What is the recommended antibiotic prophylaxis for an adult undergoing elective hip replacement surgery?

Recommended Antibiotic Prophylaxis for Hip Replacement

For elective hip replacement surgery, administer cefazolin 2g IV as a slow infusion 30-60 minutes before surgical incision, with re-dosing of 1g if the procedure exceeds 4 hours, limiting prophylaxis to the operative period (maximum 24 hours). 1

Primary Prophylaxis Regimen

First-Line: Cefazolin

• Administer 2g IV slow infusion as the initial dose, given 30-60 minutes before surgical incision to ensure adequate tissue and serum concentrations at the time of incision 1, 2
• Re-dose with 1g IV if the surgical duration exceeds 4 hours to maintain therapeutic levels throughout the procedure 1
• Limit prophylaxis to the operative period, with a maximum duration of 24 hours postoperatively 1
• Cefazolin achieves the highest bone concentrations among first-generation cephalosporins (30 micrograms per gram at peak), reaching levels 60 times higher than the minimum inhibitory concentration for penicillin-resistant staphylococci 3

Alternative First-Generation Cephalosporins

If cefazolin is unavailable, alternative options include:

• Cefamandole 1.5g IV slow infusion, with re-dosing of 0.75g if duration exceeds 2 hours 1
• Cefuroxime 1.5g IV slow infusion, with re-dosing of 0.75g if duration exceeds 2 hours 1
• Both alternatives are limited to the operative period (maximum 24 hours) 1

Penicillin/Beta-Lactam Allergy Alternatives

For patients with documented beta-lactam allergy, administer clindamycin 900 mg IV slow infusion as a single dose, with re-dosing of 600 mg if the procedure exceeds 4 hours, limited to the operative period. 1, 4

Clindamycin Dosing Details

• Initial dose: 900 mg IV slow infusion within 60 minutes before incision, ideally 30 minutes before 4
• Re-dose with 600 mg IV if surgical duration exceeds 4 hours 4
• Limit to the operative period (maximum 24 hours) 1

Vancomycin for High-Risk Scenarios

Vancomycin 30 mg/kg IV over 120 minutes (single dose) is indicated for:

• Documented allergy to beta-lactams 1
• Suspected or proven colonization with methicillin-resistant Staphylococcus aureus (MRSA) 1
• Reoperation in a patient hospitalized in a unit with MRSA ecology 1
• Previous antibiotic therapy 1

Critical timing: The 120-minute vancomycin infusion must be completed at the latest at the beginning of the intervention, ideally 30 minutes before incision. 1

Target Pathogens

The prophylaxis regimen targets the most common organisms causing prosthetic joint infections:

• Staphylococcus aureus (including methicillin-susceptible strains) 1
• Staphylococcus epidermidis and other coagulase-negative staphylococci 1
• Streptococcus species 1

Evidence Supporting Efficacy

Infection Rate Reduction

• Without antibiotic prophylaxis, the incidence of postoperative infection in prosthetic joint surgery is 3-5%, which can be reduced to less than 1% with appropriate prophylaxis 1
• A large multicenter trial demonstrated that cefazolin prophylaxis reduced hip infections from 3.3% (placebo) to 0.9%, representing a 73% relative risk reduction 5
• One day of cefuroxime prophylaxis was as effective as three days of cefazolin, with deep infection rates of 0.5% vs 1.2% respectively for primary hip arthroplasty 6

Bone Penetration

First-generation cephalosporins achieve excellent bone penetration, with cefazolin reaching peak bone levels of 30 micrograms per gram within 25-40 minutes after injection, maintaining a bone half-life of 42 minutes 3

Common Pitfalls and Caveats

Timing Errors

• Administering antibiotics too early (>60 minutes before incision) or too late (after incision) significantly reduces prophylaxis effectiveness 1, 2
• For vancomycin, failure to account for the 120-minute infusion time is a critical error that results in inadequate tissue levels at incision 1

Duration Errors

• Extending prophylaxis beyond 24 hours (or up to 5 days in some older protocols) does not provide additional benefit and increases antibiotic resistance risk 1, 2
• The FDA label mentions that prophylaxis "may be continued for 3 to 5 days following completion of surgery" for prosthetic arthroplasty 2, but current guideline consensus strongly favors limiting to the operative period (maximum 24 hours) 1

Re-dosing Failures

• Failure to re-dose during prolonged procedures (>4 hours for cefazolin, >2 hours for cefuroxime/cefamandole) results in subtherapeutic tissue levels 1

Special Considerations for Gram-Negative Coverage

• Recent evidence suggests that adding expanded gram-negative coverage (gentamicin or aztreonam) to cefazolin for hip arthroplasty reduced surgical site infections from 1.19% to 0.55% 7
• This approach may be considered in institutions with high rates of gram-negative infections following hip arthroplasty 7
• However, this is not yet incorporated into standard guidelines and represents an emerging practice pattern 7

Operating Theater Environment

• The benefit of antibiotic prophylaxis is most pronounced in conventional operating theaters; hypersterile theaters show lower baseline infection rates 5
• This does not eliminate the need for prophylaxis but contextualizes the magnitude of benefit 5