What is the recommended prophylactic antibiotic regimen (drug, dose, timing, repeat dosing, alternatives for β‑lactam allergy or MRSA colonization, and site‑specific modifications) for an otherwise healthy adult undergoing an elective clean or clean‑contaminated operation?

Antibiotic Prophylaxis Protocol for Elective Surgery

For most clean and clean-contaminated elective operations in healthy adults, administer cefazolin 2g IV as a slow infusion 30-60 minutes before surgical incision, with a single redose of 1g if the procedure exceeds 4 hours, and discontinue prophylaxis within 24 hours postoperatively. 1, 2, 3

Standard First-Line Regimen

Drug Selection and Dosing

• Cefazolin 2g IV administered as a slow infusion is the preferred agent for most clean and clean-contaminated procedures 1, 4
• Alternative first-generation cephalosporins include cefamandole or cefuroxime 1.5g IV 1
• Cefazolin provides adequate coverage for the most common surgical site infection pathogens: S. aureus, S. epidermidis, and gram-negative bacteria 5

Critical Timing Requirements

• Administer within 30-60 minutes before surgical incision to ensure adequate tissue concentrations at the time of initial incision 3, 4, 5, 6
• If the incision is delayed beyond 1 hour after initial administration, redose with the full initial dose 3
• Preoperative administration (within 2 hours before incision) is associated with the lowest surgical site infection rate (0.6%) compared to perioperative (1.4%), postoperative (3.3%), or early administration 2-24 hours before (3.8%) 6

Intraoperative Redosing

• Redose with cefazolin 1g if surgical duration exceeds 4 hours 1, 2, 4
• For cefamandole or cefuroxime, redose with 0.75g if duration exceeds 2 hours 1
• Redosing is based on the antibiotic's half-life and is necessary only for prolonged procedures 3, 7

Duration of Prophylaxis

• Limit prophylaxis to the operative period, with a maximum of 24 hours postoperatively 1, 2, 3, 7
• Never extend beyond 24 hours, as this provides no additional benefit and increases antimicrobial resistance risk 2, 3, 7
• The presence of surgical drains does not justify extending prophylaxis 1, 2

β-Lactam Allergy Alternatives

Standard Allergy Regimen

• Vancomycin 30 mg/kg IV (based on actual body weight) infused over 120 minutes 1, 8
• The infusion must be completed at the latest by the beginning of surgery, ideally 30 minutes before incision 1, 2, 8
• Administer at a maximum rate of 1000 mg/hour to minimize Red Man syndrome and hypotension 1, 8
• Maximum single dose is 4g 1

Alternative Non-Vancomycin Regimens

• Clindamycin 900 mg IV slow as a single dose for most procedures 1
• For procedures requiring gram-negative coverage, add gentamicin 5 mg/kg/day as a single dose 1
• Redose clindamycin 600 mg if duration exceeds 4 hours 1

MRSA Colonization or High-Risk Scenarios

Specific Indications for Vancomycin

Vancomycin should replace cefazolin when any of the following apply: 1, 2, 8

• Documented β-lactam allergy
• Known or suspected MRSA colonization
• Reoperation in a patient hospitalized in a unit with MRSA ecology
• Recent antibiotic therapy
• Procedures involving prosthetic material in high-MRSA-prevalence settings

Vancomycin Dosing Protocol

• 30 mg/kg IV (actual body weight) over 120 minutes 1, 8
• Single dose for most procedures 8
• No routine trough monitoring required for single-dose prophylaxis 8

Site-Specific Modifications

Cardiac Surgery

• Cefazolin 2g IV + 1g added to cardiopulmonary bypass priming solution 1, 2
• Redose 1g at the 4th hour intraoperatively if surgery continues 1, 2
• For pacemaker insertion and endovascular procedures, use the same cardiac surgery protocol 1, 2

Colorectal Surgery

• Cefoxitin 2g IV + metronidazole 1g IV infusion as single doses 1
• Redose cefoxitin 1g if duration exceeds 2 hours 1
• Oral antibiotics given the day before surgery should be combined with IV prophylaxis 1
• For allergy: metronidazole 1g infusion + gentamicin 5 mg/kg as single doses 1

Bariatric Surgery

• Cefazolin 4g (30-minute infusion) for gastric band procedures 1
• Cefoxitin 4g (30-minute infusion) for gastric bypass or sleeve gastrectomy 1
• Doses calculated on actual body weight 1
• Redose cefazolin 2g if duration exceeds 4 hours, or cefoxitin 2g if exceeds 2 hours 1

Orthopedic Procedures with Prosthetic Material

• Cefazolin 2g IV as a single dose 1
• Redose 1g if duration exceeds 4 hours 1
• For allergy: vancomycin 30 mg/kg over 120 minutes or clindamycin 900 mg IV 1
• Arthroscopy without implant requires no prophylaxis 1

Neurosurgery with Prosthetic Material

• Cefazolin 2g IV as a single dose for CSF shunts, craniotomy, and spine surgery with implants 1
• Redose 1g if duration exceeds 4 hours 1
• For allergy: vancomycin 30 mg/kg over 120 minutes 1

Gynecologic Surgery

• Cefazolin 2g IV for hysterectomy and cesarean section 1
• Cefamandole or cefuroxime 1.5g IV are alternatives 1
• Diagnostic laparoscopy, hysteroscopy, IUD placement, and abortion require no prophylaxis 1

Vascular Surgery

• Cefazolin 2g IV for aortic, lower limb arterial, and carotid surgery with patch 1
• Redose 1g if duration exceeds 4 hours 1
• Carotid surgery without patch and vein surgery require no prophylaxis 1

Hernia Repair

• Cefazolin 2g IV only when prosthetic mesh is placed 1
• Hernia repair without mesh requires no prophylaxis 1
• Redose 1g if duration exceeds 4 hours 1

Common Pitfalls and How to Avoid Them

Timing Errors

• Do not administer antibiotics more than 2 hours before incision, as this increases infection risk 6.7-fold compared to administration within 60 minutes 6
• Do not delay administration, as antibiotics given more than 3 hours after incision increase infection risk 5.8-fold 6
• If incision is delayed beyond 1 hour after initial dose, always redose 3

Duration Errors

• Do not extend prophylaxis beyond 24 hours postoperatively under any circumstances 1, 2, 3, 7
• Studies demonstrate that extending prophylaxis beyond the operative period provides no additional benefit 7
• The presence of drains, prolonged ICU stay, or patient anxiety are not valid reasons to continue prophylaxis 1, 2

Dosing Errors in Obesity

• Do not use weight-based dosing for cefazolin in obese patients beyond the standard 2g dose 9
• Cefazolin is hydrophilic and does not penetrate adipose tissue regardless of dose 9
• A 1g dose provides serum concentrations of ~185 mcg/mL, which is adequate for at least 6 hours 9
• Higher doses (3g) increase costs significantly without improving outcomes 9

Vancomycin Administration Errors

• Do not infuse vancomycin faster than 1000 mg/hour to avoid Red Man syndrome and hypotension 1, 8
• Do not use vancomycin routinely—reserve it only for documented β-lactam allergy or MRSA risk 2, 8
• The 120-minute infusion must be completed before surgical incision 1, 8

Procedure-Specific Errors

• Do not give prophylaxis for truly clean procedures without risk factors: simple breast lumpectomy, diagnostic laparoscopy, arthroscopy without implant, closed fractures with extrafocal fixation 1
• Always give prophylaxis when prosthetic material is implanted, even in otherwise clean procedures 1