CICM SAQ 2015.1 Q27
Questions
Discuss the factors that may affect your choice of antimicrobial agent in a critically ill septic patient, giving examples where relevant.
Answers
Answer and interpretation
Patient Factors
- History of current acute illness
- Allergies
- Previous antibiotic exposure
- Co-morbidities like immunocompetence, Diabetes.
- Social history e.g. nursing home resident, alcohol/drug abuse, occupation, contact with birds/animals, travel
Organism
- Sensitivity profile
- Inducible beta-lactamase producers (e.g. ESCAPPM)
- Tendency to develop resistance to antimicrobial during treatment course e.g. Pseudomonas aeruginosa
- Intracellular (e.g. aminoglycosides poorly active against strictly intracellular bacteria e.g. Rickettsia, Chlamydia, Coxiella burnetti)
Site of infection
- Organs with non-fenestrated capillaries (e.g. brain, prostate, anterior chamber of eye) – poor penetration of non lipid-soluble drugs
- Biliary and urinary sepsis – select drugs with hepatic (e.g. ceftriaxone) and urinary excretion (cefotaxime) respectively
- Lung – e.g. daptomycin inactivated by surfactant, vancomycin poor penetration
Organ dysfunction
- Renal or hepatic dysfunction may result in decreased elimination and increased toxicity
Toxicity
- Renal and ototoxicity of aminoglycosides
- Renal toxicity of vancomycin
- Neurotoxicity of imipenem
Drug interactions
- Synergy – beta lactams and aminoglycosides
- Pharmacodynamic interactions e.g. macrolides plus other agents causing prolongation of QT
Non anti-microbial effects of antimicrobial
- Anti-inflammatory effect of macrolides – may underlie outcome benefit when combined with beta lactams for bacteraemic pneumococcal pneumonia
- Inhibition of toxin synthesis in toxic-shock syndrome by clindamycin and linezolid
Hospital factors
- Local microbiology/ecology
- Ability of monitoring drug levels (TDM)
- Presence of an ID physician / Antibiotic Stewardship team in the hospital and their policies
Route of administration
- Certain routes of administration may be unreliable in critically ill patients and drugs which can only be administered by that route are less desirable e.g. inhaled zanamivir
Cost
- Cost-effectiveness of the antibiotic
Bactericidal vs bacteriostatic
- Theoretical benefit from bactericidal drugs. Controversial whether there is a clinical benefit
- Pass rate: 23%
- Maximum mark: 6.0
Additional comments:
- Candidates were not expected to provide long lists of antimicrobial agents but to mention some examples where relevant. Overall, the question was poorly answered with superficial answers showing a lack of depth of understanding of the topic.
- Some wrote about dosing and dose adjustment but not about the choice of antimicrobial agent.
- Some candidates included key phrases e.g., “time dependent killing” without any demonstration of understanding of how that concept affected the choice of antibiotic.
Examination Library
CICM
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
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