Surgical site infection (SSI) risk is reduced most effectively when antibiotics are administered before contamination occurs - typically 30–60 minutes before the first incision. The purpose of prophylaxis is to reduce microbial load at the operative site, not to sterilise it. Prophylaxis should always be procedure-specific and time-limited.

💡 Key Principles:

Give IV antibiotic 30–60 minutes before incision (usually at anaesthetic induction).
Single-dose prophylaxis is sufficient for most operations.
Re-dose if surgery >4 h or blood loss >1.5 L.
Avoid routine postoperative doses to limit antimicrobial resistance.
Adjust for renal function and allergy; involve Microbiology for complex or prolonged cases.

Procedure / Surgical Area	Likely Pathogens	Recommended Prophylaxis	Penicillin Allergy Alternative
Oesophageal / Gastroduodenal	Upper GI flora, Gram-negative enterics	Co-amoxiclav 1.2 g IV single dose at induction	Gentamicin 120 mg IV single dose
Hepatobiliary (incl. open cholecystectomy)	Gram-negative bacilli, Enterococci, Anaerobes	Co-amoxiclav 1.2 g IV at induction	Gentamicin 120 mg IV + Metronidazole 500 mg IV at induction
Colorectal Surgery	Enteric Gram-negative bacilli, Enterococci, Anaerobes	Co-amoxiclav 1.2 g IV at induction (repeat >5 h)	Gentamicin 120 mg IV + Metronidazole 500 mg IV at induction
Genitourinary Procedures – Rigid cystoscopy – TRUS biopsy – TURP	Gram-negative enterics, Enterococci	Rigid cystoscopy → Gentamicin 120 mg IV single dose TRUS biopsy → Ciprofloxacin 1 g PO + Gentamicin 120 mg IV + Metronidazole 1 g PR TURP → Gentamicin 120 mg IV at induction	As above, adjust according to culture results
Obstetric / Gynaecological – Caesarean section – Termination of pregnancy	Enteric Gram-negatives, Enterococci, Anaerobes	Caesarean → Co-amoxiclav 1.2 g IV post-clamping Termination → Metronidazole 1 g PR + Doxycycline 100 mg PO BD × 7 days	Caesarean → Gentamicin 120 mg IV + Metronidazole 500 mg IV Termination → as above
Orthopaedic – Joint replacement / open fracture	S. aureus, S. epidermidis, Clostridium spp.	Joint replacement → Flucloxacillin 1 g IV + Gentamicin 120 mg IV at induction Compound fracture → Co-amoxiclav 1.2 g IV q8h as needed	Teicoplanin 400 mg IV + Gentamicin 120 mg IV (at induction) For compound fracture → Teicoplanin 400 mg IV + Metronidazole 500 mg IV + Gentamicin 120 mg IV
Vascular Surgery	Staphylococci, Streptococci	Co-amoxiclav 1.2 g IV at induction + repeat 8 h later	Teicoplanin 400 mg IV + Gentamicin 120 mg IV (repeat 12 h)
Thoracic Surgery	Staphylococci, Streptococci, Gram-negative enterics	Co-amoxiclav 1.2 g IV at induction	Teicoplanin 400 mg IV + Gentamicin 120 mg IV at induction
Endocarditis Prophylaxis (for high-risk cardiac patients)	Streptococci, Enterococci	Consult Microbiology - tailor to procedure and risk	Consult Microbiology - tailor to procedure and risk
Pacemaker Implantation	Skin flora (Staphylococci)	Co-amoxiclav 1.2 g IV before procedure	Teicoplanin 400 mg IV before procedure (esp. if MRSA risk)
Splenectomy / Hyposplenia	S. pneumoniae, H. influenzae, N. meningitidis	Phenoxymethylpenicillin 500 mg PO BD lifelong + vaccinations (see below)	Erythromycin 500 mg PO OD lifelong + vaccinations

🧠 Educational Notes

MRSA Screening: Screen high-risk patients pre-operatively; add Teicoplanin + Gentamicin if colonised.
Renal Impairment: Seek dosing guidance for Gentamicin, Teicoplanin, or Vancomycin.
Vaccinations after Splenectomy: Pneumococcal, Meningococcal, and H. influenzae b vaccines ≥2 weeks pre-surgery if possible; annual influenza vaccine advised.
Stewardship: Never extend prophylaxis into the postoperative period unless there is established infection.

In summary, surgical prophylaxis aims to prevent contamination rather than treat infection. A single, correctly timed dose at induction offers the best protection with minimal resistance risk. Always verify dosing against BNF and NICE local policy.

📚 References

NICE NG125: Surgical site infections: prevention and treatment
British National Formulary (BNF)
Public Health England (PHE) / UKHSA: Antimicrobial Prescribing Guidance (2024)

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Surgical prophylaxis

💊 Surgical Antibiotic Prophylaxis

🧠 Educational Notes

📚 References

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