BACKGROUND: Matrix metalloproteinases (MMPs) likely have an important role in the pathophysiology of acute lung injury. In a recent study, high matrix metalloproteinases (MMP-8) levels in tracheal aspirates of pediatric acute respiratory distress syndrome (ARDS) patients were associated with worse outcome. In patients with sepsis, an imbalance between MMPs and their tissue inhibitors (TIMPs) has been associated with impaired survival. We hypothesized that the elevated systemic MMP-8 and TIMP-1 are associated with worse outcome in acute respiratory failure.
METHODS: This was a substudy of the observational FINNALI study conducted in 25 Finnish intensive care units over an 8-week period. All patients older than 16 years requiring mechanical ventilation for >6 hours were included. MMP-8 and TIMP-1 levels were analyzed from blood samples taken on enrollment in the study and 48 hours later. Laboratory analyses were performed by using immunofluorometric assay for MMP-8 and ELISA for TIMP-1. MMP-8 and TIMP-1 levels were compared between 90-day survivors and nonsurvivors. Survival was compared in quartiles based on TIMP-1 levels, and ROC analysis was performed to calculate areas under the curves. The relationship between MMP-8 and TIMP-1 levels and degree of hypoxemia was examined.
RESULTS: The final analyses included 563 patients. Admission TIMP-1 levels were higher in nonsurvivors, median 367 ng/mL (interquartile range 199–562), than survivors, median 240 ng/mL (interquartile range 142–412), WMWodds 1.68 (95% confidence interval [CI], 1.43–2.08). MMP-8 levels may have differed between survivors and nonsurvivors, WMWodds 1.20 (95% CI, 1.01–1.43), but no difference was found in the MMP-8/TIMP-1 molar ratio, WMWodds 0.83 (95% CI, 0.67–1.04). Difference in survival between quartiles based on TIMP-1 was significant (log-rank, P < 0.001). ROC analysis produced an area under the curve 0.63 (95% CI, 0.58–0.69) for TIMP-1. TIMP-1 was associated with severity of hypoxemia. TIMP-1 levels were higher in an ARDS subgroup than in the whole cohort, WMWodds 1.65 (95% CI, 1.15–2.44).
CONCLUSIONS: MMP-8 levels were possibly higher in 90-day nonsurvivors but performed poorly in predicting outcome. Increased systemic levels of TIMP-1 were associated with more severe hypoxemia and worse outcome in a large cohort of mechanically ventilated critically ill patients and in a subgroup of ARDS patients.
From the *Intensive Care Units, Helsinki University Hospital; †Department of Oral and Maxillofacial Diseases, Helsinki University Hospital and Biomedicum Helsinki, Helsinki; ‡Intensive Care Unit, South Carelia Central Hospital, Lappeenranta; and §Department of Anesthesiology and Intensive Care, Kuopio University Hospital, Kuopio, Finland.
Accepted for publication December 20, 2013.
Funding: Supported by EVO-grant from Helsinki University Hospital [T102010070], [TYH 2012210] and Academy of Finland.
The authors declare no conflicts of interest.
The results of this study have been partly presented as a poster in the annual congress of the European Society of Intensive Care Medicine in Lisbon on October 16, 2012.
Reprints will not be available from the authors.
Address correspondence to Johanna Hästbacka, MD, PhD, Intensive Care Units, Helsinki University Hospital, Intensive Care Unit, Jorvi Hospital, Turuntie 150, 02740 Espoo, Finland. Address e-mail to firstname.lastname@example.org.