Objective: To determine the impact of methicillin-resistant Staphylococcus aureus (MRSA) on length of stay in the intensive care unit (ICU) for patients with ventilator-associated pneumonia (VAP) and to control for the effect of initially inappropriate antibiotic treatment on outcomes by focusing only on persons who were given appropriate antibiotic therapy for their infection.
Design: Retrospective analysis of pooled, patient-level data from multiple clinical trials in VAP.
Setting: Multiple ICUs in France.
Subjects: Persons with bronchoscopically confirmed VAP due to either MRSA or methicillin-susceptible S. aureus (MSSA) and who received initially appropriate antibiotic treatment. All persons with MRSA VAP received vancomycin (15 mg/kg intravenously, twice daily).
Interventions: None.
Measurements and main results: We compared patients with MRSA VAP to persons with MSSA VAP. ICU length of stay represented the primary end point and ICU-free days served as a secondary end point. We recorded information regarding multiple confounders, including demographics, reasons for ICU admission and mechanical ventilation (MV), severity of illness at both ICU admission and time of diagnosis of VAP, and duration of mechanical ventilation before and following the onset of VAP. The final cohort included 107 patients, and one third of cases were due to MRSA. Despite receiving initially appropriate antibiotic treatment, median ICU length of stay was significantly longer for persons with MRSA infection (33 days vs. 22 days; p=.047). The median number of ICU-free days was concomitantly lower in MRSA VAP (0 days vs. 5 days; p=.011). Survival analysis employing a Cox proportional hazards model identified several predictors of remaining in the ICU: Pao2/Fio2 ratio at diagnosis of VAP, duration of MV before VAP, duration of MV after diagnosis of VAP, and reason for MV. Additionally, infection with MRSA as opposed MSSA doubled the probability of needing continued ICU care (hazard ratio, 2.08; 95% confidence interval, 1.09-3.95; p=.025).
Conclusions: MRSA VAP independently prolongs the duration of ICU hospitalization, and in turn, increases overall costs, even for patients initially given appropriate antibiotic treatment. Confronting the adverse impact of MRSA will require efforts that address more than the initial antibiotic prescription.