Time to clinical stability in patients with ventilator-associated pneumonia due to Methicillin-resistant staphylococcus aureus treated with Linezolid versus Vancomycin: results from the IMPAC-HAP study

Abstract

Background: Time to clinical stability is a well-defined early clinical outcome in hospitalized patients with community-acquired pneumonia, but it has not been evaluated in patients with ventilator-associated pneumonia (VAP). The objective of this study was to compare time to clinical stability in patients with MRSA VAP treated with linezolid versus vancomycin. Methods: This was a secondary analysis of the IMPACT-HAP study database. VAP was defined according to CDC criteria. MRSA VAP was considered when MRSA was isolated from a tracheal aspirate or bronchoalveolar lavage. A patient was considered to reach clinical stability the day that the following four criteria were met: 1) Afebrile for 24 hours, 2) Decrease in WBC >10% or WBC within normal range, 3) Improving of PaO 2 /FiO 2 ratio of >20%, or PaO 2 /FiO 2 ratio >250, or extubation, or FiO 2 ≤ 30% if extubated, and 4) Systolic blood pressure >90 mmHg. Time to clinical stability for linezolid and vancomycin were compared using the Chi-Squared and Student's t-tests. Results: A total of 89 patients treated with linezolid and 75 patients treated with vancomycin met study criteria. From the population of linezolid treated patients, 79% reached clinical stability, compared to 75% of the population of vancomycin treated patients (P=0.463). Median time to clinical stability was 6 days (IQR 8) for patients treated with linezolid, versus 7 days (IQR 12) for patients treated with vancomycin (P=0.490). Conclusions:This study failed to demonstrate a statistically significant difference in time to clinical stability in patients with MRSA VAP treated with linezolid or vancomycin. The number of days for patients to reach clinical stability can be used as an early clinical outcome in patients with VAP.