Metabolomic Biomarkers Measured at Patient Discharge Predict Long-Term Physical Function in Survivors of Acute Respiratory Failure

RATIONALE: Long-term quality of life is a significant concern for survivors of sepsis and acute respiratory failure (ARF). Financial burdens await as many patients never return to work. Notably, the duration of the ICU stay significantly correlates with the severity of physical impairment and up to 25% of skeletal muscle is lost within one week in the ICU. The recent pandemic due to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV2) is likely to exacerbate these issues. We have previously reported that metabolites related to mitochondrial bioenergetics status can predict acute patient outcomes. Here, we propose that these same metabolomic and mitochondrial biomarkers of mortality also predict physical function in survivors. METHODS: To test this hypothesis, we performed a retrospective analysis of metabolomic changes in ARF survivors using ultrahigh performance liquid chromatography mass spectrometry. Six months after ICU admission, physical function was determined by the short physical performance battery (SPPB), an objective physical function measurement assessing gait speed, balance and lower extremity strength. A total of 70 consecutively enrolled patients were selected, of which 35 had good physical function (SPPB ≥ 7) and 35 had poor physical function (SPPB ≤6). The patients were matched for age, race and sex. Metabolomic analysis of patient's serum was measured at ICU admittance (n=70), 5d-post admittance (n=20) and discharge (n=20). RESULTS: More than 1250 named compounds were identified. There were only 19 metabolites that were significantly different at admittance (ANOVA;p < 0.05), of which seven were bile acids. However at discharge, despite less patient samples tested, 151 metabolites were significantly different (ANOVA;p < 0.05). Specifically, we found that 10 lysophospholipids, eight bile acids, three TCA cycle metabolites, eight kynurenine-related metabolites and nine urea cycle metabolites were significantly different. Many of these pathways have previously been shown to be altered in nonsurvivors of sepsis and ARF. CONCLUSIONS: Findings suggest that bioenergetic abnormalities arising during the acute phase of recovery may be persistent and predict longer-term decrements of physical function in survivors of ARF. Larger retrospective and prospective studies are needed to confirm these preliminary findings;however, predicting poor physical function in survivors as well as identifying the affected metabolic pathways may lead to improved therapies and long-term patient outcomes.