Tracing Of Real-time glu13Cose Metabolism in Human Immune Cells - Intensive Care Unit

The purpose of this study is to understand how cells of the immune system use the common sugar glucose during critical illness. Investigators will intravenously infuse a non-radioactive carbon-13 glucose tracer into adult intensive care unit (ICU) participants over a few hours and collect immune cells from the blood to track uptake and usage of this glucose within these immune cells.

Inclusion Criteria: * Adults aged 18 or older * Admitted to one of the following VUMC adult ICUs: Medical ICU, Pulmonary ICU * The participant or legally authorized representative must agree to the genetic analyses required as part of this study Exclusion Criteria: * Pregnant * Prisoner or in police custody * Patient desires comfort measures only or has a goals-of-care plan inconsistent with participation in non-beneficial research procedures * Hemoglobin less than 8 g/dL * Uncontrolled hyperglycemia (persistent blood glucose \>300 mg/dL) or any clinical condition in which additional IV glucose administration is not appropriate in the opinion of the Study Coordinator, PI, or treating ICU team * Current participation in another study where the total volume of blood drawn, when added to this study blood draw volume, exceeds 500 mL in an 8-week period * Unable to safely obtain vascular access required for study infusion and blood collection * Clinical instability or anticipated clinical care needs that would make the study procedure inappropriate at that time in the opinion of the Study Coordinator, PI, or treating ICU team * Any medical issue or pharmacologic exposure which, in the opinion of the study investigator, might interfere with the study objectives * Any reason which, in the opinion of the study investigator, adds additional risk to the patient