Antimicrobial Stewardship (AMS)

Resources to help you ensure the safe and effective use of antimicrobials in NSHA patients.

Surgical Site Infection Prophylaxis

Principles for antimicrobial prophylaxis of surgical site infections (SSIs)

  1. Patients having surgery for which prophylactic antibiotics are recommended should receive them as a standard of care.
  2. The choice of surgical prophylaxis should cover pathogens that commonly cause SSI for that procedure. 
    • It is not necessary to cover or eradicate all possible microorganisms in the surgical field.
  3. Patients labelled with an antibiotic allergy should be asked what antibiotic caused the reaction, how was it administered, what was the reaction, and when did the reaction occur. 
  4. Antibiotics should be dosed to optimize tissue concentrations.
  5. Antibiotics should be administered within 60 minutes before surgical incision.
    • Vancomycin and aminoglycosides require longer infusion times and should be timed to ensure completion within 60 minutes prior to incision.
  6. Antibiotics should be re-dosed intra-operatively if the duration of the procedure exceeds 2 half-lives of the antibiotic.
    • Should also re-dose if there is excessive blood loss (more than 1.5L in adults) for all antibiotics except vancomycin.
  7. Antibiotics should not be given postoperatively unless there is an indication other than prophylaxis (i.e., treatment of contamination or infection).
    • Postoperative prophylaxis which does not exceed 24 hours may be considered in cardiovascular, orthopedic, vascular and orthognathic surgery.
    • Patients who have indwelling drains or intravascular catheters do not require extension of prophylaxis duration.
    • A 2019 survey of surgical prophylaxis in NS Health found that surgical prophylaxis was given longer than 24h in 39% of patients (national comparison 29%).

Last reviewed January 2024

Dosing and re-dosing recommendations for antimicrobials commonly used for surgical prophylaxis

  • Cefazolin is the preferred agent for surgical prophylaxis 
    • Cefazolin is safe in most patients with a penicillin allergy
      • Except for a history of severe delayed skin reaction/organ dysfunction (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms) to any beta-lactam antimicrobial OR a history of anaphylaxis to cefazolin
    • Cefazolin can be administered quickly and has a favorable side-effect profile
    • Cefazolin is effective for pathogens that commonly cause SSIs


  • Clindamycin was excluded from these recommendations because pathogens that cause SSI are often resistant to clindamycin; and clindamycin is not as safe because even one dose can be complicated by C. difficile infection.
    • If emergent surgery precludes the infusion time for vancomycin, clindamycin may be used instead when there is a contraindication to cefazolin


Adult dose Pediatric dose*
(max dose should not exceed
the recommended adult dose)
(from time of administration of pre-op dose)
Cefazolin 2 g
Consider 3g if weight above 120 kg

30 mg/kg/dose
Max 2000mg/dose

Every 4 h (Max 6 g/24h)
2.5 mg/kg
(Round to nearest 20 mg)
2.5 mg/kg/dose 
Max 120mg/dose
At 6h x 1 (if CrCl greater than or equal to 60 ml/min)
Pediatrics: none required
Metronidazole 500 mg 15 mg/kg/dose
Max 500mg/dose 
At 12 hrs x 1 
Pediatrics: see IWK Firstline App

15 mg/kg round nearest 250 mg
(Max 2000 mg/dose)


  • 1g or less over 60 min,
  • 1g-1.5g over 90 min,
  • More than 1.5 g over 120 min

15 mg/kg/dose
Max 1000mg/dose

At 12h x 1 (if CrCl greater than or equal to 60 ml/min)

Pediatrics: see IWK Firstline App

*For more detailed pediatric recommendations, please refer to the IWK Firstline App

Last reviewed January 2024

Systemic surgical prophylaxis recommendations:

Note: for detailed pediatric recommendations, please refer to the IWK Spectrum App

Type of Surgery Recommended Antimicrobial(s)

Alternative Antimicrobial(s) if anaphylaxis to cefazolin or severe delayed reaction to any beta-lactam such as SJS/TEN, DRESS, AGEP


Coronary artery bypass (CABG),
valve replacement (+/- CABG), 
other cardiac procedures

cefazolin vancomycin
Ventricular assist devices
Device insertion (e.g., pacemaker)
cefazolin vancomycin
Cardiac catheterization
Transesophageal echocardiogram
none none
Gastroduodenal/esophageal cefazolin vancomycin + 
PEG insertion  cefazolin vancomycin
Biliary tract - laparoscopic procedure – Low risk none none

Biliary tract - laparoscopic procedure – High risk 
Non-elective, inserting prosthetic device, diabetes, duration greater than 120min, risk of intraoperative gallbladder rupture/conversion to open, age of 70 years or more, ASA greater than or equal to 3, reintervention within a month, acute cholecystitis, jaundice, pregnancy, immunosuppression

cefazolin vancomycin + 
Biliary tract - open procedure cefazolin vancomycin + 
Colorectal, small bowel, appendectomy 
cefazolin + 
vancomycin +     
aminoglycoside + 
Hernia repair - Hernioplasty, herniorrhaphy cefazolin vancomycin
Low risk anorectal procedures: hemorrhoidectomy, fistulotomy, sphincterotomy none none
Non-cardiac procedures
(e.g., lobectomy, pneumonectomy, lung resection, and thoracotomy) 
Video-assisted thoracoscopic surgery
cefazolin vancomycin
Thoracentesis or chest tube insertion for non-traumatic indications (e.g., spontaneous pneumothorax) none none
Head and Neck
Clean: no incision through oral/nasal/pharyngeal mucosa (e.g., parotidectomy, thyroidectomy, and submandibular gland excision) none none
Clean with placement of prosthetic material (excludes tympanostomy tubes that do not require prophylaxis) cefazolin vancomycin
Clean-contaminated (incision through oral/pharyngeal mucosa): cancer surgery and other clean-contaminated procedures with the exception of tonsillectomy and functional endoscopic sinus procedures cefazolin + 
vancomycin + 
Elective craniotomy, stereotactic brain biopsy, cerebrospinal fluid-shunting procedures, ICP monitor, external ventricular drain, and implantation of intrathecal pumps cefazolin vancomycin
Arthroscopy without graft implantation none none
Spinal procedures with and without instrumentation, hip fracture repair, Implantation of internal fixation devices (e.g., nails, screws, plates, wires), and total joint replacement cefazolin vancomycin
In addition to the prophylaxis recommendations below, obtain urine culture prior to stone removal or invasive procedures involving mucosal bleeding/trauma. If bacteria are found in the culture, treat based on sensitivities prior to performing the procedure.
Cystoscopy/Shock-wave lithotripsy 
  • No risk factors, urine culture negative

Cystoscopy/Shockwave lithotripsy:

Risk factors:

  • Advanced age, immunocompromised, anatomic abnormalities, poor nutrition, diabetes mellitus, smoking, prolonged catheters
  • Manipulation (prostatectomy, biopsy, foreign body removal, urethral dilation, stent placement/removal, ureteroscopy)

If no hospitalization in last year, recent antibiotic use from the class, or other risks for resistance:

  • cefazolin 2g IV x 1 dose or
  • ciprofloxacin 500 mg PO or 
  • trimethoprim/sulfamethoxazole (TMP-SMX) 1 DS tablet (800/160 mg) PO
  • give 1-2 hours pre-procedure

If risk of Gram-negative bacteria resistance (including prolonged hospitalization, infection or colonization with resistant bacteria, or recent fluoroquinolone/TMP-SMX use) select one of the following instead:

  • Ceftriaxone 1g IM/IV 1 hour pre-procedure


  • Tobramycin 1.5 mg/kg IV/IM (round to nearest 20 mg; maximum IM dose 120 mg) 1 hour pre-procedure
Transrectal prostate biopsy

Give 1-2 hours pre-procedure:

  • ciprofloxacin 500 mg PO or 
  • trimethoprim/sulfamethoxazole (TMP-SMX) 1 DS tablet (800/160 mg) PO

If risk of Gram-negative bacteria resistance:

  • Prior episode of post biopsy sepsis
  • Health care worker who works directly with patients 
  • Fluoroquinolone use 6 months prior to biopsy 
  • Recent international travel (particularly Asia) in last 90 days
  • Diabetes 
  • Immunosuppression due to medications, prior transplant or medical conditions 
  • Recent hospital admission in last 90 days 
  • Prior infection with fluoroquinolone resistant bacteria


  • Ceftriaxone 1 g IM/IV 


  • Tobramycin 1.5 mg/kg IM or IV (rounded to nearest 20 mg; max dose of 120 mg for IM)
Percutaneous renal surgery cefazolin vancomycin
Open or Laparoscopic:
without entry into bowel/vagina
cefazolin vancomycin + 
Open or Laparoscopic:
involving manipulation of bowel/vagina
cefazolin + 
vancomycin + 
aminoglycoside + 
Arterial surgery
Graft placement or repair
cefazolin vancomycin
Clean without risk factors none none
Clean - high risk 
  • prosthetic material, skin irradiation, traumatic/crush hand injuries, flap reconstruction, panniculectomy, injuries requiring amputation/reconstructive limb surgery, injuries involving bone, joint, tendon (except open flexor tendon injuries) or nerve
cefazolin vancomycin
Breast surgery cefazolin vancomycin
Caesarean section cefazolin vancomycin + 
Hysterectomy cefazolin +/- 
vancomycin + 
aminoglycoside +/- 
Laparoscopic procedures that involve no direct access from the abdominal cavity to the uterine cavity or vagina none none

Last reviewed January 2024

1. University of Toronto Best Practice in Surgery Program.

2. World Health Organization. Global Guidelines for the Prevention of Surgical Site Infection.

Last reviewed January 2024