Chpater 182 - Strategies for Treating Infections in Critically Ill Patients

Question 1

In small animals, if you collect some sample from an open skin wound for cytology and find gram-positive cocci, what is it most likely to be?

Answer 1

S. pseudintermedius

Question 2

In critically ill patient, what are the general rules of the use of antibiotics, in terms of the dose regimen, timing and duration?

Answer 2

Hit hard (aggressive treatment) and hit fast (early intervention), for a short duration

Question 3

If an organism is suspected to be P. aeruginosa but the culture and antibiotic susceptibility results are still pending, what are appropriate type of antibiotics to choose?
A) Fluoroquinolones
B) Aminoglycosides
C) Extended-spectrum penicillin (e.g. ticarcillin or piperacillin)
D) Third generation cephalosporins (except ceftazidime)
* P. aeruginosa tends to have inherent resistance to many drugs

Answer 3

A, B, C

Question 4

When we talk about the drug diffusion into the tissue, there are two types of models that have been discussed, which are perfusion rate–limited drug diffusion and permeability rate–limited drug diffusion. What are the tissues for examples in both models?

Answer 4

1. Perfusion rate–limited drug diffusion: Diffusion of most antibiotics from plasma to tissues is limited by tissue blood flow, rather than drug lipid solubility
2. Permeability rate–limited drug diffusion: In some tissues a lipid membrane (e.g., tight junctions on capillaries) presents a barrier to drug diffusion
   These tissues include the central nervous system, eye, and prostate
3. Blood-bronchus or blood-alveolar barrier

Question 5

What are the factors that can affect the effectiveness of antibiotics?

Answer 5

1. Local tissue factors - pus, cell debris, foreign materials
2. Presence of cations
3. Acid/base
4. Anaerobic environment
5. Tissue perfusion

Question 6

How does the foreign materials in the wound or a lesion affect the effectiveness of antibiotics?

Answer 6

It allows bacteria to form a biofilm (glycocalyx) at the site of infection

Question 7

What are the two groups of antibiotics that can be affected by the presence of cations (Mg, Al, Fe, and Ca)?

Answer 7

Fluoroquinolones, Aminoglycosides

Question 8

Please draw the pharmacokinetic/pharmacodynamic relationships for antimicrobials and explain the concentration-dependent medicine and time-dependent medicine.

Answer 8

Textbook figure 182-1