Empirical decision-making for antimicrobial therapy in critically ill patients

Question 1

Pharmacokinetic and dynamic differences in critically ill patients

Answer 1

• Delayed or no GI absorption
• AKI
• Hypoalbuminaemia
• Vasoplegia
• Capillary leak syndrome
• Altered volume of distribution
• ## Continuous RRT

Question 2

Common sources of infection in critical care patients, suggested sampling and examples of source control

Answer 2

Lungs- BAL, ETT aspirate- drainage of developing empyema
Urinary Tract- urinary cultures- remove catheter, nephrostomy
Abdomen- surgical sampling in source control- drainage and debridement
CNS- LP- removal of invasive devices, surgical decompression
Soft tissue and bones- wound swabs, surgical sampling- debridement
Bloodstream- blood cultures- removal of invasive lines

Question 3

Why are B-lactams effective in treating sepsis in critically ill patients

Answer 3

• Hydrophilic therefore easy to spread to extravascular spaces
• Wide therapeutic window- good for altered Vd
• Will cross BBB if the blood brain barrier is oedematous and leaky

Question 4

Common MDR pathogens in intensive care

Answer 4

• Enterococcus resistant to vancomycin
• Klebsiella resistant to B-lactams
• Acinetobacter resistant to carbapenem
• Pseudomonas
• MRSA
• Enterobacter

Question 5

Risk factors for developing a MDR infection in critical care

Answer 5

• Severity of disease process (e.g. APACHE II score)
• known colonisation with MDR
• Broad spectrum abx use in the preceding 90 days
• Mechanical ventilation for >48 hours
• Immunosupression

Question 6

Mechanisms bacteria develop drug resistance

Answer 6

• Presence of B-lactamases
• Modification of permeability of the bacterial wall
• Presence of drug efflux pumps in the bacterial wall
• Presence of modified protein binding sites