What is the recommended preoperative antibiotic prophylaxis (pre-op antibiotic) regimen?

Preoperative Antibiotic Prophylaxis Recommendations

Administer cefazolin 2g IV as a single dose 30-60 minutes before surgical incision for most clean and clean-contaminated procedures, with re-dosing of 1g if surgery exceeds 4 hours or blood loss exceeds 1.5L. 1, 2

Timing of Administration

• Antibiotic prophylaxis must be administered within 60 minutes before incision for most antibiotics (cefazolin, cephalosporins) to ensure adequate serum and tissue concentrations during the period of potential contamination 1
• For fluoroquinolones and vancomycin, begin infusion 120 minutes prior to incision due to longer infusion requirements 1
• Administration earlier than these timeframes is unnecessary and potentially dangerous; administration later is less effective 3

First-Line Antibiotic Selection by Procedure Type

Clean and Clean-Contaminated Surgery (Orthopedic, Cardiac, Vascular, Gynecologic)

• Cefazolin 2g IV is the preferred agent targeting S. aureus, S. epidermidis, and common Gram-negative bacteria 1, 4
• Alternative first-generation cephalosporins: cefuroxime 1.5g IV or cefamandole 1.5g IV with re-injection of 0.75g if duration exceeds 2 hours 1
• For beta-lactam allergy: clindamycin 900mg IV slow infusion plus gentamicin 5mg/kg IV as single dose 1, 4
• For suspected MRSA colonization or high-risk settings: vancomycin 30mg/kg IV over 120 minutes (maximum 4g) 1

Colorectal and Gastrointestinal Surgery

• Cefoxitin 2g IV plus metronidazole 1g IV infusion targeting Enterobacteriaceae and anaerobes including B. fragilis 1
• For beta-lactam allergy: metronidazole 1g IV plus gentamicin 5mg/kg IV 1
• Oral antibiotics given the day before surgery should be combined with IV prophylaxis 1

Biliary Tract Surgery

• Cefazolin 2g IV or cefuroxime 1.5g IV targeting E. coli, Klebsiella, and Enterococcus 1
• For beta-lactam allergy: gentamicin 5mg/kg IV plus clindamycin 900mg IV 1

Penetrating Trauma (Abdominal, Thoracic)

• Broad-spectrum coverage with aminopenicillin plus beta-lactamase inhibitor 2g IV for aerobic and anaerobic bacteria 1
• For beta-lactam allergy: clindamycin 900mg IV plus gentamicin 5mg/kg IV 1
• Continue for up to 24 hours postoperatively in contaminated cases; longer duration not supported by evidence 1

Open Fractures

• Type I and II fractures: first-generation cephalosporin (cefazolin 2g IV) for 3 days 1
• Type III fractures: add aminoglycoside to cephalosporin, continue for 5 days 1
• For severe injuries with soil contamination: add penicillin for Clostridium coverage 1

Duration of Prophylaxis

• A single preoperative dose is sufficient for the majority of procedures 1, 3
• Prophylaxis should not exceed 24 hours postoperatively for most surgeries 1
• Post-procedural doses beyond 24 hours are unnecessary and harmful, increasing antibiotic resistance without reducing infection rates 1, 4
• Exception: cardiac surgery and prosthetic arthroplasty may continue for 3-5 days following completion of surgery 2

Intraoperative Re-dosing

• Re-dose when surgery duration exceeds two half-lives of the antibiotic (typically >2-4 hours) 1
• Re-dose with significant blood loss (>1.5L) 1
• Cefazolin: re-inject 1g if duration exceeds 4 hours 1, 2
• Cefuroxime/cefamandole: re-inject 0.75g if duration exceeds 2 hours 1

Special Populations

Obese Patients (≥120 kg)

• Higher doses required based on actual body weight 1
• Bariatric surgery: cefazolin 4g IV (30-minute infusion) or cefuroxime 3g IV 1

Renal Impairment

• Adjust doses for creatinine clearance <55 mL/min 2
• CrCl 35-54 mL/min: full dose every 8 hours minimum 2
• CrCl 11-34 mL/min: half usual dose every 12 hours 2
• CrCl <10 mL/min: half usual dose every 18-24 hours 2

Patients Colonized with Multidrug-Resistant Organisms

• Screen for extended-spectrum cephalosporin-resistant Enterobacterales (ESCR-E) before colorectal and liver transplant surgery according to local epidemiology 1
• Ertapenem is preferred carbapenem for ESCR-E carriers due to single administration and sparing other carbapenems for severe infections 1
• Confirm susceptibility with preoperative cultures and adjust prophylaxis accordingly 1
• Avoid broad-spectrum antibiotics if other options available 1

Common Pitfalls to Avoid

• Never administer prophylaxis after cord clamping in cesarean section or after incision in other procedures 4
• Avoid fluoroquinolones for routine surgical prophylaxis due to resistance concerns and adverse effect profile 4
• Do not use third-generation cephalosporins (ceftriaxone, ceftazidime, cefotaxime) for routine prophylaxis despite their widespread use; they are not recommended and promote resistance 3, 5
• Avoid aminoglycosides in combination with other nephrotoxic drugs or in renal dysfunction 1
• Do not prolong prophylaxis beyond 72 hours postoperatively as this increases resistance without benefit 1
• Prophylaxis alone cannot prevent surgical site infections; must combine with infection prevention and control strategies including hand hygiene, meticulous surgical technique, and perioperative optimization 1