Antibiotic Prophylaxis After CABG
Preoperative antibiotics should be administered to all CABG patients, using a first- or second-generation cephalosporin (cefazolin 2g IV or cefuroxime 1.5g IV) given within 60 minutes before incision, with prophylaxis discontinued within 24 hours postoperatively. 1
Recommended Antibiotic Regimen
First-Line Prophylaxis
- Cefazolin 2g IV administered 30-60 minutes before surgical incision is the standard of care 1, 2
- Alternative first-generation or second-generation cephalosporins (cefuroxime 1.5g IV, cefamandole 1.5g IV) are equally effective 1
- Redose cefazolin 1g IV if surgery duration exceeds 4 hours to maintain adequate tissue levels 2
MRSA-Colonized or High-Risk Patients
- Vancomycin 30 mg/kg IV over 120 minutes (ending at incision time) is recommended for patients with proven or suspected methicillin-resistant Staphylococcus aureus colonization 1
- Vancomycin may be used in combination with cefazolin when risk of both MRSA and methicillin-susceptible organisms is high 1
- Vancomycin is indicated for patients with beta-lactam allergy, recent hospitalization in units with high MRSA prevalence, or prior MRSA infection 1
Beta-Lactam Allergic Patients
- Clindamycin 900 mg IV is the alternative for patients with documented beta-lactam allergy 1
Critical Timing Principles
The preoperative dose must be given 30-60 minutes before surgical incision to ensure adequate serum and tissue antibiotic levels at the time of initial incision 1, 2
- Cephalosporins should be infused within 60 minutes of incision 1
- Vancomycin requires 120-minute infusion and must end at or before incision time 1
Duration of Prophylaxis
Antibiotic prophylaxis should be limited to the operative period and discontinued within 24 hours postoperatively. 1
Evidence Against Prolonged Prophylaxis
- Continuing antibiotics beyond 48 hours after CABG does not reduce surgical site infection rates but significantly increases antimicrobial resistance (adjusted OR 1.6 for acquired resistance) 3
- Studies comparing 48-hour versus 72-hour prophylaxis regimens show no difference in infection rates (7.6% vs 10.2%, p>0.05) 4
- Prolonged prophylaxis is ineffective, increases costs, and promotes resistant organisms 5, 3
Exception for High-Risk Surgery
- In surgeries where infection would be particularly devastating (open-heart surgery, prosthetic valve replacement), prophylaxis may be continued for 3-5 days, though this represents older practice patterns 2
Microbiological Coverage
The primary pathogens requiring coverage are:
- Staphylococcus aureus (both methicillin-susceptible and resistant strains) 1, 6
- Coagulase-negative staphylococci (most common cause of incisional SSI and catheter-related infections) 6
- Gram-negative enterobacteriaceae (secondary concern) 7, 6
First-generation cephalosporins provide excellent coverage against the predominant Gram-positive organisms (68% of isolates) while maintaining activity against common Gram-negative pathogens 6
Common Pitfalls to Avoid
- Do not delay the preoperative dose - antibiotics given more than 1 hour before incision or after incision provide suboptimal protection 1, 2
- Do not continue prophylaxis beyond 24 hours in uncomplicated cases - this practice is widespread but increases resistance without reducing infection 3
- Do not use vancomycin as routine first-line prophylaxis - it is less effective than cefazolin against methicillin-susceptible organisms and should be reserved for specific indications 1
- Verify reported penicillin allergies - patients receiving second-line antibiotics have 50% higher odds of developing SSI 1
- Ensure adequate redosing during lengthy procedures - failure to redose when surgery exceeds two half-lives of the antibiotic compromises tissue levels 2
Adjunctive Infection Prevention Measures
Beyond antibiotic prophylaxis, aggressive perioperative glycemic control with continuous IV insulin to maintain blood glucose ≤180 mg/dL reduces deep sternal wound infection risk 1