Antibiotic Guidelines in ICU

Revised and reviewed 17 December 2015

OVERVIEW

• Antibiotic guidelines vary between ICUs
• This variation is based on local causes of infections, resistance patterns, availability and patient factors
• However, the principles of appropriate use of antibiotics are universal… as are the common errors!

PRINCIPLES OF APPROPRIATE USE OF ANTIBIOTICS

Adapted from Lipman:

• Take cultures before administering antibiotics
• Take two sets of cultures, not from a line
• Timing of blood cultures with fever is not critical
• Do not delay the administration of antibiotics
• Use empirical therapy first; narrow the spectrum later
• Ensure initial doses are sufficient – under-doing must be avoided
• use monotherapy where possible (reduces cost and toxicity).
• If the microbiology results suggest decreased susceptibility, consider whether the antibiotics working clinically. If there is direct bedside evidence that they are working, then continue them in spite of laboratory evidence. In vitro sensitivity does not always predict in vivo effect
• A shorter course (e.g. 7 days) is probably as good as a standard 2-week course in most cases
• Infectious diseases specialists should be consulted when managing serious infections
• Know antimicrobial pharmacokinetics and pharmacodynamics; consider tissue penetration and dose adjustment to correct for altered clearance
• Monitor antibiotic levels when available
• Limit “prophylactic” use to appropriate situations
• Consider non-infective causes of inflammation (sepsis mimics are surprisingly common)
• Adhere to infection control policies
• Have an antimicrobial stewardship program in the ICU

COMMON ERRORS IN ANTIBIOTIC USE

Adapted from Lipman:

• Delay in antibiotic administration in severe sepsis
• Antibiotics given before cultures taken
• Contaminated or insufficient blood culture collection
• Excessively long courses of antibiotics
• Erratic changes of antibiotics in non-resolving sepsis
• Inadequate doses
• Poor choice of empirical antibiotics, failing to account for resident flora
• Failure to predict toxicity or account for interactions
• Failure to consider tissue penetration of different antibiotics
• Inappropriate use of antibiotic polypharmacy or failure to de-escalate to monotherapy

FACTORS THAT DETERMINE INITIAL CHOICE OF ANTIBIOTICS

Table from Deranged Physiology — General principles and common errors of antimicrobial use:

EXAMPLE OF AN ICU ANTIBIOTIC GUIDELINE

General rules

• investigate first, start aggressively, and streamline quickly to reduce resistance
• ideally 3 sets of blood cultures first from fresh sites, 10 mL each
• empiric antibiotic choices based on syndromic approach

Pneumonia

• ceftraixone + azithromycin (community acquired)
• ceftriaxone + metronidazole (aspiration)

Abdominal focus

• ampicilin + gentamicin + metronidazole

Neurosurgical infection

• vancomycin 1g q6h + ceftazidime 2g q6h
• no need for routine prophylaxis if EVD inserted

Necrotizing fasciitis

• meropenem 1g q8h + benzylpenicilin 2.4g q4h + lincomycin 900mg q8h
• if GPC on biopsy = suspect group A streptococcus -> IvIg 1g/kg on day 1, 0.5 g/kg/d on days 2 and 3

Sepsis unknown source or VAP

• always cover prior resistant bacteria even if found much earlier (e.g. VRE if previously colonised)
• tazocin + gentamicin
  if mild rash to penicillin then cefepime + gentamicin
  if anaphylaxis/ DRESS/ Steven-Johnson to penicillin then vancomycin + aztreonam + gentamicin
  use ciprofloxacin not gentamicin if eGFR <50, age >65y or recently on gentamicin
• add vancomycin if:
  hospitalised >7 days or recent admission past 3 months
  prior MRSA
  pre-existing longterm lines
• teichoplanin if VRE colonised
• add fungal cover in severe sepsis using fluconazole if ECMO or yeast isolated
  if already on fluconazole change to caspofungin
  if already on posaconazole or voriconazle talk to ID!

When to stop antibiotics

• Day 2
  vanc/ gent/ cipro/ flucon/ caspo
  if patient improved and no MRSA, resistant GNBs or candida
  streamline tazocin when sensitivities available
  switch gentamicin to ciprofloxacin if 2nd agent still needed
• Day 6
  stop all antibiotics unless specific diagnosis requires longer – discuss with ID
• Line sepsis
  Staph aureus – change lines, perform TOE -> Rx for 14d if no endocarditis or low risk
  Coag neg staph – change lines -> Rx 2-5 days

References and Links

LITFL

• CCC — Antimicrobial dosing and kill characteristics
• CCC — Antibiotic Dosing in Renal Replacement Therapy
• CCC — Antibiotic timing
• CCC — Unresolved sepsis

FOAM and web resources

• Deranged Physiology — General principles and common errors of antimicrobial use

Journal articles and textbooks

• Lipman, J. Principles  of  antibiotic  use. Chapter 72  in Oh’s Intensive Care Manual
• Leekha S, Terrell CL, Edson RS. General principles of antimicrobial therapy. Mayo Clinic proceedings. 86(2):156-67. 2011. [pubmed] [free full text]