgical Prophylaxis

• Antibiotics are administered before contamination of previously sterile tissues or fluids to prevent infection. The goal is to prevent infections from developing.
• Common surgical pathogens after clean procedures include skin flora like S. Aureus and coagulase-negative staphylococci (e.g., Staphylococcus epidermidis).
• In clean-contaminated procedures (e.g., abdominal, heart, kidney, and liver transplantations), the predominant organisms are gram-negative rods and enterococci, in addition to skin flora.

Antimicrobial Selection

• The choice of prophylactic antimicrobial depends on the type of procedure, pathogen likelihood, safety, efficacy, current evidence, and cost.
• Gram-positive coverage is usually included in the choices for surgical prophylaxis because organisms like S. aureus and S. epidermidis are common skin flora.
• Parenteral antibiotic administration is preferred for reliable and substantial tissue concentrations.
• First-generation cephalosporins (particularly cefazolin) are preferred for clean surgical procedures.
• Cefoxitin or cefotetan are used when broad-spectrum anaerobic and gram-negative coverage is needed.
• Vancomycin may be considered for procedures with high MRSA risk if a B-lactam allergy exists. Clindamycin can be substituted for cefazolin to limit vancomycin use, if the MRSA risk is low.

Types of Surgical Operations & Wound Classification

• Surgical operations are classified as clean, clean-contaminated, contaminated, or dirty based on risk of infection.
• In clean operations, no inflammation, and the respiratory, alimentary, genital or uninfected urinary tracts aren't entered.
• Clean-contaminated operations involve entering the respiratory, alimentary, genital, or urinary tracts under controlled conditions without unusual contamination (e.g., biliary tract, appendix, vagina, oropharynx). Clean procedures performed emergently or with a major technique are also considered.
• Contaminated involves open, fresh, accidental wounds, surgical procedures with broken sterile techniques (e.g., open cardiac massage, or gastrointestinal tract spillage) or incisions with acute non-purulent inflammation.
• Dirty operations involve preexisting infections (e.g., abscess, pus, or necrotic tissue).

Principles of Antimicrobial Prophylaxis

• Intravenous (IV) administration of antibiotics provides more reliable serum and tissue concentrations compared to intramuscular.
• Oral administration can be used in some bowel operations, but it's typically supplemental rather than a replacement for IV. Nonabsorbable oral antibiotics (e.g., erythromycin or neomycin), given 24 hours before surgery, can help reduce bowel microbes.

Timing of First Dose

• Administration timing is crucial to maintaining therapeutic levels of antibiotics in the blood and tissues during surgery.
• Antibiotics should be infused within 60 minutes of the first incision.
• Exceptions include fluoroquinolones and vancomycin, where administration 120 minutes prior to the procedure can avoid infusion-related reactions.

Dosing and Redosing

• Maintaining antibiotic concentrations above the Minimum Inhibitory Concentration (MIC) of the suspected organisms for the whole operation is the goal.
• If an operation exceeds the antimicrobial's two half-lives, another dose is required to maintain effective concentrations. For example, cefazolin's half-life is approximately 2 hours. Prolonged operations, therefore, necessitate additional doses.

Duration

• The continuation of prophylaxis beyond wound closure is generally unnecessary.
• The standard duration should not exceed 24 hours, except for cardiac surgery, which may extend prophylaxis up to 48 hours.
• Giving antibiotics until drains are removed is not supported by evidence. Prolonged antimicrobial administration can encourage resistance and increase cost. Longer durations are not universally recommended.

Combination Antimicrobial Therapy

• Combinations of antibiotics are often used to widen the spectrum of coverage, achieve synergistic action against organisms and prevent resistance.
• Mixed infections (e.g., intra-abdominal and female pelvic infections) require broader coverage.

Thromboprophylaxis

• Deep vein thrombosis (DVT) occurs more often in surgical patients above 40. Postoperative platelet increase and venous trauma contribute. Patients without prophylaxis have a 30% chance of developing DVT and 0.1-0.2% risk of pulmonary embolism (PTE).
• Thromboprophylaxis includes mechanical devices (e.g., TED stockings) and drugs impacting the clotting cascade (e.g., heparin, low-molecular-weight heparin).

Regimen

• National protocols require assessment of all surgical patients for DVT risk factors upon admission.
• Risk factors include procedure duration, immobility, age, malignancies, inflammatory conditions, dehydration, obesity, diabetes, heart or respiratory issues, oral contraceptives, hormone therapy, and family history of blood clots.
• Risks of blood clots must be balanced against possible bleeding risks or other complications from prophylaxis.