A 74-year-old woman is evaluated in the intensive care unit for a new-onset fever and increased oxygen requirement. She was admitted 5 days ago for a severe ischemic stroke and currently requires mechanical ventilation. Her temperature is 39.1°C (102.4°F), blood pressure is 88/54 mmHg, and heart rate is 118/min. She has a documented history of a severe anaphylactic reaction to penicillin, characterized by hives and airway edema. A portable chest radiograph shows a new right lower lobe consolidation. A tracheal aspirate is sent for Gram stain and culture. Which of the following medications are most appropriate to include in this patient's initial empiric pharmacologic regimen? (Select all that apply)
- LinezolidAnswer
- AztreonamAnswer
- CPiperacillin-tazobactam
- DCeftriaxone
- EDaptomycin
Answer
The correct selections are Linezolid and Aztreonam.
The patient is presenting with ventilator-associated pneumonia (VAP) and septic shock, which requires immediate empiric antibiotic therapy targeting methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. Because of the patient's severe, IgE-mediated anaphylactic allergy to penicillin, cross-reactive beta-lactams must be avoided. Aztreonam is a monobactam that provides excellent gram-negative coverage, including Pseudomonas, and is safe for this patient because it lacks the bicyclic ring structure that causes cross-reactivity with penicillins. Linezolid provides the necessary MRSA coverage and has excellent penetration into pulmonary tissues.
Step-by-Step Solution
Key Concept
Empiric treatment of ventilator-associated pneumonia requires broad-spectrum coverage for MRSA and Pseudomonas aeruginosa. In patients with severe IgE-mediated penicillin allergies, monobactams (e.g., aztreonam) provide safe antipseudomonal coverage. For MRSA coverage in pneumonia, linezolid or vancomycin are used, whereas daptomycin is absolutely contraindicated because it is inactivated by pulmonary surfactant.